Association between serum magnesium levels and dementia patients

Motherisk Int J 2020;1;28

 

Research submitted for fulfillment of the degree Doctor of Philosophy

By

Sarah Ben-Zaken

 

This work was prepared under the supervision of Prof. Gideon Koren

 

 

 

Table of Contents

 

Page
English abstract ……………………………………………………………………………… 4
Hebrew abstract  תקציר ……………………………………………………………………………… 5
Introduction ……………………………………………………………………………… 6
Aging and maturation ……………………………………………………… 6
Dementia ……………………………………………………………………. 11
Diagnosing dementia...……………………………………………… 13
Clinical evaluation of dementia..…………………………………… 13
Brief cognitive tests..……………………………………………….. 14
Topic review ………………………………………………………………………………. 20
Alzheimer's disease..………………………………………………………... 20
Historical information….…………………………………………… 20
Pathology of the disease..………………………………….………... 21
Types of Alzheimer's disease….……………………………………. 22
Diagnosing the disease...……………………………………………. 22
Understanding the etiology of the disease..………….……………… 23
Clinical features of Alzheimer's disease…………….………………. 27
Molecular features of Alzheimer's disease..………………………… 28
Risk factors of Alzheimer's disease….……………………………… 32
Comparing Alzheimer's disease to normal aging…………………… 33
Vascular dementia...………………………………………………………… 35
Magnesium (Mg)….………………………………………………………… 36
Regulation and homeostasis……….………………………………... 37
Absorption…………………………………………………………... 38
Excretion…………………………………………………………….. 40
Storage and distribution……………………………………………... 41
Measuring magnesium levels……………………………………….. 43
Magnesium deficiency……………………………………………… 44
Magnesium and dementia…………………………………………… 45
Key words ………………………………………………………………………….…… 47
Research objectives ……………………………………………………………………………… 47
Articles review ……………………………………………………………………………… 48
Methods ……………………………………………………………………………… 49
Statistical analysis………………………………………………………….. 51
Article #1 ……………………………………………………………………………… 52
Article #2 ……………………………………………………………………………… 58
Article #3 ……………………………………………………………………………… 64
Discussion and summary ……………………………………………………………………………… 67
References ……………………………………………………………………………… 71

 

 

Abstract

Aging is related to several chronic diseases, one of them is dementia. Current treatment or preventive options for dementia are limited, therefore there's an urgent need to identify potential risk factors. The role of magnesium in dementia and other degenerative disorders has been the focus of increased attention in recent years. Research so far have shown controversial results while trying to show a connection between serum magnesium levels and increased risk of dementia. In this research, we wanted to sharpen this connection, using three different research approaches:

  1. A big data analysis, using Maccabi Healthcare Service central computerized database.
  2. A comparison between two populations very similar in their confounders but diverse in their exposure to desalinated water (DSW) in daily urban living.
  3. A systematic review and meta-analysis, summarizing all articles, in any language, reporting on serum magnesium concentrations in plasma or serum of patients with dementia, compared to patients without dementia.

First approach research showed that dementia patients did not exhibit lower means, medians, or modes of serum magnesium levels, and thus not being able to support the hypothesis that hypomagnesemia has a major role in the pathogenesis of dementia. However, more episodes of hypomagnesemia were shown in dementia patients, compared to controls.

The results in the second study showed serum magnesium levels were significantly lower following the switch to desalinated water, yet the prevalence of dementia was similar in the two cities screened. This study could not rule out some possible effect of hypomagnesemia on dementia morbidity, but the effect if exists, is not that significant.

Results of systematic review and meta-analysis showed a significant heterogeneity in the results, and no significant difference in Mg2+ concentrations between patients with dementia and controls.

Overall results of our study show that, based on large numbers of dementia patients and controls, low serum magnesium concentrations are not associated with increased likelihood of dementia. Hence, serum magnesium should be used with caution to predict the status and activity of dementia in patients.

More studies are needed in order to identify biological markers of magnesium disposition in dementia, particularly comparing different types of dementia.

 

תקציר

תהליך ההזדקנות הנו נושא הנחקר באופן נרחב בעקבות העלייה בתוחלת החיים. לתהליך זה נלווים גם מחלות כרוניות, ביניהן דמנציה. הידע הקיים כיום אודות הגורמים לדמנציה והדרכים למנוע ולטפל בה הנו מוגבל, ולכן קיים צורך להגדיר את גורמי הסיכון המזרזים את הופעת המחלה ולנטרל אותם. רמות אלקטרוליטים, וביניהם מגנזיום, ותפקידם במחלת הדמנציה הנו נושא הנחקר רבות בשנים האחרונות. מחקרים שבוצעו עד כה הראו תוצאות סותרות בניסיון להסביר את הקשר בין רמות מגנזיום ודמנציה, כאשר בחלק מהמחקרים נטען שרמות מגנזיום בסרום יורדות בחולי דמנציה, ואילו מחקרים אחרים הראו עליה.

במחקר שלנו רצינו למצוא קשר מובהק יותר בין רמות מגנזיום בסרום והשכיחות של דמנציה, כאשר השערת המחקר הייתה שבחולי דמנציה נראה רמות נמוכות יותר של מגנזיום בסרום.

חקרנו את השערת המחקר תוך שימוש ב-3 גישות מחקר שונות:

  1. אנליזה של מאגר מידע ממוחשב גדול, הנמצא בשימוש "מכבי שירותי בריאות".
  2. השוואה בין 2 אוכלוסיות הדומות מאוד במאפיינים שלהן אך שונות ברמת החשיפה למים מותפלים כחלק מאורח החיים העירוני.
  3. סיכום של כל המאמרים שדיווחו על השוואה בין רמות מגנזיום בסרום או פלסמה במטופלים עם דמנציה, בהשוואה לכאלה ללא דמנציה (סקירה שיטתית ומטה-אנליזה).

במחקר הראשון ראינו שמטופלים חולי דמנציה לא הציגו ממוצע, חציון ושכיח נמוכים יותר בהשוואה למטופלים בעלי תכונות דומות אך ללא דמנציה. בכך למעשה שללנו את השערת המחקר, אולם במקביל גילינו שבחולי דמנציה ישנם יותר פרקי זמן שבהם נצפו רמות נמוכות של מגנזיום בסרום, בהשוואה לקבוצת הביקורת.תוצאות המחקר השני הראו שרמות מגנזיום בסרום היו משמעותית נמוכות יותר בתושבי העיר רחובות, שעברה לשימוש עיקרי במים מותפלים, יחד עם זאת השכיחות של דמנציה הייתה זהה ב-2 הערים שנבדקו. מחקר זה לא יכול לשלול לחלוטין השפעה אפשרית של היפו-מגנזמיה על ההיארעות של דמנציה, אבל כן ניתן להניח שההשפעה (אם בכלל קיימת) אינה כל כך משמעותית.

תוצאות הסקירה השיטתית והמטה-אנליזה הראו הטרוגניות נרחבת בתוצאות, כאשר לא נצפה שינוי משמעותי ברמות מגנזיום בסרום בהשוואה בין חולי דמנציה וקבוצת הביקורת.

סך כל התוצאות שקיבלנו במחקרים שביצענו מראות שבהתבסס על קבוצה גדולה של חולי דמנציה מול קבוצת ביקורת בהתאמה, לא נמצא קשר בין רמות מגנזיום נמוכות לשכיחות גבוהה יותר של דמנציה. לכן יש להתייחס לרמות מגנזיום בסרום בזהירות יתרה כחלק מניבוי השכיחות לדמנציה בחולים.

יש צורך לבצע מחקרים נוספים במטרה לזהות סמנים ביולוגיים אחרים (כולל מגנזיום) שיכולים להופיע בחולי דמנציה, בפרט בסוגים שונים של דמנציה.

Introduction

Aging and maturation

Aging has become a subject for increased research, due to changes in the demography of world population and the prolongation of human life expectancy. It is a complex multifactorial process of molecular and cellular decline that affects tissue function over time, rendering organisms frail and susceptible to disease and death (1). It occurs at different rates in different species, and inter-individual variations exist within a species and in different tissues of an individual (1).

Potential biomarkers of aging may align with the central molecular mechanisms of aging, and studies have identified and categorized nine critical cellular and molecular hallmarks of the aging process (2). These hallmarks are generally considered to contribute to the aging process and together determine the aging phenotype (Figure 1).

Figure 1. | The Hallmarks of Aging |

The scheme enumerates the nine hallmarks of aging: genomic instability, telomere attrition, epigenetic alterations, loss of proteostasis, deregulated nutrient-sensing, mitochondrial dysfunction, cellular senescence, stem cell exhaustion, and altered intercellular communication

 

Each ‘hallmark’ should ideally fulfil the following criteria: (i) it should manifest during normal aging; (ii) its experimental aggravation should accelerate aging; and (iii) its experimental amelioration should retard the normal aging process and, hence, increase healthy lifespan.

The last criterion is the most difficult to achieve, even if restricted to just one aspect of aging.

  1. Genomic instability and DNA damage.

One common denominator of aging is the accumulation of genetic damage throughout life (3). Moreover, numerous premature aging diseases, such as Werner syndrome and Bloom syndrome, are the consequence of increased DNA damage accumulation (4). The integrity and stability of DNA is continuously challenged by exogenous physical, chemical and biological agents, as well as by endogenous threats including DNA replication errors, spontaneous hydrolytic reactions, and reactive oxygen species (ROS) (5). The genetic lesions arising from extrinsic or intrinsic damage are highly diverse and include point mutations, translocations, chromosomal gains and losses, telomere shortening, etc. To minimize these lesions, organisms have evolved a complex network of DNA repair mechanisms that are collectively capable of dealing with most of the damage to nuclear DNA (6). Several types of DNA damage, including bulky adducts, DNA single-strand breaks, DNA double-strand breaks, base mismatches, insertions and deletions, are associated with neurodegeneration (7). Oxidative DNA damage from endogenous reactive oxygen species (ROS) can increase inflammation, accelerate ageing, and increase susceptibility to cancer and neurodegenerative diseases

  1. Telomere attrition.

Accumulation of DNA damage with age appears to affect the genome near-to-randomly, but there are some chromosomal regions, such as telomeres, that are particularly susceptible to age-related deterioration (8). Telomeres are regions composed of DNA and protein at the ends of the linear chromosomes. Telomeres become shorter as cells divide, unless either the parental cell expresses telomerase, or another mechanism is present to prevent telomere attrition. Telomere shortening causes cellular senescence and is probably involved in organismal aging. Defects in telomere maintenance accelerate aging in mice and humans (9).

  1. Epigenetic alterations.

A variety of epigenetic alterations affects all cells and tissues throughout life (10). Epigenetic changes involve alterations in DNA methylation patterns, post-translational modification of histones, and chromatin remodeling. The multiple enzymatic systems assuring the generation and maintenance of epigenetic patterns include DNA methyltransferases, histone acetylases, deacetylases, methylases and demethylases, as well as protein complexes implicated in chromatin remodeling. Epigenetic modifications including methylation and acetylation of DNA and histones collectively influence chromatin tertiary structure. Epigenetic markers strongly influence chromatin activity and function, including transcription and replication. Epigenetic age-related mechanisms have roles in pathologies associated with neurodegenerative diseases (11).

  1. Loss of proteostasis.

The balance between protein synthesis and degradation creates a steady state known as proteostasis. The maintenance of proteostasis in eukaryotic cells depends on proper regulation of the proteasome and on the process of autophagy (9), as well as on the ubiquitination machinery and lysosomal system. Ubiquitinated proteins are often destined for degradation. Autophagy is an intracellular degradation system that facilitates lysosomal degradation of misfolded or unfolded proteins and of damaged organelles, thereby reducing secretion of inflammatory cytokines (12). Aging and some aging-related diseases are linked to impaired protein homeostasis or proteostasis (13). All cells take advantage of an array of quality control mechanisms to preserve the stability and functionality of their proteomes. Proteostasis involves mechanisms for the stabilization of correctly folded proteins, most prominently the heat-shock family of proteins, and mechanisms for the degradation of proteins by the proteasome or the lysosome ((14);(15);(16)). All these systems function in a coordinated fashion to restore the structure of misfolded polypeptides or to remove and degrade them completely, thus preventing the accumulation of damaged components and assuring the continuous renewal of intracellular proteins. Accordingly, many studies have demonstrated that proteostasis is altered with aging (15). Additionally, chronic expression of unfolded, misfolded or aggregated proteins contributes to the development of some age-related pathologies and neurodegenerative disorders, such as Alzheimer’s disease, Parkinson’s disease etc (13).

  1. Mitochondrial dysfunction and mitophagy.

As highly metabolically active cells, neurons have high energy demands to perform neuronal activities and are particularly sensitive to changes in mitochondrial function. As cells and organisms age, the efficacy of the respiratory chain tends to diminish, thus increasing electron leakage and reducing ATP generation (17). The relation between mitochondrial dysfunction and aging has been long suspected but dissecting its details remains as a major challenge for aging research. The mitochondrial free radical theory of aging proposes that the progressive mitochondrial dysfunction that occurs with aging results in increased production of reactive oxygen species (ROS), which in turn causes further mitochondrial deterioration and global cellular damage. The production of ROS is amplified in damaged mitochondria and is implicated in the normal ageing process and in a majority of known neurodegenerative diseases. Besides ATP production, mitochondria also have key roles in several intercellular pathways, including lipid biosynthesis, calcium signaling and cell apoptosis, all of which are central processes in the development of neurodegenerative disease (18). Brain mitochondrial function becomes impaired with age and is believed to be a major and early contributor to the ageing process.

  1. Cellular senescence.

Cellular senescence is a state of stress-induced stable cell cycle arrest and a senescence associated secretory phenotype that occurs with age. This phenomenon was originally described by Hayflick in human fibroblasts serially passaged in culture (19). Today, we know that the senescence observed by Hayflick is caused by telomere shortening (20), but there are other aging-associated stimuli that trigger senescence independently of this telomeric process. Cellular senescence can be considered a response that aims to maintain survival of healthy cells and remove damaged cells under conditions of stress. Research suggest that the efficiency of DNA repair decreases with age, but also that more complex DNA repair mechanisms are used during ageing, leading to more mutations being introduced. These less efficient DNA repair processes are associated with ageing and cancer and might also have a role in neurodegeneration (21).

  1. Deregulated nutrient sensing and altered metabolism.

Calorie restriction, which downregulates nutrient signaling pathways, extends lifespan in several species including mice, and might have neuroprotective effects in human tissues (22). Major nutrient-sensing pathways and molecules include insulin, insulin-like growth factor 1 (IGF-1), mechanistic target of rapamycin (mTOR), AMP activated protein kinase (AMPK) and sirtuins (9). mTOR, AMPK and sirtuins are being explored as therapeutic targets for neurodegenerative diseases.

  1. Stem cell exhaustion.

The decline in the regenerative potential of tissues is one of the most obvious characteristics of aging. Functional stem cells are needed for optimal health in later life. However, stem cell function and proliferative capacity decline over an organism’s lifespan. This functional loss can be caused by age related high levels of DNA damage, low DNA repair capacity, defects in proteostasis, epigenetic deregulation, mitochondrial dysfunction, telomerase inactivation and/or cell senescence (23). Targeting of aged stem cell regeneration might alleviate age-associated neurodegenerative diseases.

  1. Altered intercellular communication and immune function.

Beyond cell-autonomous alterations, aging also involves changes at the level of intercellular communication, be it endocrine, neuro-endocrine or neuronal ((24);(25);(26);(27)). Thus, neurohormonal signaling (eg, renin-angiotensin, adrenergic, insulin-IGF-1 signaling) tends to be deregulated in aging as inflammatory reactions increase, immunosurveillance against pathogens and premalignant cells declines, and the composition of the peri- and extracellular environment changes, thereby affecting the mechanical and functional properties of all tissues.

Alterations in levels of hormones such as leptin, ghrelin, insulin and IGF-1 regulate neuronal damage and neurodegeneration. The immune system is essential for shaping the brain during development, and both the nervous system and the immune system change with age, so the loss of regulation of immune responses in the brain is likely to be a factor in neurodegeneration (28).

All nine hallmarks of aging and their expression in neurodegenerative disease are summarized in Figure 2.

 

 

 

Figure 2 | The hallmarks of aging in neurodegenerative disease | Nine hallmarks of ageing as seen in the main neurodegenerative diseases. AD, Alzheimer disease; ALS, amyotrophic lateral sclerosis; AT, ataxia telangiectasia; HD, Huntington disease; PD, Parkinson disease.

 

Aging is related to several chronic diseases from cardiovascular and metabolic origin and is the primary risk factor for most neurodegenerative diseases, such as Alzheimer's disease and Parkinson disease. For instance, one in ten individuals aged over 65 years has Alzheimer's disease and its prevalence continues to increase with increasing age (Figure 3) (29).

Figure 3 | Neurodegenerative disease' prevalence | a. Prevalence of Alzheimer's disease per 1,000 men and women by age in the USA b. Prevalence of Parkinson disease per 100,000 men and women by age globally c. Prevalence of amyotrophic lateral sclerosis (ALS) per 100,000 population in the USA in 2014

 

Dementia

Dementia (ICD-9 code 294.20) is a clinical syndrome characterized by a progressive decline in two or more cognitive domains, including memory, language, executive and visuospatial function, personality, and behavior. This decline causes loss of abilities to perform instrumental and/or basic activities of daily living (30). Dementia is a complex process involving an interplay between specific molecular pathways affecting cellular functions, leading to loss of synaptic connections, cell death, gliosis, inflammation, and disruption of functional networks underlying cognition, personality, behavior and sensorimotor functions, eventually attacking an individual’s autonomy (31). According to reliable estimates, approximately 154,000 individuals in Israel have some form of dementia and it is expected to rise to around 290,000 by 2030, in tandem with the expected increase in the number of older adults (32).

Dementias are classified based on their underlying pathologies, which are largely defined by accumulation of abnormal protein aggregates in neurons and glia, as well as in the extracellular compartment, in vulnerable regions of the brain. The vast majority of nonvascular dementias fall into six main categories of neurodegenerative proteinopathies: amyloid-β (Aβ), microtubule-associated protein tau, TAR DNA-binding protein 43 (TDP-43), fused in sarcoma (FUS), α-synuclein, and prion protein (Figure 4) (31).

Figure 4. |Clinicopathological spectrum of neurodegenerative proteinopathies| Schematic representation of the molecular underpinnings of neurodegenerative diseases and their main clinical manifestations. The figure lists genes with full penetrance that are considered causative and risk genes that influence molecular processes culminating in the misfolding and/or aggregation of six fundamental proteins: cellular prion protein (PrPC), Aβ42 (and, to a lesser extent, Aβ40), tau, TAR DNA-binding protein 43 (TDP-43), fused in sarcoma (FUS), and α-synuclein. These normal proteins misfold and/or accumulate in intracellular or extracellular compartments in specific areas of the CNS. Four major pathological disease categories are recognized: prion disease, Alzheimer disease (AD), frontotemporal lobar degeneration (FTLD) and Lewy body diseases (LBD). The pathologies can involve multiple molecules; for example, AD is a dual proteinopathy with Aβ and tau aggregates. Genetic pleiotropy is also at play: mutations in certain genes — for example, GRN, have full penetrance for one pathology (FTLD-TDP) and associated FTD syndromes, while representing a risk factor for another pathology (AD).

Abbreviations: Aβà amyloid-β; CJDà Creutzfeldt–Jakob disease; FTD–MNDà FTD with motor neuron disease; PPAà primary progressive aphasia.

 

Diagnosing dementia

The diagnostic process in dementia has 3 major conceptual components:

  1. Clinical diagnosis
  2. A logical search for the cause
  3. Identification of treatable comorbid conditions and other contributing factors, such as the degree of cerebrovascular disease.

The diagnostic process should involve 6 main steps: taking the patient’s history, interviewing a caregiver or family member, physical examination, brief cognitive tests, basic laboratory tests, and structural imaging for patients meeting certain criteria.

As part of the assessment of dementia, laboratory studies are necessary to identify causes of dementia and coexisting conditions that are common in the elderly. Measurements of factors in the blood such as a complete blood count, thyroid-stimulating hormone, vitamin B12, urea, nitrogen, electrolytes, liver-functions, or screening for heavy metals should be performed in order to rule out historical features or clinical circumstances like infections, inflammatory diseases or exposure to toxins which may contribute to the dementia (33).

Clinical evaluation of dementia

Despite the remarkable progress that has been made in the basic neurosciences, the diagnosis of dementia is one that is still made clinically in the office, and includes 3 steps:

  1. Medical history screen from the patient
  2. Collateral history from an informant
  3. Physical examination

All these steps must be supplemented by a cognitive assessment. The sensitivity for each of these components in detecting dementia varies strongly with the degree of dementia, moderate dementia being far less challenging to detect than very mild dementia.

The history taking should focus on the cadence of the illness and the relation to any vascular events such as stroke. Causes of dementia such as alcohol abuse and renal failure should be assessed. Vascular risk factors, including hypertension, diabetes mellitus, smoking history, family history of stroke and lipid status, should be ascertained. Risk factors such as family history of dementia or repetitive head trauma, and protective factors such as high education level, should also be ascertained.

A separate history taken from a caregiver or family member with the patient absent is obligatory. It is necessary to ascertain whether the memory complaint represents a consistent change from the previous level of function. Frontotemporal dementia is characterized by early personality changes that the patient will almost invariably fail to note or report. Functional impairment should be directly assessed, and significant impairment documented. This involves questioning the caregiver or family member about the patient’s independent performance of activities of daily living, such as feeding and using the toilet. In early dementia, the functional impairment is more likely to emerge in “higher” functions, such as the ability to carry out complicated financial affairs like banking, the ability to use public transport or to drive, normal attention to hobbies, and the ability to learn to use new machines or appliances.

Brief cognitive tests

All patients evaluated for dementia should have their cognitive function evaluated. Brief cognitive tests serve to determine the presence and overall severity of memory and cognitive deficits and can be recommended for both primary care and specialty practice (Table 1).

Table 1 |Brief cognitive screening tests to assist in the diagnosis of dementia|

All brief cognitive tests have a lower sensitivity and specificity than does a full neuropsychological evaluation, but they are far faster and more accessible than specialized testing. The Mini-Mental State Examination (MMSE) (34) remains the most widely used instrument, with high sensitivity and specificity for separating moderate dementia from normal cognition. It requires little training, is administered in about 10 minutes and has vast medical acceptance. A rough rule of thumb is that patients with mild dementia usually have a score of 18–26 out of 30, those with moderate dementia a score of 10–18, and those with severe dementia a score of less than 10. The Mini-Mental State Examination focuses on memory, attention, construction and orientation domains.

The clock-drawing test evaluates general executive functioning of the frontal lobe, as well as visuospatial abilities (Figure 5)(35). It requires 5–10 minutes to administer and has achieved widespread clinical use.

Figure 5. |Clock drawings and test scores for patients without dementia and those with Alzheimer disease or suspected frontotemporal dementia| Patients are instructed to draw a clock face with all the numbers in it, and to show the time as 10 minutes past 11. Fifteen items are used to evaluate the drawing and 1 point is given for each item that is present. The following criteria are used:

The shape of the circle is acceptable ; It is not too small, overdrawn or repeated ; only numbers 1 to 12 are present ; all numbers are in Arabic numerals ; the numbers are in the correct order ; the paper is not rotated while drawing the numbers ; the numbers are in the correct position ; all numbers are inside the contour ; the clock has a center where the hands meet ; the clock has 2 hands ; the target number for the hour hand is indicated ; the minute hand is longer than the hour hand ; no superfluous markings are present ;the hands are joined or are within 1.27 cm of each other

Several newer tests have been developed to provide improved sensitivity. Of these, it is worth mentioning the Montréal Cognitive Assessment (36), DemTect (37), the 7-Minute Screen (38), the General Practitioner Assessment of Cognition (39) and the Behavioral Neurology Assessment short form (40). All these tests have been shown to be more accurate than the Mini-Mental State Examination in discriminating between dementia and normal cognition, particularly in cases of very mild dementia.

The challenges in diagnosing dementia should not be understated. It can be difficult in some individuals with mild dementia to reliably demonstrate objective cognitive impairment as well as functional impairment. Some individuals without dementia can score low in the Mini-Mental State Examination, and only a score below 20 provides specific evidence for dementia (41). Conversely, dementia is possible even with a Mini-Mental State Examination score greater than 26 (RW.ERROR - Unable to find reference:doc:621646f68f08f85e5526df63). Furthermore, the score may vary by several points from one evaluation to the next. Language barriers, advanced age and low education can also confound the results and provide false-positive scores. A briefer test, such as the clock-drawing test, has the same challenges. No brief cognitive test has been found to be superior over the others. No brief cognitive test has been developed to differentiate between subtypes of dementia, and none can be recommended for this purpose.

Table 2 summarizes the common causes of dementia and associated characteristics: (42)

 

Cause Characteristics
Alzheimer's disease Alzheimer's disease is the most common cause of dementia, accounting for an estimated 60% to 80% of cases. Difficulty remembering recent conversations, names or events is often an early clinical symptom; apathy and depression are also often early symptoms. Later symptoms include impaired communication, disorientation, confusion, poor judgment, behavioral changes and, ultimately, difficulty speaking, swallowing and walking.

The hallmark pathologies of Alzheimer's disease are the accumulation of the protein fragment beta-amyloid (plaques) outside neurons in the brain and twisted strands of the protein tau (tangles) inside neurons. These changes are accompanied by the death of neurons and damage to brain tissue. Alzheimer's is a slowly progressive brain disease that begins many years before symptoms emerge.

Cerebrovascular disease Cerebrovascular disease refers to the process by which blood vessels in the brain are damaged and/or brain tissue is injured from not receiving enough blood, oxygen or nutrients. People with dementia whose brains show evidence of cerebrovascular disease are said to have vascular dementia. About 5% to 10% of individuals with dementia show evidence of vascular dementia alone. However, it is more common as a mixed pathology, with most people living with dementia showing the brain changes of cerebrovascular disease and Alzheimer's disease.

Impaired judgment or impaired ability to make decisions, plan or organize may be the initial symptom, but memory may also be affected, especially when the brain changes of other causes of dementia are present. In addition to changes in cognitive function, people with vascular dementia commonly have difficulty with motor function, especially slow gait and poor balance.

Vascular dementia occurs most commonly from blood vessel blockage, such as that which occurs with stroke, or damage leading to areas of dead tissue or bleeding in the brain. The location, number and size of the brain injuries determine whether dementia will result and how the individual's thinking and physical functioning will be affected.

Lewy body disease Lewy bodies are abnormal aggregations (or clumps) of the protein alpha-synuclein in neurons. When they develop in the cortex, dementia with Lewy bodies (DLB) can result. People with DLB have some of the symptoms common in Alzheimer's but are more likely to have initial or early symptoms of sleep disturbance, well-formed visual hallucinations and visuospatial impairment. These symptoms may occur in the absence of significant memory impairment but memory loss often occurs, especially when the brain changes of other causes of dementia are present. About 5% of individuals with dementia show evidence of DLB alone, but most people with DLB also have Alzheimer's disease pathology.
Frontotemporal lobar degeneration (FTLD) FTLD includes dementias such as behavioral-variant FTLD, primary progressive aphasia, Pick's disease, corticobasal degeneration and progressive supranuclear palsy.

Typical early symptoms include marked changes in personality and behavior and/or difficulty with producing or comprehending language. Unlike Alzheimer's, memory is typically spared in the early stages of disease.

Nerve cells in the frontal lobe and temporal lobes of the brain are especially affected, and these regions become markedly atrophied (shrunken). In addition, the upper layers of the cortex typically become soft and spongy and have abnormal protein inclusions (usually tau protein or the transactive response DNA-binding protein, TDP-43).

The symptoms of FTLD may occur in those age 65 years and older similar to Alzheimer's, but most people develop symptoms at a younger age. About 60% of people with FTLD are ages 45 to 60. FTLD is believed to be the most common cause of dementia in people younger than 60. Its prevalence was found to be about 3% of dementia cases in studies that included people 65 and older and about 10% of dementia cases in studies restricted to those younger than 65.

Parkinson's disease (PD) Problems with movement (slowness, rigidity, tremor and changes in gait) are common symptoms of PD. Cognitive symptoms develop either just before movement symptoms or later in the disease.

In PD, clumps of the protein alpha-synuclein appear in the substantia nigra. These clumps are thought to cause degeneration of the nerve cells that produce dopamine.

As PD progresses, alpha-synuclein can also accumulate in the cortex of the brain (similar to dementia with Lewy bodies), leading to dementia.

Hippocampal sclerosis (HS) HS is the hardening of tissue in the hippocampus. Since the hippocampus plays a key role in forming memories, the most pronounced symptom of HS is memory loss.

HS brain changes are often accompanied by accumulations of a misfolded form of a protein called TDP-43.

HS is a common cause of dementia in individuals aged 85 or older.

Mixed pathologies An individual showing brain changes of more than one cause of dementia is considered as mixed dementia. The likelihood of having mixed dementia increases with age and is highest in people aged 85 or older.

 

Having established the presence of a dementia, the specific cause should be determined. This determination relies on clinical evaluation, along with laboratory investigations and structural imaging. In considering diagnosis of a degenerative dementia, it is important to exclude delirium, a condition that is a transient, usually reversible, acute confusional state.

 

 

  

 

 

Topic Review

Alzheimer's disease

Alzheimer’s disease (AD) (ICD-9 code 331.0) is by far the most common cause of dementia and accounts for 60% to 80% of all dementia diagnoses (30). Less than half of the cases are pure AD, since the majority are mixed dementias. The other most common causes of dementia include vascular dementia, Lewy body dementia and Parkinson’s disease with dementia (43).

Historical information

AD was first reported in 1907 by Alois Alzheimer, a clinical psychiatrist and neuroanatomist, who reported “A peculiar severe disease process of the cerebral cortex”. He described a 50-year-old woman (Auguste Deter) whom he had followed from her admission for paranoia, progressive sleep and memory disturbance, aggression and confusion, until her death 5 years later (44). He first saw her in 1901. Auguste’s husband Karl brought her to a mental hospital after she began exhibiting unusual behavior, including hiding items, threatening neighbors, and accusing her husband of adultery. She also lost the ability to do daily activities such as cooking and housework. Auguste came under Alzheimer’s care at a mental hospital in Frankfurt. There he observed and recorded her behavioral patterns: she could speak but not write her own name, she could name objects such as a pencil but not the food she was eating, she was polite sometimes but loud and offensive at other times. He diagnosed Auguste with “presenile dementia” (45). Upon her death in 1906, Alzheimer’s biopsy of her brain revealed diffuse cortical atrophy and “particular changes in cortical cell clusters” (46). Alzheimer described plaques and tangles of nerve fibers which researchers would identify in the 1980’s as beta amyloid (Aβ) plaques and neurofibrillary tangles of tau (47, 48) which became the hallmark for AD confirmation (figure 6).

Figure 6. | The hallmark for AD confirmation | A representation of the basic histology of Alzheimer’s Disease, consisting of intracellular neurofibrillary tangles composed of hyperphosphorylated tau and extracellular collections of misfolded Aβ peptide forming amyloid plaques (49)

 

Pathology of the disease

Amyloid plaques and neurofibrillary tangles are the cardinal features of Alzheimer histopathology. The amyloid plaques consist of extracellular accumulations of misfolded Aβ sheets consisting of 40 or 42 amino acids (Aβ40 and Aβ42), the two by-products of amyloid precursor protein metabolism (49). Amyloid plaques are located extracellularly, and initially develop in the basal, temporal, and orbitofrontal cortex of the brain, and later progress to involve the neocortex, hippocampus, amygdala, diencephalon, and basal ganglia. These aggregates of Aβ trigger the formation of neurofibrillary tangles (NFS), which are composed mostly of hyperphosphorylated tau protein. These NFS are found in the locus coeruleus and trans - entorhinal and entorhinal areas of the brain. In the last critical stage, these histopathological entities are spread to the hippocampus and neocortex (50).

 

 

Types of Alzheimer's disease

Dominantly inherited familial AD (FAD) can be caused by mutations in amyloid precursor protein (APP), presenilin 1 (PSEN1) or PSEN2 genes. These rare familial forms of AD which account for less than 1% of the cases. FAD can present as early as age 20, with the average age of onset of 46.2 years.

Early onset Alzheimer’s disease (EOAD) is defined by those affected before age 65; and though they are slightly more common than FAD cases, they account for fewer than 5% of the pathologically diagnosed AD cases. EOAD often has an atypical presentation and an aggressive course. Similarly, most Down’s syndrome patients with a partial or full chromosome 21 trisomy, which includes the region on chromosome 21 where APP resides, have Alzheimer type pathology by age 40 with many developing clinical symptoms after 50; the majority have dementia by age 65.

More common late onset AD (LOAD) is considered sporadic, although genetic risk factors have been identified, most notably apolipoprotein E gene (APOE). Age, family history in a first degree relative, and APOE4 genotype confer the greatest risks of developing AD (43).

 

Diagnosing the disease

The diagnosis of Alzheimer’s disease is based on the criteria developed by the National Institute of Neurologic and Communicative Disorders and Stroke–Alzheimer’s Disease and Related Disorders Association (NINCDS–ADRDA) (51), according to which the diagnosis is classified as definite (clinical diagnosis with histologic confirmation), probable (typical clinical syndrome without histologic confirmation), or possible (atypical clinical features but no alternative diagnosis apparent; no histologic confirmation).

According to DSM-V (52), dementia has been renamed as major neurocognitive disorder and minor neurocognitive disorder. The DSM-V diagnostic criteria for major or mild neurocognitive disorder due to Alzheimer’s disease includes the following:

  • Insidious onset with gradual decline in one or more cognitive abilities (for major neurocognitive disorder, at least two domains must be impaired).
  • Criteria are met for major or mild neurocognitive disorder due to probable or possible Alzheimer’s disease as follows:

For major neurocognitive disorder:

Probable Alzheimer’s disease is diagnosed if either of the following is present; otherwise, possible Alzheimer’s disease should be diagnosed.

  • Evidence of a causative Alzheimer’s disease genetic mutation from family history or genetic testing.
  • All three of the following are present:
  • Clear evidence of decline in memory and learning and at least one other cognitive domain (based on detailed history or serial neuropsychological testing).
  • Steadily progressive, gradual decline in cognition, without extended plateaus.
  • No evidence of mixed etiology (i.e., absence of other neurodegenerative or cerebrovascular disease, or another neurological, mental, or systemic disease or condition likely contributing to cognitive decline).

For mild neurocognitive disorder:

  • Probable Alzheimer’s disease is diagnosed if there is evidence of a causative Alzheimer’s disease genetic mutation from either genetic testing or family history.
  • Possible Alzheimer’s disease is diagnosed if there is no evidence of a causative Alzheimer’s disease genetic mutation from either genetic testing or family history, and all three of the following are present:
  • Clear evidence of decline in memory and learning.
  • Steadily progressive, gradual decline in cognition, without extended plateaus.
  • No evidence of mixed etiology (i.e., absence of other neurodegenerative or cerebrovascular disease, or another neurological or systemic disease or condition likely contributing to cognitive decline).

Understanding the etiology of the disease

AD is a complex, multifactorial, neurodegenerative disease, resulting from complicated interactions of one’s genetic makeup, education, age, and environment. Many hypotheses have laid the foundation to gain understanding of the etiology of the disease, among them:

1) The cholinergic hypothesis, based upon the fact that AD patients show reduction in activity of choline acetyltransferase and acetylcholinesterase in the cerebral cortex, compared with the normal brain (53). Post-mortem brain tissue from patients with AD confirmed the reduced neurotransmitter pathway activity, revealing that degeneration of cholinergic neurons and loss of cholinergic neurotransmission significantly contributes to the cognitive impairment seen in those with AD (53).

 

 

2) The Tau hypothesis, considering AD histopathology reveals intraneuronal neurofibrillary lesions made up of tau proteins. Tau proteins are mainly found in neurons and are involved in the assembly and stabilization of the neuronal microtubule network. Tau protein becomes pathological when the phosphorylation regulation becomes unchecked and hyperphosphorylated tau proteins polymerize into filaments and become neurofibrillary tangles. This leads to malfunction of the structural and regulatory actions of the cytoskeleton and then leads to abnormal morphology, axonal transport, and synaptic function of neurons, thus leading to neurodegeneration (53).

3) The amyloid cascade hypothesis. attributes clinical sequelae of the disease to the overproduction or decreased clearance of amyloid beta (Aβ) peptides, which then leads to increased deposition of Aβ, leading to neuronal damage (Figures 7-8). The length of Aβ varies depending on the posttranslational cleavage pattern of the transmembrane amyloid precursor protein (APP). Aβ is generated by cleavage of APP via either b- or g-secretases, resulting in the infamous insoluble Aβ fibrils (54). Two main types of Aβ polymers play a direct role in the pathology of AD: Aβ40 and Aβ42. Aβ40/Aβ42 then oligomerizes, travels to synaptic clefts, and interferes with synaptic signaling. These eventually further polymerize into insoluble amyloid fibrils that aggregate into amyloid plaques (50). Within the plaques, Aβ peptides in β-sheet conformation polymerize into structurally distinct forms, including fibrillar, protofibers and polymorphic oligomers. It is the deposition of these plaques diffusely throughout the brain that lead to microglial activation, cytokine release, reactive astrocytosis, and an overall inflammatory response. These structural changes lead to synaptic and neuronal loss and eventual gross cerebral atrophy (figure 9) (53).

This hypothesis is widely accepted for the pathogenesis of AD.

Figure 7. | Amyloid cascade hypothesis | Aβ=amyloid β. APP=amyloid precursor protein. APP is processed into Aβ, which accumulates inside neuronal cells and extracellularly, where it aggregates into plaques. In the amyloid cascade hypothesis, these Aβ deposits are toxic and cause synaptic dysfunction and neuronal cell death

 

 

Figure 8. | Putative Amyloid Cascade |

This hypothesis of the amyloid cascade, which progresses from the generation of the beta-amyloid peptide from the amyloid precursor protein, through multiple secondary steps, to cell death, forms the foundation for current and emerging options for the treatment of Alzheimer’s disease. APP denotes amyloid precursor protein, and Aβ beta-amyloid.

 

Figure 9. | The amyloid (Aβ) cascade hypothesis |(49)

 

Clinical features of Alzheimer's disease

Alzheimer's disease is a progressive and fatal neurodegenerative disorder manifested by cognitive and memory deterioration, progressive impairment of activities of daily living, and a variety of neuropsychiatric symptoms and behavioral disturbances (55). Almost all patients diagnosed with AD also have neuropsychiatric symptoms during some stage of their disease, of which depression and apathy are the most dominant early on. Verbal and physical aggression are frequently observed throughout all stages. As the disease progresses, delusions, hallucinations, and aggression are more often seen and additionally, circadian sleep-wake rhythms are more exaggerated as compared to those with normal aging.

The classic clinical features of Alzheimer’s disease are an amnesic type of memory impairment, deterioration of language and visuospatial deficits. Functional and behavioral disturbances are also characteristics of the disease. Motor and sensory abnormalities, gait disturbances and seizures are uncommon until the late phases of the disease. Patients tend to progress from the loss of higher-level activities of daily living, such as writing and the use of public transportation, through abnormalities of basic activities of daily living, such as eating, grooming and using the toilet, as the disease enters advanced phases. Behavioral disturbances also progress over the course of the illness. Mood change and apathy commonly develop early and continue for the duration of the disease. Psychosis and agitation are characteristic of the middle and later phases of the disease (55).

 

Molecular features of Alzheimer's disease

In the molecular level, AD is a dual proteinopathy disease defined by a widespread but regionally specific pattern of intraparenchymal diffuse and neuritic β-amyloid (Aβ) plaques and intracytoplasmic (initially), then extracellular, neurofibrillary tangles with synaptic and neuronal loss and gliosis. Neurofibrillary tangles consist of intracellular (then extracellular) deposits of hyperphosphorylated tau protein, which is a microtubule stabilizing protein (56).

Aβ protein seems to exert its neurotoxic effects through a variety of secondary mechanisms, including oxidative injury and lipid peroxidation of cell membranes, inflammation, hyperphosphorylation of tau protein, and increased glutamatergic excitotoxicity (55).

 

The pathologic diagnosis of AD remains the gold standard for diagnosis. While certain features of AD can be ascertained on macroscopic examination, no single feature or combination of features is specific, but certain features are highly suggestive of AD (43).

Neuroimaging plays an important role in the diagnosis of Alzheimer’s disease and is particularly helpful in excluding alternative causes of dementia. It is currently recommended that patients undergo structural imaging of the brain with computed tomography (CT) or magnetic resonance imaging (MRI) (Figure10 and Figure 11A) at least once in the course of their dementia (33). Functional imaging with positron-emission tomography (Figure 11B) or single-photon-emission CT may be helpful in the differential diagnosis of disorders associated with dementia (57).

 

 

Figure 10. |The difference between a healthy brain and an Alzheimer's brain| MRI scans (grey) and illustration (color) show the difference between a healthy brain and a brain affected by Alzheimer's. Massive cell loss denotes advanced Alzheimer’s disease. Moreover, in the Alzheimer's brain:

  • The cortex shrivels up, damaging areas involved in thinking, planning, and remembering.
  • A severe shrinkage is seen in the hippocampus, damaging the area responsible of forming new memories.
  • Ventricles grow larger.

Origin: https://www.keepmemoryalive.org/

Figure 11. |Scans of Patients with Probable Alzheimer’s Disease| In Panel A, a magnetic resonance image (MRI) shows cortical atrophy and ventricular enlargement. In Panel B, a positronemission tomographic scan shows reduced glucose metabolism in the parietal lobes bilaterally (blue-green) as compared with more normal metabolism in other cortical areas (yellow). (55)

 

 

The AD brain often has at least moderate cortical atrophy that is most marked in multimodal association cortices and limbic lobe structures. The frontal and temporal cortices often have enlarged sulcal spaces with atrophy of the gyri, while primary motor and somatosensory cortices most often appear unaffected. There is an increasing recognition of atrophy in posterior cortical areas in AD, most notable the precuneus and posterior cingulate gyrus. As a result of this atrophy, there is often enlargement of the frontal and temporal horns of the lateral ventricles, and decreased brain weight is observed in most affected individuals (49). Medial temporal atrophy affecting amygdala and hippocampus, usually accompanied by temporal horn enlargement is typical of AD, but can be seen in other age-related disorders such as hippocampal sclerosis or argyrophilic grain disease. Another macroscopic feature commonly observed in AD is loss of neuromelanin pigmentation in the locus coeruleus (Fig.12).

 

Figure 12. | Gross Anatomy of Alzheimer’s Brain. Lateral view of an Alzheimer’s brain can show widening of sulcal spaces and narrowing of gyri compared to a normal brain. This may be more readily observed in coronal sections as indicated by the arrowheads, and this atrophy is often accompanied by enlargement of the frontal and temporal horns of the lateral ventricles as highlighted by the arrows. Additionally, loss of pigmented neurons in the locus coeruleus is commonly observed in the pontine tegmentum as shown with the open circle| (49)

 

 

Risk factors of Alzheimer's disease

Alzheimer's disease is caused by many risk factors which have been described in the literature, like environmental factors, nutrition, vitamins, and other elements (58). About 40 percent of Alzheimer’s disease risk factors are modifiable. Table 3 and figure 13 summarize the known risk factors for Alzheimer’s disease incidence as well as the evidence or efficacy of interventions used to reduce them. These risk factors appear to have different effect magnitudes depending on the stage of life in which they occur (59).

 

Table 3. Modifiable risk factors and their contributions to Alzheimer’s disease

Abbreviation: PAF, population attributable fraction.

 

 

Figure 13. | Population attributable fraction of potentially modifiable risk factors for dementia | (60)

 

 

Comparing Alzheimer's disease to normal aging

Differentiation of Alzheimer's disease from normal aging and other common dementias is important to implement an appropriate treatment plan and to avoid wrong prognostic information for the patients. Table 4 details all behaviors applied to normal aging, compared to AD. (42)

 

 

 

 

Table 4. Signs of Alzheimer’s Dementia Compared with Typical Age-Related Changes

 

 

 

Vascular dementia

Vascular dementia (VaD, (ICD-9 code 290.42)), dementia caused by cerebrovascular disease, is the second most caused form of dementia. Cerebrovascular disease is a risk factor for Alzheimer's disease, but can also coexist with Alzheimer's disease, hence creating a form of "mixed" dementia.

Although deaths from other major causes have decreased significantly or remained approximately the same, official records indicate that deaths from Alzheimer’s disease have increased significantly. Between 2000 and 2019, the number of deaths from Alzheimer’s disease as recorded on death certificates in the US more than doubled, increasing 145.2%, while deaths from the number one cause of death (heart disease) decreased 7.3% (Figure 14). The increase in the number of death certificates listing Alzheimer’s as the underlying cause of death probably reflects both a real increase in the actual number of deaths from Alzheimer’s due in large part to Alzheimer’s becoming a more common cause of death as the population ages, as well as increased reporting of Alzheimer’s deaths on death certificates over time by physicians (42).

Figure 14. | Percentage changes in selected causes of death (all ages) between 2000 and 2019. Created from data from the National Center for Health Statistics |

 

 

Treatment or preventive options for neurodegenerative diseases are unfortunately limited, and they tend to progress in an irreversible manner. Hence, there's an urgent need to identify potential risk factors of this diseases and prevent their appearance and distribution.

Several vascular and lifestyle factors are established as potential risk factors of neurodegenerative diseases. Electrolytes have also emerged as possible candidates, as electrolyte disturbances are associated with a variety of neurologic manifestations. In previous years, magnesium gained a specific interest in research, as low serum magnesium levels were associated with an increased risk of migraine, depression, epilepsy and potentially dementia.

 

Magnesium (Mg)

Magnesium (atomic number 12, atomic mass 24.30 Da) is classed as an alkaline earth metal belonging to the second group of the periodic table of the elements. Like calcium, its oxidation state is 2+ and, owing to its strong reactivity, it frequently occurs as free cation Mg2+ in aqueous solution or as the mineral part of a substantial variety of compounds, including chlorides, carbonates, and hydroxides rather than in a native metallic state (61).

Magnesium is the fourth most abundant mineral in the human body after calcium, potassium and sodium  (Ca2+ > K+ > Na+ > Mg2+) (62), and the second most abundant intracellular cation. It plays an important role in molecular, biochemical, physiological, and pharmacological functions in the body, and is essential for the stability of cell function, cell repair, as well as maintaining the antioxidant status of the cell.

Mg2+ is involved in practically every major metabolic and biochemical process within the cell and is responsible for numerous functions in the body, including bone development, neuromuscular function, signaling pathways, energy storage and transfer, glucose, lipid and protein metabolism, and cell proliferation (61).

Magnesium is an essential component of RNA and DNA synthesis since it influences both tertiary structures.

RNA: magnesium plays a role in polynucleotide chain binding, being a known structure stabilizer of transfer RNA (t-RNA).

DNA: magnesium forms hydrogen bonds to stabilize the DNA conformation (63). It is also an important factor in DNA repair mechanisms.

In addition, magnesium is an important cofactor for many biological processes and for the activation of a wide range of transporters and enzyme (62). It plays a critical role in nerve transmission, cardiac excitability - particularly maintaining normal heart rhythm, neuromuscular conduction, muscular contraction, blood pressure and glucose and insulin metabolism.

Because of its involvement in many functions within the body, it plays a major role in disease prevention and overall health (64).

 

 

Figure 15.  | The biochemical involvement of magnesium in many cellular processes |(61)

 

Regulation and homeostasis

Magnesium homeostasis is facilitated by intestinal absorption, bone which acts as a reservoir/store, and kidneys which are responsible for magnesium excretion (figure 16) (65).

 

 

Figure 16. | Magnesium balance |

 

 

  

Absorption

Based on literature review, magnesium is absorbed mostly in the small intestine and to some

extent in the large intestine. The mechanism of magnesium absorption is based on a dual kinetic process that involves two pathways: a saturable (transcellular) active pathway and a non-saturable (paracellular) passive pathway, which is responsible for 80–90% of uptake (66).

Various factors influence the intestinal uptake of magnesium and are of substantial importance for the supply of the mineral. Dietary magnesium uptake in the intestine varies within a broad range and depends on dose, the food matrix, enhancing and inhibiting factors. Furthermore, several studies have shown that the absorption of magnesium from food supplements and pharmaceutical preparations under standard conditions is slightly influenced by the type of magnesium salt. Nevertheless, an approach that focuses on one or a few aspects is insufficient from a nutritional and medical point of view. To understand the true absorption of magnesium, numerous endogenous and exogenous factors must be considered, as shown in figure 17 (67).

Figure 17. | Intestinal magnesium absorption and influencing factors |

 

As stated, the intestinal absorption occurs predominantly in the small intestine-mainly in the distal jejunum and ileum via the paracellular pathway, which is regulated by the paracellular tight junctions. The fine-tuning of magnesium uptake occurs in the caecum and colon of the large intestine via the magnesium-specific transporters TRPM6 and TRPM7 (67).

In humans, magnesium absorption starts approximately 1 hour after oral intake, reaches a plateau after 2-2.5 hours up to 4-5 hours and then declines. At 6 hours, the magnesium absorption is approximately 80% complete (67).

The urinary magnesium excretion increases as there is increased load presented to the kidneys; therefore, sustained hypermagnesemia usually does not occur in the presence of normal renal magnesium excretory function (68). This relationship is depicted in figure 18.

Figure 18. | Relation between urinary and plasma magnesium levels in a healthy subject on a magnesium-free diet |

Blue line - Plasma Magnesium, Red line - Urinary Magnesium.

 

 

 

Excretion

Kidneys play a major role in magnesium homeostasis. Under normal physiological conditions,

around 90–95% of the filtered magnesium is reabsorbed with only 3–5% excreted in the urine.

Approximately 15–20% of the filtered magnesium is absorbed in the proximal convoluted tubule. The thick ascending limb (TAL) of the loop of Henle is the major site for reabsorption with 65–75% being reabsorbed here. A small percentage is reabsorbed in the distal small tubule (figure 19) (62).

 

 

 

 

 

 

 

 

←A     B→

 

 

 

 

 

 

Figure 19. | Schematic illustration of the reabsorption of magnesium by different segments of the nephron | (A) Parts of a nephron (B) Approximately 10%–30% of the filtered magnesium is absorbed in the proximal tubule, 40%–70% of filtered magnesium is absorbed in the thick ascending limb, and the remaining 5%–10% of magnesium is reabsorbed in the distal convoluted tubule. CD, connecting duct; DCT, distal convoluted tubule; PCT, proximal convoluted tubule.(69)

 

Storage and distribution

Around 99% of the magnesium in the body is in storage form and less than 1% is in serum and

red blood cells (70). Bone tissue is the largest store of magnesium in the body. Approximately one-third of this is concentrated on the bone surface and is related to the serum magnesium concentration (66). The remaining magnesium is found in skeletal muscles and soft tissues. Since around 0.3% of the total body magnesium is in serum, serum magnesium estimations may not accurately reflect the status of magnesium stores (70). Table 5 reflects the distribution of magnesium in the body (65).

Table 5: distribution of magnesium in the adult human body

Tissue % Of total body magnesium
Serum 0.3
Red blood cells 0.5
Soft tissues 19.3
Muscle 27.0
Bone 52.9
Total 100

 

Humans need to consume magnesium regularly, in order to prevent magnesium deficiency, but as the recommended daily allowance (RDA) for magnesium varies among ages, it is difficult to define accurately what the exact optimal intake should be (65). Balance studies suggest a daily magnesium requirement of 3.0-4.5 mg per kg body weight. The recommended intake derived from these data varies in different countries. Whereas the Institute of Medicine (71) recommends 310-320 mg per day for women and 400-420 mg per day for men as adequate, the European Food Safety Authority (67) recently defined an adequate intake of 300 and 350 mg per day for women and men, respectively. Table 6 shows the RDA of magnesium in Americans.

 

Table 6: American recommended dietary allowances (RDA) for magnesium

(in milligrams) (72)

Age Male Female Pregnancy Lactation
Birth to 6 months 30 30
7–12 months 75 75
1–3 years 80 30
4–8 years 130 130
9–13 years 240 240
14–18 years 410 360 400 360
19–30 years 400 310 350 310
31–50 420 310 360 320
51+ 420 320

 

While drinking water accounts for approximately 10% of daily magnesium intake, chlorophyll (and thus green vegetables) is the major source of magnesium. Nuts, seeds and unprocessed cereals are also rich in magnesium. Legumes, fruit, meat and fish have an intermediate magnesium concentration. Low magnesium concentrations are found in dairy products. It is noteworthy that processed foods have much lower magnesium content than unrefined grain products and that dietary intake of magnesium in the western world is decreasing owing to the consumption of processed food. With the omnipresence of processed foods, boiling and consumption of de-mineralized soft water, most industrialized countries are deprived of their natural magnesium supply. On the other hand, magnesium supplements are very popular food supplements, especially in people physically active (65).

Since the importance of magnesium in human health has been understood, two questions have been posed: which is the correct sample reflecting the magnesium status and which is the important fraction of this element? In other words, is it better to consider the ionized free Mg2+ or its total amount composed by both the free ion and the fraction bound to cellular and extracellular elements? (61)

Measuring magnesium levels

There are several methods of measuring magnesium. The easiest samples to obtain are those derived from urine or blood. Urine is relatively simple to collect, but its magnesium content is heavily affected by several factors, such as hormones or drugs, and by the complex homeostasis between the dietary intake and the mobilization mainly from bones and/or muscle. Age and gender also affect urinary excretion. Furthermore, the more reliable urine sample seems to be the 24 hours collected samples, but often the urine sample consists of the first urine in the morning. For all these reasons, urine magnesium level seems poorly correlated with the magnesium status of the body. Blood samples could consist of serum, plasma, or the corpusculated part, i.e., erythrocytes, peripheral blood mononuclear cells (PBMC), and platelets. However, several papers claimed that serum magnesium does not give an appropriated estimation of total body magnesium, being, as previously stated, around 0.3–1% of total magnesium. However, the corpusculated blood constituents also represent a similarly small fraction of total magnesium, corresponding to 0.5% in the erythrocytes and an even lower fraction in PBMC or platelets. Therefore, 99% of magnesium mainly resides in bones, muscle, and soft tissues. Tissue magnesium could represent the more reliable sample to assess, but its withdrawal could obviously be highly invasive (61).

Following these arguments, nowadays the most used test is the total serum magnesium concentration, though its disadvantages (73, 74)

Serum magnesium can be categorized into three fractions. It is either free/ionized, bound to protein or complexed with anions such as phosphate, bicarbonate, citrate or sulphate, as described in figure 20. Of the three fractions, however, ionized magnesium has the greatest biological activity (65). Serum magnesium is present in three states: two-thirds in ionized form, one-third is protein bound mostly to albumin, and a very small state complexed to anions.

Figure 20 |Total serum magnesium in the body, present in three different states |

Body storage of nutrients depends on the balance between daily intake and renal loss. Particularly, magnesium homeostasis in the body is regulated by a delicate interplay among intestinal absorption, skeletal resorption and renal re-absorption (74).

Emerging evidence confirms that nearly two-thirds of the population in the western world is not achieving the recommended daily allowance (RDA) for magnesium, due to an inadequate dietary intake thus contributing to magnesium deficiency. It can also result from reduced absorption or increased excretion of magnesium (71).

Magnesium deficiency

Hypomagnesemia is an electrolyte disturbance caused when there is a low level of serum magnesium in the blood. Hypomagnesemia can be attributed to chronic disease, alcohol use disorder, gastrointestinal losses, renal losses, and other conditions. Signs and symptoms of hypomagnesemia include anything from mild tremors and generalized weakness to cardiac ischemia and death (75). The causes of hypomagnesemia can be broadly classified into three categories: decreased intake, redistribution from extracellular to intracellular compartment, and increased losses via renal or gastrointestinal systems (Table 7).

 

 

 

 

Table 7. Causes of hypomagnesemia.

Decreased Intake

Decreased Dietary consumption

Alcohol Dependence

Parenteral Nutrition

Redistribution from Extracellular to Intracellular Compartment

Refeeding Syndrome

Hungry Bone Syndrome

Treatment of Diabetic Ketoacidosis

Acute Pancreatitis

Gastrointestinal Losses

Diarrhea

Vomiting

Nasogastric suction

Fistulas

Malabsorption

Small bowel bypass surgery

Proton Pump Inhibitors

Renal Losses

Familial

Bartter syndrome

Gitelman syndrome

Familial hypomagnesemia with hypercalciuria

nephrocalcinosis (FHHNC)

 

 

Acquired

Medications: Thiazide Diuretic, Aminoglycoside Antibiotics, Amphotericin B, Cisplatin, Pentamidine, Tacrolimus, Cyclosporine,

Alcohol Dependence

Hypercalcemia

 

Low levels of magnesium have been associated with a number of chronic diseases, including migraine headaches, Alzheimer's disease, stroke, hypertension, cardiovascular disease, osteoporosis, and type II diabetes mellitus (76).

Magnesium and dementia

The role of magnesium in dementia and other degenerative disorders have been the focus of increased attention in recent years (58). In the current literature, there are 2 hypotheses for the role of magnesium in dementia. One is the direct effect of neuronal magnesium on regulation of the NMDA receptors.

Synaptic transmission is central to the ability of the nervous system to process and store information. Synapses are specialized contacts between neurons, where the release of neurotransmitter by the presynaptic neuron activates neurotransmitter receptors on the membrane of the postsynaptic neuron. Excitatory synaptic transmission in the mammalian brain is mediated primarily by the amino acid glutamate, activating two different groups of glutamate receptors: ionotropic and metabotropic. Ionotropic glutamate receptors are ligand-gated ion channels further divided with respect to their pharmacological properties into the following sub-groups: GluA (AMPA, 2-amino-3-3- hydroxy-5-methyl-isoxazol-4-yl propanoic acid), GluK (kainate), GluN (NMDA, N-Methyl-D-aspartic acid), and GluD (δ) receptors (77).

It has been demonstrated that ionized magnesium closed cation channels which had been opened by glutamate on NMDA receptors (78).

NMDA receptors serve in critical functions in the physiological and pathological processes of the central nervous system, including neuronal development, plasticity and neurodegeneration. These channels are permeable for calcium, sodium and potassium ions and voltage-gated channels blocked by magnesium ions. Transient glutamate release from the presynaptic region occurs during the normal learning and memory process. This release cause depolarization on the postsynaptic membrane, after which ionized magnesium (Mg2+) leaves voltage-gated channels on NMDARs, and Ca2+ influx inside the neuron occurs. Increase in Ca2+ levels inside the neuron initiate a signal transmission process and this facilitates the memory and learning process. At the end of stimulation, Mg2+ stops Ca2+ influx inside the neuron by closing channels on NMDA receptors.

It is suggested that glutamate release and intake are chronically disturbed in pathological conditions such as Alzheimer’s disease, and glutamate levels are possibly increased in the synaptic cleft. Increased glutamate levels cause depolarization of the postsynaptic membrane and magnesium ions to leave channels on NMDARs, with resulting Ca2+ influx to postsynaptic neurons. Continuous Ca2+ influx to the neuron causes an increase in the intracellular Ca2+ level, which results in activation of the calcium-related enzyme system and of free radicals, alterations in nuclear chromatin, protein destruction, lipid peroxidation, and neuron death with DNA destruction (79).

A second hypothesis through which serum magnesium can influence dementia is oxidative stress. Magnesium deficiency has been found to stimulate secretion of inflammatory mediators like interleukins, tumor necrosis factors and nitric oxide. These mediators are thought to stimulate atherosclerosis and thereby increase the risk of dementia (78).

Magnesium levels were found decreased in various tissues of patients with Alzheimer’s disease in clinical, experimental and autopsy studies (hypomagnesemia) (79). A reduction in the frequency of intracellular magnesium deposits in the neurons of Alzheimer’s patients was observed when compared to normal controls. Decrease in magnesium, potassium, and glutamic acid have been shown in the hippocampal tissue of Alzheimer’s patients (80). There are also some studies reporting a positive effect of magnesium in the treatment of various degenerative illnesses. Improvement in memory and other symptoms was reported with nutritional magnesium support in patients with dementia (81). Higher self-reported dietary intake of magnesium was found to be associated with a decreased risk of dementia (82).  Kieboom et al. found that both low and high serum magnesium levels were associated with an increased risk of Alzheimer's disease and mixed dementia (78).

These contrasting results remain the effect of magnesium levels in dementia restricted and unclear, leading to the conclusion that more research is required to further elucidate magnesium's effect. Large-population based research is essential for better understanding of these findings. Since the current treatment and prevention options for dementia are limited, it is needed to identify new risk factors for dementia that could potentially be adjusted. If people could reduce their risk for dementia through diet or supplements, that could be very beneficial.

 

Key words: magnesium, dementia, Alzheimer's disease, aging, NMDA

 

 

 

Research objectives

According to previous published research and clinical evidence, there is a connection between serum magnesium levels and potential development of dementia. We wanted to examine whether dementia is associated with any change in levels of serum magnesium as compared to controls matched for major confounders.

 

 

 

Articles review

In order to examine this connection, we have chosen three different research methodologies:

  1. A large population-based sample, using Maccabi healthcare' database

Since previous research have had controversial results and dealt with relatively small research and control groups, we hypothesized that using a big database would produce unequivocal conclusions. We expected to see significantly low levels of magnesium in research group, compared to controls. The results published on September 2020 at Journal of Alzheimer's Disease Reports showed no significant differences in mean, mode, and median magnesium levels between the dementia and control groups. However, there were marginally but significantly more cases with low magnesium levels among dementia patients than among controls: a total of 9.4% of tests done in patients with dementia and 7.81% done in non-dementia subjects were hypomagnesemic (p < 0.00001). These results led to the conclusion that it is possible that patients with dementia have more episodes of hypomagnesemia compared to controls, despite similar overall mean levels of magnesium.

 

  1. A comparison between two populations very similar in their confounders but diverse in their exposure to desalinated water (DSW) in daily urban living. Since DSW contains no magnesium, we hypothesized that relying on it for drinking water can lead to an increased incidence of hypomagnesemia, hence influencing on the prevalence of dementia.

In this study we had two objectives:

  1. To examine whether the switch to DSW led to lower serum concentrations as compared with the period prior to desalination.
  2. To examine whether a community which begins to rely on DSW exhibits a higher prevalence of dementia.

We selected two cities in Israel, Rehovot and Kfar Saba. These cities differ in terms of their access to underground aquifers but are otherwise relatively similar in terms of their demographic composition and the prevalence of dementia. Rehovot has no underground water and uses over 90% DSW, whereas Kfar Saba relies almost entirely on its own aquifers.

Using medical records for all subjects insured by the Maccabi Health Services in Rehovot (n = 23,991) and Kfar Saba (n = 20,541), we examined mean serum concentrations of magnesium in the period prior to desalination (2001-2006) and post-desalination (2007-2018). Dementia prevalence is taken from 2007 to 2020 for the same coverage population. The results were published on October 2020 at Journal of Water and Health, showing that serum magnesium levels were significantly lower in Rehovot following the switch to DSW, compared to Kfar Saba, which continued to rely on groundwater. However, this change was not associated with a higher prevalence of dementia. While this association study cannot rule out some effect of hypomagnesemia on dementia morbidity, it suggests that the effect, if it exists, is relatively small.

  1. A systematic review and meta-analysis, summarizing all articles, in any language, reporting on serum magnesium concentrations either in plasma or serum of patients with dementia, compared to patients without dementia. All types of dementia were included (Alzheimer's, vascular, mixed). Studies reporting on proportion of hypomagnesaemia patients and not mean levels were excluded. We hypothesized that a significant connection between Mg2+ and the prevalence of dementia would be found.

The results were published in August 2021 at Journal of Parkinson’s Disease & Alzheimer’s disease.

Out of 214 potentially eligible titles, seven studies described in six peer review papers were accepted for the meta-analysis. Results showed a significant heterogeneity, and the difference in Mg2+ concentrations between patients with dementia and controls was not significant. In addition, there were no significant differences in the measured levels of the different types of dementia.

Methods

Maccabi Healthcare Service is Israel's second largest health fund, providing healthcare services to over 2 million citizens. Maccabi Healthcare Service maintains a central computerized database which contains ethnic, demographic and medical data, including diagnoses, drug purchases (all prescriptions and part of the OTC drugs), laboratory data, hospitalizations and physician visits.

Our study was totally based on anonymous electronic patient records. All personal and clinical data was anonymized and saved in a passcoded and locked computer.

There are approximately 22,500 dementia patients documented in Maccabi Healthcare Service database, diagnosed by a geriatrician, a psychiatrist or a neurologist. We focused on patients of both genders with Alzheimer's disease or mixed dementia aged 65 and older, excluding alcohol abuse history, endocrine malfunction, hepatic or heart failure. We also excluded patients on dialysis or with significant decline in renal function, patients with Parkinson's disease, brain injury and other rare types of dementia.

Our control group were patients of the same age (+/- 1 year), and same sex without dementia. Both groups included the same proportions of males and females, as far as possible.

Serum magnesium test used in Maccabi Healthcare Service "Mega Lab" is a photometric color test which measures a quantitative determination of magnesium in human serum on Beckman Coulter analyzers.  The magnesium reagent utilizes a direct method in which magnesium ions form a colored complex with xylidyl blue in a strongly basic solution. The color produced is measured bichromatically at 520/800 nm and is proportional to the magnesium concentration in the sample. Calcium interference is eliminated by glycoletherdiamine-N,N,N`,N`-tetraacetic acid (GEDTA) (83-85).

The chemical reaction of the test is described above:

Magnesium normal range expected values vary with age, sex, sample type, diet and geographical location. Each laboratory verifies the transferability of the expected values to its own population and determines its own reference interval according to good laboratory practice. Magnesium reference intervals in Maccabi's Mega Lab have been stable since 2004, as shown in table 8:

  (86)Table 8: reference intervals of serum Mg test

Normal range Sex
0.73 – 1.06 mmol/L (1.8 – 2.6 mg/dL) Male
0.77 – 1.03 mmol/L (1.9 – 2.5 mg/dL) Female

 

Magnesium levels below 1.8 mg/dL in men or 1.9 mg/dL in women are defined as hypomagnesemia, while levels above 2.6 mg/dL in men or 2.5 mg/dL in women are defined as hypermagnesemia.

From the electronic charts documented since 1999 until 2020 we collected all diagnoses, drug therapy, causes of magnesium changes (e.g. diuretic use), of the study and control groups, as close as possible to the index date defined for each couple.

For each patient with Alzheimer's or mixed dementia and controls extracted all results for serum magnesium levels before establishing the diagnosis and compared them to the results afterwards. Multiple levels were averaged, and dramatically abnormal results due to sporadic illness were excluded.

 

Statistical analysis

The dependent variable in our study was the existence of dementia and the independent variable were mean serum magnesium levels.

In a multiple logistic regression, we included all the confounders affecting magnesium levels; either factors appearing statistically different between the groups in univariate analysis, or factors known to affect magnesium levels, as shown in table 9.

Table 9: factors affecting magnesium levels (RW.ERROR - Unable to find reference:doc:61d1c47dc9e77c000133fec0)

(i) age

(ii) gender

(iii) dietary intake

(iv) gastrointestinal absorption

(v) loss of magnesium from gastrointestinal tract (due to diarrhea, vomiting, celiac disease, Crohn's disease)

(vi) increased renal loss (on average 30% of dietary intake is lost in urine) e.g. alcoholism

(vii) Induced medications (e.g. use of diuretics, laxatives or antibiotics).

(viii) excessive sweating (on average 10-15% of total output of magnesium may be recovered in sweat)

(ix) endocrine causes (e.g. diabetes mellitus)

(x) increased requirements (pregnancy and growth)

(xi) stress

 

Article #1:

 

 

 

Article #2:

 

 

 

 

Article #3:

Discussion and summary

Alzheimer’s disease is the leading cause of dementia in the elderly. It is a progressive neurodegenerative condition that results in loss of higher cognitive functions. The incidence of Alzheimer’s disease is increasing at an alarming rate along with aging of populations of industrialized countries, therefore there are constant efforts to enlighten the biochemical process in the etiopathogenesis of AD. Magnesium deficiency is present in several chronic, age-related diseases, including cardiovascular, metabolic and neurodegenerative diseases. Magnesium is essential because of its role in more than 300 intracellular enzymatic process. Its concentration affects many biochemical mechanisms, including the NMDA-receptor response to excitatory amino acids, cell membrane fluidity and stability, and the toxic effects of calcium.

Though serum magnesium test has limited profits, it is the major test used for monitoring magnesium levels in the human body. Other methods acquire invasive operations with little known results nor advantages.

Based on previous research, we believe that there is a connection between serum magnesium levels and the prevalence of dementia. Most research published so far assume that dementia patients exhibit low levels of magnesium in their blood prior and during their illness.

On the other hand, all studies done until now have been based on small control and test groups and led to restricted and unequivocal results.

Hence, in our study we wanted to establish the connection between both factors and strengthen their impact on each other.

This was done using three different approaches.

Maccabi healthcare database was an excellent mean for creating a large population-based group since the database is a comprehensive registry of Israeli patients in general, and dementia patients in particular. Over 25,000 cases have been found and allowed us to match individuals without dementia based on variables that may affect magnesium levels, such as use of diuretics, laxatives, and diseases like Crohn’s. It was also hoped that it will have statistical power to discern small effects of magnesium on dementia. This method showed no significant differences in mean, mode, and median magnesium levels between the dementia and control groups. However, there were a slight but statistically significant more cases with low magnesium levels among dementia patients than among controls. Hypermagnesemia was negligible in both genders and both dementia and control groups.

Overall, our results indicate that dementia patients did not exhibit lower means, medians, or modes of serum magnesium levels, and thus not being able to support the hypothesis that hypomagnesemia has a major role in the pathogenesis of dementia. It is possible, however, that patients with dementia exhibit more episodes of hypomagnesemia than controls.

Lemke et al. (87) have previously reported decreased total magnesium plasma values in patients with severe AD. Barbagallo et al.(79), in their research were even more decisive, claiming that their results extend Lemke et al.'s, showing that already in patients with mild to moderate stage AD there is an alteration in magnesium homeostasis, revealed by a significant decrease of Mg-ion when compared to age-matched controls without AD. Both research were based on small research and control groups (Lemke et al. – 12 AD patients and 12 controls, Barbagallo et al. – 36 AD and 65 controls). Our large population research has a much more powerful statistical significance, comparing with these two others.

These results are consistent with the findings of our second method study, in which we analyzed in a treat-control context how the switch to desalinated drinking water affected serum magnesium concentrations and the prevalence of dementia. We chose two Israeli cities which are of similar sizes and comparable demographics: Rehovot, a city which has relied almost entirely on DSW since 2007 and Kfar Saba, which experienced no change.

In both cities we examined whether the switch to DSW led to lower magnesium serum concentrations in the population as compared with the period prior to desalination, and if a community which begins to rely on DSW exhibits a higher prevalence of dementia.

The results in this study showed serum magnesium levels were significantly lower following the switch to desalinated water, yet the prevalence of dementia was similar in the two cities.

While this ecological study could not rule out some effect of hypomagnesemia on dementia morbidity, it suggested, like the previous study, that the effect if exists, is not that significant.

The results of our study strengthen the conclusion of a previous related study (Koren et al. (88)), which claimed that introduction of DSW is associated with an increased proportion of subjects with lower than normal magnesium levels. Both studies submitted their conclusions on large populations, therefor having a significant statistical stability.

We concluded this research by examining the data from all independent studies dealing with the connection between serum or plasma magnesium levels and dementia, in order to determine its overall trend. Results of this meta-analysis showed no differences in mean magnesium levels related to patient age. There was a significant heterogeneity in the results, and the difference in Mg2+ concentrations between patients with dementia and controls was not significant.

In a previous systematic review Veronese and colleagues identified an additional paper comparing magnesium levels in CSF, as well as hair magnesium (89). In their review they included four articles comparing serum magnesium in 190 Alzheimer patients and 189 controls, not showing significant differences. It was possible that this lack of difference might have been the result of small sample size, thus limited statistical power. Our present analysis has identified seven reports with tenfold more dementia subjects and 220-fold more controls. Our results, failing to show significant changes in serum magnesium with very large numbers of subjects and controls corroborate the much smaller sample size in Veronese study.

Of potential importance, Veronese’ study also compared small numbers of studies comparing cerebrospinal fluid levels (n=2) and hair concentrations (n=2) showing significantly lower levels in Alzheimer patients vs. controls (89). Using serum magnesium as a biological marker of magnesium status has inherent shortcomings, as it does not reflect intracellular or total body magnesium status (74). On the other hand, measuring magnesium concentrations in CFS and hair samples require invasive methods in order to conceive them, thus leading to few samples.

Several recent studies have suggested an association between low or high magnesium intake and the prevalence of dementia (Kieboom et al. 2017 (78); Lo et al. 2019(90)). However, opposing and inconclusive results make it difficult to drive at conclusions toward identifying preventative measures. While this association study cannot rule out the effect of hypomagnesemia on dementia morbidity in some patients, it suggests that overall such effect, if it exists, is marginal.

Several limitations of this study must be acknowledged. For obvious reasons serum magnesium is much more available than tissue magnesium; however, the lack of strong correlation between serum   magnesium   and   tissue   magnesium   makes   it   difficult   to interpret serum magnesium. The heterogeneity of the reported serum magnesium among the different studies may reflect inconsistencies in time of measurement of magnesium (e.g. upon admission to hospital vs. in the community, in dietary supplementation and inclusion/ exclusion of drugs affecting magnesium levels).

Despite these limitations, our study adds important information regarding factors that have an influence on the development and progression of dementia. Our study, based on large numbers of dementia patients and controls, suggests that low serum magnesium concentrations are not associated with increased likelihood of dementia. Hence, serum magnesium should be used with caution to predict the status and activity of dementia in patients. More studies are needed in order to identify biological markers of magnesium disposition in dementia, particularly on the direct comparison of different types of dementia.

 

 

 

 

References

  1. Mizushima N, Levine B, Cuervo AM, Klionsky DJ. Autophagy fights disease through cellular self-digestion. Nature. 2008;451(7182):1069-1075. doi:10.1038/nature06639
  2. Koga H, Kaushik S, Cuervo AM. Protein Homeostasis and Aging: the importance of exquisite quality control. Ageing Res Rev. 2011;10(2):205-215. doi:10.1016/j.arr.2010.02.001
  3. Elahi FM, Miller BL. A clinicopathological approach to the diagnosis of dementia. Nat Rev Neurol. 2017;13(8):457-476. doi:10.1038/nrneurol.2017.96
  4. Jeppesen DK, Bohr VA, Stevnsner T. DNA Repair Deficiency in Neurodegeneration. Prog Neurobiol. 2011;94(2):166-200. doi:10.1016/j.pneurobio.2011.04.013
  5. DeTure MA, Dickson DW. The neuropathological diagnosis of Alzheimer's disease. Mol Neurodegener. 2019;14(1):32. doi:10.1186/s13024-019-0333-5
  6. Koren G, Shlezinger M, Katz R, Shalev V, Amitai Y. Seawater desalination and serum magnesium concentrations in Israel. Journal of Water and Health. 2016;15(2):296-299. doi:10.2166/wh.2016.164
  7. Fiorentini D, Cappadone C, Farruggia G, Prata C. Magnesium: Biochemistry, Nutrition, Detection, and Social Impact of Diseases Linked to Its Deficiency. Nutrients. 2021;13(4). doi:10.3390/nu13041136
  8. Gragossian A, Bashir K, Friede R. Hypomagnesemia. Hypomagnesemia. StatPearls Publishing; 2022. http://www.ncbi.nlm.nih.gov/books/NBK500003/.Accessed Mar 18, 2022
  9. Schwalfenberg GK, Genuis SJ. The Importance of Magnesium in Clinical Healthcare. Scientifica (Cairo). 2017;2017. doi:10.1155/2017/4179326
  10. Fawcett WJ, Haxby EJ, Male DA. Magnesium: physiology and pharmacology. Br J Anaesth. 1999;83(2):302-320. doi:10.1093/bja/83.2.302
  11. Blaine J, Chonchol M, Levi M. Renal Control of Calcium, Phosphate, and Magnesium Homeostasis. Clin J Am Soc Nephrol. 2015;10(7):1257-1272. doi:10.2215/CJN.09750913
  12. Reinhart RA. Magnesium metabolism. A review with special reference to the relationship between intracellular content and serum levels. Arch Intern Med. 1988;148(11):2415-2420. doi:10.1001/archinte.148.11.2415
  13. de Baaij, Jeroen H. F., Hoenderop JGJ, Bindels RJM. Regulation of magnesium balance: lessons learned from human genetic disease. Clin Kidney J. 2012;5(Suppl 1):i15-i24. doi:10.1093/ndtplus/sfr164
  14. de Baaij, Jeroen H. F., Hoenderop JGJ, Bindels RJM. Magnesium in man: implications for health and disease. Physiol Rev. 2015;95(1):1-46. doi:10.1152/physrev.00012.2014
  15. 2021 Alzheimer's disease facts and figures. Alzheimer's & Dementia. 2021;17(3):327-406. doi:10.1002/alz.12328
  16. Lane CA, Hardy J, Schott JM. Alzheimer's disease. European Journal of Neurology. 2018;25(1):59-70. doi:10.1111/ene.13439
  17. Tiwari S, Atluri V, Kaushik A, Yndart A, Nair M. Alzheimer's disease: pathogenesis, diagnostics, and therapeutics. Int J Nanomedicine. 2019;14:5541-5554. doi:10.2147/IJN.S200490
  18. Shao W, Peng D, Wang X. Genetics of Alzheimer's disease: From pathogenesis to clinical usage. J Clin Neurosci. 2017;45:1-8. doi:10.1016/j.jocn.2017.06.074
  19. Barage SH, Sonawane KD. Amyloid cascade hypothesis: Pathogenesis and therapeutic strategies in Alzheimer's disease. Neuropeptides. 2015;52:1-18. doi:10.1016/j.npep.2015.06.008
  20. Brion JP, Couck AM, Passareiro E, Flament-Durand J. Neurofibrillary tangles of Alzheimer's disease: an immunohistochemical study. J Submicrosc Cytol. 1985;17(1):89-96
  21. Glenner GG, Wong CW. Alzheimer's disease: initial report of the purification and characterization of a novel cerebrovascular amyloid protein. Biochem Biophys Res Commun. 1984;120(3):885-890. doi:10.1016/s0006-291x(84)80190-4
  22. Soria Lopez JA, González HM, Léger GC. Chapter 13 - Alzheimer's disease. Dekosky ST, Asthana S, eds. Vol 167. Elsevier; 2019:231-255. https://www.sciencedirect.com/science/article/pii/B9780128047668000133.Accessed Mar 3, 2022
  23. Yang HD, Kim DH, Lee SB, Young LD. History of Alzheimer's Disease. Dement Neurocogn Disord. 2016;15(4):115-121. doi:10.12779/dnd.2016.15.4.115
  24. McGirr S, Venegas C, Swaminathan A. Alzheimers Disease: A Brief Review. Journal of Experimental Neurology. 2020;1(3). doi:10.33696/Neurol.1.015
  25. Diagnostic and statistical manual of mental disorders : DSM-5. American Psychiatric Association; 2013
  26. Hippius H, Neundörfer G. The discovery of Alzheimer's disease. Dialogues in clinical neuroscience. 2003;5(1):101-108. doi:10.31887/DCNS.2003.5.1/hhippius
  27. Feldman H, Levy AR, Hsiung G-, et al. A Canadian cohort study of cognitive impairment and related dementias (ACCORD): study methods and baseline results. Neuroepidemiology. 2003;22(5):265-274. doi:10.1159/000071189
  28. Shiroky JS, Schipper HM, Bergman H, Chertkow H. Can you have dementia with an MMSE score of 30? Am J Alzheimers Dis Other Demen. 2007;22(5):406-415. doi:10.1177/1533317507304744
  29. Siu AL. Screening for dementia and investigating its causes. Ann Intern Med. 1991;115(2):122-132. doi:10.7326/0003-4819-115-2-122
  30. Darvesh S, Leach L, Black SE, Kaplan E, Freedman M. The behavioural neurology assessment. Can J Neurol Sci. 2005;32(2):167-177. doi:10.1017/s0317167100003930
  31. Brodaty H, Pond D, Kemp NM, et al. The GPCOG: a new screening test for dementia designed for general practice. J Am Geriatr Soc. 2002;50(3):530-534. doi:10.1046/j.1532-5415.2002.50122.x
  32. Solomon PR, Hirschoff A, Kelly B, et al. A 7 minute neurocognitive screening battery highly sensitive to Alzheimer's disease. Arch Neurol. 1998;55(3):349-355. doi:10.1001/archneur.55.3.349
  33. Kalbe E, Kessler J, Calabrese P, et al. DemTect: a new, sensitive cognitive screening test to support the diagnosis of mild cognitive impairment and early dementia. Int J Geriatr Psychiatry. 2004;19(2):136-143. doi:10.1002/gps.1042
  34. Nasreddine ZS, Phillips NA, Bédirian V, et al. The Montreal Cognitive Assessment, MoCA: a brief screening tool for mild cognitive impairment. J Am Geriatr Soc. 2005;53(4):695-699. doi:10.1111/j.1532-5415.2005.53221.x
  35. Shulman KI. Clock-drawing: is it the ideal cognitive screening test? Int J Geriatr Psychiatry. 2000;15(6):548-561. doi:10.1002/1099-1166(200006)15:6<548::aid-gps242>3.0.co;2-u
  36. Folstein MF, Folstein SE, McHugh PR. "Mini-mental state". A practical method for grading the cognitive state of patients for the clinician. J Psychiatr Res. 1975;12(3):189-198. doi:10.1016/0022-3956(75)90026-6
  37. Zhang G, Li J, Purkayastha S, et al. Hypothalamic programming of systemic ageing involving IKK-β, NF-κB and GnRH. Nature. 2013;497(7448):211-216. doi:10.1038/nature12143
  38. Russell SJ, Kahn CR. Endocrine regulation of ageing. Nat Rev Mol Cell Biol. 2007;8(9):681-691. doi:10.1038/nrm2234
  39. Rando TA, Chang HY. Aging, rejuvenation, and epigenetic reprogramming: resetting the aging clock. Cell. 2012;148(1-2):46-57. doi:10.1016/j.cell.2012.01.003
  40. Laplante M, Sabatini DM. mTOR signaling in growth control and disease. Cell. 2012;149(2):274-293. doi:10.1016/j.cell.2012.03.017
  41. Bodnar AG, Ouellette M, Frolkis M, et al. Extension of life-span by introduction of telomerase into normal human cells. Science. 1998;279(5349):349-352. doi:10.1126/science.279.5349.349
  42. Hayflick L, Moorhead PS. The serial cultivation of human diploid cell strains. Experimental Cell Research. 1961;25(3):585-621. doi:10.1016/0014-4827(61)90192-6
  43. Green DR, Galluzzi L, Kroemer G. Mitochondria and the autophagy-inflammation-cell death axis in organismal aging. Science. 2011;333(6046):1109-1112. doi:10.1126/science.1201940
  44. Hartl FU, Bracher A, Hayer-Hartl M. Molecular chaperones in protein folding and proteostasis. Nature. 2011;475(7356):324-332. doi:10.1038/nature10317
  45. Powers MB, Zum Vorde Sive Vording, Maarten B., Emmelkamp PMG. Acceptance and commitment therapy: a meta-analytic review. Psychother Psychosom. 2009;78(2):73-80. doi:10.1159/000190790
  46. Talens RP, Christensen K, Putter H, et al. Epigenetic variation during the adult lifespan: cross-sectional and longitudinal data on monozygotic twin pairs. Aging Cell. 2012;11(4):694-703. doi:10.1111/j.1474-9726.2012.00835.x
  47. Blackburn EH, Greider CW, Szostak JW. Telomeres and telomerase: the path from maize, Tetrahymena and yeast to human cancer and aging. Nat Med. 2006;12(10):1133-1138. doi:10.1038/nm1006-1133
  48. Lord CJ, Ashworth A. The DNA damage response and cancer therapy. Nature. 2012;481(7381):287-294. doi:10.1038/nature10760
  49. Hoeijmakers JHJ. DNA damage, aging, and cancer. N Engl J Med. 2009;361(15):1475-1485. doi:10.1056/NEJMra0804615
  50. Burtner CR, Kennedy BK. Progeria syndromes and ageing: what is the connection? Nat Rev Mol Cell Biol. 2010;11(8):567-578. doi:10.1038/nrm2944
  51. Moskalev AA, Shaposhnikov MV, Plyusnina EN, et al. The role of DNA damage and repair in aging through the prism of Koch-like criteria. Ageing Res Rev. 2013;12(2):661-684. doi:10.1016/j.arr.2012.02.001
  52. Dementia prevention, intervention, and care: 2020 report of the Lancet Commission. The Lancet. 2020;396(10248):413-446. doi:10.1016/S0140-6736(20)30367-6
  53. Silverman DH, Small GW, Chang CY, et al. Positron emission tomography in evaluation of dementia: Regional brain metabolism and long-term outcome. JAMA. 2001;286(17):2120-2127. doi:10.1001/jama.286.17.2120
  54. Knopman DS, DeKosky ST, Cummings JL, et al. Practice parameter: diagnosis of dementia (an evidence-based review). Report of the Quality Standards Subcommittee of the American Academy of Neurology. Neurology. 2001;56(9):1143-1153. doi:10.1212/wnl.56.9.1143
  55. McKhann G, Drachman D, Folstein M, Katzman R, Price D, Stadlan EM. Clinical diagnosis of Alzheimer's disease: Report of the NINCDS‐ADRDA Work Group* under the auspices of Department of Health and Human Services Task Force on Alzheimer's Disease. Neurology. 1984;34(7):939
  56. Cummings JL. Alzheimer's disease. N Engl J Med. 2004;351(1):56-67+110
  57. Tisher A, Salardini A. A Comprehensive Update on Treatment of Dementia. Semin Neurol. 2019;39(2):167-178. doi:10.1055/s-0039-1683408
  58. Atri A. The Alzheimer’s Disease Clinical Spectrum: Diagnosis and Management. Medical Clinics of North America. 2019;103(2):263-293. doi:10.1016/j.mcna.2018.10.009
  59. Hou Y, Dan X, Babbar M, et al. Ageing as a risk factor for neurodegenerative disease. Nat Rev Neurol. 2019;15(10):565-581. doi:10.1038/s41582-019-0244-7
  60. Bentur N, Sternberg S. Dementia care in Israel: top down and bottom up processes. Israel Journal of Health Policy Research. 2019;8. doi:10.1186/s13584-019-0290-z
  61. Weller J, Budson A. Current understanding of Alzheimer's disease diagnosis and treatment. F1000Res. 2018;7. doi:10.12688/f1000research.14506.1
  62. Amor S, Woodroofe MN. Innate and adaptive immune responses in neurodegeneration and repair. 2014;141(3):287-291. doi:10.1111/imm.12134
  63. Oh J, Lee YD, Wagers AJ. Stem cell aging: mechanisms, regulators and therapeutic opportunities. Nat Med. 2014;20(8):870-880. doi:10.1038/nm.3651
  64. Fontana L, Partridge L, Longo VD. Extending healthy life span--from yeast to humans. Science. 2010;328(5976):321-326. doi:10.1126/science.1172539
  65. Vaidya A, Mao Z, Tian X, Spencer B, Seluanov A, Gorbunova V. Knock-in reporter mice demonstrate that DNA repair by non-homologous end joining declines with age. PLoS Genet. 2014;10(7):e1004511. doi:10.1371/journal.pgen.1004511
  66. Johri A, Beal MF. Mitochondrial dysfunction in neurodegenerative diseases. J Pharmacol Exp Ther. 2012;342(3):619-630. doi:10.1124/jpet.112.192138
  67. Tanaka K, Matsuda N. Proteostasis and neurodegeneration: The roles of proteasomal degradation and autophagy. Biochimica et Biophysica Acta (BBA) - Molecular Cell Research. 2014;1843(1):197-204. doi:10.1016/j.bbamcr.2013.03.012
  68. Bradley-Whitman MA, Lovell MA. Epigenetic changes in the progression of Alzheimer's disease. Mech Ageing Dev. 2013;134(10):486-495. doi:10.1016/j.mad.2013.08.005
  69. López-Otín C, Blasco MA, Partridge L, Serrano M, Kroemer G. The hallmarks of aging. Cell. 2013;153(6):1194-1217. doi:10.1016/j.cell.2013.05.039
  70. Carmona JJ, Michan S. Biology of Healthy Aging and Longevity. Rev Invest Clin. 2016;68(1):7-16
  71. The multifaceted and widespread pathology of magnesium deficiency. Medical Hypotheses. 2001;56(2):163-170. doi:10.1054/mehy.2000.1133
  72. Witkowski M, Hubert J, Mazur A. Methods of assessment of magnesium status in humans: a systematic review. Magnesium research. 2011;24(4):163-180. doi:10.1684/mrh.2011.0292
  73. Li W, Yu J, Liu Y, et al. Elevation of brain magnesium prevents synaptic loss and reverses cognitive deficits in Alzheimer’s disease mouse model. Molecular brain. 2014;7(1):65. doi:10.1186/s13041-014-0065-y
  74. Ageing is associated with physical deterioration that leads to an increased risk of disease and death 1 . Ageing occurs at different rates in different species, and inter- individual variations exist within a species and in the different tissues of an individual.
  75. Hoffman JL, Faccidomo S, Kim M, et al. Alcohol drinking exacerbates neural and behavioral pathology in the 3xTg-AD mouse model of Alzheimer's disease. International review of neurobiology. 2019;148:169-230. doi:10.1016/bs.irn.2019.10.017
  76. Glick JL. Dementias: the role of magnesium deficiency and an hypothesis concerning the pathogenesis of Alzheimer's disease. Medical Hypotheses. 1990;31(3):211. doi:10.1016/0306-9877(90)90095-v
  77. magnesium and potassium status.
  78. Tzeng N, Chung C, Lin F, et al. Magnesium oxide use and reduced risk of dementia: a retrospective, nationwide cohort study in Taiwan. Current Medical Research and Opinion. 2017;34(1):163. doi:10.1080/03007995.2017.1385449
  79. Karr JE, Graham RB, Hofer SM, Muniz-Terrera G. When Does Cognitive Decline Begin? A Systematic Review of Change Point Studies on Accelerated Decline in Cognitive and Neurological Outcomes Preceding Mild Cognitive Impairment, Dementia, and Death. Psychology and aging. 2018;33(2):195-218. doi:10.1037/pag0000236
  80. Gottfries C. Clinical classification of dementias. Archives of Gerontology and Geriatrics. 1995;21(1):1. doi:10.1016/0167-4943(95)00651-z
  81. Biessels GJ, Despa F. Cognitive decline and dementia in diabetes mellitus: mechanisms and clinical implications. Nature reviews. Endocrinology. 2018;14(10):591-604. doi:10.1038/s41574-018-0048-7
  82. Dominguez LJ, Barbagallo M. Nutritional prevention of cognitive decline and dementia. Acta bio-medica : Atenei Parmensis. 2018;89(2):276-290. doi:10.23750/abm.v89i2.7401
  83. Andr~isi E, Farkas, Scheibler H, R6ffy A, Beztir. AI, Zn, Cu, Mn and Fe levels in brain in Alzheimer's disease.
  84. Hozumi I, Hasegawa T, Honda A, et al. Patterns of levels of biological metals in CSF differ among neurodegenerative diseases. Journal of the neurological sciences. 2011;303(1):95-99. doi:10.1016/j.jns.2011.01.003
  85. Cloutier S, Chertkow H, Kergoat M, Gauthier S, Belleville S. Patterns of Cognitive Decline Prior to Dementia in Persons with Mild Cognitive Impairment. JAD. 2015;47(4):901. doi:10.3233/jad-142910
  86. Lemke MR. Plasma magnesium decrease and altered calcium/magnesium ratio in severe dementia of the Alzheimer type. Biological Psychiatry. 1995;37(5):341. doi:10.1016/0006-3223(94)00241-t
  87. Barbagallo M, Belvedere M, Di Bella G, Dominguez LJ. Altered ionized magnesium levels in mild-to-moderate Alzheimer's disease. Magnesium research. 2011;24(3):S115-121. doi:10.1684/mrh.2011.0287
  88. Veronese N, Zurlo A, Solmi M, et al. Magnesium Status in Alzheimer’s Disease. American journal of Alzheimer&#39;s disease and other dementias. 2016;31(3):208-213. doi:10.1177/1533317515602674
  89. Cilliler AE, Ozturk S, Ozbakir S. Serum Magnesium Level and Clinical Deterioration in Alzheimer’s Disease. Gerontology (Basel). 2008;53(6):419-422. doi:10.1159/000110873
  90. Vural H, Demirin H, Kara Y, Eren I, Delibas N. Alterations of plasma magnesium, copper, zinc, iron and selenium concentrations and some related erythrocyte antioxidant enzyme activities in patients with Alzheimer’s disease. Journal of trace elements in medicine and biology. 2010;24(3):169-173. doi:10.1016/j.jtemb.2010.02.002
  91. Gustaw-Rothenberg K, Kowalczuk K, Stryjecka-Zimmer M. Lipids' peroxidation markers in Alzheimer's disease and vascular dementia. Geriatrics &amp; gerontology international. 2010;10(2):161-166. doi:10.1111/j.1447-0594.2009.00571.x
  92. Besser LM, Litvan I, Monsell SE, et al. Mild cognitive impairment in Parkinson’s disease versus Alzheimer’s disease. Parkinsonism &amp; related disorders. 2016;27:54-60. doi:10.1016/j.parkreldis.2016.04.007
  93. Andrási E, Páli N, Molnár Z, Kösel S. Brain aluminum, magnesium and phosphorus contents of control and Alzheimer-diseased patients. Journal of Alzheimer&#39;s disease. 2005;7(4):273-284. doi:10.3233/JAD-2005-7402
  94. Albert MS. Changes in cognition. Neurobiology of aging. 2011;32(1):S58-S63. doi:10.1016/j.neurobiolaging.2011.09.010
  95. Basheer MP, Pradeep Kumar KM, Sreekumaran E, Ramakrishna T. A study of serum magnesium, calcium and phosphorus level, and cognition in the elderly population of South India. Alexandria journal of medicine. 2016;52(4):303-308. doi:10.1016/j.ajme.2015.11.001
  96. Lo K, Liu Q, Madsen T, et al. Relations of magnesium intake to cognitive impairment and dementia among participants in the Women's Health Initiative Memory Study: a prospective cohort study. BMJ Open. 2019;9(11):e030052. doi:10.1136/bmjopen-2019-030052
  97. Andrási E, Farkas É, Scheibler H, Réffy A, Bezúr L. Al, Zn, Cu, Mn and Fe levels in brain in Alzheimer's disease. Archives of Gerontology and Geriatrics. 1995;21(1):89-97. doi:10.1016/0167-4943(95)00643-Y
  98. Glick JL. Use of magnesium in the management of dementias. Medical Science Research. 1990;18(21):831-833
  99. Wong E. Clinical Laboratory Diagnostics: Use and Assessment of Clinical Laboratory Results. Lothar Thomas. Frankfurt/Main, Germany: TH-Books Verlagsgeselschaft, 1998, 1727 pp., $149.00. ISBN 3-9805215-4-0. Clin Chem. 1999;45(4):586-587. doi:10.1093/clinchem/45.4.586a
  100. Mann CK, Yoe JH. Spectrophotometric determination of magnesium with 1-azo-2-hydroxy-3-(2.4-dimethylcarboxanilido)-naphtha- lene-1-(2-hydroxybenzene). Analytica Chimica Acta. 1957;16:155-160. doi:10.1016/S0003-2670(00)89905-5
  101. Bohuon C. Microdosage du magnésium dans divers milieux biologiques. Clinica Chimica Acta. 1962;7(6):811-817. doi:10.1016/0009-8981(62)90064-5
  102. Mann C, Yoe J. Spectrophotometric Determination of Magnesium with Sodium 1-Azo-2-hydroxy-3-(2,4-dimethylcarboxanilido)-naphthalene-1'-(2-hydroxybenzene-5-sulfonate). Analytical Chemistry - ANAL CHEM. 1956;28. doi:10.1021/ac60110a016
  103. Healthcare in Israel. https://en.wikipedia.org/w/index.php?title=Healthcare_in_Israel&oldid=963134536.Updated 2020. Accessed Jun 18, 2020
  104. Maccabi Healthcare Services. 2020. https://en.wikipedia.org/w/index.php?title=Maccabi_Healthcare_Services&oldid=936709919.Accessed Jun 18, 2020
  105. Ozawa M, Ninomiya T, Ohara T, et al. Self-Reported Dietary Intake of Potassium, Calcium, and Magnesium and Risk of Dementia in the Japanese: The Hisayama Study. Journal of the American Geriatrics Society. 2012;60:1515-20. doi:10.1111/j.1532-5415.2012.04061.x
  106. Mann CK, Yoe JH. Spectrophotometric Determination of Magnesium with Sodium 1-Azo-2-hydroxy-3-(2,4-dimethylcarboxanilido)-naphthalene-1´-(2-hydroxybenzene-5-sulfonate). Anal Chem. 1956;28(2):202-205. doi:10.1021/ac60110a016
  107. Slutsky I, Abumaria N, Wu L, et al. Enhancement of learning and memory by elevating brain magnesium. Neuron. 2010;65(2):165-177. doi:10.1016/j.neuron.2009.12.026
  108. Durlach J. Magnesium depletion and pathogenesis of Alzheimer's disease. Magnes Res. 1990;3(3):217-218
  109. Kieboom BCT, Licher S, Wolters FJ, et al. Serum magnesium is associated with the risk of dementia. Neurology. 2017;89(16):1716-1722. doi:10.1212/WNL.0000000000004517
  110. Camicioli R. Distinguishing different dementias. dementia (PDD). 2006;8:9
  111. Ozturk S, Cillier AE. Magnesium supplementation in the treatment of dementia patients. Medical Hypotheses. 2006;67(5):1223-1225. doi:10.1016/j.mehy.2006.04.047
  112. Gröber U, Schmidt J, Kisters K. Magnesium in Prevention and Therapy. Nutrients. 2015;7(9):8199-8226. doi:10.3390/nu7095388
  113. Vyklicky V, Korinek M, Smejkalova T, et al. Structure, function, and pharmacology of NMDA receptor channels. Physiol Res. 2014;63 Suppl 1:191
  114. Uwitonze AM, Razzaque MS. Role of Magnesium in Vitamin D Activation and Function. J Am Osteopath Assoc. 2018;118(3):181-189. doi:10.7556/jaoa.2018.037
  115. Schuchardt JP, Hahn A. Intestinal Absorption and Factors Influencing Bioavailability of Magnesium-An Update. Curr Nutr Food Sci. 2017;13(4):260-278. doi:10.2174/1573401313666170427162740
  116. Dietary Reference Intakes for Calcium, Phosphorus, Magnesium, Vitamin D, and Fluoride. National Academies Press (US); 1997. http://www.ncbi.nlm.nih.gov/books/NBK109825/.Accessed Jun 16, 2020
  117. Jahnen-Dechent W, Ketteler M. Magnesium basics. Clinical kidney journal. 2012;5(Suppl 1):i3-i14. doi:10.1093/ndtplus/sfr163
  118. Noronha JL, Matuschak GM. Magnesium in critical illness: metabolism, assessment, and treatment. Intensive Care Med. 2002;28(6):667-679. doi:10.1007/s00134-002-1281-y
  119. Kirkland AE, Sarlo GL, Holton KF. The Role of Magnesium in Neurological Disorders. Nutrients. 2018;10(6). doi:10.3390/nu10060730
  120. Swaminathan R. Magnesium metabolism and its disorders. The Clinical biochemist. Reviews. 2003;24(2):47-66. https://www.ncbi.nlm.nih.gov/pubmed/18568054