Motherisk Int J 2020;1;27
Mohamed Mari, Gideon Koren
school of Medicine
Although stress is not necessarily associated with adverse effects, high or continuous levels of stress or poor coping resources can make it a trigger for physical and mental health disorders which can negatively affect the quality of life. Consequently, in recent years, there has been a growing interest in quantifying stress levels. 1
The normal human response to stress is modulated by several complementary systems, including the autonomic nervous system and the hypothalamic-pituitary-adrenal axis (HPAA) 2. ACTH, upon release into the general circulation, binds to high-affinity membrane receptors on cells in the zona fasciculate of the adrenal cortex, is rapidly inducing the production and release of the glucocorticoid, cortisol. After adrenocortical stimulation, ACTH acts on the hypothalamus to decrease the production of CRH, ultimately suppressing its production in negative feedback. Cortisol has been well studied in many populations as it is an important measure of the biological reactivity to stress and both excessive and deficient cortisol responses have been associated with dysregulation of the HPA axis 3,4.
Biomarkers of acute stress have been focused and measured by catecholamine release 5. However, finding a ‘‘gold standard’’ biomarker for chronic stress has been challenging due to its complex etiology and highly individual manifestations 6.
In humans, non-human primates and many larger mammals’ cortisol is the most common glucocorticoid, while in other vertebrates including rodents, corticosterone is the primary stress hormone and there are only very few studies on corticosterone in hair 6.
During times when an organism undergoes physiologic duress, cortisol acts to mobilize energy stores and modulate the immune system. Despite its well-recognized role in stress in both animals and humans, the ability of cortisol to reflect stress levels over long periods has been limited. This is largely due to the nature of the traditional matrices in which cortisol has been sampled. To date, the majority of studies have investigated cortisol responses using samples of serum, saliva, or urine. The most commonly used assays to detect cortisol in these samples are radio-immunoassays (RIAs), liquid chromatography-mass spectrometry (LC-MS/ MS), and enzyme-linked immunosorbent assays (ELISA) 7.
Both saliva and serum samples provide a measurement of the cortisol concentration at a single point in time. They can, therefore, be used to test acute changes, but are subject to major physiological daily fluctuations, making the assessment of overall long-term systemic cortisol exposure difficult if not impossible. In healthy individuals, plasma cortisol levels peak in the early morning, and gradually decrease thereafter. Hence, a single measurement cannot reflect the integration of systemic exposure. To help overcome this challenge, most contemporary studies obtain multiple salivary samples from the time of waking until sleep, but this is experimentally complex, the adherence of individual participants with the sampling schedule may vary 8, and this methodology is difficult to apply to large populations. Besides, measuring cortisol in serum samples assesses total serum cortisol that includes both protein-bound and bioactive (free) cortisol. However, total serum cortisol is affected by changes in levels of cortisol-binding globulin (e.g., by birth control pills or pregnancy) that can result in increases in total cortisol concentration measured, even though there is no increase in stress or free cortisol concentrations. Besides, the procedure of obtaining a sample via venipuncture could by itself be a source of stress and increased cortisol 9. Salivary cortisol concentrations correlate well with serum concentrations 9,10. In contrast to serum cortisol, salivary cortisol reflects free (unbound) cortisol and is collected by a less-invasive method. Yet, salivary cortisol concentrations still fluctuate significantly throughout the day. A similar strategy is employed when urine is used; 24-h urine collections provide an integration of the free cortisol concentrations through the day, thus overcoming the issue of its diurnal rhythm 11. However, the collection is labor-intensive for participants, and cannot be used in cases of chronic renal failure or dialysis 6.
Advantages of Hair Cortisol (HC) Analysis
Fifteen years ago, our laboratories at the University of Toronto and Western Ontario pioneered the use of hair cortisol as a biomarker of chronic stress 6. There are various advantages to using cortisol in hair as a biomarker of chronic stress. Hair has a fairly predictable growth rate of approximately 1 cm/month. Hence, the most proximal 1 cm segment to the scalp approximates the last month’s cortisol production, the second most proximal 1 cm segment approximates the production during the month before that, and so on 12. This phenomenon enables researchers to retrospectively examine cortisol production at the times when a stressor was most salient, without needing to take a sample right at that time. Alternatively, it can provide a baseline cortisol assessment for a time period during which the stress had not yet occurred. This was demonstrated in a study in rhesus macaques in which hair samples for cortisol were obtained both at baseline and after a major stressful event (relocation to a new habitat) 13. The sample could be collected noninvasively by simply cutting a 1 cm diameter sample of hair at the base of the vertex posterior of the head. This eliminates the risk that the sampling itself may impact cortisol production. Furthermore, as each centimeter sample represents approximately 1 months’ worth of cortisol production, the issue of intra- and inter-day cortisol fluctuations is mitigated. Finally, unlike the bodily fluids that require special storage conditions before analysis, hair samples are easily transported and stored in envelopes or vials at room temperature 14. A summary of the different properties of existing matrices for cortisol measurement is presented in Table 16.
|Table 1: A comparison of properties of the various matrices for cortisol measurement.|
|Subjective level of invasiveness associated with sample collection||High||Low||Moderate||Low|
|Cortisol affected by stress of sampling procedure?||Possibly||Possibly||Possibly||No|
|Storage requirements||Spinning and refrigeration
followed by freezing
stable for years
|Periods of cortisol
|Single point measure
|Single point measure||12—24 h; integral
|Months to years;
integral of exposure
|Affected by changes in
cortisol binding globulin?
|Yes; total cortisol
|No; only free
|No; only free
|No; only free
|Clinically relevant reference
Another matrix that may be capable of providing cumulative cortisol exposure is fingernails. Recently a pilot study was performed to determine whether cortisol and dehydroepiandrosterone (DHEA) could be detected in fingernails 15. Using a methanol extraction and ELISA, both cortisol and DHEA were detected in fingernails from 33 university students. During times of exam stress, the ratio of cortisol over DHEA was found to be significantly increased compared to baseline levels obtained at the beginning of the school year. One of the limitations identified by the authors was how fingernail growth is known to change depending on environmental factors (e.g., seasonal changes) and differences in personal behavior (e.g., nail-biting habits). Thus, controlling for such variables would be important for fingernail cortisol concentrations to accurately reflect the time of periods of interest. Another study used an extraction and ultra-performance mass spectrometry analysis to investigate whether cortisol, cortisone, and DHEA could be detected in fingernails 16. Further studies are required to validate fingernails as a reliable matrix, but they may present an alternative for cumulative cortisol measurement when hair analysis is not possible, such as in cases of balding or cultural objections against hair sample collection 6.
Hair Cortisol Analysis
Overall, the methods used for the measurement of cortisol in the hair are very similar, with some variations in procedures amongst laboratories. Briefly, to extract cortisol from hair, the sample is carefully sectioned into segment lengths that will approximate the time of period of interest (e.g., the most proximal 3 cm for the last 3 months of cortisol production). Then, the hair is finely minced with scissors or ground with a ball mill, and incubated in a solvent such as methanol. The resulting solution is evaporated to dryness and then reconstituted in a solution such as phosphate-buffered saline 17. Following the extraction, ELISA, RIA, or LC-MS/MS have all been used for cortisol quantification 14. Presently, there can be significant intraassay variability in the commercially available immunoassays. The immediate implication is that researchers in this field must try to perform all tests of a particular protocol using the same batch of cortisol immunoassay, using internal positive controls as standards, and preferably 6.
Mechanism of Cortisol Incorporation into Hair
From its inception as a tool to monitor stress and cortisol concentrations, there have been some persistent questions about the nature of hair cortisol analysis and the underlying pathophysiology. A frequently raised question is the mechanism by which cortisol enters the hair. Several mechanisms have been proposed (see Fig. 1). 6
The most commonly suggested hypothesis is based upon the complex multi-compartment model 18. Cortisol is thought to enter hair primarily at the level of the medulla of the hair shaft via passive diffusion from the blood. In this scenario, hair cortisol would be hypothesized to reflect the integrated free cortisol fraction rather than the total cortisol concentration in serum. Because growing hair is in contact with sweat and sebum excreted by the skin, one needs to consider also the possibility that chemicals may also be deposited externally to the hair shaft. This mechanism is important in the disposition of ethanol in hair. It is not yet known how cortisol enters the hair shaft. It is assumed that cortisol enters the hair shaft through passive diffusion, and therefore represents cumulative free circulating cortisol levels. This is further supported by the circumstantial evidence that oral contraception, which is known to increase total cortisol levels due to the effect of estrogens on corticosteroid-binding globulin levels 19, does not seem to have a major influence on hair cortisol concentration (HCC). However, the active transport of steroids from the bloodstream to the hair follicle cannot be excluded. Apart from incorporation from blood, sebum and sweat could also contribute to HCC 20,21. Cortisol has been demonstrated in human sweat, and it has been suggested that increased sweating may increase HCC, which may acutely influence HCC and therefore undermine the validity of HCC as a marker of long-term cortisol exposure 22. However, Stalder et al. recently showed that two sweat-inducing interventions (exercise and sauna bathing) do not seem to acutely influence the HCC 23,24.
Factors Affecting hair cortisol concentration (HCC)
In addition to clinical states and stressors, several other factors can potentially affect HCC. In large published studies, HCC has been shown to increase with age 25,26. In contrast, children have been found to have significantly lower HCC than adults 27. While several published studies have reported higher HCC in males than among females 25, 28, 29, in other studies no sex differences were observed 20, 26, 30. In two studies carried out in older adults, men had higher HCC, indicating that the sex difference in HCC becomes more pronounced later in life 25, 28. The associations between ethnicity and HCC have largely been unexplored, and need further study 23.
Multiple studies have confirmed a hair growth rate close to 10 mm/month 31. Slight differences in hair growth rate between ethnic groups have been reported, with African hair growing slower than Caucasian hair, which in turn grows more slowly than East Asian hair 32. Small variations in growth rate are not expected to have a large impact on studies using single measurements of long-term cortisol but should be considered when creating longer retrospective timelines 23.
Hair treatments such as hair dying, permanent curling, or straightening have been reported to decrease HCC 26, 30, 33, although other studies have not found such effects 20, 34, 35, 36, 37. In the largest published HCC study thus far, in which hair glucocorticoids were measured in 1258 individuals using LC-MS/MS, cortisol and cortisone were lower in hair that was colored, permanently curled, or straightened. Furthermore, the amount of cortisone decreased with higher hair washing frequency in this study 26. Another hair-specific limitation is the phenomenon of a wash-out, which means that hair cortisol is lower more distally in the hair, for instance, due to wear and tear, subsequent hair washings, or exposure to ultraviolet light. Another study found that HCC was stable in subsequent hair segments in 28 women over a hair length of 18 cm measured using an immunoassay 30, but the authors observed a decrease in cortisol levels along the hair shaft in LC-MS/MS-based method 38. Others have described a washout effect in HCC as well 19, 34. Therefore, wash-out of hair steroids is an important consideration, especially in studies involving retrospective timelines using segmental hair analysis 23.
Multiple studies have measured both cortisol and cortisone in scalp hair using LC-MS/MS 26, 38. In a study by Stalder et al 26. HCC correlated stronger with cardiovascular risk factors than hair cortisol did. This suggests that HCC offers valuable information about systemic glucocorticoid exposure. Furthermore, the determination of both cortisol and cortisone in hair may provide information about the activity of 11b hydroxysteroid dehydrogenase (11b-HSD) enzymes, which convert the active cortisol into cortisone and vice versa. However, 11b-HSD enzymes are expressed in the skin as well 39, and may, therefore, impact the ratio between cortisol and cortisol in hair locally, potentially limiting the value of this ratio as a marker of systemic 11b-HSD activity 23.
Medication use is known to influence different types of cortisol measurements, but until now this does not seem to be a major limiting factor in HCC measurements 19. It is important, however, to consider the use of topical steroids which may contaminate hair samples, and falsely increase HCC through cross-reactivity with the immunoassay. In general, topical or inhalation corticosteroids may also exert some systemic effects, and thereby decrease HCC. One study described that corticosteroid use, which was not further specified, increased HCC33. LC-MS/MS is not limited by cross-reactivity, but false increases may still occur with synthetic corticosteroids that are structurally similar to cortisol 23.
METHODOLOGY OF CORTISOL HAIR DETECTION
Collecting head hair is less intrusive and causes less embarrassment than observed urine collection, and hair does not require refrigeration and can be stored indefinitely as cortisol is relatively stable in hair, and as such a second representative hair sample can be collected and analyzed months later.
Because hair grows at an average rate of 1 cm per month and a sample cut from the posterior scalp, it is preferred as this region of the scalp is associated with the least variation in growth rates. The root of the hair follicle itself must not be included in the analysis as it was found that hair follicles are capable of producing cortisol in response to corticotropin-releasing hormone stimulation and thus may skew the results. The amount of hair required for analysis is around 50 mg, corresponding to a pencil thickness of hair. It is important to collect sufficient hair to carry out a repeat analysis or confirmation test when needed 40.
Recommendations for sample collection: 40
- The collection of hair samples should be undertaken by a competent individual within a secure contamination-free facility with access restrictions in place.
- A hair collection kit with clear instructions for collection should be provided and the collector must observe a chain of custody procedures and wear gloves when handling hair.
- The collection kit should include:
- Chain of custody form
- Foil and collection envelope
- Security seal
- Evidence bag
- Transportation envelope
- Instructions for the collection of a hair sample
- The color, length, site of collection, and any obvious cosmetic treatments should be recorded.
- The head hair sample should be aligned with the root end of the sample identified and secured, e.g., with foil.
- Hair samples must be stored in a dry, dark environment at room temperature, away from direct sunlight. Hair samples should not be stored in the refrigerator or freezer, since swelling may occur and drugs may be lost.
- Hair samples that are wet on a submission must be dried before storage and analysis.
The preparation of hair samples involves several steps including washing, segmentation (optional), and obtaining a representative sample from the material available 40.
Washing of hair samples before analysis has two main purposes. First, to remove hair care products, sweat, sebum, or surface material (e.g., skin cells, head lice, body fluids, etc.) that may interfere with the analysis or that may reduce extraction recovery. Second, to remove potential external cortisol. Several approaches have been described to discriminate between external contamination and cortisol. It is generally accepted that organic solvent such as isopropanol will remove only surface contamination whereas aqueous solutions or methanol will swell the hair and extract cortisol from within the hair matrix 40.
Incubation and Extraction
Method efficiency significantly depends on the use of a suitable extraction procedure that targets specifically cortisol. The hair sample and 1– 1.5 mL of methanol (MeOH) are incubated for 16 h at 50 OC for steroid extraction. Subsequently, the methanol is removed and dried under a gentle stream of nitrogen gas at 50 OC. The remaining residue is reconstituted with 250 mL of phosphate-buffered saline solution (PBS).
Screening for a range of drugs in hair is achieved through immunological or chromatographic methodologies. Immunoassays commonly used for rapid screening of cortisol in biological fluids are also available for hair. The sample is vortexed and analyzed in duplicate using a commercially available high sensitivity salivary cortisol enzyme immunoassay kit from Salimetrics. We will describe their instructions, and both positive and negative controls are used to ensure accuracy 40.
HAIR CORTISOL CONCENTRATION (HCC) IN DIFFERENT CLINICAL CONDITIONS
Higher-stressed mothers exhibit significantly lower HCC compared to lower-stressed mothers, consistent with other research showing that chronic stress leads to blunted HPA axis activity over time. Furthermore, HCC in daughters was significantly and positively associated with previously assessed salivary cortisol stress reactivity. Finally, mother-daughter HCC associations were significantly moderated by negative parenting styles, such that associations became stronger as the quality of parenting decreased. 41
People at older ages are at increased risk for developing stress-related diseases associated with chronically elevated cortisol secretion. However, the main factors contributing to such endocrine alterations in this age group are still largely unknown.
Kirschbaum et al have found HCC to increase with participants’ age and higher in men compared to women. HCC also showed positive associations with waist-to-hip ratio, waist circumference, smoking, prevalent type 2 diabetes mellitus, mental health, daytime sleeping, and being unemployed or retired–—as well as a negative association with diastolic blood pressure. After full mutual adjustment, only age and smoking remained independent predictors of HCC. The association between prevalent type 2 diabetes mellitus and HCC was attenuated but persisted independently in women. Similarly, a positive relationship between HCC and alcohol consumption was found in women. These results confirm previous evidence of positive associations of HCC with age, sex, alcohol consumption, and type 2 diabetes mellitus and add new knowledge on factors such as smoking–—that may contribute to elevated cortisol levels in people at older ages. 25
Alme la et al Have shown that lower HCC was consistently related to worse working memory, learning, short-and long-term verbal memory. In contrast, higher mean levels and higher diurnal area under the curve of diurnal salivary cortisol were related to worse attention and short-term verbal memory, respectively. Interestingly, a higher ratio of mean levels of diurnal salivary cortisol over HCC was related to worse performance on working memory and short-term verbal memory. 42
Several factors are known to contribute to HCC in adults. However, there is less research on the determinants of HCC in children and adolescents. In a systematic review 43, 36 eligible pediatric studies were identified and selected for qualitative synthesis. Higher HCC was associated with male sex and anthropometry, particularly increased body mass index and waist circumference. There was preliminary evidence to suggest that socioeconomic status is inversely related to child HCC, particularly concerning caregiver education and income. Of note, most of the studies analyzing socio-economic variables were performed in relatively equal societies. Hair wash frequency and use of hair products and treatments did not affect HCC when proximal segments of hair were used. There is conflicting evidence regarding the relationship between HCC and age in children and adolescents. Further investigation is required to better delineate if and how the following are associated with HCC in children: hair color, hair type, exposure to trauma and stressors, psychiatric illness, atopic illness, steroid use (including topical and inhaled steroids), and perinatal variables.
Relatively few studies have examined hair cortisol as a marker for chronic stress in pediatric patients 44. The first reported HCC in newborns receiving neonatal intensive care has shown that those requiring mechanical ventilation had higher HCC than nonventilated term infants. Palmer et al 45 found significantly higher hair HCC in African American infants compared with white infants at 1 year of age, correlated with measures of prenatal adversity, maternal postpartum depression, parenting stress, and the child’s socio-emotional development at age 1 year. Among preschool children, HCC was negatively correlated with the parent’s educational level, but not parental income 46. Longitudinal studies found a natural decrease in HCC with increasing age from 1 to 8 years 47. Groneveld et al 48 reported that HCC increased in children after starting school, with greater increases among the children who were fearful before starting school.
Koren and coworkers did not find any significant association between any of the stressors or psychological distress measures and spontaneous preterm birth. They found that spontaneous preterm birth was consistently and independently associated only with pregnancy-related anxiety, among a large number of the stressor and psychological distress measures they studied.
In the subgroup of participants with a sufficient maternal hair sample, hair cortisol was positively associated with gestational age. Neither maternal plasma CRH, hair cortisol, nor placental histopathologic features of infection/inflammation, infarction, or maternal vasculopathy was significantly associated with pregnancy-related anxiety or any other stress or distress measure. 49
Yamada, and co-workers have detected no significant differences between the hair HCC of term infants compared to preterm infants in the neonatal intensive care unit (NICU). When compared to a group of healthy term infants, hospitalized infants had significantly higher HCC. A subgroup analysis of the term NICU infants showed a statistically significant association between the total number of ventilator days and HCC. For every extra day on the ventilator, HCC increased on average by 0.2 nmol/g. 21% of the variance in HCC was explained by the total number of days on the ventilator. 44
Koren et al have detected a positive correlation between HCC and perceived chronic stress in healthy pregnant women. 50
Terrya et al concluded that there are a few associations between stress and HCC observed from preconception to the 3rd trimester. Observed differences in HCC based on educational attainment and anxiety were generally restricted to the preconception and 1st trimester when circulating cortisol concentrations are at their lowest compared to later in pregnancy. 51
Koren and his group found among a large number of stress and distress measures studied, only pregnancy-related anxiety was consistently and independently associated with spontaneous preterm birth. They did not find any significant relationships between any of the stressors or psychological distress measures and spontaneous preterm birth. Nor did they observe any associations between the stressors or measures of psychological distress and maternal plasma CRH or HCC. hair cortisol was positively associated with gestational age. Neither maternal plasma CRH, hair cortisol, nor placental histopathologic features of infection/inflammation, infarction, or maternal vasculopathy was significantly associated with pregnancy-related anxiety or any other stress or distress measure. 49
Karlen et al found in a sample of healthy students, that elevated HCC was found in participants who reported serious life events (e.g., death of a close relative, serious illness, etc.) during the months that were represented in the hair samples compared to participants without such an event. 52
Schmid et al study studied participants in five institutions employing Trauma-informed care (TIC) practices (intervention group). and found significantly lower HCC at T4and occurrences of client physical aggression were assessed at four annual measurement time points (T1 to T4). They compared HCC between trained staff vs. staff members from institutions who did not receive training in TIC (control groups). There were reduced physiological stress levels and HCC at T4, such that the intervention group reported significantly less physical aggression than the control group and lower HCC. 53
Culture and Environment
Marca et al had investigated the effect of 10-week basic military training (BMT) on HCC and found that military training increased perceived stress from the first to the second examination but did not affect HCC. In line with this, there was no correlation between HCC and perceived stress ratings. This could be interpreted as a lack of effect of mainly physical stress (e.g., exercise) on HCC. In contrast, significant correlations were found between HCC and ambient temperature, humidity, and education. 37
Henley et al. found no difference in HCC between volunteers from the slum settlements in Naivasha living adjacent to large floriculture farms and volunteers from Mogotio, who lived in slum settlements well-removed from large floriculture operations. Of some interest, HCC in individuals living in these settlements was higher than in Canadian of European descent. Also, they found no difference in the HCC of the 9 members of the Kenyan clinical team and the Canadians sampled.
Henley et al. reported that participants who were female, divorced, feeling unsafe using sanitation facilities, and (or) collecting water, and making less than the minimum wage in Kenya, have significantly higher HCC than their comparative controls.
After conducting a multiple linear regression with mutual adjustment for all factors, income remained the significant determinant of HCC. Individuals from these settlement communities who self-identified with the marital break-up, low income, and (or) fear, have elevated HCC. 54
People residing near wind turbines claim higher levels of stress and disease. In a large Canadian study, Michaud et al. concluded that there was no evidence that self-reported or objectively measured stress reactions are significantly influenced by exposure to increasing levels of wind turbine noise (WTN) up to 46 dB. 55
Goldberg et al. found HCC to be significantly decreased from baseline to one month after the quit smoking attempt in the entire sample. They concluded that smoking cessation intervention is associated with decreased HCC and that reduced hair cortisol may be specifically associated with mindfulness training and smoking abstinence. 56
Chan J et al found there was no difference in perceived stress (PSS) between non-obese and obese subjects. HCC was significantly correlated with weight and systolic blood pressure, while the correlation with BMI did not reach statistical significance. HCC did not correlate with age or urinary cortisol. There was a negative correlation between hair testosterone and age and BMI. The correlation between hair testosterone and free androgen index (FAI) did not reach statistical significance. The ratio of hair cortisol over hair testosterone (C/T) was higher in the obese group than in the young non-obese group. The C/T ratio correlated positively with age, waist circumference, and BMI, while the correlation between the C/T ratio and FAI did not reach statistical significance. 57
In 2017 Jackson et al examined associations between long-term cortisol levels, as assessed in hair, and adiposity in a large population-based sample. In cross-sectional analyses, HCC was positively correlated with body weight, BMI, and waist circumference and was significantly elevated in participants with obesity and raised waist circumference. 58
In 2018, the same group found obesity, BMI, and perceived weight discrimination were independently associated with elevated HCC. Perceived weight discrimination significantly mediated associations between obesity and hair cortisol. 59
Medical conditions can lead to medical stress, with a lot of factors generating stress in patients. We will provide 2 pieces of evidence that medical health can lead to medical stress and been measured by hair cortisol.
Russel and coworkers reported that HCC was significantly associated with the use of antidepressants, hazardous drinking, smoking, and disability after adjusting for sub-study and potential confounders (sex, body-mass index, use of glucocorticoids, and hair dyed). Besides, preliminary analyses suggest a significant curvilinear relationship between HCC and perceived stress; specifically, HCC increased with higher perceived stress but decreased at the highest level of stress. Overall, HCC was associated with mental health-related variables mainly reflecting substance use or experiencing a disability. 33
Abelson et al have found hair cortisol and depressive responses increased with stress, but they were decoupled, following distinct trajectories that likely reflected different aspects of stress reactivity. While depressive symptoms correlated with stressor demands and stress perceptions, the longitudinal pattern of hair cortisol suggested that it responded to contextual features related to anticipation, novelty/familiarity, and social evaluative threat. 60
A study by Van Uum et al demonstrated that HCC is significantly elevated in patients with severe chronic non-malignant pain syndromes as compared to non-obese control subjects. 61
Higher attention has been dedicated to the role of psychosocial stress in cardiovascular disease (CVD) as a result of increasing knowledge of its adverse physiological consequences for both mental and physical health.
We summarize here the cardiovascular consequences of HCC and provide an overview of recent studies investigating the relationship of HCC with CVD. The clinical implications and limitations of the evidence are discussed.
Hair cortisol may be a reliable biomarker of chronic stress since its present quantification of total cortisol secreted into the hair over several weeks to months. A growing body of evidence proposes that elevated HCC is associated with CVD. Moreover, increased HCC has been related to established cardiometabolic risk factors for CVD including high blood pressure, diabetes, and adiposity.
A systematic review of all published studies up to November 2020 revealed 14 studies examining the association of HCC with the incidence of recovery from CVD (Table 2)89. Four case-control studies found evidence for higher HCC in patients with acute coronary syndrome (ACS) 62, myocardial infarction (MI) 63, coronary heart disease (CHD) 64, and aneurysmal subarachnoid hemorrhage 65 compared with control participants. Furthermore, a population-based study revealed that higher HCC was associated with an increased incidence of coronary heart disease, stroke, and peripheral arterial disease 28. In contrast, coronary heart disease diagnosis or the experience of a stroke was unrelated to HCC in a large observational cohort 66. However, HCC was positively associated with other CVD risk factors (i.e., BMI, diabetes) and CVD medication in this study and the authors suggest that HCC might be more predictive of CVD risk than being an actual marker of CVD.
|Table 2: Association of hair cortisol with the incidence and prognosis of CVD|
|Factors||Significant association||Sample Size||Duration||Refs|
|Acute coronary syndrome||Yes||166||Cross-sectional||62|
|Acute myocardial infarction||Yes||112||Cross-sectional||63|
|Aneurysmal subarachnoid hemorrhage||Yes||32||Cross-sectional||65|
|Coronary heart disease||Yes||598||Cross-sectional||64|
|Coronary heart disease/stroke/peripheral arterial disease||Yes||283||Cross-sectional||28|
|Coronary heart disease/stroke||No||3675||Cross-sectional||66|
|Chronic heart failure||Symptom severity||Yes||44||Prospective||67|
|Coronary artery disease||Recovery||Yes||56||Prospective||68|
|Acute coronary syndrome||Psychological distress||No||121||Cross-sectional||36|
|Aneurysmal subarachnoid hemorrhage||Psychological distress||Yes||32||Cross-sectional||65|
|Structural heart disease||Psychological distress||Yes||261||Prospective||70|
|Structural heart disease||Physical health status||Yes||261||Cross-sectional||70|
HCC has also been investigated as a prognostic factor in CVD. One of the studies revealed a positive relationship between HCC and the severity of symptoms in a sample of patients with chronic heart failure 67. Over a 1-year follow-up, there was also a positive albeit non-significant trend towards higher HCC in patients who had CVD-related hospitalizations compared with non-hospitalized patients. Elevated HCC predicted poorer memory improvement in a sample of patients with coronary artery disease attending a 1-year cardiac rehabilitation intervention 68, while another study demonstrated that higher HCC was associated with larger lesion volume and worse cognitive results 6-, 12- and 24-months following stroke 69. Elevated HCC has also been associated with greater psychological distress in patients with aneurysmal subarachnoid hemorrhage 65. Another study found that higher HCC was related to worse subjective physical health status in patients with structural heart disease (cardiomyopathy, congenital heart disease, or coronary heart disease), while a more favorable mental health status predicted a decline in cortisol levels at 12- week follow-up 70. By contrast, another study of patients with acute coronary syndrome found no evidence supporting the link between HCC and depressive symptoms.36
Verhamme et al showed that children with asthma have a significantly lower HCC than children without asthma after adjustment for age, sex, and BMI, but the HCC range completely overlapped between asthmatic and non-asthmatic subjects. Besides, they observed a nonsignificant trend of decreasing HCC with higher dosages of inhaled corticosteroids. 71
Smy and co-workers have tested pregnant women with asthma and found hair cortisol showed the expected change in cortisol over the course of pregnancy which hair cortisol may be a useful biomarker of HPA axis function during pregnancy and sensitive enough to detect the effects of asthma, both with and without inhaled corticosteroid treatment, on systemic cortisol levels.72
Carleton et al suggested that HCC may be a potential biomarker for detecting chronic adrenal suppression due to inhaled corticosteroid use in children with asthma since 5.6% of inhaled corticosteroid-treated children had HCC <2.0 ng/g compared to none in the control groups. 73
Koren and Carleton found that during ICS therapy, median HCC were twofold lower compared with the period of no ICS use, leading them to suggest hair cortisol is an effective biomarker of the HPA suppression associated with ICS therapy and can be a sensitive tool for determining systemic effects of ICS use and monitoring adherence. 74
Psychosocial Long-term Stress
Hair cortisol has the potential of providing insight into young children's long‐term stress response to social adversity. Psychosocial exposures are increasingly recognized as being critical to health throughout life. A possible mechanism could be physiologic dysregulation due to stress. Cortisol in hair is a new biomarker assessing long-term hypothalamic-pituitary-adrenal axis activity
Children born into families fraught with multiple adverse psychosocial exposures seem to have increased long-term HPA axis activity and are more likely to be affected by common childhood diseases in a dose-response manner. 75
Steudte et al studied hair cortisol and generalized anxiety disorder (GAD), which is characterized by long-lasting anxiety that is not specific to one situation or object, but rather is related to excessive worry and being overly concerned with everyday matters for six or more months, impairing daily functioning. The researchers found 50—60% lower HCC in GAD patients than in matched healthy controls. 76
Manenschijn and colleagues found that HCC was not statistically different in bipolar disorder (BD) patients compared to healthy controls and were not associated with the disease state at the moment of sample collection. 77
In contrast, Coello et al. found a higher HCC in 181 patients with newly diagnosed or first episode BD compared with 101 healthy individuals. 78
Streit et al. found that perceived stress was higher in BD patients compared to controls, and was lower in outpatients in remission compared to inpatients on admission. In BD patients’ manic symptoms were correlated with HCC. In BD inpatients, perceived stress decreased over the 6 - month study period, while HCC did not change significantly over that period. Moreover, in controls, but not in the patient groups, the genetic risk score for BD was associated with HCC. 79
Staufenbiel et al found an association between the number of negative life events and increased HCC, in particular in patients with BD subtype I or in those who had an age of onset before 30 years. 80
Dowlati et al and colleagues inspected the relationship between HCC and depression in patients with coronary artery disease and found no association between cortisol concentration and the diagnosis of depression or between cortisol levels and the severity of depressive symptoms. 36
Dettenborn and colleagues conducted an analysis of hair cortisol in unipolar depressed medicated patients and showed that these patients had slightly higher HCC than healthy controls. 81
Rietschel et al showed moderate but significant associations between HCC and depressive symptoms. 82
Van Rossum showed that Cushing Syndrome (CS) patients had higher HCC than patient controls and healthy controls. Analysis of hair cortisol offers diagnostic accuracy for CS similar to currently used first-line tests and can be used to investigate cortisol exposure in CS patients months to years back in time, enabling estimation of disease onset. 83
Stratakis et al conducted the first study to evaluate segmental hair cortisol in patients with Cushing syndrome and compared it to urine and serum cortisol evaluation. Proximal hair contained the HCC and had the most significant relationship between serum and urine cortisol measurements. 84
Stratakis has concluded that hair cortisol can detect months’ worth of exposure to elevated cortisol levels and has been shown to stratify patients with and without Cushing syndrome. Recent evidence suggests increased sensitivity and specificity of hair cortisol in detecting Cushing syndrome. 85
Thomson et al have conducted a major initial study comparing hair cortisol in healthy subjects and six patients with Cushing syndrome. They found that HCC was significantly higher in patients with CS than in healthy control subjects and that the levels decreased following successful therapy. Segmental hair analysis provided information for up to 18 months before the time of sampling. HCC appeared to vary per the clinical course. 86
Won Hann has found that the mean HCC in chronic hepatitis B (CHB) patients to be lower than other studies of adults over 50 years of age whose mean of hair cortisol ranged from 21.0 to 40.5 pg/mg. It suggests long-term suppression of hair cortisol production in the course of HBV infection and antiviral therapy. Low hair cortisol might indicate a specific pathogenic mechanism with cortisol production. This may explain the low HCC observed in CHB patients who are allegedly under chronic stress while suffering from CHB for years, most of them infected with HBV since birth. The rate of cortisol metabolism is decreased in liver disease. 87
In this study, HCC was significantly higher in patients with sarcoidosis than in general population controls. No differences were found in hair cortisol and testosterone levels between fatigued and non-fatigued sarcoidosis patients. Hair cortisol of sarcoidosis patients correlated significantly with psychological distress (anxiety, depression, and Short Form 36 (SF-36) Survey mental domain), but not with fatigue. The study suggested that hair cortisol is a promising non-invasive biomarker for psychological distress in patients with sarcoidosis. 88
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