Abstract
Inconsistent results were found throughout the literature regarding factors affecting hair cortisol levels. Hair cortisol level in humans was not studied for its associations to scalp hair sweating or hair wash frequency in a patient-based way. Factors affecting hair cortisol levels must be precisely known in order to interpret the results correctly. The aims of the study are to assess if BMI, Perceived Stress Scale (PSS), hair wash frequency, and sweating with scalp hair affect hair cortisol levels. It will assess which of these factors are more significant predictors of hair cortisol levels. In a study on healthy adults, information about history, socio-demographics, PSS, hair wash frequency, hair treatment, and scalp hair sweating were collected, and hair samples were taken and analyzed for their hair cortisol level. Associations of hair cortisol levels with each of the variables were investigated and significant predictors of hair cortisol levels among the variables were found. Mean hair cortisol level in the study participants was 16.84 pg/mg hair. Hair cortisol has a significant positive association with weight, BMI, PSS, and scalp hair sweating, p < 0.05. Scalp hair sweating significantly predicts hair cortisol levels by 12.3%, while other variables did not significantly predict hair cortisol levels, p < 0.05. Scalp hair sweating significantly predicts hair cortisol levels. Age, hair wash frequency, hair treatment, and stressful events have no associations with hair cortisol levels. Although BMI and PSS are associated with hair cortisol levels, they do not significantly predict it. Obesity is significantly associated with profuse sweating, thus the increase in hair cortisol levels in obese individuals could partly be the result of a higher incidence of sweating in these individuals. Thus, scalp hair sweating should be taken into consideration during the study and interpretation of hair cortisol levels.
Highlights
The median age of the study participants was 32.5 years, with a median hair cortisol level of 16.84 pg/mg hair and a mean Perceived Stress Scale (PSS) level of 18.97. 57% of the participants responded that they had no scalp hair sweating, and among those with scalp sweating, only 8% had profuse sweating
Significant correlation between hair cortisol and PSS was found in the current study, after correcting for other confounders, PSS was not a significant predictor of hair cortisol levels
Positive associations between PSS and hair cortisol level were found in a cross-sectional study on middle-aged w omen[38], while negative associations were found in a collected database of community samples
Summary
To find significant predictors of hair cortisol level among socio-demographic and other confounders, such as PSS, hair wash frequency, use of hair products (gel or cream), and scalp hair sweating, with the focus on two important related parameters; BMI and sweating, to investigate which one of them is a better predictor of hair cortisol level. This is important, as subjects with a high BMI are usually associated with profuse sweating. We hypothesized that the pattern of scalp hair sweating will affect hair cortisol level after correction for BMI and other confounders
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