Jalil Ghassemi Nejad, Mostafa Ghaseminezhad, Kyung-Il Sung, Fatemeh Hoseinzadeh, Jennette B.A. Cabibi and Jongho Lee
Current methods for measuring cortisol levels can be challenging due to the need to take multiple urine, saliva or serum samples. Therefore, it seems necessary to find alternative matrices which can be used as stress indicators in which sample collection methods are non-invasive. Two experiments were conducted to first to test the feasibility of cortisol levels in facial hair and second to find a correlation among facial hair cortisol and cortisol levels in nails. In the first experiment, facial hair from five subjects was analyzed to confirm the presence of cortisol. The results of the assessment of facial hair showed that facial hair may be used to measure cortisol levels over a short period of time. In the second experiment, nineteen university students (males who regularly partake in martial artsaged: 22 ± 3.15) provided fingernail, toenail and facial hair samples at set intervals throughout the school year; 1) The Study Period-during the student's every-day life (minimal stress conditions, baseline), 2) The Exam Periodfollowing student's final exams (mental stress), and 3) The Fighting Period- following intensive martial arts training (physical stress). Cortisol in facial hair, toenails, and fingernails showed higher levels during both the Exam Period and the Fighting Period when compared to the baseline Study Period (p<0.05). However, no differences in cortisol levels were observed among the indices during the Exam Period and Fighting Period (p>0.05). A higher correlation in cortisol levels was observed between facial hair samples and toenails (r=0.73) than between fingernails and toenails (r=0.61). Overall, cortisol levels showed significant correlations between fingernails and toenails (p=0.001, r=0.61), fingernails and facial hair (p=0.01, r=0.54), and toenails and facial hair (p=0.001, r=0.73). Further research is needed to understand the relationship between facial hair and nail cortisol and their possible relationship with health disorders.