Hair dyeing, hair washing and hair cortisol concentrations among women from the healthy start study

Background; Hair cortisol concentration (HCC) has been suggested as a promising marker for chronic stress. However, studies investigating the influence of hair dyeing and hair washing frequency on HCC have shown inconsistent results. Objective: To examine associations between HCC and hair dyeing status or weekly hair washing frequency among women. Methods: This cross-sectional study was based on data from 266 mothers participating in the Healthy Start intervention study. HCC was measured in the proximal end of the hair (1-2 cm closest to the scalp) while hair dyeing status, frequency of hair washing and covariates were reported by the women. Linear regression analyses were applied to assess the associations between HCC and hair dyeing or weekly frequency of hair washing. Results: No statistically significant difference (p = 0.91) in HCC was found between women who dyed hair (adjusted mean: 137 pg/mg [95% CI: 122,153]) and women with natural hair color (adjusted mean: 139 pg/mg [95% CI: 123,155]). Frequency of hair washing was not associated with HCC (beta: -3.7 [95% CI: -9.0, 1.5; P = 0.20]). Conclusions: This study of 266 Danish women provides no evidence in support of an association between HCC and hair dyeing status or hair washing frequency. (C) 2017 Elsevier Ltd. All rights reserved.