Elevated Hair Cortisol Concentrations Are Associated With Poor Sleep Quality Evaluated Using the Pittsburgh Sleep Quality Index but Not With Actigraphy.

There is growing interest in studying how habitual sleep disturbance affects biological risk factors that may underscore adverse health outcomes. This study examined associations between hair cortisol concentrations and self-reported sleep quality and objectively measured sleep metrics derived using actigraphy. Data were collected from 306 female and 177 male adults, aged 18-79 years. Hair cortisol was analysed from 3-cm proximal hair segments from the head to represent cortisol accumulation over approximately 90 days. Sleep quality measures included Pittsburgh Sleep Quality Index (PSQI) scores and five actigraphy-derived metrics: sleep latency, total sleep time, wake after sleep onset, sleep efficiency and awakening bouts. In the fully adjusted multiple regression model, higher hair cortisol concentrations were associated with poor self-reported sleep quality (i.e., PSQI > 5; p = 0.020), and higher mean PSQI scores (p = 0.027). No significant relationships were observed with actigraphy-derived sleep measures. The findings support hair cortisol as a promising biomarker for evaluating chronic stress that often coincides with self-reported sleep disturbance. The results suggest the importance of aligning time reference periods for biomarker and self-reported outcomes and highlight the need for further research to reconcile discrepancies between subjective and objective sleep measures.