Hair cortisol as a marker of physiologic stress in residency training

Hair cortisol analysis allows assessment of long-term cortisol exposure and may provide insight into chronic hypothalamic-pituitary-adrenal activation in medical residents and residency on-call responsibilities. To determine the hair cortisol concentration (HCC) representing 3 months of medical residency and secondarily, its association with various on-call models (in-hospital, night float, home call and no call). Cross-sectional study of 66 medical residents who were recruited to provide hair samples collected after a three-month block in medical residency. Academic, tertiary health care system. Volunteer sample of first through third year medical and primary care residents. Three cm of hair was divided into 3 segments of 1 cm each; each segment represented 1 month of cumulative cortisol production. HCC results were compared to a published, cortisol assay-specific normative population reference interval. HCC results were interpreted according to a priori categorizations of moderate (+ 1.5SD), considerable (+ 2SD) or extreme ( > + 3SD) HCC elevations. Associations with various on-call models were an exploratory secondary outcome. The median age was 28 (26–30) years with median sleep duration of 2 h on in-hospital call. 40% of trainees had at least one HCC segment above the threshold deemed marked elevation. Median HCC was significantly higher for in-hospital and night float vs. no call (285 ng/g and 335 ng/g vs. 78 ng/g p < 0.05) and approached significance compared to home call (190 ng/g, p = 0.06). We have described chronic exposure to endogenous cortisol in medical residency. Nearly half of trainees experienced at least one month of severe hypothalamic-pituitary-adrenal axis activation in a 3-month timeframe; many had marked chronic cortisol elevations across the entire 3 month observation frame. HCC was higher in months where in-hospital on-call was required. This may have implications for long-term health of trainees and raises questions about the structure of duty hours and sequence of care acuity blocks within residency training programs.