Shiftwork and diurnal salivary cortisol patterns among police officers

Objective: To investigate associations between shiftwork and diurnal salivary cortisol among 319 police officers (77.7% men). Methods: Information on shiftwork was obtained from the City of Buffalo, NY electronic payroll records. Saliva was collected using Salivettes at seven time points and analyzed for free cortisol concentrations (nmol/L) using a chemiluminescence immunoassay. Mean slopes and areas under the curve were compared across shift schedule using analysis of variance (ANOVA)/analysis of covariance (ANCOVA). Results: Officers working primarily on the night shift had a significantly shallower slope. Mean slope (nmol/L/minutes) of the cortisol curve varied significantly across shifts (day: -0.00332±0.00017, afternoon: -0.00313±0.00018, night: -0.00257±0.0002); adjusted P=0.023. Conclusions: Our results suggest that night shiftwork is a workplace factor that may alter the response of the hypothalamic-pituitary-adrenal (HPA) axis to the circadian cues responsible for the pattern of the diurnal cortisol curve.