Religion, spirituality and diurnal rhythms of salivary cortisol and dehydroepiandrosterone in postmenopausal women

Background: Religion and spirituality (R/S) are important resources for coping with stress and are hypothesized to influence health outcomes via modulation of the hypothalamic-pituitary-adrenal (HPA) axis, though this has not been evaluated extensively. In this study, we examined associations between several measures of religiosity or spirituality (R/S) and three HPA axis biomarkers: cortisol, dehydroepiandrosterone (DHEA), and cortisol:DHEA ratio. Methods: Sample included 216 female postmenopausal Nurses’ Health Study II participants who provided up to five timed saliva samples: immediately upon awakening, 45 min, 4 h, and 10 h after waking, and prior to going to sleep during a single day in 2013. Multivariable-adjusted linear mixed models with piecewise cubic spline functions and adjustment for potential covariates were used to estimate the cross-sectional associations of eight R/S measures with diurnal rhythms of cortisol, DHEA, and the cortisol/DHEA ratio. Results: There was little evidence of association between the eight R/S measures analyzed and diurnal rhythms of cortisol, DHEA, and the cortisol/DHEA ratio. Women who reported that R/S was very involved in understanding or dealing with stressful situations had slower night rise in cortisol than those who did not. Greater levels of religious struggles were associated with higher cortisol levels throughout the day. Higher non-theistic daily spiritual experiences scores were associated with slower DHEA night rise, and a higher cortisol/DHEA ratio upon waking and at night. However, these associations were significantly attenuated when we excluded women reporting bedtimes at least 30 min later than usual. Conclusion: Observed associations were driven by those with late sleep schedules, and given the number of comparisons made, could be due to chance. Future research using larger, more diverse samples of individuals is needed to better understand the relationship between R/S and HPA axis biomarkers.