Stress-Related Trajectories of Diurnal Cortisol in Older Adulthood Over 12 Years.

OBJECTIVE:Although evidence shows that stress experiences can predict both hyper- and hypo-cortisol regulation, there is a lack of research examining these associations longitudinally. Our study assessed whether levels and increases in psychological stress experiences predicted 12-year changes in circadian cortisol levels (area under the curve; AUC) and cortisol slopes in a sample of community-dwelling older adults. METHODS:In 2004, 190 community dwelling older adults (57 to 94 years) started providing three days of diurnal cortisol and stress experience data every two years for a total of seven waves of data. All analyses controlled for relevant covariates including: SES, BMI, age, sex, cortisol-related medication, chronic illness, and smoking status. RESULTS:Growth-curve modeling documented that compared to participants who reported generally lower stress experiences (T-ratio = -5.57, p < .01), their counterparts with higher stress experiences showed significantly steeper declines in cortisol AUC over time (T-ratio = -9.23, p < .01). Higher stress experience was associated with generally flatter cortisol slopes. In addition, among participants with high and increasing stress experience over 12 years, cortisol slopes became increasingly flatter over time (T-ratio = 2.78, p < .01). CONCLUSIONS:Among individuals with high, as compared to low, levels of chronic stress experience, cortisol levels displayed steeper declines across the study period. Moreover, cortisol slopes became increasingly flatter as a function of high and increasing stress experience. Implications for theory and research on the associations between stress experience and cortisol in the context of longitudinal observations are discussed.