Diurnal cortisol profiles, inflammation, and functional limitations in aging: Findings from the MIDUS study

Objective: The current study examined the association between diurnal cortisol profiles, inflammation, and functional limitations, among adults ranging in age from 34-84 years. Method: Participants (N = 799) completed Waves 2 (between 2004 and 2006) and 3 (between 2014 and 2016) of the Midlife Development in the United States Survey. At Wave 2, participants provided saliva samples across 4 consecutive days, from which cortisol was assayed. Previously validated diurnal cortisol profiles (i.e., normative, flattened, or elevated) were examined in relation to concurrent inflammation risk burden and to predict long-term changes in functional limitations. Results: Compared with participants with normative profiles across all interview days, participants with dysregulated profiles across all interview days (i.e., all days elevated, flattened, or a combination of elevated and flattened) showed greater concurrent inflammation risk burden and more functional limitations at follow-up. Regions of significance testing indicated that the association was significant beginning at age 60 for inflammation risk burden and beginning at age 66 for functional limitations. Variable profiles (i.e., a mix of normative and flattened and/or elevated across the four days of assessment) were not significantly associated with these health indices. Conclusions: Findings, consistent with the theoretical model of Strength and Vulnerability Integration, illustrate the importance of considering age when examining cortisol and its association with other health indices.