The Association Between Stress Across the Lifespan and Cognitive Function Among Older Adults: The Moderating Role of Healthy Lifestyle Behaviours

Psychological stress is a known predictor of poor cognitive health outcomes among older adults. The majority of research to date, however, has limited the assessment of stress to short-term experiences in older adulthood, neglecting stressful experiences accrued throughout different life stages and failing to capture the cumulative nature of stress as it pertains to health outcomes. Moreover, individual differences exist in the relationship between stress and cognitive function such that some older adults are better able to withstand the adverse effects of stress on cognition. Engagement in healthy lifestyle behaviors contributes to enhanced stress resiliency and has been found to have a neuroprotective role in age-related cognitive decline. A healthy lifestyle may therefore buffer the association between stress and cognition among older adults. The goal of this dissertation was to address existing gaps in the literature using three separate studies by examining the association between different indices of stress and cognitive function, and the moderating role of a healthy lifestyle in the stress-cognition relationship among older adults. Using longitudinal data from the NuAge study, Study 1 did not find a moderating role of a healthy lifestyle in the relationship between distress and cognitive decline but did show a sex-specific relationship between distress and cognitive decline. Study 2 used data from the MIDUS study and found that, while cumulative stress exposure was associated with baseline cognitive function and cognitive decline in a sex-specific manner, a healthy lifestyle did not moderate the cumulative stress-cognition relationship. Study 3 collected new data using comprehensive measurements of cumulative stress severity across the lifespan, lifestyle behaviours, and cognitive function. This study found that a healthy lifestyle score moderated the relationship between stress severity at different life stages and cognitive function by buffering the association between early life stress and cognitive function and enhancing resilience to the associations between midlife and late life stress and cognitive function. Together, this program of research contributes to our understanding of stress resiliency in the context of cognitive aging using a life course perspective, and sheds light on a number of methodological considerations in the field of stress and cognitive health.