Late-Life Depression Trajectories in Relation to Health and Aging

Abstract

Depression is common in older adults and has been associated with a myriad of adverse health and quality of life outcomes. However, most studies rely on a classification of depression symptoms at a single time point rather than investigating depressive symptoms over time. This reliance on a stationary dichotomous depression status results in issues of heterogeneity in which potentially distinct and clinically important variation in the longitudinal trajectories of depression are grouped together rather than investigated as having possibly diverging effects and underlying mechanisms. In our analyses, we first explored depression patterns measured up to 3 times among Nurses’ Health Study (NHS) participants to determine if patterns of depression were associated with subsequent global or domain-specific cognitive decline. Depressive symptom patterns were categorized as non-depressed, variable, or persistent, based on published severity cutpoints. Outcomes were global, verbal, and executive function-attention composite scores. A variable pattern of depressive symptom severity related to subsequent decline in verbal memory, while a persistent pattern related to decline in executive function-attention. Findings could signal differences in underlying neuropathologic processes among persons with differing depression patterns antecedent to late-life cognitive decline. In our next two analyses, we explored how baseline factors were associated with subsequent trajectories of depressive symptoms measured every 4 years from 1992-2012. Group-based trajectories of symptoms were identified using latent class growth-curve analyses. Multinomial logistic models were used to relate baseline factors to the probabilities of group assignment to subsequent depressive symptom trajectories. We identified four depressive symptom trajectory groups: minimal depressive symptoms (≈60%), worsening depressive symptoms (≈14%), improving depressive symptoms (19%), and persistent severe depressive symptoms (5%). In the first of these two analyses, we explored a comprehensive set of demographic, lifestyle, social and health risk factors that were previously associated with of the binary outcome of incident depression in later-life. In the final of these trajectory analyses, we examined associations between baseline relative telomere length (RTL) and subsequent group-based depressive symptom trajectories among NHS participants. Longer RTLs were related to significantly lower odds of being in the worsening symptoms trajectory but were not related to other trajectories.