AbstractBackground and ObjectivesStudies on longitudinal trajectories of diet and the influence on aging in older adults are limited. We characterized diet quality trajectories over the past 2 decades among adults aged ≥85 years and examined their associations with cognitive and psychosocial outcomes.Research Design and MethodsWe used data from 861 participants in the population-based Singapore Chinese Health Study. Dietary intakes were assessed at baseline (mean age [range]: 65 [60–74] years) and at follow-ups 3 (85 [81–95]) and 4 (88 [85–97]) years. Diet quality was measured by adherence to the Dietary Approaches to Stop Hypertension pattern, and group-based trajectory modeling was used to derive diet quality trajectories. At Follow-up 4, we assessed cognition using the Singapore-modified Mini-Mental State Examination, depressive symptoms using the 15-item Geriatric Depression Scale, social engagement, and self-rated health. Multivariable logistic regression models examined associations of diet quality trajectories with these outcomes.ResultsAbout 49.7% had a trajectory with consistently low diet quality scores, whereas 50.3% had a trajectory with consistently high diet quality scores. Compared to the “consistently low” trajectory, the “consistently high” trajectory had 29% and 26% lower likelihoods of cognitive impairment and depressive symptoms, respectively (odds ratio, 95% confidence interval: 0.71 [0.51, 0.99] and 0.74 [0.55, 0.99], respectively); as well as 47% higher likelihood of social engagement (1.47 [1.09, 1.98]). No statistically significant association was observed between the trajectories and self-rated health.Discussion and ImplicationsMaintaining high diet quality throughout the older adult life course was associated with better cognitive and psychosocial well-being in adults aged ≥85 years.