Long-Term Depressive Symptom Trajectories and Midlife Cognition: The CARDIA Study.

Background And Objectives: The nature of associations between depressive symptoms and cognition early in the life course remains unclear, and racial differences in these associations are not well characterized. The aim of this study was to examine the relationship between trajectories of depressive symptom over 20 years, beginning in young adulthood, and cognitive functions in middle-age among Black and White adults.

Methods: We used prospective data from participants of the Coronary Artery Risk Development in Young Adults Study. Depressive symptoms were measured at 5 study visits between 1990 and 2010 using the Center for Epidemiologic Studies Depression scale. We used latent class group-based modeling to identify 4 trajectories: "persistently low," "persistently medium," "medium decreasing," and "high increasing" depressive symptoms. In 2015, cognitive function was measured using the Digit Symbol Substitution Test (DSST), Stroop test (reverse coded), and Rey Auditory-Verbal Learning Test (RAVLT).We excluded participants who missed the cognitive battery or had no depressive symptoms measurements, resulting in a total of 3,117 participants. All cognitive tests were standardized, and linear regression was used to relate depressive trajectories with 2015 cognitive functions.

Results: The mean [SD] baseline age was 30.1 [3.6] years, and 57% were female. The associations between depressive symptoms and cognition significantly differed by race ( < 0.05). Among Black individuals, compared with having "persistently low," having "medium decreasing," "persistently medium," or "high increasing" depressive symptoms were associated with worse verbal memory, processing speed, and executive function scores (RAVLT persistently medium vs low: β = -0.30, 95% CI -0.48 to -0.12; and high increasing vs low: β = -0.49, 95% CI -0.70 to -0.27; DSST persistently medium vs low: β = -0.28, 95% CI -0.47 to -0.09; and high increasing vs low: β = -0.64, 95% CI -0.87 to -0.42; Stroop persistently medium vs low: β = -0.46, 95% CI -0.70 to -0.23; and high increasing vs low: β = -0.76, 95% CI -1.04 to -0.47). Associations were slightly weaker among White individuals, but we still found that having 'high increasing' depressive symptoms was associated with worse verbal memory and processing speed scores (high increasing vs low: β = -0.38, 95% CI -0.61 to -0.15; and β = -0.40, 95% CI -0.63 to -0.18, respectively).

Discussion: Prolonged exposure to elevated depressive symptoms beginning in young adulthood may result in worse cognitive function over midlife. This association was stronger among Black adults.