Depression, Cognitive Functions, and Impaired Functioning in Middle-Aged Adults From the CONSTANCES Cohort

OBJECTIVE: This large-scale population-based prospective study examined the association between depressive symptoms and cognitive performance at baseline with later functioning in middle-aged adults. METHODS: The Center for Epidemiologic Studies Depression Scale, the Digit Symbol Substitution Test (DSST), the Trail Making Test B (TMT-B), and the Semantic Verbal Fluency test (SVF) were completed at baseline by 7,426 participants aged ≥ 45 years from February 2012 to December 2013. Role limitations and social functioning were later assessed with the second version of the 12-Item Short Form Health Survey. The association between depressive symptoms and cognitive performance at baseline with functioning at follow-up was examined using general linear models and mediation analyses including sex, age, education, alcohol intake, and cannabis use as covariates. RESULTS: Altered functioning at follow-up was predicted by depressive symptoms (β per standard deviation [95% confidence intervals]: -1.10 [-1.16 to -1.03] and -1.02 [-1.08, -0.96] for role limitations and social functioning, respectively) and DSST, TMT-B, and SVF performance (for role limitations: 0.11 [0.09 to 0.14], -0.11 [-0.13 to -0.08], and 0.03 [0.01 to 0.06], respectively; for social functioning: 0.10 [0.07 to 0.12], -0.08 [-0.11 to -0.06], and 0.04 [0.01 to 0.05], respectively) at baseline. Depressive symptoms were associated with poorer cognitive performance at baseline (-0.19 [-0.25 to -0.13], 0.15 [0.08 to 0.21], and -0.11 [-0.17 to -0.04], respectively). Cognitive performance accounted for only 0.3%-1.4% of the relationship between depressive symptoms and functioning. In contrast, depressive symptoms accounted for 19.5%-43.7% of the association between cognitive performance and functioning. CONCLUSIONS: In middle-aged adults from the general population, cognitive impairment is unlikely to substantially explain the association between depressive symptoms and later role limitations and social functioning.