Late-Life Depressive Symptoms as Partial Mediators in the Associations between Subclinical Cardiovascular Disease with Onset of Mild Cognitive Impairment and Dementia

Objective: To study whether depression contributes to the association between subclinical cardiovascular disease (CVD) and dementia, and identify the contribution's magnitude. Methods: Among participants from the Cardiovascular Health Study Cognition Study who did not have baseline CVD-related events (N = 2,450), causal mediation methodology was implemented to examine whether late-life depressive symptoms, defined as 10-item Center for Epidemiologic Studies-Depression (mCES-D) Scale scores ≥8 from 2 to 3 years after baseline, partially mediated the association of baseline subclinical CVD (CAC, carotid intimal medial thickness, stenosis, and ankle brachial index) with mild cognitive impairment (MCI)/dementia onset occurring between 5 and 10 years from baseline. The total effect was decomposed into direct and indirect effects (via late-life depressive symptoms), obtained from an accelerated failure time model with weights derived from multivariable logistic regression of late-life depressive symptoms on subclinical CVD. Analyses were adjusted by baseline covariates: age, race, sex, poverty status, marital status, body mass index, smoking status, ApoE4 status, and mCES-D. Results: Participants contributed 20,994 person-years of follow-up with a median follow-up time of 9.4 years. Subclinical CVD was associated with 12% faster time to MCI/dementia (time ratio [TR]: 0.88; 95% CI: 0.83, 0.93). The total effect of subclinical CVD on MCI/dementia onset was decomposed into a direct effect (TR: 0.95, 95% CI: 0.92, 0.98) and indirect effect (TR: 0.92, 95% CI: 0.88, 0.97); 64.5% of the total effect was mediated by late-life depressive symptoms. Conclusions: These data suggest late-life depressive symptoms partially mediate the association of subclinical CVD with MCI/dementia onset.