Associations of cumulative depressive symptoms with subsequent cognitive decline and adverse health events: Two prospective cohort studies

The course of depression is variable; however, few studies examined the relationship between long-term cumulative depressive symptoms and adverse health outcomes in the elderly.In this cohort study, we used data from the Health and Retirement Study (HRS) over 24 years and the English Longitudinal Study of Ageing (ELSA) over 16 years. Cumulative depressive symptoms were estimated by calculating the areas under the curve based on the Center for Epidemiological Research Depression scale assessed at four examinations. Outcomes include cognitive decline, incident dementia, cardiovascular disease (CVD), cancer, and all-cause mortality.A total of 8284 American (mean age: 60.1 years; male: 35.4 %) and 4314 British (60.1 years; 42.4 %) were included in the analysis. The median follow-up was 16.1 years in the HRS and 9.9 years in the ELSA. Similar results were observed in two cohorts. Comparing with the first tertile of cumulative depressive symptoms, the third tertile experienced faster cognitive decline (p = 0.013 in the ELSA and p < 0.001 in the HRS), increased risk of dementia (both p < 0.001), CVD (both p < 0.001) and all-cause mortality (p = 0.002 in the HRS). Strong dose-response relationships were observed. We did not found clearly association between cumulative depressive symptoms and incident cancer.This study suggests that long-term cumulative depressive symptoms were associated with subsequent faster cognitive decline and greater risks for dementia, CVD and all-cause mortality, but not cancer. These findings provide insights on potential effective strategy that may improve health in the elderly, future clinical trials are needed to determine causality.