The impact of depressive symptoms on cognitive function in early old age: A longitudinal fixed-effect study.

Depression is associated with cognitive decline, but the causal nature of this association in early old age has not yet been established. We examined the impact of depressive symptoms on changes in cognitive function using data from 27,315 adults aged 50-65 in the Survey of Health, Ageing and Retirement in Europe (SHARE) followed for 8 years (2010/2011 -2017/2018), using fixed effect models. Results suggest that an increase in depressive symptoms is associated with a significant decline in overall cognitive function (β =-0.069, 95% Confidence Interval (CI) -0.082 to -0.057), episodic memory (β =-0.052, 95% CI -0.065 to -0.038), working memory (β =-0.075, 95% CI -0.091 to -0.059) and verbal fluency (β =-0.039, 95% CI -0.043 to -0.016). Symptoms capturing difficulties to concentrate, loss of appetite, loss of enjoyment, loss of interest, pessimism, sleep problems and suicidality have stronger effects that depressed mood symptoms such as sadness and tearfulness. Results are robust to an expanded set of controls and to an instrumental variable approach for depressive symptoms. Findings provide novel evidence of a potentially causal relationship between depressive symptoms and cognitive function in early old age.