Depressive Symptoms and Cognitive Decline: A Longitudinal Analysis of Potentially Modifiable Risk Factors in Community Dwelling Older Adults

Background: Depressive symptoms have been associated with increased risk of cognitive decline in later life. There are no interventions proven to reduce risk of cognitive decline in older adults with depression, and it is unclear how these effects are mediated. We aim to determine what mediates the relationship between depressive symptoms and cognitive decline in later life.

Methods: Seven thousand six hundred and sixty six community dwelling older adults (age ≥ 50) from the English Longitudinal study of Ageing (ELSA) underwent clinical assessment. Inflammation was assessed with C Reactive Protein and depressive symptoms were assessed with the 8-item version of the Center for Epidemiologic Studies (CESD) scale.

Results: Five thousand, five hundred and ninety (73.5%) had a follow-up cognitive assessment after a median of 47 months. Depressive symptoms were independently associated with cognitive decline (B=0.09, p<0.001). Low physical activity, inflammation, metabolic syndrome and vascular risk factors were associated with elevated depressive symptoms. Low physical activity (z=2.16, p=0.03) and inflammation (z=2.3, p=0.02) mediated the relationship between depressive symptoms and cognitive decline while hypertension, diabetes and smoking also contributed.

Limitations: This is an observational study with a limited duration of follow up. Not all variables related to cognitive decline were accounted for in this analysis.

Conclusions: The relationship between depressive symptoms and cognitive decline in later life appears to be mediated by low physical activity, increased inflammation and vascular risk factors that may be amenable to modification.