Previous studies have provided conflicting evidence on whether depression is a risk factor for or a prodromal symptom of dementia. To avoid confounding by a shared neuropathological cause, this study measured depression already 20–29 years before the follow-up for dementia. We estimated hazard ratios for incident dementia at the age of 65+ in a population-based sample of Finnish residents (n=146,709) in 2000–2012. Depression 20–29 years before baseline and dementia during the follow-up were identified from linked hospital registers. A history of depression was related to a 1.43-fold hazard (95% CI 1.21–1.68) of developing dementia. This excess hazard was only modestly related to earlier-life health conditions and was not moderated by cognitive reserve indicated by education. Adjustment for later-life health conditions attenuated the excess hazard by 20–35%. The results provide evidence for that depression is a risk factor for dementia and suggest that later-life health conditions make important targets for intervention.
Presented in Session 6. Health & Mortality & Aging