Is depression in elderly people followed by dementia? A retrospective cohort study based in general practice

We used a retrospective cohort study design to test the hypothesis of a relation between old-age depression and subsequent dementia. The study sample comprised 19 103 patients aged 50 or more and born after 1910, included in a family-practice-based registration network. We estimated odds ratio (OR) and 95% confidence interval (95% CI) for a diagnosis of dementia in patients with or without previous late-onset depression and survival analysis, including hazard ratios resulting from Cox regression analysis. The OR for a diagnosis of dementia subsequent or not to late-onset depressions was 2.38 (95% CI 1.08-5.06). No significant difference between patients with or without old-age depression was found at survival analysis: p = 0.26 (log rank test). Hazard ratio for patients with and without previous old age depression was 2.55 (95% CI 1.19-5.47). We conclude that there is a significant relation between old-age depression and subsequent dementia in patients aged 50 or more and born after 1910. This supports the hypothesis of old-age depression being a predictor, and possibly a causal factor, of subsequent dementia.