The association between depressive disorders and dementia in very old adults - A longitudinal 5-year follow-up study

Studies have identified depression as a risk factor for developing dementia in later life; however, some studies have suggested that this risk may be limited to younger older adults. The aim of this study was to longitudinally study the association between depressive disorders and the development of dementia among very old adults (85+) after five years. Further, this study aimed to explore factors associated with the development of dementia among very old adults.

This longitudinal population-based cohort study utilized data from the Umeå 85+/GERDA (GErontological Regional DAtabase) home visit interviews with data collected 2000-2017. The sample consisted of 421 participants who did not have dementia at baseline. Descriptive statistics, chi-square tests and independent sample t-tests were utilized to describe the sample and explore differences. A multivariate logistic regression model was calculated to explore factors associated with the development of dementia.

Of those with no depressive disorder at baseline, 110 (33.4%) had developed dementia five years later. Of those with a depressive disorder at baseline, 38 (41.3%) had developed dementia. Factors associated with the development of dementia were: having been outside independently ≥ 1 per week at baseline (inversely associated), stroke between baseline and follow-up, and MMSE at baseline.

No independent association was found between baseline depressive disorders and dementia five years later among very old adults. However, those who developed dementia often also developed depressive disorders, suggesting shared underlying factors. As spending time outdoors was inversely associated with dementia, increasing outdoor opportunities may have potential benefits for mental health in very old adults, although further research is needed to confirm this association and assess potential reverse causation.