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Background: Depression and dementia are known to be associated. The identification of characteristics distinguishing depression prodromal to dementia from other depressive symptoms would be of value for early identification of dementia. The study of risk factors for depressive symptoms prodromal to dementia could improve preventive care and provide clues to the causes of dementia.

Method: Dementia-free 82-year-old participants were stratified into groups that did (n = 126) and did not (n = 378) subsequently develop dementia. Examinations took place from 2003 to 2005 and follow-up ended 1 January 2015. Their baseline characteristics and depressive symptoms, measured using the 15-item Geriatric Depression Scale (GDS-15), were compared. Multivariate regression analyses were performed for the two groups separately, with the total GDS-15 score as the dependent variable.

Results: The groups did not differ significantly in answers to any of the GDS-15 questions, or mean +/- SD score, which was 2.4 +/- 2.5 among those who developed dementia and 2.1 +/- 2.3 among those who did not. (p = 0.33). Stroke before the age of 82 years and the inability to use stairs had significant impacts on the GDS-15 scores in both groups. For those who did not develop dementia, age, dependence in activities of daily living, and cancer also had significant impacts. Cancer had opposite associations with depressive symptoms in the two groups.

Conclusions: No difference was found in depressive symptoms preceding and not preceding dementia using the GDS-15. The results suggest that risk factors for depressive symptoms may differ depending on whether they precede dementia.