Increased risk of developing dementia in patients with major affective disorders compared to patients with other medical illnesses

Background: The association between affective disorder and subsequent dementia is unclear. Our aim was to investigate whether patients with unipolar or bipolar affective disorder have an increased risk of developing dementia compared to patients with other chronic illnesses. Method: By linkage of the psychiatric and somatic nation-wide registers of all hospitalised patients in Denmark, 2007 patients with mania, 11,741 patients with depression, 81,380 patients with osteoarthritis and 69,149 patients with diabetes were identified according to diagnosis at first-ever discharge from a psychiatric or somatic hospital between 1 January 1977 and 31 December 1993. The risk of receiving a diagnosis of dementia on subsequent re-admission was estimated with the use of survival analyses. Results: Patients with unipolar or bipolar affective disorder had a greater risk of receiving a diagnosis of dementia than patients with osteoarthritis or diabetes. Differences in age and gender and the effect of alcohol- or drug-abuse did not explain these associations. Conclusion: Patients with unipolar or bipolar affective disorder seem to have an increased risk of developing dementia compared to patients with other illnesses. Limitation: The study includes only patients who have been hospitalised at least once. Clinical relevance: Patients with unipolar or bipolar affective disorder may be at increased risk of developing dementia.