Increased risk of developing dementia in patients with bipolar disorder: a nested matched case-control study

The association between bipolar disorder and subsequent dementia risk is not well established. The objective of this study was to investigate whether patients with bipolar disorder were at an increased risk for developing dementia.

A conditional logistic regression model was performed using data from the National Health Insurance Research Database, a nationwide dataset in Taiwan. The study sample included 9,304 patients with incident dementia first diagnosed between 2000 and 2009, and 55,500 gender-, age-, and index date-matched subjects without dementia. Cerebrovascular disease, diabetes, hypertension, head injury, chronic pulmonary disease, alcohol-related disorders, substance use disorders, and health system utilization were treated as covariates in the analyses.

After controlling for the covariates, bipolar disorder was significantly associated with an increased risk of subsequent dementia [adjusted odds ratio (aOR) = 4.32, 95% confidence interval (CI): 3.21-5.82]. An increased risk of developing dementia was observed in males and females alike (aOR = 4.01, 95% CI: 2.53-6.35 in males; aOR = 4.55, 95% CI: 3.07-6.73 in females). Moreover, a significantly increased risk was observed in subjects diagnosed with dementia before the age of 65 years (aOR = 3.77, 95% CI: 1.78-8.01).

Findings from this study suggest a positive association between the presence of a lifetime history of bipolar disorder and an increased risk of developing dementia. Furthermore, our results also suggest that subjects with bipolar disorder tend to develop dementia in middle age. Going forward, it will be of importance to confirm our findings in different populations.