This meta-analysis identified 10 studies (including 6,859 people with bipolar disorder) investigating the link between bipolar disorder and dementia.1 Bipolar disorder increased the risk of dementia compared with controls by 2.96-times (p<0.001).1 The increased risk appeared to be related to the number of mood episodes a person had experienced.1 However, the increased risk was halved by treatment with lithium (odds ratio 0.51, p<0.001).1 Furthermore, an analysis of medical register data has shown that the increased risk of dementia in people with bipolar disorder is related to the number of depressive episodes, with the risk of dementia increasing by 6% with every mood episode leading to hospital admission in people with bipolar disorder.2
References:
1. Velosa J, Delgado A, Finger E, et al. Risk of dementia in bipolar disorder and the interplay of lithium: a systematic review and meta-analyses. Acta Psychiatr Scand 2020; 141 (6): 510–521.
2. Kessing LV, Andersen PK. Does the risk of developing dementia increase with the number of episodes in patients with depressive disorder and in patients with bipolar disorder? J Neurol Neurosurg Psychiatry 2004; 75 (12): 1662–1666.