Cognitive Impairment of Older-Age Bipolar Disorder: A Narrative Review

Older-age bipolar disorder (OABD), which constitutes approximately 10%-25% of all late-life mood disorders in clinical practice, is frequently underrecognized or misdiagnosed as unipolar depression, a medical comorbidity, or dementia.Cognitive deficits are one of the common features of OABD, yet disease heterogeneity and inconsistent patterns of cognitive manifestations make it difficult to conduct a proper assessment.A literature review was conducted through PubMed to provide an overview of cognitive decline associated with OABD and to suggest clinical assessments for OABD in primary care settings.Patients with OABD tend to have more pervasive and severe cognitive deficits compared with late-life depression.The risk of dementia in OABD is estimated to increase two-to fourfold, but unlike that in Alzheimer's disease, it does not appear to be associated with apolipoprotein E genotyping.Cognitive impairment in OABD may be associated with allostatic load, with modifiable factors, including increased homocysteine levels, vitamin B12/folate deficiency, and chronic benzodiazepine or antipsychotic use.The cognitive problems in OABD, particularly in memory domains, can be chronic and episode-independent.Furthermore, it is important to address certain correctable factors, such as lifestyle modifications and participation in cognitive rehabilitation.