'Bipolar disorder' in the elderly: what's in a name?

Bipolar disorder is a chronic disorder of mood which leads to episodes of either elevated mood or depression in a sizable number of adults in the community (1%). Though the prevalence rates in the elderly are lower in the community (up to 0.1%), there is significantly higher morbidity in protected environments like care homes and hospital settings where prevalence rates may be as high as 10%. Bipolar disorder in the elderly is probably heterogenous and its etiopathogenesis is complex. Bipolar disorder may be divided into two distinct subtypes, the late onset bipolar (LOB) and the early onset bipolar (EOB) groups. LOB patients tend to have a milder illness in terms of manic severity but they have higher medical and neurological burden. They also have lower familial burden of bipolar illness as compared to EOB patients. There is an increased risk of dementia and stroke in patients with late life bipolar disorder (and there may be a protective effect of lithium in preventing dementia). White matter changes, as seen by increased white matter hyperintensities on neuroimaging, are also increased, providing further evidence of cerebrovascular disease. Treatment of late life bipolar is currently based on guidelines drawn up for younger bipolar disorder patients. Good quality intervention studies are needed to estimate the possible protective effect of cognitive enhancers and/or vascular prevention strategies. This review suggests that late life bipolar disorder, particularly late onset bipolar disorder, is probably a distinct diagnostic entity compared to the younger bipolar patients as it has a different presentation, etiology and hence perhaps needs different treatment strategies.