Epidemiological studies of the effect of stroke on incident dementia: a systematic review.

BACKGROUND AND PURPOSE Stroke is implicated in the incidence of dementia, and the risk of poststroke dementia is well characterized, but the excess risk of dementia in those with stroke compared with those without stroke is not well known. METHODS We conducted a systematic review of the excess risk of incident dementia conferred by stroke. Studies of the risk of incident dementia in the population with stroke compared with the population without stroke were identified and compared. RESULTS Sixteen studies were identified with all but one conducted in a community setting. A history of stroke doubles the risk of incident dementia in the older population. This increase is not explained by demographic or cardiovascular risk factors or by prestroke cognitive decline. The excess risk of incident dementia diminishes with time after stroke and may be higher in those without an APOE epsilon4 allele. There is no excess risk of incident dementia in those aged >85 years with a history of stroke compared to those aged >85 years without stroke. CONCLUSIONS The effect of stroke on dementia incidence in the population is not explained by common risk factors. At this time of population aging and increased stroke survival, more research is needed to determine to what extent efforts to reduce the incidence of stroke will affect the incidence of dementia.