The role of cerebrovascular disease in dementia

Improvements in health care over the last 50 years have lengthened average life expectancy significantly, resulting in considerable growth of the population over 65 years of age. With increased age, however, comes an increased risk for Alzheimer's disease (AD), and the prevalence of AD is predicted to reach epidemic proportions by the later half of the 21st century. The prevalence of cerebrovascular disease also increases with age, and recent evidence suggests that cerebrovascular risk factors such as hypertension and hypercholesterolemia also increase an individual's risk for AD, suggesting a potential interaction between these two very common disorders. The potential impact of cerebrovascular disease on general cognitive health is not yet well understood, but is now being actively explored and clarified.

Cerebrovascular disease may manifest itself in many ways, and this review begins by discussing the possible spectrum of brain injury associated with common cerebrovascular risk factors. The prominent role of brain imaging to detect clinically silent cerebrovascular disease is recognized and reviewed. The neuropsychological consequences of cerebrovascular disease across the cognitive spectrum is also reviewed, including potential mechanisms by which cerebrovascular disease may interact with AD to increase the expression or hasten the progression of dementia.

Cerebrovascular risk factors, common to the elderly, lead to pernicious brain injury and subtle cognitive impairment that most probably places the individual at greater lifetime risk for dementia. The cause of dementia among individuals with cerebrovascular disease, however, remains AD. Recognition of the potential role of cerebrovascular disease as an independent risk factor for AD offers the possibility of primary prevention through treatment of well-recognized risk factors and deserves further study. In the meantime, clinicians presented with an individual suffering from a slowly progressive dementia and findings of clinically silent cerebrovascular brain injury should recognize the potential role of cerebrovascular disease in the dementia process but not ignore the likely overwhelming effects of AD and treat appropriately.