Similarities between Alzheimer's disease and vascular dementia.

Alzheimer's disease (AD) and vascular dementia (VaD) are the two most common forms of dementia. In Europe, 800,000 people have a diagnosis of VaD out of 3.7 million people with clinical dementia. These two dementia types share many common pathological, symptomatic and neurochemical features, and cholinergic treatments that have demonstrated robust, broad-ranging and long-term efficacy in AD are now being assessed for the treatment of dementia related to cerebrovascular disease (CVD). There has been recent recognition that dementia in the elderly is a continuum of pathologies, with pure AD and VaD representing the two extremes, and 'mixed' dementia (AD with CVD) in between and perhaps comprising the majority of cases. 'Mixed' dementia is rarely diagnosed in the clinic, however, as the majority of diagnostic procedures are biased toward a diagnosis of AD. Here, the risk factors, pathophysiological mechanisms and clinical symptoms of AD and VaD are described, identifying their overlap as well as some of the differences in both cognitive and noncognitive symptoms. Important findings indicating the high prevalence of 'mixed' dementia in the clinical dementia population are also discussed. In particular, evidence of a causal connection between stroke or CVD and AD is addressed. Regarding effective therapeutic management of dementia patients, further concerted epidemiological study of these related dementia types should aid in clinical decisions on the applicability of cholinergic treatments.