Epidemiology of vascular dementia

Although epidemiological studies are limited by diagnostic uncertainties, t hey suggest that stroke increases the risk of dementia. The mortality rate is higher in vascular dementia (VaD) than in Alzheimer's disease (AD). Comm unity-based studies have provided several consistent findings: (i) age depe ndence with prevalence rates doubling every 5 years, (ii) a higher frequenc y in men and (iii) nation-to-nation differences. The prevalence of VaD rang es from 2.2% in 70- to 79-year-old women, to 16.3% in men >80 years. One si xth of acute stroke patients have preexisting dementia. The incidence of Va D has been studied much less extensively than that of AD, and substantial v ariations in the incidence rates have been observed: annual incidence rates (per 100,000) range from 20 to 40 between 60 and 69 years of age and from 200 to 700 over 80. The incidence rate of VaD declined over the last 2 deca des, probably as a consequence of effective stroke prevention. It is genera lly assumed that risk factors for VaD are those of stroke, with arterial hy pertension as leading factor, followed by atherosclerotic disease, low educ ation level, alcohol abuse and heart disease. Stroke characteristics, such as lacunar infarction and left-sided hemispheric lesions, are major determi nants of VaD. The cerebrovascular lesions are likely to be the only cause o f dementia in strategic infarcts, in lacunar state, in hereditary cystatin C amyloid angiopathy and in CADASIL. However, white matter changes, and ass ociated Alzheimer pathology, which are both frequent in this age category, may also contribute to the cognitive decline.