Epidemiology of vascular dementia.

Vascular dementia (VaD) is the second commonest dementia after Alzheimer's disease (AD). Epidemiological studies of this condition suffer from many shortcomings related to definition of the disease, diagnostic criteria and assessment of subjects. The prevalence of VaD increases linearly with age and varies greatly from country to country, ranging from 1.2 to 4.2% of people over 65 years old, even after adjustment for age and sex. The incidence of VaD is more homogeneous than prevalence and is estimated at 6-12 cases per 1,000 persons over 70 years per year. The mean duration of the disease is around 5 years and survival is less than for the general population and for AD. The major risk factors for VaD appear to be hypertension, diabetes, heart disease and stroke. Although some of these risk factors are modifiable, there is no study on efficacy of prevention of VaD.