Vascular Dementia

With the varying conceptions of vascular dementia, one understanding of epidemiology has been affected by variations in the definition of the disorders, the clinical criteria used, and the clinical methods applied.

Prevalence. VaD is the second most common single cause of dementia, accounting for 10 to 50 percent of the cases, depending on the geographic location, patient population and clinical methods used (Hebert, Brayne; Lobo et al.). The prevalence of VaD seems to be higher in China and Japan than in Europe and North America. In a recent European collaborative study using population-based studies of persons aged sixty-five years and older conducted in 1990s the age-standardized prevalence of dementia was 6.4 percent (all causes), 4.4 percent for AD and 1.6 percent for VaD (Lobo et al.). In this study 15.8 percent of the cases had VaD and 53.7 percent AD. As expected, a large variation in VaD prevalence was seen across studies. The prevalence ranged from 0.0 percent to 0.8 percent at age sixty-five to sixty-nine years, and from 2 percent to 8.3 percent at age ninety years and over in different studies. There was a difference in prevalence Figure 1 Complex interactions between vascular etiologies, brain changes, host factors, and cognition. SOURCE: Author between men and women; under eighty-five years of age the prevalence of VaD was higher in men compared to women and thereafter the prevalence was higher in women.

Incidence. The incidence of VaD has varied between six to twelve cases per year in one thousand persons aged seventy years and older (Hebert and Brayne). The incidence of VaD increases with increasing age, without any substantial difference between men and women.

Prognosis. The mean duration of any VaD is around five years (Hebert and Brayne), and their survival is less than for the general population or AD. Post-stroke dementia is an independent predictor of mortality.