Frequency and distribution of vascular dementia

It remains difficult to draw conclusions about the frequency and distribution of vascular dementia (VaD). The data from current studies cannot be compared and reconciled easily. Disagreement on diagnostic criteria and their field implementation remains the major problem. In particular, there is uncertainty about the classification of patients who show both vascular and degenerative features, about the advantages and disadvantages of using brief clinical scales (e.g., the Hachinski Ischemic Score), about the use of imaging findings in defining VaD, and about the minimal level of severity to be included in epidemiologic studies. Nevertheless, we can tentatively summarize current epidemiologic data in four points. (1) Both the prevalence and the incidence of VaD increase steeply with age. (2) The prevalence of VaD is generally higher among men than among women; the sex difference is more controversial for incidence. (3) There are sizeable differences in both incidence and prevalence across countries. (4) A declining trend in both the prevalence and the incidence of VaD was reported from one population; however, the decline was restricted to the age class 80-89 years. No trends data are available after the 1970s.