Frequency and distribution of vascular dementia

It remains difficult to draw conclusions about the frequency and distributi on of vascular dementia (VaD). The data from current studies cannot be comp ared and reconciled easily. Disagreement on diagnostic criteria and their f ield implementation remains the major problem. In particular, there is unce rtainty about the classification of patients who show both vascular and deg enerative features, about the advantages and disadvantages of using brief c linical scales (e.g., the Hachinski Ischemic Score), about the use of imagi ng findings in defining VaD, and about the minimal level of severity to be included in epidemiologic studies. Nevertheless, we can tentatively summari ze current epidemiologic data in four points. (1) Both the prevalence and t he 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 co ntroversial for incidence. (3) There are sizeable differences in both incid ence and prevalence across countries. (4) A declining trend in both the pre valence 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 ar e available after the 1970s.