n), with 25,000 new cases occurring annually (Clarfield, 1989). Jorm et al. (1988) project that until the year 2025 Canada will experience a growth in the prevalence of dementia, more rapid than the rise if the number of elderly aged over 65. The majority of dementia cases are attributable to AD, vascular dementias, or a combination of these (Table 1). In the past there were hopes that up to 40% of dementias had reversible causes. However, recent reports (Clarfield, 1988; Barry and Moskowitz, 1988) suggest that the true incidence of reversible dementias is at the most 11% and is probably far lower, with drugs, metabolic causes and depression accounting for about two thirds of the cases (Clarfield, 1989).Overall, there are no significant gender differences in prevalence and incidence rates for dementia as a whole. However, for AD, there is an increased prevalnce in females. Jorm et al. (1987) estimate a female to male AD prevalence ratio of 1.6. Ethnically there seem to be important differences in both prevalence and subtype of dementia. Prevalence wise, Heyman et al. (1991) found that out of a random sample of 4116 16% of African Americans had dementia compared to only 3.1% of Caucasians. The same study also found that mixed and MID were more likely to occur in African Americans (26% of dementias in African Americans compared to 14% in Caucasians). Moreover, in both Europe and North America most studies point to AD as the most common dementing illness; whereas in Asia (especially Japan) MID predominates (Morris, 1994). The observed high rate of stroke in Japan is consistent with a high MID rate. Possibly the higher level of stress in Japan leads to more strokes and therefore a higher incidence of MID.Table 1. Etiology of Progressive Dementia and Approximate Incidencesenile dementia of the Alzheimer type50%Multi-infract dementia10-15%Mixed SDAT and MID10-15%Alcoholic-nutritional dementia5-10%Normal pressure hydrocephalus5%Mi...
