Worldwide prevalence and incidence of dementia

Dementia is a common and disabling disorder in the elderly. Because of the worldwide aging phenomenon, existing in both developed and developing count ries, dementia has a growing public health relevance. This article reviews the prevalence and incidence data for dementia reported in the internationa l literature in the last 10 years. Results from 36 prevalence and 15 incide nce studies have been examined. Prevalence is equal to 0.3 to 1.0 per 100 p eople in individuals aged 60 to 64 years, and increases to 42.3 to 68.3 per 100 people in individuals 95 years and older. The incidence varies from 0. 8 to 4.0 per 1000 person years in people aged 60 to 64 years, and increases to 49.8 to 135.7 per 1000 person years when the population was alder than 95 years. The international comparison allows the following conclusions: (i ) both prevalence and incidence show little geographical variation, as diff erences between countries seem to reflect methodological rather than real d ifferences [the: low prevalence of dementia in Africa needs to be confirmed by incidence data]; (ii) both incidence and prevalence figures increase wi th age even in the advanced ages; (iii) regarding dementia types, most of t he inconsistency in results from different studies is due to vascular demen tia rather than to Alzheimer's disease (AD); (iv) it is still unclear if th e reported higher frequency of vascular dementia in Asian populations is du e to differential distribution of genetic and/or environmental factors, or due to methodological differences; (v) different dementia types might have different age distributions.