In this study, the worldwide occurrence of dementia in 2000 and during the period 1950–2050 was estimated. The calculations were based on worldwide demographics of the elderly and age-specific prevalence and incidence values of dementia, estimated from a meta-analysis. In a sensitivity analysis, different prevalence sources were used. The worldwide number of persons with dementia in 2000 was estimated at about 25 million persons. Almost half of the demented persons (46%) lived in Asia, 30% in Europe, and 12% in North America. Fifty-two percent lived in less developed regions. About 6.1% of the population 65 years of age and older suffered from dementia (about 0.5% of the worldwide population) and 59% were female. The number of new cases of dementia in 2000 was estimated to be 4.6 million. The forecast indicated a considerable increase in the number of demented elderly…