Elderly population has increased around all over the world. This process is more pronounced in developing countries with impact on psychiatric disorders, mainly dementia, which is more prevalent in older people. However, previous meta-analysis and reviews have shown high variability in world dementia prevalence rates.
Objective: The aim of this study was to realize a review of the most recent dementia prevalence studies, evaluating prevalence rates and their distribution on several social-demographic factors, considering a greater homogeneity of diagnostic criteria observed in recent years.
Materials and Methods: The search was made in Medline, Lilacs, and Embase, from 1994 to 2000, with inclusion criteria being an original study, estimating dementia prevalence, using universally accepted diagnostic criteria, investigating community samples, and written in English, Portuguese, or Spanish. The data obtained was first analyzed descriptively and then submitted to statistical tests (univariate and multivariate analysis).
Results: The final selection included 42 papers, from all continents. The mean prevalence rate of dementia, over 65 years, among continents, varied from 2.2% in Africa, to 9.4% in Europe, and among countries, from 1.3% in India to 14.9% in Spain. However, there was a trend of approximation of the world prevalence rates with the majority of studies reporting rates over 65 years between 4.2% and 7.2%. The ratio of Alzheimer's disease/vascular dementia was higher in South America and lower in Asia, but there was a historical trend of change in Japan. Age directly influenced the rates, with a mean prevalence rate of 1.2% for the 65-69 year old group and 39.9% for the 90-94 year old group. Corroborating the results of the descriptive analysis, the statistical tests showed a less pronounced age influence with increasing age, specifically in the very elderly group. The rural samples had higher rates, and there was not a significant gender difference, despite a trend of higher female rates. The diagnostic instruments did not uniformly influence the dementia prevalence rates.
Conclusion: Results were similar to reviews done before, mainly the age influence over dementia rates, leveling off on the very elderly group. The finding that rural populations can be at higher risk for dementia should be confirmed by additional studies. Probably a trend to similar dementia prevalence rates around the world was influenced by greater homogeneity in the diagnostic criteria.
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