Systematic review of dementia prevalence 1994 to 2000

Ageing has occurred in all regions of the world, with impact on neuropsychiatric disorders, particularly dementia. However, previous meta-analysis and reviews have shown high variability in world dementia prevalence rates.

The aim of this study was to perform a wide-ranging review of the dementia prevalence studies published in recent years.

The search was made on Medline, Lilacs and Embase databases for research conducted between 1994 and 2000. The main inclusion criteria were: use of standard diagnostic criteria and investigation of community samples.

The final selection included 42 papers, from all continents. The mean prevalence rate of dementia in subjects aged 65 years and older, for continents, ranged from 2.2% in Africa to 8.9% in Europe, and among countries, from 1.3% in India to 14.9% in Spain. However, there was a trend of clustering of the world prevalence rates with the majority of studies reporting rates between 4.2% and 7.2% (≥65 years). Age directly influenced the rates, with a mean prevalence rate of 1.2% (95% CI: 0.8.1.5) for the 65-69 years group and 39.9% (95% CI: 34.4.45.3) for the 90-94 year group, but showing less pronounced influence in the very elderly age group. The urban samples had higher rates, where no significant gender difference was evidenced.

The age influence over dementia rates apparently leveled off in the very elderly group while a trend toward similar dementia prevalence rates around the world was probably influenced by greater homogeneity in diagnostic criteria.