Background: The increasing number of patients with dementia in Japan, together with the rapid aging of society, is currently considered to have a substantial impact on Japan's medical, economic and sociological systems. Therefore, the longitudinal estimation of changes in the prevalence of dementia based on accurate diagnostic evaluation has important implications.
Methods: We undertook three separate epidemiological studies on long-term changes, 10 years apart (1980, 1990 and 2000), in the prevalence of dementia in an elderly population using identical methods (DSM-III and Hachinski's ischemic score) for the same rural area in Japan (Daisen-cho).
Results: The percentage of the population that was elderly (over 65 years of age) increased steadily from 16.0% in 1980 to 21.7% in 1990 and 27.1% in 2000. The prevalence of dementia (cases/100 people aged 65 years or older, adjusted to the population structure of 1980) in 1980, 1990 and 2000 was 4.4, 4.5 and 5.9, respectively, for all types of dementia, 1.9, 2.5 and 3.6, respectively, for Alzheimer-type dementia (DAT) and 2.0, 1.7 and 2.2, respectively, for vascular dementia (VaD).
Conclusions: These findings of an increase in the number of cases and prevalence of DAT and VaD in a Japanese rural community have important implications for interventional medicine.