Prevalence of Dementia Among the Elderly in a Japanese Community Population—Comparative Study on the 1983 and 1996 Survey: The Aichi Study

Background: An epidemiological survey of dementia among community residents over 65 years of age in Aichi Prefecture (Japan) was conducted in 1983 and 1996. We compared the prevalence rates of dementia in 1996, with the previously published rates of 1983.
Methods: The study employed a two-stage design. First stage: A test based on the DSM-III-R criteria for dementia was administered to all participating residents, who were randomly drawn from the resident register (856,879) of Aichi Prefecture in 1995 (495,923 in 1983). Second stage: A detailed clinical and cognitive evaluation (including MMSE and neurological examination) of the subjects identified in the first stage was carried out by trained psychiatrists.
Results: The prevalence rate for dementia in 1996 was 4.8% (moderate and severe 2.1%) compared with 5.8% (2.2%) in 1983; for senile dementia of Alzheimer type (SDAT) it was 2.8% in 1996 and 2.4% in 1983; for cerebrovascular dementia (CVD), 1.8% in 1996 and 2.8% in 1983.
Conclusion: Up to this time, the cases of CVD have been more frequent than those of SDAT in Japan, especially in the urban areas. However, the relationship between CVD and SDAT has now reversed. These data suggest that SDAT is a common condition and that its public health impact will continue to increase with the increasing longevity of the population in Japan.