Prevalence of Senile Dementia in Okinawa, Japan

Methods. The prevalence of dementia was investigated in Okinawa Prefecture, Japan. In all, 3524 subjects, ≥65 years old, were sampled randomly (urban and rural populations 61.1% and 38.9% respectively). Phase 1 of the survey was carried out by specially trained students of the Faculty of Medicine who used the Mini-Mental State (MMS) scale (interview rate 94.3%) to screen 522 (15.8%) of the 3312 subjects for the phase 2 survey, Phase 2, conducted by psychialrists using the Diagnostic and Statistical Manual of Mental Disorders (DSM-III-R) criteria, detected 172 cases of dementia. Results. The estimated prevalence of dementia was 6.7% For women, the rate increased sharply in the 90–99 year old group, and was 41.4% for men in the 90–99 year old group prevalence was 21.2%. The ratio of Alzheimer-type dementia to multi-infarct dementia was 1.5:1 (men 1.2:1, women 1.7:1). The breakdown of the seventy of dementia in the total cases was: mild 16.9%, moderate 30.8%, and severe 52.3%. The number of severe cases increased with age.