PREVALENCE OF SENILE DEMENTIA IN OKINAWA, JAPAN

Methods. The prevalence of dementia was investigated in Okinawa Prefec ture, Japan. In all, 3524 subjects, greater than or equal to 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 tr ained students of the Faculty of Medicine who used the Mini-Mental Sta te (MMS) scale (interview rate: 94.3%) to screen 522 (15.8%) of the 33 12 subjects for the phase 2 survey. Phase 2, conducted by psychiatrist s using the Diagnostic and Statistical Manual of Mental Disorders (DSM -III-R) criteria, detected 172 cases of dementia. Results. The estimat ed prevalence of dementia was 6.7%. For women, the rate increased shar ply in the 90-99 year old group, and was 41.4%; for men in the 90-99 y ear old group prevalence was 21.2%. The ratio of Alzheimer-type dement ia to multi-infarct dementia was 1.5:1 (men 1.2:1, women 1.7:1). The b reakdown of the severity of dementia in the total cases was: mild 16.9 %, moderate 30.8%, and severe 52.3%. The number of severe cases increa sed with age.