Increased prevalence of vascular dementia in Japan - A community-based epidemiological study

Background and Objective: It has been suggested that there is a major difference in the ratio of AD to vascular dementia (VaD) between Japan and Western countries. To determine the type-specific prevalence of dementia in community-dwelling elderly from the Japanese community of Nakayama, all patients with dementing illness underwent a CT scan. Methods: A door-to-door three-phase population survey was carried out on all persons aged 65 years and older residing at home on the prevalence day (January 1, 1997). The ascertainment of cases was made between January 1997 and March 1998. The study included a psychiatric interview; physical, neurologic, and neuropsychologic examinations; comprehensive laboratory tests; and cranial CT. A public health nurse also interviewed a person close to each subject. Dementia was defined according to the Diagnostic and Statistical Manual of Mental Disorders, third edition-revised, criteria, AD according to the National Institute of Neurological and Communicative Disorders and Stroke-Alzheimer's Disease and Related Disorders Association, and VaD according to Diagnostic and Statistical Manual of Mental Disorders, fourth edition, combined with information from the patient's neurologic history and CT scanning. Results: Of 1438 inhabitants, 1162 (81.0%) completed the protocol. The prevalence of dementia was 4.8%. Of the 60 subjects with dementia, 35% had AD, 47% had VaD, and 17% had dementia resulting from other causes. Conclusions: The prevalence of dementia was similar to previous reports, but, contrary to results of virtually all studies conducted in developed countries and those recently conducted in Japan, almost half of the cases in the present study appeared to have VaD with neuroradiologic confirmation.