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

Background and Objective: It has been suggested that there is a major diffe rence in the ratio of AD to vascular dementia (VaD) between Japan and Weste rn countries. To determine the type-specific prevalence of dementia in comm unity-dwelling elderly from the Japanese community of Nakayama, all patient s 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 o lder residing at home on the prevalence day (January 1, 1997). The ascertai nment of cases was made between January 1997 and March 1998. The study incl uded a psychiatric interview; physical, neurologic, and neuropsychologic ex aminations; comprehensive laboratory tests; and cranial CT. A public health nurse also interviewed a person close to each subject. Dementia was define d according to the Diagnostic and Statistical Manual of Mental Disorders, t hird edition-revised, criteria, AD according to the National Institute of N eurological and Communicative Disorders and Stroke-Alzheimer's Disease and Related Disorders Association, and VaD according to Diagnostic and Statisti cal Manual of Mental Disorders, fourth edition, combined with information f rom the patient's neurologic history and CT scanning. Results: Of 1438 inha bitants, 1162 (81.0%) completed the protocol. The prevalence of dementia wa s 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 de mentia was similar to previous reports, but, contrary to results of virtual ly all studies conducted in developed countries and those recently conducte d in Japan, almost half of the cases in the present study appeared to have VaD with neuroradiologic confirmation.