EPIDEMIOLOGY OF DEMENTIA IN OLDER JAPANESE AMERICANS

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Literature from Japan suggests that the prevalence rate of vascular dementia far exceeds that of Alzheimer's disease in that country. In the U.S., the opposite trend is observed. However, direct comparison of prevalence rates is confounded by the lack of standardized diagnostic criteria. A population-based study of dementia in Japanese-Americans over age 65 residing in King County, WA is proposed. The project has five main aims: (1) to establish age- and gender-specific prevalence rates for dementia subtypes in this population, (2) to gather information on potential risk factors for dementia, specifically for Alzheimer's disease, (3) to follow prevalent cases longitudinally to describe disease progression and survival in dementia subtypes, and to obtain autopsy diagnosis on cases dying during the course of the study, (4) to develop a cognitively intact fixed cohort, and (5) to compare our assessments of Japanese-American elderly to parallel studies being conducted in Honolulu, Hawaii and Japan. The base population will be censused to identify persons of Japanese-American origin over age 65. A screening instrument (CAST) will be administered to all identified persons. A validation study will determine the CAST cut-off score, and this score will determine whether or not a person continues the diagnostic process or becomes a member of the cognitively intact cohort. Persons screening positive will be referred to an algorithmic evaluation, which will determine whether cognitive impairment was acquired and progressive, and if so, whether associated with cerebrovascular disease or not. Persons determined to have such a dementia will be further referred to a clinical evaluation for conventional diagnosis. The first two phases are designed in parallel with methods used in Honolulu, Hawaii, where the Honolulu Heart Watch cohort is being evaluated for prevalence and incidence of dementia. Methods in Japan will also be standardized with those in Honolulu. Cross-national comparison of prevalence rates of dementia associated with cerebrovascular disease and primary degenerative dementia will use diagnostic classifications from the algorithmic evaluation. Clinical evaluations in the proposed study will be based on the CERAD battery (Consortium to Establish a. Registry for Alzheimer's Disease). A case-control study will be conducted to examine risk factors using both prevalent and incident cases. Prevalent cases will be followed to study disease progression and survival among dementia subtypes, and to obtain neuropathologic diagnoses for cases who die during the course of the study. During the study period, a fixed cohort of cognitively intact persons will bc formed and monitored bi-annually. A renewal application will be submitted for continued followup of the cohort, to study incidence and risk factors associated with dementia subtypes in this ethnic population.