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International Journal of Alzheimer’s Disease
Volume 2012 (2012), Article ID 956354, 11 pages
Review Article

Trends in the Prevalence of Dementia in Japan

1Department of Neurology, Oregon Health & Science University, CR131, 3181 SW Sam Jackson Park Road, Portland, OR 97239-3098, USA
2Department of Epidemiology, University of Pittsburgh Graduate School of Public Health, Pittsburgh, PA 15213, USA
3Department of Neurology, University of Michigan, Ann Arbor, MI 48190, USA
4Institute for Social Research, University of Michigan, Ann Arbor, MI 48106, USA
5Department of Environmental Medicine, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
6Department of Geriatric Behavioral Neurology, Tohoku University Graduate School of Medicine, Sendai, Japan
7Department of Neurology, Portland Veterans Affairs Medical Center, Portland, OR, USA

Received 17 February 2012; Accepted 23 May 2012

Academic Editor: Kaarin Anstey

Copyright © 2012 Hiroko H. Dodge et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


There is a paucity of data regarding trends in dementia and its subtype prevalence in Japan. Our aims in the current paper are to: (1) summarize epidemiological studies of dementia in Japan including relevant details of study protocol and diagnostic criteria, (2) compare the age-specific prevalence of all-cause dementia among studies, and (3) assess the trends in Alzheimer's disease (AD) versus vascular dementia (VaD) over time. We reviewed diagnostic criteria, all-cause dementia prevalence, and the AD/VaD ratio from 8 large population studies of dementia in Japan. Compared with the Okinawa 1992 study, studies conducted in 1994, 1998, 2005, and 2008 had a higher prevalence of all-cause dementia using Poisson regression models, after controlling for age and sex. In contrast to the US and some European countries, all-cause dementia prevalence is increasing in Japan. The prevalence of AD as opposed to VaD seems to be increasing over time, but large variability in diagnostic criteria, possible regional variability, and differences in prevalence of subtypes of dementia between men and women make it difficult to draw a conclusion about this trend at the national level. Further studies, for example, comparing the population attributable risk of vascular diseases to the prevalence and incidence of dementia could help to clarify the regional variations in etiological subtypes.