• Kenichi Meguro, Naofumi Tanaka, Mari Kasai, Kei Nakamura, Hiroyasu Ishikawa, Masahiro Nakatsuka, Masayuki Satoh, and Yoshitaka Ouchi.
• Department of Geriatric Behavioral Neurology, Tohoku University Graduate School of Medicine, Sendai, Japan. k-meg@umin.ac.jp
• Psychogeriatrics. 2012 Dec 1; 12 (4): 226-34.

BackgroundThere have been no reports on the prevalence of dementia among the old-old people in Japan.MethodsWe studied the old-old population in Kurihara, northern Japan. Analysis 1 of Participants 1 (n=590) was performed to evaluate the prevalence of dementia and dementing diseases by intensive evaluation including MRI. Analysis 2 aimed to determine a good indicator for detecting 'suspected dementia condition' based on the Long-Term Care Insurance index. Analysis 3 of Participants 2 (n=3915) aimed to estimate the prevalence of 'suspected dementia condition'.ResultsIn Analysis 1, 73 people (12.4%) were diagnosed with dementia. The most common cause was Alzheimer's disease with cerebrovascular disease. In Analysis 2, level I of the Impairment Level of Dementia was found to be a good indicator of 'suspected dementia condition'. In Analysis 3, the overall estimated prevalence of 'suspected dementia condition' was 23.6%. In men, the ratio increased gradually from 75 to 87 years old to about 20%, increased to 40% at the age of 88 and became stable thereafter. In contrast, in women, the ratio increased from 75 to 95+ years old, reaching about 70%.ConclusionsThe prevalence was higher than that reported previously. There was a difference between the sexes: an 'age-related' increase occurred in men and an 'ageing-related' increase in women. Alzheimer's disease with cerebrovascular disease was the most common cause, which coincided with the previous findings of individuals aged 65 years and older; however, the ratio of mixed dementia was greater.© 2012 The Authors. Psychogeriatrics © 2012 Japanese Psychogeriatric Society.

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