Prevalence of dementia and dementing diseases in the old-old population in Japan: the Kurihara Project. Implications for Long-Term Care Insurance data

Psychogeriatrics. 2012 Dec;12(4):226-34. doi: 10.1111/j.1479-8301.2012.00406.x.


Background: There have been no reports on the prevalence of dementia among the old-old people in Japan.

Methods: We 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'.

Results: In 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%.

Conclusions: The 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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aged
  • Aged, 80 and over
  • Aging / psychology*
  • Dementia / diagnosis
  • Dementia / epidemiology*
  • Female
  • Humans
  • Insurance, Long-Term Care / statistics & numerical data*
  • Japan / epidemiology
  • Magnetic Resonance Imaging
  • Male
  • Pilot Projects
  • Prevalence
  • Program Evaluation
  • Sex Distribution
  • Sex Factors