Prevalence of dementia in people with intellectual disabilities: Cross-sectional study

Shintaro Takenoshita, Seishi Terada, Ryozo Kuwano, Tomokazu Inoue, Atsushi Cyoju, Shigeru Suemitsu, Norihito Yamada

Research output: Contribution to journalArticlepeer-review

15 Citations (Scopus)


Background: There are only a few studies of the prevalence of dementia in people with intellectual disability (ID) without Down syndrome (DS), and there is a large difference in the prevalences between reported studies. Moreover, the prevalence of mild cognitive impairment (MCI) in ID has not been reported. We aimed to evaluate the prevalence of dementia in adults of all ages and the prevalence of MCI in people with ID. Furthermore, we tried to clarify the differences depending on the various diagnostic criteria. Methods: The survey included 493 adults with ID at 28 facilities in Japan. The caregivers answered a questionnaire, and physicians directly examined the participants who were suspected of cognitive decline. Dementia and MCI were diagnosed according to ICD-10, DC-LD, and DSM-5 criteria. Results: The prevalence of dementia was 0.8% for the 45 to 54 years old group, 3.5% for the 55 to 64 years old group, and 13.9% for the 65 to 74 years old group in people with ID without DS. The prevalence of MCI was 3.1% for patients 45 to 54, 3.5% for patients 55 to 64, and 2.8% for patients 65 to 74 with ID without DS. DSM-5 was the most inclusive in diagnosing dementia and MCI in people with ID. Conclusions: People with ID without DS may develop dementia and MCI at an earlier age and higher rate than the general population. Among the diagnostic criteria, DSM-5 was the most useful for diagnosing their cognitive impairment.

Original languageEnglish
Pages (from-to)414-422
Number of pages9
JournalInternational Journal of Geriatric Psychiatry
Issue number4
Publication statusPublished - Apr 1 2020


  • dementia
  • intellectual disability
  • mental retardation
  • mild cognitive impairment
  • prevalence of dementia

ASJC Scopus subject areas

  • Geriatrics and Gerontology
  • Psychiatry and Mental health


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