title: Multicenter population-based study on the prevalence of early onset dementia in Japan: vascular dementia as its prominent cause.
abstract: OBJECTIVE
  In Japan, the government and media have become aware of the issues of early onset dementia (EOD), but policies for EOD have not yet been established and support systems are inadequate. To provide practical data about EOD, a two-step postal survey was performed.
  
  
  METHODS
  A questionnaire requesting information on EOD cases was sent to target institutions in five catchment areas in Japan. According to the answers from the institutions, we estimated the prevalence of EOD using census data and determined the illnesses causing EOD. As a quality control study, the authors reviewed every diagnosis in a quarter of the reported cases using the medical and psychiatric records and neuroimaging data. This study was conducted from 2006 to 2007.
  
  
  RESULTS
  Information from 2469 patients was collected from 12,747 institutions, and 2059 subjects with EOD were identified. The estimated prevalence of EOD was 47.6 per 100,000 (95% confidence interval, 47.1-48.1) for all of Japan. Of the illnesses causing EOD, vascular dementia (VaD) was the most frequent (39.8%), followed by Alzheimer's disease.
  
  
  CONCLUSIONS
  The prevalence of EOD in Japan appeared to be similar to that in Western countries. However, unlike previously reported international experience, VaD was the most frequent cause of EOD in all catchment areas in Japan.
authors.affiliation: Department of Disaster Psychiatry, Faculty of Medicine, University of Tsukuba, Ibaraki, Japan; Department of Neuropsychiatry, Faculty of Medicine, University of Tsukuba, Ibaraki, Japan.
authors.forename: Chiaki
authors.initials: C
authors.lastname: Ikejima
authors.forename: Manabu
authors.initials: M
authors.lastname: Ikeda
authors.forename: Mamoru
authors.initials: M
authors.lastname: Hashimoto
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Ogawa
authors.forename: Satoshi
authors.initials: S
authors.lastname: Tanimukai
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Kashibayashi
authors.forename: Kazuo
authors.initials: K
authors.lastname: Miyanaga
authors.forename: Kimie
authors.initials: K
authors.lastname: Yonemura
authors.forename: Tatsuyuki
authors.initials: T
authors.lastname: Kakuma
authors.forename: Kenta
authors.initials: K
authors.lastname: Murotani
authors.forename: Takashi
authors.initials: T
authors.lastname: Asada
mesh_terms: D000293:Adolescent; D000328:Adult; D017668:Age of Onset; D003704:Dementia / Q000453:epidemiology*; D015140:Dementia, Vascular / Q000453:epidemiology; D005260:Female; D006801:Humans; D007564:Japan / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D011795:Surveys and Questionnaires; D055815:Young Adult
keywords: Alzheimer's disease; early onset dementia; prevalence; vascular dementia