title: Prevalence and causes of early-onset dementia in Japan: a population-based study.
abstract: OBJECTIVE
  Few studies are available that have addressed the prevalence of early-onset dementia (EOD), including early-onset Alzheimer disease and other forms of dementia in Japan.
  
  
  METHODS
  A 2-step postal survey was sent to all of the 2475 institutions providing medical or care services for individuals with dementia in Japan's Ibaraki prefecture (population, 2 966 000) requesting information on EOD cases. Data were then reviewed and collated.
  
  
  RESULTS
  We identified 617 subjects with EOD. The estimated prevalence of EOD in the target population was 42.3 per 100 000 (95% CI, 39.4 to 45.4). Of the illnesses that cause EOD, vascular dementia was the most frequent (42.5%) followed by Alzheimer disease (25.6%), head trauma (7.1%), dementia with Lewy bodies/Parkinson disease with dementia (6.2%), frontotemporal lobar degeneration (2.6%), and other causes (16.0%).
  
  
  CONCLUSIONS
  The prevalence of EOD in Japan appeared to be similar to that in Western countries with the notable exception that vascular dementia was the most frequent cause of EOD in Japan.
authors.affiliation: Department of Neuropsychiatry, University of Tsukuba, 1-1-1 Tennoudai, Tsukuba, Ibaraki 305-8575, Japan.
authors.forename: Chiaki
authors.initials: C
authors.lastname: Ikejima
authors.forename: Fumihiko
authors.initials: F
authors.lastname: Yasuno
authors.forename: Katsuyoshi
authors.initials: K
authors.lastname: Mizukami
authors.forename: Megumi
authors.initials: M
authors.lastname: Sasaki
authors.forename: Satoshi
authors.initials: S
authors.lastname: Tanimukai
authors.forename: Takashi
authors.initials: T
authors.lastname: Asada
mesh_terms: D000328:Adult; D017668:Age of Onset; D000544:Alzheimer Disease / Q000150:complications / Q000453:epidemiology; D006259:Craniocerebral Trauma / Q000150:complications / Q000453:epidemiology; D003704:Dementia / Q000453:epidemiology* / Q000209:etiology*; D015140:Dementia, Vascular / Q000150:complications / Q000453:epidemiology; D005260:Female; D006306:Health Surveys; D006801:Humans; D007564:Japan / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D055815:Young Adult