title: Prevalence studies of dementia in mainland china, Hong Kong and taiwan: a systematic review and meta-analysis.
abstract: BACKGROUND
  Many studies have considered the prevalence of dementia in mainland China, Hong Kong and Taiwan. However, area level estimates have not been produced. This study examines area differences across mainland China, Hong Kong and Taiwan adjusting for the effect of methodological factors with the aim of producing estimates of the numbers of people with dementia in these areas.
  
  
  RESULTS
  A search of Chinese and English databases identified 76 dementia prevalence studies based on samples drawn from mainland China, Hong Kong and Taiwan between 1980 and 2012. A pattern of significantly decreasing prevalence was observed from northern, central, southern areas of mainland China, Hong Kong and Taiwan. Area variations in dementia prevalence were not explained by differences in methodological factors (diagnostic criteria, age range, study sample size and sampling method), socioeconomic level or life expectancy between areas. The results of meta-analysis were applied to current population data to provide best estimate. Based on the DSM-IV diagnostic criteria, the total number of people aged 60 and over with dementia in mainland China, Hong Kong and Taiwan is 8.4 million (4.6%, 95% CI: 3.4, 5.8) and in northern, central and southern areas are 3.8 (5.1%, 95% CI: 4.1, 6.1), 3.2 (4.4%, 95% CI: 3.2, 5.6) and 1.2 (3.9%, 95% CI: 2.3, 5.4) million respectively. These estimates were mainly based on the studies existing in highly developed areas and potentially affected by incomplete and insufficient data.
  
  
  CONCLUSIONS
  The findings of this review provide a robust estimate of area differences in dementia prevalence. Application of the estimated prevalence to population data reveals the number of people with dementia is expected to double every 20 years, areas in mainland China will be facing the greatest dementia challenge.
authors.affiliation: Department of Public Health and Primary Care, Institute of Public Health, University of Cambridge, Cambridge, United Kingdom. ytw22@medschl.cam.ac.uk
authors.forename: Yu-Tzu
authors.initials: YT
authors.lastname: Wu
authors.forename: Hsin-Yi
authors.initials: HY
authors.lastname: Lee
authors.forename: Samuel
authors.initials: S
authors.lastname: Norton
authors.forename: Chuanfeng
authors.initials: C
authors.lastname: Chen
authors.forename: Hongxia
authors.initials: H
authors.lastname: Chen
authors.forename: Chenglin
authors.initials: C
authors.lastname: He
authors.forename: Jane
authors.initials: J
authors.lastname: Fleming
authors.forename: Fiona E
authors.initials: FE
authors.lastname: Matthews
authors.forename: Carol
authors.initials: C
authors.lastname: Brayne
mesh_terms: D002681:China / Q000453:epidemiology; D003704:Dementia / Q000453:epidemiology*; D005260:Female; D006801:Humans; D008297:Male; D013624:Taiwan / Q000453:epidemiology