title: Global prevalence of dementia: a Delphi consensus study.
abstract: BACKGROUND
  100 years after the first description, Alzheimer's disease is one of the most disabling and burdensome health conditions worldwide. We used the Delphi consensus method to determine dementia prevalence for each world region.
  
  
  METHODS
  12 international experts were provided with a systematic review of published studies on dementia and were asked to provide prevalence estimates for every WHO world region, for men and women combined, in 5-year age bands from 60 to 84 years, and for those aged 85 years and older. UN population estimates and projections were used to estimate numbers of people with dementia in 2001, 2020, and 2040. We estimated incidence rates from prevalence, remission, and mortality.
  
  
  RESULTS
  Evidence from well-planned, representative epidemiological surveys is scarce in many regions. We estimate that 24.3 million people have dementia today, with 4.6 million new cases of dementia every year (one new case every 7 seconds). The number of people affected will double every 20 years to 81.1 million by 2040. Most people with dementia live in developing countries (60% in 2001, rising to 71% by 2040). Rates of increase are not uniform; numbers in developed countries are forecast to increase by 100% between 2001 and 2040, but by more than 300% in India, China, and their south Asian and western Pacific neighbours.
  
  
  CONCLUSIONS
  We believe that the detailed estimates in this paper constitute the best currently available basis for policymaking, planning, and allocation of health and welfare resources.
authors.affiliation: Section of Epidemiology, Institute of Psychiatry, King's College, London, UK. c.ferri@iop.kcl.ac.uk
authors.forename: Cleusa P
authors.initials: CP
authors.lastname: Ferri
authors.forename: Martin
authors.initials: M
authors.lastname: Prince
authors.forename: Carol
authors.initials: C
authors.lastname: Brayne
authors.forename: Henry
authors.initials: H
authors.lastname: Brodaty
authors.forename: Laura
authors.initials: L
authors.lastname: Fratiglioni
authors.forename: Mary
authors.initials: M
authors.lastname: Ganguli
authors.forename: Kathleen
authors.initials: K
authors.lastname: Hall
authors.forename: Kazuo
authors.initials: K
authors.lastname: Hasegawa
authors.forename: Hugh
authors.initials: H
authors.lastname: Hendrie
authors.forename: Yueqin
authors.initials: Y
authors.lastname: Huang
authors.forename: Anthony
authors.initials: A
authors.lastname: Jorm
authors.forename: Colin
authors.initials: C
authors.lastname: Mathers
authors.forename: Paulo R
authors.initials: PR
authors.lastname: Menezes
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Rimmer
authors.forename: Marcia
authors.initials: M
authors.lastname: Scazufca
mesh_terms: D000368:Aged; D000544:Alzheimer Disease / Q000191:economics / Q000453:epidemiology*; D017281:Cost of Illness; D003697:Delphi Technique; D005260:Female; D014943:Global Health; D006801:Humans; D008297:Male; D015201:Meta-Analysis as Topic; D008875:Middle Aged; D015995:Prevalence