title: Recent global trends in the prevalence and incidence of dementia, and survival with dementia.
abstract: Current projections of the scale of the coming dementia epidemic assume that the age- and sex-specific prevalence of dementia will not vary over time, and that population ageing alone (increasing the number of older people at risk) drives the projected increases. The basis for this assumption is doubtful, and secular trends (that is, gradual decreases or increases in prevalence over long-term periods) are perfectly plausible.
  
  
  
  We carried out a systematic review of studies of trends in prevalence, incidence and mortality for people with dementia, conducted since 1980.
  
  
  
  We identified nine studies that had tracked dementia prevalence, eight that had tracked dementia incidence, and four that had tracked mortality among people with dementia. There was some moderately consistent evidence to suggest that the incidence of dementia may be declining in high-income countries. Evidence on trends in the prevalence of dementia were inconsistent across studies and did not suggest any clear overall effect. Declining incidence may be balanced by longer survival with dementia, although mortality trends have been little studied. There is some evidence to suggest increasing prevalence in East Asia, consistent with worsening cardiovascular risk factor profiles, although secular changes in diagnostic criteria may also have contributed.
  
  
  
  We found no evidence to suggest that the current assumption of constant age-specific prevalence of dementia over time is ill-founded. However, there remains some uncertainty as to the future scale of the dementia epidemic. Population ageing seems destined to play the greatest role, and prudent policymakers should plan future service provision based upon current prevalence projections. Additional priorities should include investing in brain health promotion and dementia prevention programs, and monitoring the future course of the epidemic to chart the effectiveness of these measures.
authors.affiliation: The Global Observatory for Ageing and Dementia Care, Health Service & Population Research Department, Institute of Psychiatry, Psychology and Neuroscience, King's College London, PO 36, David Goldberg Centre, De Crespigny Park, London, SE5 8AF, UK. martin.prince@kcl.ac.uk.
authors.forename: Martin
authors.initials: M
authors.lastname: Prince
authors.affiliation: The Global Observatory for Ageing and Dementia Care, Health Service & Population Research Department, Institute of Psychiatry, Psychology and Neuroscience, King's College London, PO 36, David Goldberg Centre, De Crespigny Park, London, SE5 8AF, UK.|Department of Public Health and Primary Care, School of Clinical Medicine, University of Cambridge, Cambridge, UK.
authors.forename: Gemma-Claire
authors.initials: GC
authors.lastname: Ali
authors.affiliation: The Global Observatory for Ageing and Dementia Care, Health Service & Population Research Department, Institute of Psychiatry, Psychology and Neuroscience, King's College London, PO 36, David Goldberg Centre, De Crespigny Park, London, SE5 8AF, UK.
authors.forename: Maëlenn
authors.initials: M
authors.lastname: Guerchet
authors.affiliation: The Global Observatory for Ageing and Dementia Care, Health Service & Population Research Department, Institute of Psychiatry, Psychology and Neuroscience, King's College London, PO 36, David Goldberg Centre, De Crespigny Park, London, SE5 8AF, UK.
authors.forename: A Matthew
authors.initials: AM
authors.lastname: Prina
authors.affiliation: Department of Psychiatry, University of Geneva, Geneva, Switzerland.
authors.forename: Emiliano
authors.initials: E
authors.lastname: Albanese
authors.affiliation: Cambridge Institute of Public Health, University of Cambridge, Cambridge, UK.
authors.forename: Yu-Tzu
authors.initials: YT
authors.lastname: Wu
mesh_terms: D003704:Dementia / Q000453:epidemiology* / Q000401:mortality*; D005260:Female; D014943:Global Health / Q000706:statistics & numerical data / Q000639:trends*; D006801:Humans; D015994:Incidence; D008137:Longitudinal Studies; D008297:Male; D015201:Meta-Analysis as Topic; D015995:Prevalence; D012189:Retrospective Studies
keywords: Dementia; Epidemiology; Global health; Meta-analysis; Projection; Systematic review; Trends; Worldwide