Global prevalence of dementia: a Delphi consensus study

Cleusa Ferri

Martin Prince

Carol Brayne

Henry Brodaty

Hugh Hendrie+7 authors

Alzheimer's Disease International, London, UK (E Rimmer MA); Section of Epidemiology, Institute of Psychiatry, King's College, London, UK (C P Ferri PhD; Prof M Prince MD); Department of Public Health and Primary Care, University of Cambridge, Cambridge, UK (Prof C Brayne PhD); University of New South Wales, Sydney, Australia (Prof H Brodaty MD); NEUROTEC- Karolinska Institute, Sweden (Prof L Fratiglioni PhD); Departments of Psychiatry and Epidemiology, School of Medicine and Graduate School of Public Health, University of Pittsburgh, Pittsburgh PA, USA (Prof M Ganguli MD); Center for Aging Research, Indiana University School of Medicine, IN, USA (K Hall PhD; Prof H Hendrie DSc); St Marianna University School of Medicine, Kanagawa, Japan (K Hasegawa MD); Institute of Mental Health, Peking University, Beijing, China (Prof Y Huang PhD); Department of Psychiatry, University of Melbourne, Melbourne, Australia (Prof A Jorm DSc); Measurement and Health Information, Evidence and Information for Policy, World Health Organization (C Mathers PhD); Department of Preventive Medicine, University of São Paulo, Brazil (P R Menezes PhD); and Department of Psychiatry, University of São Paulo, Brazil (M Scazufca PhD).

Contributors All authors participated in the study concept and design. C P Ferri and M Prince participated in the coordination of data collection, revision of literature provided to the panel, analysis and interpretation of data, and drafted the manuscript. C Mathers participated in the analysis. All authors critically reviewed the paper for important intellectual content. All authors were part of the consensus panel with the exception of C P Ferri (who managed the Delphi consensus exercise and prepared the anonymised syntheses of estimates) and E Rimmer.

Correspondence to: Cleusa P Ferri, Section of Epidemiology, PO Box 060, De Crespigny Park, London SE5 8AF, UK ku.ca.lck.poi@irref.c

Summary

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.

Findings

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.

Interpretation

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.

Summary

Footnotes

Conflict of interest statement We declare that we have no conflict of interest.

Footnotes

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