Global prevalence of dementia: a Delphi consensus study.
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.
Ferri
Cleusa P
CP
Section of Epidemiology, Institute of Psychiatry, King's College, London, UK. c.ferri@iop.kcl.ac.uk
Prince
Martin
M
Brayne
Carol
C
Brodaty
Henry
H
Fratiglioni
Laura
L
Ganguli
Mary
M
Hall
Kathleen
K
Hasegawa
Kazuo
K
Hendrie
Hugh
H
Huang
Yueqin
Y
Jorm
Anthony
A
Mathers
Colin
C
Menezes
Paulo R
PR
Rimmer
Elizabeth
E
Scazufca
Marcia
M
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