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Global prevalence of dementia: a Delphi consensus study
Ferri CP, Prince M, Brayne C, Brodaty H, Fratiglioni L, Ganguli M, Hall K, Hasegawa K et al.. Lancet (London, England), 2005-12-01
Topic: Risk, prevention and care in population studies
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.
Cite this study APA, Vancouver, BibTeX · download .bib or .ris
APA 7th
Ferri, C. P., Prince, M., Brayne, C., Brodaty, H., Fratiglioni, L., Ganguli, M., et al. (2005). Global prevalence of dementia: a Delphi consensus study. Lancet (London, England). https://doi.org/10.1016/s0140-6736(05)67889-0
Vancouver
Ferri CP, Prince M, Brayne C, Brodaty H, Fratiglioni L, Ganguli M, et al. Global prevalence of dementia: a Delphi consensus study. Lancet (London, England). 2005. doi:10.1016/s0140-6736(05)67889-0. PMID: 16360788.
BibTeX
@article{ferri2005-16360788,
author = {Ferri, C. P. and Prince, M. and Brayne, C. and Brodaty, H. and Fratiglioni, L. and Ganguli, M. and Hall, K. and Hasegawa, K. and others},
title = {{Global prevalence of dementia: a Delphi consensus study}},
journal = {Lancet (London, England)},
year = {2005},
doi = {10.1016/s0140-6736(05)67889-0},
pmid = {16360788},
url = {https://doi.org/10.1016/s0140-6736(05)67889-0}
}
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Key findings
- 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.
Why it matters
This consensus study estimates how many people have dementia worldwide and projects that the number will grow substantially by 2040, especially in developing countries. It provides no information about treating, curing or preventing Alzheimer's disease.
New to this subject? Start with our plain-English guide: Alzheimer's in numbers →
Study details
- Study designsystematic review
- Evidence strengthHigh
How this study scored 79/100
Published in a top-tier journal, and it is a systematic review of all the studies on the question. Scored zero for sample size, effect reported and studied in people because the record does not state it.
| Component | Points | Why |
|---|---|---|
| Journal tier | 10 / 10 | Tier 1 — top-tier general journal (Lancet (London, England)) |
| Journal's citation record | 4 / 4 | The Lancet: journal h-index 1,205 (OpenAlex, 2026-10-29) |
| Study design | 12 / 12 | A systematic review of all the studies on the question |
| Strength of evidence | 5 / 5 | Rated “high” in our summary |
| Peer-review validation | 10 / 10 | Peer-reviewed. Published as an article in a named peer-reviewed journal. |
| How recent | 1 / 5 | 2005 — older than 20 years, still counted |
| Sample size | 0 / 4 | Participant count not stated — scores zero (not stated in the record — scored 0) |
| Effect reported | 0 / 3 | No effect size reported — scores zero (not stated in the record — scored 0) |
| Studied in people | 0 / 3 | Not stated whether this was studied in people — scores zero (not stated in the record — scored 0) |
| Randomised / blinded | 0 / 2 | A review of other studies — randomisation is not credited here |
| Times cited | 7 / 7 | Cited 5,343 times (OpenAlex, 2026-10-10) |
| Citations per year | 5 / 5 | 232.3 citations a year over 23 year(s) since 2005 |
| Impact for its field and year | 6 / 6 | Cited 89.1× the average for papers of its field and year (OpenAlex FWCI) |
| Cited by studies here | 5 / 6 | Cited by 194 other studies in this library |
| Still being cited | 4 / 4 | Cited 286 times in 2024–2026 (2026 still in progress; OpenAlex) |
| Senior author's track record | 3 / 4 | Last-listed author Márcia Scazufca: h-index 54 (OpenAlex, whole career) |
| Institution's track record | 2 / 3 | University of Cambridge: institution h-index 1,973 (OpenAlex) |
| Multi-centre collaboration | 3 / 3 | OpenAlex lists 12 institution(s) in 8 countries |
| Indexed in PubMed | 2 / 2 | Indexed in PubMed (PMID 16360788) |
| Free to read | 0 / 2 | Behind a paywall — scores zero |
| Total | 79 / 100 | — |
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