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Body mass index and risk of dementia: Analysis of individual-level data from 1.3 million individuals
Kivimäki M, Luukkonen R, Batty GD, Ferrie JE, Pentti J, Nyberg ST, Shipley MJ, Alfredsson L et al.. Alzheimer's & dementia : the journal of the Alzheimer's Association, 2017-11-21
Topic: Risk, prevention and care in population studies
Introduction Higher midlife body mass index (BMI) is suggested to increase the risk of dementia, but weight loss during the preclinical dementia phase may mask such effects. Methods We examined this hypothesis in 1,349,857 dementia-free participants from 39 cohort studies. BMI was assessed at baseline. Dementia was ascertained at follow-up using linkage to electronic health records (N = 6894). We assumed BMI is little affected by preclinical dementia when assessed decades before dementia onset and much affected when assessed nearer diagnosis. Results Hazard ratios per 5-kg/m 2 increase in BMI for dementia were 0.71 (95% confidence interval = 0.66-0.77), 0.94 (0.89-0.99), and 1.16 (1.05-1.27) when BMI was assessed 10 years, 10-20 years, and >20 years before dementia diagnosis. Conclusions The association between BMI and dementia is likely to be attributable to two different processes: a harmful effect of higher BMI, which is observable in long follow-up, and a reverse-causation effect that makes a higher BMI to appear protective when the follow-up is short.
Key findings
- Results Hazard ratios per 5-kg/m 2 increase in BMI for dementia were 0.71 (95% confidence interval = 0.66-0.77), 0.94 (0.89-0.99), and 1.16 (1.05-1.27) when BMI was assessed 10 years, 10-20 years, and >20 years before dementia diagnosis.
Why it matters
In 1.3 million people from 39 cohort studies, the link between body mass index and dementia depended on when weight was measured. Each 5-unit higher BMI went with higher dementia risk when measured more than 20 years before diagnosis (hazard ratio 1.16), but with lower risk when measured nearer to diagnosis (0.71). The authors attribute the second pattern to reverse causation, weight loss in the years before dementia is diagnosed. This is an observational study of all-cause dementia: it suggests midlife weight may matter, but it does not show that changing weight changes dementia risk.
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Study details
- Study designcohort study
- Participants6,894
- Evidence strengthModerate
How this study scored 73/100
Published in a leading specialty journal, and it is a cohort study following people over time. Scored zero for effect reported and randomised / blinded because the record does not state it.
| Component | Points | Why |
|---|---|---|
| Journal tier | 9 / 10 | Tier 2 — leading specialty journal (Alzheimer's & dementia : the journal of the Alzheimer's Association) |
| Journal's citation record | 2 / 4 | Alzheimer s & Dementia: journal h-index 228 (OpenAlex, 2026-10-29) |
| Study design | 7 / 12 | A cohort study following people over time |
| Strength of evidence | 3 / 5 | Rated “moderate” in our summary |
| Peer-review validation | 10 / 10 | Peer-reviewed. Published as an article in a named peer-reviewed journal. |
| How recent | 2 / 5 | 2018 — within 10 year(s) of the newest study here |
| Sample size | 3 / 4 | 6,894 participants |
| Effect reported | 0 / 3 | No effect size reported — scores zero (not stated in the record — scored 0) |
| Studied in people | 3 / 3 | Studied in people (participant count stated) |
| Randomised / blinded | 0 / 2 | No randomisation or blinding stated — scores zero (not stated in the record — scored 0) |
| Times cited | 6 / 7 | Cited 444 times (OpenAlex, 2026-10-10) |
| Citations per year | 4 / 5 | 44.4 citations a year over 10 year(s) since 2018 |
| Impact for its field and year | 5 / 6 | Cited 20.8× the average for papers of its field and year (OpenAlex FWCI) |
| Cited by studies here | 4 / 6 | Cited by 40 other studies in this library |
| Still being cited | 3 / 4 | Cited 155 times in 2024–2026 (2026 still in progress; OpenAlex) |
| Senior author's track record | 3 / 4 | Last-listed author Markus M. Jokela: h-index 88 (OpenAlex, whole career) |
| Institution's track record | 2 / 3 | University College London: institution h-index 2,029 (OpenAlex) |
| Multi-centre collaboration | 3 / 3 | OpenAlex lists 21 institution(s) in 4 countries |
| Indexed in PubMed | 2 / 2 | Indexed in PubMed (PMID 29169013) |
| Free to read | 2 / 2 | Free to read |
| Total | 73 / 100 | — |
What each of these 20 components measures, and what this score is not →
Read the original
- DOI: 10.1016/j.jalz.2017.09.016
- PubMed: 29169013
- Original source →
- Free full text: Alzheimer s & Dementia →
Full text: free to read — OpenAlex lists this copy as free to read: the link above (checked 6 Feb 1020).
Cite this study APA, Vancouver, BibTeX · download .bib or .ris
Built from the record alzhub holds for this paper, not looked up. Volume, issue and page numbers are not held in the record. The record's author list ends in “et al.”, so not every author is named. Check the citation against the original before you use it.
APA 7th
Kivimäki, M., Luukkonen, R., Batty, G. D., Ferrie, J. E., Pentti, J., Nyberg, S. T., et al. (2018). Body mass index and risk of dementia: Analysis of individual-level data from 1.3 million individuals. Alzheimer's & dementia : the journal of the Alzheimer's Association. https://doi.org/10.1016/j.jalz.2017.09.016
Vancouver
Kivimäki M, Luukkonen R, Batty GD, Ferrie JE, Pentti J, Nyberg ST, et al. Body mass index and risk of dementia: Analysis of individual-level data from 1.3 million individuals. Alzheimer's & dementia : the journal of the Alzheimer's Association. 2018. doi:10.1016/j.jalz.2017.09.016. PMID: 29169013.
BibTeX
@article{kivimaki2018-29169013,
author = {Kivimäki, M. and Luukkonen, R. and Batty, G. D. and Ferrie, J. E. and Pentti, J. and Nyberg, S. T. and Shipley, M. J. and Alfredsson, L. and others},
title = {{Body mass index and risk of dementia: Analysis of individual-level data from 1.3 million individuals}},
journal = {Alzheimer's \& dementia : the journal of the Alzheimer's Association},
year = {2018},
doi = {10.1016/j.jalz.2017.09.016},
pmid = {29169013},
url = {https://doi.org/10.1016/j.jalz.2017.09.016}
}
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