Body Mass Index and Risk of Dementia

2017 Nov 21. pii: S1552-5260(17)33811-6. doi: 10.1016/j.jalz.2017.09.016. [Epub ahead of print]

Body mass index and risk of dementia: Analysis of individual-level data from 1.3 million individuals.

Kivimäki M1, Luukkonen R2, Batty GD3, Ferrie JE4, Pentti J5, Nyberg ST5, Shipley MJ6, Alfredsson L7, Fransson EI8, Goldberg M9, Knutsson A10, Koskenvuo M2, Kuosma E2, Nordin M11, Suominen SB12, Theorell T13, Vuoksimaa E14, Westerholm P15, Westerlund H13, Zins M9, Kivipelto M16, Vahtera J17, Kaprio J14, Singh-Manoux A18, Jokela M19



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.


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.


Hazard ratios per 5-kg/m2 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.


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.