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

Abstract

IntroductionHigher 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.MethodsWe 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.ResultsHazard 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.ConclusionsThe 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.

Temporal trends in cognitive function of older US adults associated with population changes in demographic and cardiovascular profiles

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Cognitive functioning and structural brain abnormalities in people with Type 2 diabetes mellitus

“…The possible role of obesity in the development of cognitive dysfunction remains controversial. It was recently shown in a large prospective study that a higher BMI could be harmful or protective for the development of dementia depending on the length of the follow‐up . However, the majority of the people with Type 2 diabetes in our cohort were overweight or obese, which did not allow us to draw conclusions regarding the association of BMI and cognitive functioning or brain volumes.…”

Models for predicting risk of dementia: a systematic review

“…It might be because high BMI is a risk factor of dementia with a follow-up time of over 20 years. But low BMI is a risk factor of dementia when the follow-up time is short 39. Besides, the effect of risk factors in different age groups is not the same.…”