Summary: UCL researchers report people with a higher body mass index are more likely to develop dementia than those of a lower weight.
People who have a high body mass index (BMI) are more likely to develop dementia than those with a normal weight, according to a new UCL-led study.
The study, published in the Alzheimer’s & Dementia journal, analysed data from 1.3 million adults living in the United States and Europe. The researchers also found that people near dementia onset, who then go on to develop dementia, tend to have lower body weight than their dementia-free counterparts.
“The BMI-dementia association observed in longitudinal population studies, such as ours, is actually attributable to two processes,” said lead author of the study, Professor Mika Kivimäki (UCL Institute of Epidemiology & Health). “One is an adverse effect of excess body fat on dementia risk. The other is weight loss due to pre-clinical dementia. For this reason, people who develop dementia may have a higher-than-average body mass index some 20 years before dementia onset, but close to overt dementia have a lower BMI than those who remain healthy.”
“The new study confirms both the adverse effect of obesity as well as weight loss caused by metabolic changes during the pre-dementia stage.”
Past research on how a person’s weight influences their risk of dementia has produced conflicting results. Some findings have suggested that being obese poses a higher dementia risk, but other studies have linked lower weight to increased dementia incidence.
In this study, researchers from across Europe pooled individual-level data from 39 longitudinal population studies from the United States, the United Kingdom, France, Sweden, and Finland. A total of 1,349,857 dementia-free adults participated in these studies and their weight and height were assessed. Dementia was ascertained using linkage to electronic health records obtained from hospitalisation, prescribed medication and death registries.
A total of 6,894 participants developed dementia during up to 38 years of follow-up. Two decades before symptomatic dementia, higher BMI predicted dementia occurrence: each 5-unit increase in BMI was associated with a 16-33% higher risk of this condition (5 BMI units is 14.5kg for a person 5’7″ (170cm) tall, approximately the difference in weight between the overweight and normal weight categories or between the obese and overweight categories). In contrast, the mean level of BMI during pre-clinical stage close to dementia onset was lower compared to that in participants who remained healthy.
In 2015, the number of people with dementia reached almost 45 million, two times more than in 1990. This study suggests that maintaining a healthy weight could prevent, or at least delay, dementia.
About this neuroscience research article
Funding: This research was supported by the NordForsk, Nordic Programme on Health and Welfare, UK Medical Research Council, and others.
Source: Rowan Walker – UCL Publisher: Organized by NeuroscienceNews.com. Image Source: NeuroscienceNews.com image is in the public domain. Original Research: Full open access research for “Body mass index and risk of dementia: Analysis of individual-level data from 1.3 million individuals” by Mika Kivimäki’Correspondence information about the author Mika Kivimäki, Ritva Luukkonen, G. David Batty, Jane E. Ferrie, Jaana Pentti, Solja T. Nyberg, Martin J. Shipley, Lars Alfredsson, Eleonor I. Fransson, Marcel Goldberg, Anders Knutsson, Markku Koskenvuo, Eeva Kuosma, Maria Nordin, Sakari B. Suominen, Töres Theorell, Eero Vuoksimaa, Peter Westerholm, Hugo Westerlund, Marie Zins, Miia Kivipelto, Jussi Vahtera, Jaakko Kaprio, Archana Singh-Manoux, and Markus Jokela in Alzheimer’s & Dementia. Published online November 20 2017 doi:10.1016/j.jalz.2017.09.016
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[cbtabs][cbtab title=”MLA”]UCL “Obesity Increases Dementia Risk.” NeuroscienceNews. NeuroscienceNews, 30 November 2017. <https://neurosciencenews.com/obesity-dementia-8074/>.[/cbtab][cbtab title=”APA”]UCL (2017, November 30). Obesity Increases Dementia Risk. NeuroscienceNews. Retrieved November 30, 2017 from https://neurosciencenews.com/obesity-dementia-8074/[/cbtab][cbtab title=”Chicago”]UCL “Obesity Increases Dementia Risk.” https://neurosciencenews.com/obesity-dementia-8074/ (accessed November 30, 2017).[/cbtab][/cbtabs]
Body mass index and risk of dementia: Analysis of individual-level data from 1.3 million individuals
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/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.
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.
“Body mass index and risk of dementia: Analysis of individual-level data from 1.3 million individuals” by Mika Kivimäki’Correspondence information about the author Mika Kivimäki, Ritva Luukkonen, G. David Batty, Jane E. Ferrie, Jaana Pentti, Solja T. Nyberg, Martin J. Shipley, Lars Alfredsson, Eleonor I. Fransson, Marcel Goldberg, Anders Knutsson, Markku Koskenvuo, Eeva Kuosma, Maria Nordin, Sakari B. Suominen, Töres Theorell, Eero Vuoksimaa, Peter Westerholm, Hugo Westerlund, Marie Zins, Miia Kivipelto, Jussi Vahtera, Jaakko Kaprio, Archana Singh-Manoux, and Markus Jokela in Alzheimer’s & Dementia. Published online November 20 2017 doi:10.1016/j.jalz.2017.09.016