Obesity linked to increased risk of multiple sclerosis

Individuals who are obese in early adulthood face a heightened risk of developing multiple sclerosis (MS), according to new research conducted by Dr. Brent Richards of the Lady Davis Institute at the Jewish General Hospital, Quebec, Canada and colleagues, published in PLOS Medicine. This result provides further confirmation of previous observational studies that had suggested the existence of such a link. MS is a progressive neurological disorder which can lead to disability and death, involving damage to the myelin which surrounds nerves in the spinal cord and brain. Causes of the disease are poorly understood, although immune-mediated mechanisms are likely. Currently available treatments have only modest effects on the disease and its symptoms, which underlines the importance of identifying preventive measures.

The team, comprised of researchers in Canada and the UK, and led by Lauren Mokry, carried out a Mendelian randomization study in large population datasets to investigate whether genetically determined obesity was associated with increased risk of MS. Such a study decreases the probability that exposures linked to obesity, such as smoking, can explain the findings. They found that a change in body mass index from overweight to obese (equivalent to an average size adult woman increasing in weight from 150 to 180 pounds) was associated with an increase of about 40% in the risk of MS.

"These findings may carry important public health implications because of the high prevalence of obesity in many countries" note the authors in their research article; "[because the] median age of onset for MS is 28-31 years ... [these findings should provide motivation] to combat increasing youth obesity rates by implementing community and school-based interventions that promote physical activity and nutrition."

In a Perspective discussing the research, Alberto Ascherio and Kassandra L. Munger note that, factoring in earlier research, Richards and colleagues' study "suggest[s] that obesity in early life is indeed causally related to multiple sclerosis risk and provide[s] a further rationale for obesity prevention."

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JBR and LEM are supported by the Canadian Institute of Health Research. JBR is supported by Fonds de la recherche en sante du Quebec (FRSQ) and Merck. NJT and GDS work within the Medical Research Council Integrative Epidemiology Unit at the University of Bristol (MC_UU_12013/1&3). SS is supported by the Cambridge NIHR Biomedical Research Centre. The funders played no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication.

GDS is a member of the Editorial Board of PLOS Medicine. The other authors declare that no competing interests exist.

Mokry LE, Ross S, Timpson NJ, Sawcer S, Davey Smith G, Richards JB (2016) Obesity and Multiple Sclerosis: A Mendelian Randomization Study. PLoS Med 13(6): e1002053. doi:10.1371/journal.pmed.1002053

Department of Epidemiology, Biostatistics and Occupational Health, McGill University, Montreal, Quebec, Canada

Centre for Clinical Epidemiology, Department of Epidemiology, Lady Davis Institute for Medical Research, Jewish General Hospital, McGill University, Montreal, Quebec, Canada

MRC Integrative Epidemiology Unit, School of Social and Community Medicine, University of Bristol, Bristol, United Kingdom

Department of Clinical Neurosciences, Cambridge Biomedical Campus, Cambridge, United Kingdom

Department of Medicine, McGill University, Montreal, Quebec, Canada

Department of Human Genetics, McGill University, Montreal, Quebec, Canada

Department of Twin Research and Genetic Epidemiology, King's College London, London, United Kingdom

IN YOUR COVERAGE PLEASE USE THIS URL TO PROVIDE ACCESS TO THE FREELY AVAILABLE PAPER: http://journals.plos.org/plosmedicine/article?id=10.1371/journal.pmed.1002053

J. Brent Richards
brent.richards@mcgill.ca

Work is funded by NIH/NINDS grant R01NS073633 (PI: AA) http://www.ninds.nih.gov/. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

The authors have declared that no competing interests exist.

Ascherio A, Munger KL (2016) Weighing Evidence from Mendelian Randomization--Early-Life Obesity as a Causal Factor in Multiple Sclerosis? PLoS Med 13(6): e1002054. doi:10.1371/journal.pmed.1002054

Harvard T. H. Chan School of Public Health, Harvard University, Boston, Massachusetts, United States of America

IN YOUR COVERAGE PLEASE USE THIS URL TO PROVIDE ACCESS TO THE FREELY AVAILABLE PAPER: http://journals.plos.org/plosmedicine/article?id=10.1371/journal.pmed.1002054