Could Avoiding Obesity Reduce Risk of Multiple Sclerosis?
Previous research has suggested a link between obesity and an increased risk of multiple sclerosis, but some experts have questioned the validity of those findings because of bias related to study design. Now a new study has clarified the association between obesity and MS risk, using a model shown to significantly minimize bias and establish causality.
Previous studies of obesity and multiple sclerosis
In earlier studies of obesity and the risk of multiple sclerosis, researchers used prospective study designs, which are capable of minimizing or eliminating bias from some sources, but unable to account for other confounding factors that could have an impact on the results. Among those former studies were two:
- One that showed a greater than twofold risk of developing MS among women who had a body mass index (BMI) of 30 or greater (obesity) at 18
- One in which individuals whose childhood BMI was in the 95th or greater percentile were 70 percent more likely to develop multiple sclerosis than their peers with a childhood BMI of less than 85th percentile.
Both of these studies, and several others, have suggested an increased risk of developing MS in the presence of obesity, yet researchers wanted more reliable information.
New obesity and MS study
In this new study, the authors used the Mendelian randomization (MR) approach, named after Gregor Mendel, who developed the main principles of inheritance and genetics. This approach is straightforward and, according to the authors, one that “further minimizes bias, as genetic variations are expected to be randomly inherited and thus not subject to confounding.”
Once the research team from the Jewish General Hospital in Quebec, Canada, used the Mendelian model using large population data sets, they reported the following:
- That a change in BMI status from overweight to obesity was linked with a 40 percent increased risk of developing multiple sclerosis. Such a change in BMI is equivalent to an average woman increasing her body weight from 150 to 180 pounds.
- That a high BMI promotes a “proinflammatory state,” which in turn has an impact on the immune system
- That “it has been proposed that adipose-derived hormones [derived from fat], such as leptin and adiponectin, might mediate this, providing a possible mechanistic link between obesity and risk of MS.”
Although these findings don’t have a direct impact on individuals who are now living with multiple sclerosis, they can serve as motivation to prevent or fight obesity among young people, as the median age of onset of MS is 28 to 31 years. The time to put the brakes on obesity is much younger, however, especially given that the childhood obesity rate is already at 17 percent.
The authors emphasized that their findings provide “evidence for a causal role for obesity in MS etiology” as well as “suggest an important consequence of childhood and/or early adulthood obesity.”
Ascherio A, Munger KL. Weighing evidence from Mendelian randomization—early-life obesity as a causal factor in multiple sclerosis? PLoS Medicine 2016 Jun 28; 13(6): e1002054
CDC. Childhood obesity facts
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