Obesity Linked to Multiple Sclerosis

Adolescent obesity is strongly associated with increased risk of multiple sclerosis later in life, according to a recent Harvard School of Public Health study that analyzed data from more than 200,000 women over a period of 40 years.

The study, published online on Nov. 9 in the journal “Neurology,” found that women ages 18 to 20 who were obese had more than twice the risk of developing MS—a degenerative disease of the nervous system in which the immune system attacks the brain or optic nerves and that currently affects more than 400,000 people in the US.

This is the first study to articulate an association between obesity and MS, according to the researchers.

“We have shown a previously unidentified risk factor for MS,” said Tanuja Chitnis, an assistant professor of neurology at Harvard Medical School and a co-author of the paper. “The results may have implications for reducing obesity in adolescence, which is certainly a big concern today.”

According to the researchers, a surprising finding was that the results showed a significant link to increased MS risk only from obesity during adolescence, but not during childhood or adulthood.

“It suggests that during adolescence or early adulthood, there may be a critical window for development of MS,” Chitnis said.

Kassandra Munger, a research associate at HSPH and the lead author of the paper, had previously conducted a study linking low levels of Vitamin D to increased MS risk.

Since obesity is known to be linked with lower levels of Vitamin D, the researchers decided to investigate the link directly.

The study suggests that several factors influencing obesity could be responsible for the increased risk of the autoimmune disease, including low levels of Vitamin D and the inflammatory chemicals secreted by fatty tissue.

Further research needs to be conducted to confirm whether the association can be extended to males and people of other ethnicities.

“Based on this study in women, it is not clear whether the same would hold true for teenage boys,” said the National Multiple Sclerosis Society in an official statement on the study.

“The authors comment that while a strength of this study is the large sample size, the reliance on ‘self-report’ is a limitation.”

Data used in this study was obtained by the researchers from the Nurses’ Health Study and Nurses’ Health Study II, which are run by Harvard Medical School and Harvard-affiliated hospitals and laboratories.

—Staff writer Helen X. Yang can be reached at hxyang@fas.harvard.edu.

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