Regular workouts may cut a woman's chances for heart disease and certain cancers, but new research suggests they won't lower the risk of multiple sclerosis (MS).
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The new study "did not provide evidence to support" the notion that exercise lowers MS risk, said study author Kassandra Munger, of the Harvard School of Public Health in Boston.
For the study, Munger's group tracked data on more than 193,000 American women involved in the Nurses' Health Study and Nurses' Health Study 2.
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These women were followed for up to 20 years. They had to fill out questionnaires regarding their current physical activity as well as the exercise they got when they were growing up. Munger's team used this information to calculate the number of hours the women exercised each week.
Over the course of the study, 341 of the women were diagnosed with MS. After considering a number of other factors such as age of the women, type of exercise, where they lived growing up, smoking status and whether or not they took vitamin D supplements, the researchers found no link between exercise and MS.
The study was published online in Neurology.
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"Overall, there was no consistent association of exercise at any age and MS," Munger said in a journal news release. "Exercise has been shown to be beneficial to people with the disease, but it seems unlikely that exercise protects against the risk of developing MS."
Two experts said exercise still has a big role to play in fighting MS, however.
"While this study did not show overall prevention in MS, many studies have shown that moderate exercise reduces MS symptoms and relapses," noted Dr Paul Wright, chair of neurology at Long Island Jewish Medical Centre in New Hyde Park, New York.
Dr Leslie Saland is a neurologist at Northern Westchester Hospital in Mount Kisco, New York. She agreed with Wright, saying that "studies have confirmed that exercising has countless benefits ranging from improving cognition and mood to increasing strength and balance in MS patients".
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Symptoms of multiple sclerosis