Obesity in girls tied to higher multiple sclerosis risk

New research suggests that obese kids - adolescent girls, in particular - are more likely to be diagnosed with multiple sclerosis (MS) than normal-weight youth.

That doesn't prove carrying around some extra weight in childhood causes MS - in which the protective coating around nerve fibers breaks down, slowing signals traveling between the brain and body.

But it does suggest rising levels of obesity in young people could mean more MS diagnoses than in the past, according to lead study author Dr. Annette Langer-Gould from Kaiser Permanente of Southern California and her colleagues.

"Obesity is increasing the risk of so many different kinds of diseases," said Kassandra Munger, who studies MS at the Harvard School of Public Health in Boston but was not involved in the new work.

"This current study now adds to the evidence that it's also dangerous and increases the risk of neurological diseases, such as multiple sclerosis," Munger told Reuters Health.

For their study, Langer-Gould and her colleagues compared the heights and weights of 75 kids with pediatric MS and its possible precursor, a condition called clinically isolated syndrome - and more than 900,000 kids without the diseases.

Just over half of the kids and teens with MS were overweight or obese, compared to 37 percent of other youth, according to findings published Wednesday in the journal Neurology.

Being overweight or moderately obese was tied to a slightly higher chance of MS in adolescent girls, but the results were based on a small number of cases and could have been due to chance. Extreme obesity, on the other hand, was linked more clearly with a three- to four-fold higher risk of MS.

A five-foot, 12-year-old girl is considered overweight at 112 pounds and extremely obese at over 155 pounds.

There was no clear pattern between boys' weights and how likely they were to be diagnosed with MS, Langer-Gould's team found.

Roughly 400,000 people in the United States have MS - usually diagnosed in adulthood. Just one or two out of every 100,000 children are diagnosed with pediatric MS, Langer-Gould said.

Based on limited evidence about any effects of weight, she said she was "actually surprised" her team found any link with MS risk.

"It's not something we think of as a risk factor for multiple sclerosis," Langer-Gould told Reuters Health.

According to Munger, there are a number of possible explanations for why heavy people could be at increased risk, including their vitamin levels and the greater amounts of chemicals - such as inflammation-inducing signaling molecules - secreted by their fat cells.

But, "It's not easy to tease those out," Munger told Reuters Health. "From a biological perspective, we don't know what the link is between obesity and MS."

Langer-Gould and her colleagues are continuing to track children in their study over time and are also working on another project to see if adults' weight affects their chance of developing MS.

"MS in children is extremely rare, but this is one more reason to encourage children to be a healthy weight," she said.