WEDNESDAY, Jan. 30, 2013 (HealthDay News) -- Overweight or obese children, particularly adolescent girls, may face a higher risk for developing multiple sclerosis, new research suggests.
And the heavier they are, the greater the risk, the study authors added.
The findings are preliminary, but other health risks of being overweight or obese include increased risk for high blood pressure, diabetes and heart disease -- even in children.
"Childhood MS is still extremely rare, but the health implications of being exceedingly obese are well understood," said study author Dr. Annette Langer-Gould, a neurologist at Kaiser Permanente, Southern California, in Pasadena. "This is another reason to help your child lead a healthier lifestyle and lose any excess weight."
MS affects between 8,000 and 10,000 children in the United States, according to the National Multiple Sclerosis Society. This autoimmune disease occurs when the body misfires against a part of its central nervous system -- the brain, spinal cord and optic nerves. Symptoms, which range in severity and tend to come and go, include numbness, vision problems, and gait and balance issues.
The new study included 75 children and adolescents with MS who were diagnosed between the ages of 2 and 18. Researchers compared these kids to more than 900,000 of their healthy peers enrolled in a larger health study. Slightly more than 50 percent of the children with MS were overweight or obese before they were diagnosed. By contrast, just shy of 37 percent of children without MS were overweight or obese.
This risk was more pronounced among overweight girls, the study showed. The same did not hold in boys. The findings appeared online Jan. 30 in the journal Neurology.
Like obesity in kids, childhood MS also seems to be increasing, but whether it is a true rise or if doctors are just getting better at recognizing it in children is not known, Langer-Gould explained. In the past, some symptoms may have been written off as viral or infectious in origin. Now, a better understanding of MS and the advent of imaging tests may catch more cases in kids, Langer-Gould said.
Still, she cautioned that the new study only shows that MS and childhood obesity are associated with one another. No clear cause-and-effect has been established, but there are some theories that link the two conditions.
"Estrogen in fat produces pro-inflammatory [substances], and obesity is known to be a low-grade inflammatory state," she said. "After going through puberty, girls have higher estrogen levels than boys, so overweight girls are getting a double whammy.
This may help explain why the risk was more pronounced in overweight or obese girls in the study. Most autoimmune diseases occur more frequently in women, and differences in sex hormones are thought to be one of the reasons why.
Several MS experts said it is too early to draw any conclusions about how -- or even if -- childhood obesity may increase MS risk, but they agree that the theories behind the link do make sense.
Dr. Stephen Thompson, chief of pediatric neurology at Hackensack University Medical Center, in New Jersey, said he is not seeing this trend in his practice yet.
"It is certainly plausible though," he said. "We know that MS is an inflammatory disease of the central nervous system and there are certain specific risks for inflammation, one of which would be obesity. Obesity is now an epidemic in children, so we would expect a rise in pediatric MS and that would be highly problematic."
Apart from physical disabilities related to the condition, childhood MS could affect learning and thinking ability during the school-aged years, he added. "Childhood obesity is a grave concern, and this is just another thing that may be related to it," Thompson said.
Dr. Nancy Sicotte, director of the multiple sclerosis program at Cedars-Sinai Medical Center, in Los Angeles, said the new study "provides us with more information about pediatric MS and lays groundwork for future evaluation."
However, she added, "The incidence of MS is very, very low in children. We are not seeing an epidemic of pediatric MS in concert with increase in childhood obesity."
Another expert agreed that MS is unusual in kids.
Dr. Karen Blitz-Shabbir, director of the Multiple Sclerosis Center at the Cushing Neuroscience Institute, part of the North Shore-LIJ Health System in Manhasset, N.Y, said many MS symptoms come and go over time, so they may be missed in kids.
"This study puts pediatric MS on our radar, but I don't think it is something to worry about," she said. "All children are at very low risk for MS."
As co-director of the Obesity Institute at the Children's National Medical Center in Washington, D.C., Dr. Evan Nadler is on the front line of the childhood obesity epidemic. "It is pretty well established that chronic inflammation can have deleterious effects on other organ systems such as the brain," he said.
While noting that more study is needed to establish a relationship between childhood obesity and MS, he added that "this is one more reason to prevent children from becoming obese."
Learn more about childhood MS at the National Multiple Sclerosis Society.