THURSDAY, Feb. 27, 2014 (HealthDay News) -- Obesity and birth control pills may play some role in the development of multiple sclerosis (MS), two new studies suggest.
One team of researchers found that people who were obese at age 20 had double the risk of developing MS in their lifetime. The researchers suspect a hormone called leptin, which influences appetite, may be causing inflammation that somehow triggers MS.
Meanwhile, a second group of scientists found that women who had taken birth control pills were 35 percent more likely to develop MS, and they suggest the hormones in the pills may have an influence in development of the disease.
"These studies are pointing us to potential factors that might contribute to MS," said Timothy Coetzee, chief research officer at the National Multiple Sclerosis Society.
However, he added that it's too soon to make any changes based on either of these studies. While both showed associations between hormones and MS risk, they did not prove a cause-and-effect link.
"There's still a way to go with the research. We need more data from both studies," said Coetzee, who was not involved with the new research.
Multiple sclerosis is a disorder of the central nervous system caused by an abnormal response of the immune system, according to the MS society. For reasons that still aren't clear, the immune system attacks a protective sheath on nerve cells known as myelin.
Common symptoms of MS include extreme fatigue, visual problems, difficulty walking, and numbness or tingling, according to the society.
In the first study, researchers from Argentina calculated the body-mass index (BMI) of 210 people with MS and 210 similar people without MS. BMI provides a rough estimate of the percentage of body fat someone has.
People who were obese at 20 were more than twice as likely to develop MS later in life as people who weren't obese. The study also found that people with higher BMIs were more likely to have higher leptin levels and lower levels of vitamin D, both of which were linked to signs of inflammation. The researchers believe it's the inflammation that may be behind the increased risk of MS.
"This study suggests that increases in leptin could have an exacerbating effect on the disease," Coetzee said. More study needs to be done to confirm this association, he said, but added, "Carrying extra weight isn't good from a general point of view, and being more active, physically fit and eating a good diet can enhance quality of life."
For those who already have MS, Coetzee said, physical activity and healthy eating can help with the fatigue, strength and mobility issues that are common with the condition.
The second study looked at 305 women with MS or its precursor -- called "clinically isolated syndrome" -- and compared them to 3,050 women without the disease. Twenty-nine percent of the women with MS used birth control pills compared with 24 percent of those without MS. Most of the women taking birth control pills used a combination pill containing both the hormones estrogen and progestin.
The women who used oral contraceptives were 35 percent more likely to develop MS, according to the study.
"These results are demonstrating an association. I don't want to say that we can firmly establish causality," said study author Dr. Kerstin Hellwig, a postdoctoral researcher at Kaiser Permanente Southern California.
If oral contraceptives do play a role in MS, Hellwig said it's probably an effect of the hormones on the immune system.
"At this point, women who take oral contraceptives shouldn't be concerned about developing MS because of oral contraceptives. It may be one of many factors, but it's not the one factor causing MS," she said.
Findings from these studies will be presented at the American Academy of Neurology's annual meeting, held April 26 to May 3 in Philadelphia. Research presented at meetings should be viewed as preliminary until published in a peer-reviewed journal.
Learn more about the causes of multiple sclerosis from the National Multiple Sclerosis Society.