(RxWiki News) It's not clear what causes multiple sclerosis (MS), an immune disorder that is typically diagnosed between ages 20 to 40. But researchers are seeking more clues.
Two recent studies being presented at a conference have found possible links to MS. One study found an increased risk of MS among individuals who were obese. The other found an increased risk for the immune disorder among women who had taken hormonal birth control.
The two studies together may offer clues about risk factors for MS.
"Ask your doctor about MS risk factors."
One study, led by Jorge Correale, MD, of the Raul Carrera Institute for Neurological Research in Buenos Aires, Argentina, looked at the risk for MS among those who are obese.
The researchers compared the body mass index for 420 participants, half of whom had MS and half of whom did not. Body mass index is a ratio of a person's height to weight and is used to determine whether someone is considered obese.
The participants' BMI measurements were recorded when they were 15 and 20 years old and then at the time of the study. The researchers found that those who were obese when they were 20 years old were twice as likely to develop MS later in life than those who were not obese.
The participants with higher BMIs also showed greater levels of the hormone leptin, which is produced in fat tissue and helps the body regulate weight and appetite. Dr. Correale explained that leptin also helps regulate the immune response and can cause inflammation in the body, which may be related to its link to MS.
Meanwhile, the second study, led by Kerstin Hellwig, MD, of the Department of Neurology at St. Josef Hospital at Ruhr University Bochum in Germany, looked for links between birth control and MS.
In that study, the researchers compared 305 women, aged 14 to 48, who had MS or its precursor syndrome to 3,050 women without MS. For each woman with MS, ten other women were matched to her in terms of age and race/ethnicity. All the women were enrolled in Kaiser Permanente Southern California.
Among the women, 29 percent of those with MS and 23.5 percent of those without MS had used hormonal birth control for at least three months within the three years before the women developed MS.
Most of the women used birth control that included a combination of estrogen and progestin.
The researchers found that the women who had used any hormonal birth control in the three years before MS symptoms developed were 1.35 times more likely to develop MS. The women who had stopped taking the birth control at least a month before the symptoms began were 1.5 times more likely to develop MS.
Together, these studies suggest that obese women using hormonal birth control may have an increased risk of developing MS, though the increased risk is small.
The studies have not yet been published in peer-reviewed journals, so their findings should be considered preliminary.
The studies will be presented at the American Academy of Neurology's 66th Annual Meeting in Philadelphia in the spring.
The research in the birth control study was funded by the Kaiser Permanente Direct Community Benefit Funds, the National Institutes of Health and the German Research Foundation.
The research in the obesity study was funded by the Raul Carrera Institute for Neurological Research. No conflicts of interest were reported for either study.