New Potential Risk Factors for Multiple Sclerosis Uncovered
When the cause of a disease is elusive as is the case with multiple sclerosis, experts often look for clues in the risk factors. The findings of two new studies introduce the possibility of adding more risk factors to the MS short list and enhancing our understanding of this neurodegenerative disease.
Risk factors for MS
Currently the list of risk factors for MS includes the following:
- Age: onset most often between 20 and 40
- Gender: females are about twice as likely to develop the disease than males
- Ethnicity: whites have the highest risk, Hispanics have the next highest risk, while blacks, Asians, and Native Americans have the lowest risk
- Infection: Epstein-Barr virus and a few others may have a role in MS
- Family history: The risk of developing MS is 1 to 3 percent among people who have a parent or sibling with the disease compared with 0.1 percent among those without a family history
- Autoimmune disease: Presence of type 1 diabetes, rheumatoid arthritis, inflammatory bowel disease, or other autoimmune conditions can slightly increase the risk
- Location: People who live farther from the equator and who are exposed to less sunlight have a greater risk, which also suggests an insufficient level of vitamin D may be involved
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Potential additions to the list are obesity and the presence of leptin, a hormone associated with being overweight; and the use of oral contraceptives, or more specifically, the hormones in these products. Here are the two study results.
Obesity and MS
The body mass index (BMI) of 210 individuals with MS and 210 disease-free volunteers, all ages 15 to 20 years, was evaluated in this first study. The investigators found that:
- Individuals who were obese at age 20 were twice as likely to develop MS at a later time than the participants who were not obese
- Study subjects who were obese also had elevated levels of a hormone and protein called leptin, a substance made by fatty tissue that is responsible for regulating fat storage, appetite, and immune response. Leptin also promotes inflammation, which may be the link between obesity and MS
Another new study, which appears in the February 5, 2014 issue of Neurology, points out the relationship between obesity during adolescence and the future development of MS. More specifically, the authors investigated the interactions between human leukocyte antigen (HLA) genotype and body mass index and the risk of developing MS.
In that report, the authors looked at the findings of two case-control studies. They found that obese individuals with a specific genotype were at greater risk of developing MS than were nonobese individuals without the genetic risk factors. They concluded that “Prevention of adolescent obesity may thus lower the risk of developing MS, predominantly among people with a genetic susceptibility to the disease.”
Hormonal contraceptives and MS
A Kaiser Permanente Southern California study evaluated 305 women who had MS or the precursor of the disease, which is known as clinically isolated syndrome, and 3,050 women who were disease-free. Hormonal contraceptive use among all the women was documented.
- During the three years before onset of MS symptoms, 29 percent of women who had MS had taken oral contraceptives for at least three months
- During that same time period, 24 percent of women without MS had used oral contraceptives
- Women who had stopped taking oral contraceptives one month before their MS symptoms appeared were 50 percent more likely to develop the disease
- The majority of oral contraceptives used contained both estrogen and progestin
Overall, women who had used birth control pills were 35 percent more likely to be diagnosed with MS when compared with their peers who had not taken the hormones. The study’s lead author, Dr. Kirstin Hellwig, noted that these findings indicate that the use of hormonal contraceptives may have a role in the rise in MS among women.
The findings of these two new studies suggest several different hormones may have a role in the risk of developing MS. Now the challenge is to use this information about potential new risk factors for MS to better prevent and manage the disease.
American Academy of Neurology
Hedstrom Ak et al. Interaction between adolescent obesity and HLA risk genes in the etiology of multiple sclerosis. Neurology 2014 Feb 5