Multiple Sclerosis: Why Are Women More at Risk?
Every week in the U.S., about 200 people are diagnosed with multiple sclerosis, or MS. According to the National Multiple Sclerosis Society, four times as many women have MS as men, and more and more women are developing it. Why? Is it genetics? Is it hormones or some other aspect of being female?
Peter Calabresi, M.D., Ph.D. , is the director of the Johns Hopkins Multiple Sclerosis Center. His team, including MS expert Ellen Mowry, M.D., is combining research with clinical treatment for a better understanding of the disease, including why it’s more common in women.
The basic cause of MS has yet to be discovered. The disease has been linked to a number of risk factors, including smoking and stress. But more studies are also pointing to the roles of female hormones, vitamin D, inflammation and even obesity.
Hormones and Other Female Factors
When a condition affects women more than men, scientists are likely to take a look at the role of sex hormones such as testosterone and estrogen.
Between boys and girls, Mowry says there’s less difference in the rate of MS among children before puberty, but in older children and adults the trend changes, striking more females in adolescence and adulthood.
Pregnancy also affects MS remissions and relapses. During pregnancy, some women with MS notice a lessening of symptoms. This can be followed by a flare-up after the baby is born. Postpartum relapse is a recognized phenomenon among MS researchers and patients.
Calabresi says newly diagnosed women should consider participating in clinical trials that are homing in on new treatments and better symptom management during childbearing.
“Women with MS can give birth to healthy babies but should discuss concerns and risks carefully with their doctor,” Mowry says. “After children are born, we stress to new moms the importance of keeping kids active and at a healthy weight to lower their risk of getting MS.”
Research Shows MS: What Happens
With MS, like other autoimmune diseases such as lupus, your body’s immune system (which is designed to fight germs and other invaders that threaten your health) mistakenly turns against your own tissues.
In the case of MS, the body’s inflammatory defenses attack myelin, the insulation that covers and protects the nerves. Like a worn electrical wire, a nerve cell with faulty myelin can “short circuit” and affect the transmission of signals to and from the brain.
The condition affects nerves in the brain and spinal cord, resulting in pain, numbness and weakness striking different areas of the body. Relapsing-remitting MS (RRMS) is the most common type. With RRMS, symptoms can change, affecting different areas of the body, or disappear (remit) and then recur (relapse).
Body Fat and Obesity
How could weight affect someone’s chances of getting MS? Inflammation plays a role in MS, and obesity is linked to inflammation.
Mowry says that the rising incidence of MS among women may relate to body fat. Obesity is epidemic in the U.S., with over a third of American adults at a body mass index of 30 or higher.
Women typically carry more fat on their bodies than men, and obesity rates are higher for women as well. Belly fat, in particular, is associated with increased inflammation.
Carrying extra body weight may be especially risky for women. Mowry says, “The inflammation chemicals in women’s bodies are different from those in men, and focusing research on these may provide clues as to why more women are affected.”
Vitamin D Deficiency
Calabresi, Mowry and their team are leading the research effort on the role of vitamin D in MS. In general, MS affects more people living farther from the equator. The skin absorbs vitamin D from sunlight. Researchers are looking at the relationship between low vitamin D levels and a higher risk of developing MS, increased frequency of relapses and greater negative impact of the disease on patients’ lives.
Mowry points out that higher vitamin D levels in patients with fewer relapses may also be linked to another factor, such as exercise. It could be that patients who are outdoors exercising absorb more vitamin D, but that the exercise itself could be lessening the MS symptoms. Conversely, Mowry says, patients who are more disabled by their MS may be spending more time indoors, which could result in less sun exposure and lower stores of vitamin D.
Mowry’s studies are exploring whether taking vitamin D supplements can help reduce the number of relapses in patients with the relapsing-remitting type of the disease.
Precision Approaches to MS
Calabresi is the director of the Johns Hopkins Precision Medicine Center of Excellence for Multiple Sclerosis , an exciting new precision medicine initiative where patients with MS can get an individualized approach to therapy while providing essential data for researchers.
“It’s important for women and men alike with MS to get on the best therapy for them as early as possible,” Calabresi says.
As research reveals more about how genetics, environment and other factors increase a woman’s chances of developing MS, new ways to address the disease are likely to emerge.