Multiple sclerosis (MS) is an autoimmune disorder in which the body’s immune system attacks cells in the brain and spinal cord.1,2 This causes damage to the nervous system that results in neurological symptoms such as vision problems, cognitive issues, numbness, trouble walking, tingling sensations, and incontinence. MS attacks often recur, happening repeatedly over time. Each episode can cause a lingering worsening of symptoms. In some people, MS gets worse slowly without attacks.
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Women Are at Higher Risk of Developing MS
While both men and women can develop MS, the disease is much more common in women. In fact, women are two to three times as likely to develop MS than men.3 Furthermore, there are differences in symptoms between men and women living with MS. This is due to a variety of factors, including genetics, hormones, body composition, and environmental factors4.
It is important to note that this article primarily refers to women who were assigned female sex at birth and do not have an intersex condition. Unfortunately, there is limited information about differences in how MS affects transgender or intersex people, who may have hormonal or genetic differences from the cisgender population. However, some evidence suggests that transgender women, who are assigned male sex at birth but identify as women, are more likely to develop MS than cisgender males, whether or not they are on hormone medications.5
Causes of MS in Women
Although scientists have identified many different factors tied to the increased risk of MS in women, the picture is still not entirely clear.3 That’s because we still do not fully understand the cause of MS in men or women. For example, MS is inheritable and commonly occurs in families, but the underlying risk genes are not entirely known.
Similarly, environmental factors like smoking, vitamin D insufficiency, and Epstein-Barr virus infection, which affects 90 percent of adults, are all linked to MS. Environmental factors occurring during pregnancy might be at play as well, as MS risk is linked to birth month.
Why Are Women at Higher Risk for MS? A Closer Look
As previously mentioned, neither the cause of MS nor the reason for the increased risk of MS in women is fully understood.4 However, research has indicated that risk may be increased in women due to genetics, hormone levels, body composition, and environmental factors.
Research has shown that people with two X chromosomes have an increased risk of MS, regardless of their hormonal balance.6 Although this would imply that a gene on the X chromosome may be at fault, no single gene on it has been identified that is strongly responsible for MS susceptibility.
Another genetic factor in women is X inactivation.7 During embryonic development, one copy of the X chromosome is randomly shut off in people with two X chromosomes in each cell. Although this is not directly linked to MS risk, some research indicates that this may be tied to whether a woman develops progressive MS or relapsing MS.
Hormones have a strong effect on MS symptoms, although the underlying reason is not entirely clear.3 One possible reason is the effect of hormones on inflammation.
High levels of estrogen or progesterone, two key female sex hormones involved in the menstrual cycle and pregnancy, are linked to a reduction in MS symptoms. As a result, many women have temporary relief from their symptoms during pregnancy, when estrogen levels are high for an extended time.
When hormone levels return to normal after birth, however, some women experience a relapse of their symptoms. Similarly, MS symptoms often worsen after menopause when sex hormone levels drop.
In addition to estrogen and progesterone, testosterone levels may be associated with a reduction in MS occurrence.3 Since testosterone levels are normally much higher in men than women, this could explain the increased levels of MS in women compared to men.
There are multiple environmental factors associated with MS.
Vitamin D is a fat-soluble vitamin that is activated by exposure to sunlight.8 Low vitamin D levels are associated with an increased risk of MS. Accordingly, people in higher latitudes with less intense sunlight tend to have reduced levels of vitamin D and are at higher risk of MS symptoms. Vitamin D is linked to immune function, and research suggests that it is more strongly related to immune function in women.8 As a result, low exposure to sunlight is more associated with MS risk in women than in men.
Tobacco smoking or exposure to tobacco smoke is another factor that increases a person’s chance of developing MS and worsens its symptoms. Smoking may also cause some MS therapies to not work as well.9,10 For this reason and the numerous other negative health effects associated with smoking, it is highly recommended that women with MS avoid smoking and secondhand smoke.
Body composition, in particular body fat, is linked to MS risk and MS symptoms.11 Obesity in childhood increases the risk of subsequently developing MS.12,13
Symptoms of MS in Women
The differences in male and female biology affect the kinds of symptoms that women develop in MS. For example, many women experience worsening MS symptoms during their periods.14 This includes incontinence, vision symptoms, coordination, and movement difficulties.
Some research indicates that hormonal birth control and hormone replacement therapy can soften the impact of menstruation on MS symptoms.14,15 However, any changes to medications must be discussed with your doctor. Fortunately, MS is not known to cause fertility issues.16 Furthermore, the disease is not linked to difficulties with fertility treatments.17
If you are a woman living with MS, you may experience differences in symptoms compared to men with the disease. There are special considerations for the treatment of MS in women, but with an appropriate medication regimen and lifestyle changes, you and your doctors can help manage your symptoms.