Researchers have established that MS affects women more often than men — it’s three times more common in women in the U.S. than in men, according to the National Multiple Sclerosis Society. Now, a new study has found that women and men may experience this condition differently as they age. At younger ages, women tend to experience more relapses than do men. Additionally, older men are more likely than older women to experience neurodegeneration (loss of nerves).
In the study, published in April in the Journal of Neurology, Neurosurgery & Psychiatry, Danish researchers analyzed data from 6,619 women and 3,028 men with MS. Some study participants had relapsing-remitting MS and others had primary progressive multiple sclerosis. The researchers measured the participants’ relapses and ability to function. They also identified key sex differences.
This research may help people living with MS and their health care providers better understand how the condition may manifest and develop over time.
Health experts use the term “disease activity” to describe how aggressive a condition is. A person who has new MS symptoms or experiences relapses (periods of time in which symptoms get worse) has more disease activity.
In the new study, researchers determined participants’ disease activity based on how often they had relapses. The researchers found that, overall, women were 16 percent more likely to experience MS relapses compared to men.
However, relapse rates didn’t stay consistent over time. For people under the age of 50, women had MS relapses at a higher rate. However, among people aged 50 and older, women and men had about the same number of relapses.
Differences in sex hormones may explain the increased risk of relapse for younger women. During puberty, women start producing hormones that affect sexual development, menstruation, and fertility. The body stops producing these hormones during menopause, which occurs at an average age of 51 among American women. Around this age, MS disease activity becomes similar in women and men.
Other studies also show that sex hormones could affect MS. For example, MS symptoms may worsen for some women during menstrual periods, and they may change following menopause.
Learn more about symptoms of MS in women.
Another important measure of multiple sclerosis is disability — the way the condition affects a person and the extent to which it impacts their functions.
Doctors often measure disability with the Expanded Disability Status Scale (EDSS). This assessment tool provides a score on a scale from 0 to 10. People with a lower score have less disability — they can walk without assistance and experience a limited amount of other MS issues. Those with a higher EDSS score have more disability. They may not be able to walk as well, or at all. They may also have impairments in other areas, such as:
In the study, researchers found that all participants’ EDSS scores increased over time, meaning their function became worse. However, men’s EDSS scores were more likely to rise at a faster rate. This means that they had a higher risk of experiencing more neurodegeneration and worse functioning. The differences in disability between women and men became more prominent after people reached the age of 45.
Health experts aren’t entirely sure why men with MS tend to experience neurodegeneration compared to women with the condition. This difference in disease course also may be caused by specific sex hormones.
The sex hormone estrogen, which is generally found at higher levels in women than in men, may help protect nerves from damage. Lower levels of estrogen may lead to more loss of nerves and worse function for those with MS.
Another sex hormone, testosterone, is usually found at higher levels in men than in women. Testosterone may also help protect the nerves. However, levels of testosterone tend to slowly decrease over time in aging men. This may help explain why men tend to have worsening disability levels as they age.
Scientists aren’t entirely sure why the risk of MS is different in men and women, but there may be several explanations:
Read more about why women are more likely to develop MS.