Yes, women do get MS more often than men. Approximately 70% of all of the patients diagnosed with MS are women. This is even more so for women under the age of 30 years. Almost four of every five persons with onset of illness under the age of 30 years will be women. In contrast, the onset of MS after the age of 40 years is slightly more common in men.
The reason for MS occurring more frequently in women than in men is unknown. Female experimental animals develop demyelinating disease more predictably and of greater severity than males. This and the fact that women have decreased disease activity during pregnancy suggest that sex hormones influence disease activity. The finding that a hormone, which is a “placental estrogen,” has a favorable effect in women with MS supports this theory. The administration of this oral estrogen prevented new active brain lesions in a recent MRI study.