About 400,000 Americans and 2.5 million people worldwide suffer from MS.
Onset generally occurs between the ages of 20 and 50 years in 70% of patients with the average age about 30. It rarely develops before age 15 or after age 60.
MS is about 2.5 times more common among women than men. The gender gap is strongest among people who develop MS at a younger age. However, some research indicates that men may be more disabled by the disease than women.
Race and Ethnicity
Multiple sclerosis occurs worldwide but is most common in Caucasian people of northern European origin, especially those of Scottish descent.
A family history of the disease may put some people at risk for MS, although the risk for someone inheriting all the genetic factors contributing to MS is only about 2 - 4%. Some research indicates that family members who have MS tend to develop the disease at around the same age. However, family history does not predict whether one family member will experience the same disease severity as another family member.
Possible Protective Factors
Estrogen and Oral Contraceptives. Higher estrogen levels may temporarily lower the risk of developing multiple sclerosis. Studies indicate that oral contraceptives (which contain estrogen) and pregnancy delay the onset of multiple sclerosis. The risk for a first clinical attack increases, however, in the first 6 months after a woman gives birth.
Review Date: 06/17/2010
Reviewed By: Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.