Multiple sclerosis (MS) is a progressive neurodegenerative condition, where the body’s immune system mistakenly attacks the myelin sheath that insulates nerve fibers. This disrupts the electric signals traveling along the nerve fibers from the brain to the rest of the body and back, and leads to symptoms such as numbness and tingling, muscle spasms, walking difficulties, and pain. 

MS symptoms usually appear when a person is between the ages of 20 and 50. However, the disease can also occur in young children and the elderly.

Is MS more common in men or women?

MS is more common in women than men, with recent studies suggesting that women are three times as likely as men to have MS.

How many people have MS?

MS is estimated to affect about one million people in the U.S. and about 2.5 million worldwide. Estimates in the U.S. used to be much lower, at around 400,000. However, a study published in the journal Neurology in 2019 showed this to be an under-representation. The worldwide numbers might, therefore, also be much higher.

The National MS Society funded the study to get better estimates of the prevalence of the disease. The study used a new method to get the numbers of people with MS in 2010 from insurance company data, and then applied the updated method to estimate numbers in 2017.

The last study of the prevalence of MS in the U.S. was conducted in 1975. This is mainly because the Centers for Disease Control and Prevention does not require U.S. health practitioners to report new cases. Previous prevalence estimates were extrapolations of this 1975 data.

What is the prevalence of MS?

The prevalence of a disease is the number of people who have that disease compared to the general population. In the U.S., the prevalence of MS was 309.2 per 100,000 people in 2010. Researchers projected this to be 337.9 to 362.6 per 100,000 people in 2017.

The prevalence of MS varies with location and increases with distance from the equator. It is unclear whether this variability has to do with an environmental influence such as vitamin D deficiency due to a lack of sunshine, genetic factors, or something else.

 

Last updated: March 5, 2020

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