About 1.9 million people worldwide are living with multiple sclerosis, a rate of roughly 22 per 100,000 people. In the United States alone, nearly 1 million adults have been diagnosed. While MS is not among the most common neurological conditions, it is far from rare, and its prevalence has been climbing steadily over recent decades.
Global and U.S. Numbers
The 2021 global estimate of 1.9 million cases comes from tracking across 204 countries. That translates to about 1 in every 4,500 people on the planet. The United States carries a disproportionate share of this burden. A 2019 prevalence study funded by the National MS Society found almost 1 million people in the U.S. have received an MS diagnosis, roughly double what earlier estimates had suggested. A follow-up analysis in 2023 examined health insurance claims from 96 million adults across every state, reinforcing that the earlier counts had significantly undercounted people living with the disease.
Who Gets MS Most Often
MS is three times more common in women than in men, and that gap has been widening over time. The increase is driven specifically by the relapsing form of the disease, which flares and then partially or fully recovers before flaring again. The progressive form, where symptoms steadily worsen from the start without distinct relapses, affects men and women at roughly equal rates.
Most people are diagnosed between ages 20 and 40, with a mean onset age of about 33. Recent data shows the age distribution is shifting toward a two-peak pattern: one cluster of diagnoses around age 30 and a second around 40 to 45. Children can also develop MS, though it’s uncommon. Data from 53 countries identified just over 31,000 pediatric MS cases worldwide.
Breakdown by Subtype
About 85% of people with MS are initially diagnosed with the relapsing-remitting form, where symptoms come and go in episodes. The remaining 10 to 15% are diagnosed with primary progressive MS, where disability accumulates gradually from the start without clear relapses. Many people with relapsing-remitting MS eventually transition to a secondary progressive phase, where the disease shifts toward steady worsening, but this transition can take years or even decades.
Geography Matters More Than You’d Expect
One of the most striking patterns in MS is its relationship to latitude. Prevalence can increase by up to tenfold between the equator and 60 degrees north or south. Countries like Canada, Scandinavia, and Scotland have some of the highest rates in the world, while equatorial regions in Africa and Southeast Asia have some of the lowest. Within the United States, prevalence rises by roughly 16 cases per 100,000 people with each degree of latitude you move north.
This gradient appears to be set very early in life. Research shows the latitude effect is actually strongest at birth and persists through about age 12 before gradually weakening. That means where you grow up matters more than where you live as an adult. The leading explanation involves sunlight exposure and vitamin D levels during childhood, along with other early-life environmental factors that shape immune system development. People who move from a high-risk region to a low-risk one after childhood carry much of their original risk with them.
Race, Ethnicity, and Shifting Assumptions
MS was long considered a disease primarily affecting white populations, but that picture has changed substantially. Recent U.S. research has found that Black Americans develop MS at rates comparable to or even higher than white Americans, and they tend to experience more aggressive disease with faster disability progression. Hispanic and Asian American populations have lower but still significant rates. The older assumption that MS is a “white disease” likely reflected gaps in diagnosis and access to care rather than true differences in who gets it.
Is MS Becoming More Common?
Yes, and the increase is real, not just an artifact of better detection. The global age-standardized prevalence rate has been rising steadily since at least 1990. Better diagnostic tools like MRI certainly play a role in identifying cases that would have been missed in earlier decades, but that alone doesn’t account for the trend. The increase is most pronounced among women with relapsing MS, suggesting that environmental or lifestyle changes over the past several decades are shifting risk in ways researchers are still working to understand. Factors under investigation include changes in obesity rates, shifts in smoking patterns, altered gut bacteria from modern diets, and reduced childhood sun exposure as more of the world’s population moves indoors.
At current trajectory, the global number of people living with MS is expected to continue climbing through at least the 2050s, driven both by rising incidence and by longer survival thanks to improved treatments keeping people alive and functional for decades after diagnosis.