Multiple sclerosis has traditionally been considered a condition that predominantly affects white people of European ancestry. However, a new analysis suggests the neurological condition is more prevalent in Black Americans than once thought. It is also far more prevalent in Northern regions of the country including New England, the Dakotas, and the Pacific Northwest.

In 2019, researchers found the prevalence of MS in the U.S. to be nearly 1 million people, twice as many as previous estimates. In the current study a team led by University of Maryland School of Medicine researchers evaluated three years’ worth of de-identified health insurance claims of 96 million adults to locate adults living with MS. They estimated in more detail how many individuals who are age 18 or older are living with MS in various states and the MS prevalence among people of different races or ethnicities living in specific regions.

The study found strong evidence of a higher prevalence of MS in northern regions of the U.S. compared to southern regions. Numerous observational studies have linked low vitamin D levels with an increased risk of MS and with more progressive disease. Other recent research found the common Epstein-Barr virus infection greatly increased the risk for developing MS with a new study demonstrating that antibodies made by the body against the virus attack a vital protein in the brain and spinal cord.

In terms of prevalence of MS within certain sub-groups of Americans, the researchers found a higher prevalence of MS in white people, followed by Black people, “other races,” and then people with Hispanic/Latinx ethnicity. MS occurs in about 4 in 1,000 white people, about 3 in 1,000 Black people, about 2 in 1,000 people of “other races” including Asians, Native Americans, Alaska natives and multi-race individuals, and about 1.5 in 1,000 people of Hispanic/Latinx origin.

Findings from the study were published in the journal JAMA Neurology.