Who Gets MS?
Estimating the number of people with MS, both in the United States and around the world, has posed many challenges. However, as international groups work together to provide data, reports such as those from the “Atlas of MS” have provided reliable figures, which are critical to the continued research into the etiology and treatment of MS. Many of the figures noted in this section are from this report, which may be accessed by visiting www.atlasofms.org, published by the MS International Federation.
Current estimates bring the worldwide MS population to nearly three million and the United States MS population to nearly one million. In addition, according to the figure of roughly eight newly diagnosed individuals per 100K citizens in the United States each year, the average number of newly diagnosed people per year is thought to be more than 25,000.
Most people with MS experience their first symptoms and are diagnosed between the ages of 20 and 50, although individuals of any age may be diagnosed with MS. MS in childhood and adolescence is now being diagnosed more frequently, due in part to an increased awareness that children can be diagnosed with MS. Known as pediatric MS, diagnosis in children has its own challenges, as experts have identified more than 40 common diseases that may initially behave similarly to early MS.
The most recent information available estimates that at least 30,000 individuals under the age of 18 have been diagnosed with MS worldwide. In the United States, most estimates range from 5,000 to 10,000 children and teens with MS. Additional studies are needed to determine a more precise number of children with pediatric MS living in the United States.
The distribution of this disease is not totally random. On average, women are three times more likely than men to develop relapsing forms of MS. However, with the primary-progressive form, genders are more equally divided. More information is provided on the different types of MS in the next section of this booklet.
Geographically, people who live farther from the equator (in more temperate climates) have a higher risk of developing MS than people living in hotter areas near the equator, or in very cold areas near the north or south poles. Individuals living beyond the 40-degree mark north or south of the equator are far more likely to develop MS, and this is especially true for people in North America, Europe, and Southern Australia.
MS is very rare in Inuit populations living in the far north. Asia continues to have a lower incidence of MS. More prevalent among those of northern European or Scandinavian ancestry, Caucasians have a higher incidence than those of African heritage to develop MS.
African Americans and Asians tend to have more symptoms at the time of diagnosis, which are usually limited to the optic nerves and spinal cord, and this is termed “opticospinal MS.” This means that African Americans and Asians may experience more problems with vision and mobility, versus other common MS symptoms.
African Americans may be older at disease onset, and the disease course tends to be more aggressive, with more frequent relapses and higher lesion volume. Additionally, African Americans are thought to respond less to disease-modifying therapies, although studies are being conducted to see which medications are the most effective for this ethnic group.
Hispanic Americans are often diagnosed at an earlier age than Caucasian Americans, and a larger percentage are diagnosed with relapsing forms of MS versus the primary-progressive form of MS. This population is also more likely to present with opticospinal MS (largely involving visual and mobility symptoms), optic neuritis (inflammation along the optic nerve), and/or transverse myelitis (causing inflammation in one location across both sides of the spinal cord).
Hispanic Americans have a much lower risk of MS compared to Caucasian Americans and African Americans. However, clinical observation reveals greater spinal-cord involvement, which more significantly affects ambulation, but more studies are needed to confirm this observation.
In general, studies continue to evaluate all of these trends among the different ethnic groups as diagnostic techniques and evaluative measures become more advanced and data become more readily available.
While MS is not contagious or hereditary, MS susceptibility is increased if a family member (blood relative) has MS. The average risk of developing MS in the United States is approximately three in 1,000. For first-degree relatives (such as a child or sibling), the risk increases to 3% or 4%, which is three or four in 100 people. This is not true for adopted children or half siblings who do not share the same parent who has MS. Both of these latter groups have a risk that is the same as unrelated individuals.