According to new research published in the Multiple Sclerosis Journal, environmental factors appear to play a much greater role in the onset of multiple sclerosis (MS) than previously recognized. The study, “Ethnicity and prevalence of multiple sclerosis in east London,” was led by scientists at Queen Mary University of London and Barts Health NHS Trust.
Residents of African and South Asian ancestry in east London were recently found to have a higher prevalence of MS than individuals in their ancestral countries, suggesting environmental factors strongly influence the development of the disease.
Epidemiological studies of MS prevalence and incidence suggest that ethnicity also may be a risk factor. Both MS incidence and prevalence are significantly higher among whites than people of other ethnicities, and associated environmental factors often include vitamin D deficiency and viral infections.
“MS is a disease where genetic ancestry and environmental factors play a role, however to what degree these two aspects are driving the risk of developing MS remains unknown,” Dr. Klaus Schmierer, the study’s lead author, said in a press release. “We found that people of Asian and African extraction in London are far more likely to have MS than people of the same ethnicity living in their ancestral countries. Our early results suggest that environmental factors play a pivotal role in the risk of developing MS, whilst the individual genetic backdrop may be of lesser importance.”
The researchers used electronic records from general practices (GPs) in four east London boroughs, and grouped people diagnosed with MS according to their ethnicity.
Of the 907,151 patients registered with GPs in east London, 776 had a diagnosis of MS. The overall prevalence of MS was 111 per 100,000 people (152/100,000 for women and 70/100,000 for men), and 180, 74, and 29 per 100,000 for the area’s white, black, and South Asian populations, respectively. In comparison, the prevalence of MS in the African country Ghana is 0.24 per 100,000 people; in India, it’s 7 per 100,000; and in Pakistan, it’s 5 per 100,000.
While these difference could be justified by fewer MS diagnoses being made in less wealthy countries, that is unlikely to justify the gap in prevalence found, Dr. Schmierer said, adding that an alternative explanation is increased exposure in the U.K. to environmental agents that lead to MS.
“If we can clearly define the cluster of risk factors, and their proportional relevance, measures could be developed to change or remove these factors — thereby potentially eradicating MS, which is our ultimate goal,” Dr. Schmierer said.
According to the research team, the findings must be interpreted with caution when generalized to the rest of the U.K. because of the risk of selection bias. It is possible that the black and South Asian populations of east London are not representative when compared to black and South Asian populations throughout the U.K.
MS is an inflammatory demyelinating and neurodegenerative disease of the central nervous system. It is the most common chronic nontraumatic cause of disability in young adults, with a current prevalence rate between 100 and 200 per 100,000 in the U.K. The cause of the disease is unknown, although evidence indicates that it is a complex disease with various contributing factors.