Vitamin D’s role?
Several mechanisms might help explain the relationship between air pollution and MS risk, he added. These include oxidative stress, which results in cell damage, inflammation, and proinflammatory cytokine release. Vitamin D also likely plays some role, Dr. Bergamaschi said. Upon penetrating the lower strata of the earth’s atmosphere, ultraviolet B radiation is absorbed and scattered by suspended pollutants.
Several studies have highlighted the correlation between living in a polluted area and vitamin D hypovitaminosis; “so air pollution can contribute to increasing the risk of MS by reducing vitamin D synthesis,” he said.
Recent research has also shown that air pollution is associated with a higher risk for other autoimmune disorders, including systemic lupus erythematosus, rheumatoid arthritis, and type 1 diabetes mellitus.
However, pollution alone is only part of the picture. MS prevalence in highly populated and polluted countries such as China and India is low, with no more than 30 to 40 cases per 100,000 population, Dr. Bergamaschi noted. “This discrepancy is explained by different genetic backgrounds. While Caucasians are particularly susceptible to MS, Asians are not,” he said.
Study limitations cited included a possible bias because the analysis did not include other possible contributing risk factors, particularly other pollutants, Dr. Bergamaschi said.
Commenting on the research, Lily Jung Henson, MD, chief of neurology at Piedmont Healthcare in Stockbridge, Georgia, said the findings provide “a fascinating glimpse” into possible causative factors for MS and warrant further investigation.
“This research also suggests other opportunities to look at, such as progression of the degree of air pollution and the incidence of MS over time,” said Dr. Henson, who was not involved with the study.
Drs. Bergamaschi and Dr. Henson have reported no relevant financial relationships.
This article first appeared on Medscape.com.