Environmental factors in MS: Air and vitamin D


REPORT FROM THE ACTRIMS-ECTRIMS – BOSTON, MA, SEPTEMBER 10-13, 2014 – Few studies have examined the potential impact of ambient air quality and airborne particulates on multiple sclerosis. A decade ago, a study in Finland suggested that the frequency of MS relapses was higher with increasing levels of inhaled particulates (Oikonen et al. Neuroepidemiology 2003;22:95-99).

A study at UCLA now suggests that exposure to air pollution may be associated with an increased risk of disability  (Amezcua et al. ECTRIMS 2014; abstract P366). A total of 68 Hispanic MS patients were included in the study. The distance from subjects’ homes to main roads was used as a surrogate for exposure to traffic-related air pollution. For the group who lived closer to main roads, the mean EDSS score was 5.1; for those who lived farther away from high-traffic areas, the mean EDSS score was 3.4. After adjustment for age at presentation, sex and other factors, MS patients living < 150 metres from a main road were six-fold more likely to have impaired ambulation, and a worse EDSS score (mean 1.82 points) than those living farther away from traffic.

The interaction between air pollution and vitamin D was examined by researchers in Iran (Heydarpour et al. ECTRIMS 2014; abstract P332). The geographic location of 2,188 MS patients in Tehran was used to determine the long-term exposure to airborne particulates, sulphur dioxide, and nitrogen oxides. Vitamin D levels were also measured in a subgroup of 580 patients. The analysis demonstrated that the main impact of air pollutants could be attributed to particulates and sulphur dioxide, with a significant difference in exposure to particulates, sulphur dioxide, and nitrogen dioxide in MS cases versus controls. Serum 25(OH)D levels were not correlated with pollutants.

A novel study in Finland examined vitamin D levels during pregnancy to investigate whether they were associated with the offsprings’ MS risk in later life (Munger et al. ECTRIMS 2014; abstract P330). The data used were from the Finnish Maternity Cohort of over 800,000 women who have provided at least one blood sample from at least one pregnancy since 1983. From that sample, 193 offspring were identified as having developed MS and for whom maternal serum 25(OH)D levels were available. Overall, 99% of serum samples were collected prior to 28 weeks’ gestation (70% before 12 weeks). In utero 25(OH)D levels were associated with a 41% decreased risk of MS for the top versus bottom quintile (median 56.8 vs. 21.1 nmol/L). Adjusting for the sex of the offspring weakened this relationship, although the overall trend remained statistically significant. Thus, exposure to adequate vitamin D levels in utero may protect against the development of MS in later life.

Guest Reviewer: Dr. Daniel Selchen, St. Michael’s Hospital, Toronto, Ontario.

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