Potential Impact of Air Pollution on Multiple Sclerosis in Tehran, Iran

Abstract

<b><i>Background:</i></b> Multiple sclerosis (MS) incidence has dramatically increased in Tehran, Iran. The health impact of air pollution in Tehran underscores the attention to a possible association to this environmental risk factor. In this study, the authors aimed to analyze the spatial distribution of prevalent MS cases and their association with the spatial patterns of air pollution. <b><i>Methods:</i></b> Patient records meeting McDonald's criteria for definite MS diagnosis with disease onset during 2003-2013 were obtained. Next, the location of 2,188 patients was successfully geo-referenced within Tehran metropolis by geographic information system (GIS) bureau of Iran's post office based on their phone numbers. A cluster analysis was performed using the average nearest neighbor index (ANNI) and quadrat analysis. The long-term exposures of MS patients to particulate matter (PM<sub>10</sub>), sulfur dioxide (SO<sub>2</sub>), nitrogen oxide (NO), nitrogen dioxide (NO<sub>2</sub>), and nitrogen oxides (NOx) were estimated using the previously developed land use regression models. <b><i>Results:</i></b> Prevalent MS cases had a clustered pattern in Tehran. A significant difference in exposure to PM<sub>10</sub>, SO<sub>2</sub>, NO<sub>2</sub>, and NOx (p < 0.001) was observed in MS cases compared with controls. <b><i>Conclusion:</i></b> This study revealed the potential role of long-term exposure to air pollutants as an environmental risk factor in MS.

Air pollution, a rising environmental risk factor for cognition, neuroinflammation and neurodegeneration: The clinical impact on children and beyond

“…Clustering pattern of MS prevalence patients were also observed in Tehran [109,110], and a significant difference in long term exposure to PM 10 , SO 2 , NO 2 , and NO x was observed in MS cases compared with controls [109]. A recent study in Tehran found higher relapse rate during the winter and following first month of the spring and MS relapses were correlated with NO levels [111].…”

No correlation was observed between vitamin D levels and disability of patients with multiple sclerosis between latitudes 18° and 30° South

“…Nonetheless, while there is mounting evidence that vitamin D exerts broad regulatory effects on cells of the adaptive and innate immune systems 2,3 , there is remarkably little evidence that treatment with vitamin D can influence MS evolution and prognosis 4,5,6,7 . So far, no clinical trial has provided any clear evidence that vitamin D alone can alter the course of an extremely complex disease like MS. Other vitamins 8,9,10 , genetic predisposition 11,12 and several environmental factors 13,14,15,16 may also play a substantial role in MS. However strong the role of vitamin D in the orchestra of factors associated with MS may be, this might be better seen in high-latitude countries.…”

Urban air quality and associations with pediatric multiple sclerosis

“…To our knowledge, the current study is the first to have looked at potential sources through industrial output and examine childhood exposure and MS risk. In other adult MS studies, increased exposure to larger particulate matter (PM 10 ) was related to both increased risk for MS in adults20, 23 and MS relapse using hospitalization records 18, 19, 24…”

“…Although some adult MS studies have suggested a relationship between air constituents and MS,18, 19, 20 not all of the Environmental Protection Agency (EPA) criteria air pollutants have been assessed, including fine PM 2.5 , ground level ozone precursors, and lead. Furthermore, the proximity of MS patients to industrial facilities that release toxic chemicals into the air has yet to be explored.…”