Italians residing in areas with high air pollution levels had a significantly greater risk of developing multiple sclerosis (MS) than those who lived in areas with cleaner air, researchers said.
MS risk was 29% higher among people in urban areas with higher levels of air contamination than among people in rural areas, even after adjusting for urbanization and deprivation, reported Roberto Bergamaschi, MD, PhD, of IRCCS Mondino Foundation in Pavia, Italy, and colleagues.
"Our findings confirm that air pollution can be one of the risk factors for MS and should be analyzed in future together with the other, already known risk factors," Bergamaschi said.
"Counter measures that cut air pollution will be important for public health, not only to reduce the deaths related to cardiac and pulmonary diseases, but also the risk of chronic autoimmune diseases such as MS," he told MedPage Today.
The findings at the 2020 Congress of the , which was held as a virtual meeting due to the COVID-19 pandemic.
Some have been associated with increased MS risk, and air quality might play a relevant role, Bergamaschi noted.
"The goal of the study was to further confirm the role of air pollutants as a risk factor for MS, performing our research in a well delimited geographical area, the province of Pavia in Northern Italy located in the Po valley," he said.
That area is affected by high levels of particulate matter concentrations due to high emissions from many industries, he noted. It also has "peculiar geographical features -- the natural barrier of the Alps extending north -- and low wind speed that favors the formation and accumulation of pollutants," he added.
Air quality is assessed by evaluating particulate matter (PM), a mixture of solid particles and droplets in the air. PM2.5 particles have a diameter of 2.5 micrometers or smaller. Particulate matter has been tied to various health conditions, including heart and lung disease, cancer, and respiratory issues.
The researchers looked at the association between PM2.5 levels and MS prevalence in 188 municipalities in the province of Pavia, adjusting for age, degree of urbanization (using the European system), and deprivation index (including low education level, lack of employment, percentage of occupied, single-parent families, and high housing density), using a Bayesian mapping approach.
"We found an MS prevalence of 169 per 100,000 population," Bergamaschi said. "This is 10-fold the value that was collected 50 years ago in the same area."
The researchers mapped the relative risk of MS across the municipalities and saw that MS was less prevalent in the southern part of the province.
They then mapped the average winter concentrations of PM2.5 from 2010 to 2017 and saw that northern areas of the province, near Milan, had the highest levels of particulate matter. The territory appeared to be divided into three bands of air pollution. Descending south, PM2.5 concentrations progressively decreased.
Matching the map of MS prevalence with the map of PM2.5 concentrations, the researchers saw that the southern area -- which corresponds to Oltrepo, a hilly territory rich in vineyards -- had a significantly lower risk of MS.
MS risk, adjusted for urbanization degree and deprivation index, was higher (RR 1.29) among people residing in areas in the medium tertile of PM2.5 concentrations than among people living in areas in the lowest tertile.
The study has several limitations and other variables may have influenced results, Bergamaschi noted. But these findings "highlight that air pollution could be one of the risk factors for MS," he said.
"Strengthened by our epidemiological observation, we are currently carrying out specific analytical studies intended to analyze multiple environmental factors in specific areas," he added.
Disclosures
The researchers did not report disclosures.
Primary Source
European Academy of Neurology
Bergamaschi R, et al "PM2.5 exposure is a risk factor of multiple sclerosis: an ecological study with a Bayesian mapping approach" EAN 2020; Abstract 1957.