TUESDAY, May 26, 2020 (HealthDay News) -- Air pollution might increase the risk for multiple sclerosis (MS), Italian researchers report.
They found that in places with low levels of tiny particles of air pollution called particulate matter, the risk for MS was lower than in areas where those levels were high. In urban areas, the risk was 29% higher than in rural areas.
"Our findings show that the prevalence of MS is lower where particulate matter concentrations are lower, suggesting that air pollution could be one of the risk factors for multiple sclerosis," said lead researcher Dr. Roberto Bergamaschi, director of the Multiple Sclerosis Center at the IRCCS Mondino Foundation in Pavia.
Bergamaschi emphasized that this study doesn't prove air pollution causes MS, only that there appears to be a link.
"Countermeasures that reduce air pollution are 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," Bergamaschi said.
More research is needed to find out why air pollution could trigger the disease.
He said MS may have many causes, and some environmental factors could trigger an abnormal immune response.
Worldwide, more people than ever are living with MS. Most suffer from its relapsing-remitting form, which causes unpredictable episodes of fatigue, walking difficulty, numbness, pain and muscle spasms.
The most studied environmental factors in MS are vitamin D levels, cigarette smoking and diet, but others deserve to be studied, air pollution included, Bergamaschi said.
"In Northern Italy, where the study was done, we are highly sensitive to air pollution problems, because our area is one of the most polluted in Europe," he said.
Fine particulate matter (PM) is among the most toxic air pollutants. The main sources are home heating, industrial activities and burning fossil fuels, Bergamaschi said.
Worldwide, about 4.2 million people die early as a result of breathing polluted air, according to the World Health Organization.
For the study, Bergamaschi's team looked at more than 900 MS patients in Italy's Lombardy region, where the number of MS cases have increased 10-fold in the last 50 years.
In 1974, the rate of MS cases stood at 16 per 100,000 people. Today, it's 170 per 100,000, researchers said.
Some of the surge is explainable as more MS patients are living longer, but it might stem from greater exposure to risk factors, they noted.
Particulate matter is a mixture of solid particles and droplets in the air that are linked to heart and lung disease, cancer and respiratory problems.
"The study adds further information on particulate matter as a potential modifiable risk factor for MS," said Dr. Asaff Harel, a neurologist at Lenox Hill Hospital in New York City who treats MS patients.
"While the results are intriguing, there are many confounders that need to be controlled for, such as age, ancestry, smoking, weight and sun exposure," he said. "Highly urban areas, for example, may be associated with decreased sun exposure, which has been suggested as a risk factor for MS."
This study is not the first to investigate air pollution and MS. There have been earlier studies in both adults and children with MS, Harel said.
While some suggested that pollution and particulate matter may contribute, the Nurses' Health Study showed no association between air pollutants and MS risk after controlling for age, smoking, body weight and sun exposure, he said. The Nurses' Health Study is among the largest to examine risk factors for major chronic diseases in women.
"It is important to further analyze the current study results and control for potential confounders that might explain these findings," Harel said.
The findings were to be presented Saturday at an online meeting of the European Academy of Neurology. Research presented at meetings is considered preliminary until publication in a peer-reviewed journal.