In a new study, researchers found that air pollution could be a risk factor for the development of multiple sclerosis (MS).
They detected a reduced risk for MS in people living in rural areas that have lower levels of air pollutants known as particulate matter (PM).
They found that the MS risk was 29% higher among those living in urban areas.
The research was conducted by a team at the European Academy of Neurology.
The number of people living with MS around the world is growing, with more than 700,000 sufferers across Europe.
The vast majority (85%) of patients present with relapsing-remitting MS, characterized by unpredictable, self-limited episodes of the central nervous system.
Whilst MS can be diagnosed at any age, it frequently occurs between the ages of 20-40 and is more frequent in women.
Symptoms can change in severity daily and include fatigue, walking difficulty, numbness, pain, and muscle spasms.
It is well known that immune diseases such as MS are linked to multiple factors, both genetic and environmental.
Some environmental factors, such as vitamin D levels and smoking habits, have been extensively studied, yet few studies have focused on air pollutants.
The team examined over 900 MS patients within the region, and MS rates were found to have risen 10-fold in the past 50 years, from 16 cases per 100,000 inhabitants in 1974 to almost 170 cases per 100,000 people today.
Whilst the huge increase can partly be explained by increased survival for MS patients, this sharp increase could also be explained by greater exposure to risk factors.
The analysis was done in the winter, given that this is the season with the highest pollutant concentrations, in the north-western Italian region of Lombardy, home to over 547,000 people.
The researchers believe that air pollution interacts through several mechanisms in the development of MS and the results of this study strengthen that hypothesis.
Particulate matter (PM) is used to describe a mixture of solid particles and droplets in the air and is divided into two categories.
PM10 includes particles with a diameter of 10 micro-meters of smaller and PM2.5 which have a diameter of 2.5 micrometers or smaller.
Both PM10 and PM2.5 are major pollutants and are known to be linked to various health conditions, including heart and lung disease, cancer, and respiratory issues.
According to the World Health Organisation, 4.2 million deaths occur every year because of exposure to ambient (outdoor) air pollution.
The lead author of the study is Professor Roberto Bergamaschi.
The study was presented at the European Academy of Neurology (EAN) Virtual Congress.
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