London, May 23 (IANS: Air pollution could be a risk factor for the development of multiple sclerosis (MS), say researchers, adding that MS risk was 29 per cent higher among people residing in urbanised areas.

Multiple sclerosis (MS) is a disease in which the immune system eats away at the protective covering of nerves. 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.

The study, presented at the European Academy of Neurology (EAN) Virtual Congress, detected a reduced risk for MS in individuals residing in rural areas that have lower levels of air pollutants known as particulate matter (PM).

According to the researchers, it is well recognised that immune diseases such as MS are associated with multiple factors, both genetic and environmental.

"We believe that air pollution interacts through several mechanisms in the development of MS and the results of this study strengthen that hypothesis," said study lead researcher Professor Roberto Bergamaschi from the IRCCS Mondino Foundation in Italy.

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 micrometres of smaller and PM2.5 which have a diameter of 2.5 micrometres 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.

The analysis was conducted 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.

For the findings, the research team included 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.

"In the higher risk areas, we are now carrying out specific analytical studies to examine multiple environmental factors possibly related to the heterogeneous distribution of MS risk", Professor Bergamaschi said.