A new study from Sweden has found that long-term exposure to air pollution may increase the risk of developing serious brain diseases like ALS.
The study also suggests that air pollution might make these diseases get worse more quickly. Researchers at Karolinska Institutet in Sweden published the findings in the journal JAMA Neurology.
ALS, or amyotrophic lateral sclerosis, is the most common type of a group of brain diseases known as motor neuron diseases (MNDs). These illnesses damage the nerve cells that control our voluntary movements—things like walking, speaking, and breathing.
Over time, the nerve cells stop working, which leads to muscle weakness, loss of control, and eventually paralysis.
Doctors and scientists still do not fully understand what causes these diseases. However, environmental factors, like air pollution, have long been suspected. This new study adds strong evidence to support that idea.
The researchers looked at 1,463 people in Sweden who had recently been diagnosed with a motor neuron disease. They compared them to 1,768 of their siblings and more than 7,000 people from the general population who were of similar age and background.
The team checked the levels of air pollutants at the participants’ home addresses going back up to 10 years before the diagnosis.
They focused on small particles in the air—known as PM2.5, PM10, and other sizes—as well as nitrogen dioxide. These pollutants often come from cars, factories, and other human-made sources. Although air pollution in Sweden is lower than in many other countries, the researchers still found a clear link.
People who lived in areas with higher levels of air pollution had a 20% to 30% higher risk of developing ALS or another motor neuron disease.
But that’s not all. After diagnosis, patients exposed to more pollution experienced faster loss of muscle strength and lung function. They were also more likely to die sooner and more likely to need help with breathing through a ventilator.
In other words, air pollution didn’t just raise the chances of getting the disease. It also seemed to make the disease progress more quickly and more severely. The same pattern held true even when the researchers focused only on ALS patients.
The scientists don’t yet know exactly how air pollution affects the brain and nervous system. However, earlier research suggests that pollution can trigger inflammation and something called oxidative stress—both of which can harm nerve cells.
Because this was an observational study, it cannot prove that air pollution directly causes ALS, but the connection is strong enough to raise serious concerns.
The researchers say this shows how important clean air is—not just for heart and lung health, but also for the brain. Even in countries like Sweden with relatively low pollution, there are still risks. The study was supported by organizations such as the U.S. Centers for Disease Control and Prevention, the Swedish Research Council, and Karolinska Institutet.
In summary, this study is an important reminder that air pollution might play a bigger role in diseases like ALS than we previously thought. It affects not only the chances of getting sick but also how fast the illness gets worse. Cleaner air could mean better brain health for all of us.
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