Air pollution tied to higher ALS risk, worse patient outcomes in study
Findings spark concerns about even low-level exposure over long term
- A new study from Sweden has found that long-term air pollution exposure increases ALS risk and accelerates disease progression.
- Higher pollution levels were linked to increased mortality and faster decline in lung function for ALS patients.
- The researchers say improving air quality is crucial for reducing ALS risk and improving patient outcomes.
Long-term exposure to air pollution, even at relatively low levels, is associated with an increased risk of developing motor neuron disease (MND), a group of conditions that includes amyotrophic lateral sclerosis (ALS), according to a new study by researchers in Sweden.
Among patients, exposure to air pollution is also linked with faster disease progression, the team found.
“Our results suggest that air pollution might not only contribute to the onset of the disease, but also affect how quickly it progresses,” Caroline Ingre, MD, PhD, a professor of neurology and coauthor of the study at the Karolinska Institutet in Stockholm, said in an institute news story detailing the findings.
The study, “Long-Term Exposure to Air Pollution and Risk and Prognosis of Motor Neuron Disease,” was published in the journal JAMA Neurology.
ALS is a neurodegenerative disorder that accounts for about 85%-90% of all MND cases. It is marked by the degeneration and death of motor neurons, the nerve cells that control muscle movement.
While the causes of ALS are not fully understood, some studies have indicated that exposure to air pollution may increase the risk of developing ALS. Still, there hasn’t been much research on how exposure to pollution affects outcomes for people with the disease or other MNDs.
Exploring how air pollution affects disease outcomes
Using national registry data from Sweden, a team of scientists identified 1,463 people diagnosed with MND between 2015 and 2023. Among them, 1,057 were found to have ALS.
Based on each person’s historical addresses over previous years, the researchers estimated the patients’ exposure to certain types of air pollution, specifically particulate matter and nitrogen dioxide.
For comparison, pollution exposure was also assessed in two non-MND groups: one involving 1,768 biological siblings of the MND patients, and another that with 7,310 people from the general population.
Armed with these data, the researchers constructed mathematical models to determine whether there was a statistically significant link between air pollution exposure and MND risk.
The results showed that increased exposure to air pollution was consistently associated with a greater likelihood of developing MND. For example, greater exposure to a type of particulate matter with up to 2.5 micrometers in diameter in the year before diagnosis was tied to a 12% higher likelihood of developing MND. More exposure to this particulate matter in the 10 years prior to diagnosis was associated with a 21% increased likelihood, the data showed.
Our study showed a consistent association between air pollution exposure and a higher risk of [motor neuron disease, conditions that include ALS] across multiple pollutants and exposure windows.
Similar findings were observed at one, three, five, and 10 years for particulate matter between 2.5 and 10 micrometers in diameter, as well as particulate matter greater than 10 micrometers in diameter, and nitric oxide.
The researchers noted that the results were replicated when only people with ALS were analyzed, but not when the analyses included individuals with other forms of MND.
“Our study showed a consistent association between air pollution exposure and a higher risk of MND across multiple pollutants and exposure windows,” the researchers wrote.
This finding is particularly noteworthy, the scientists said, because this study was conducted in Sweden — a country with relatively little air pollution compared with other parts of the world.
“We can see a clear association, despite the fact that levels of air pollution in Sweden are lower than in many other countries,” said Jing Wu, PhD, study coauthor at Karolinska Institutet.
According to Wu, “this underlines the importance of improving air quality.”
Exposure linked to higher risk of death for people with ALS
The models also indicated that, among all MND patients and ALS patients alone, exposure to higher air pollution levels was associated with a higher risk of death, faster disease progression, and faster declines in lung function.
“Long-term exposure to air pollution was further found to be associated with an increased risk of mortality and need of invasive ventilation after MND diagnosis,” the researchers wrote, also noting “a faster loss of motor and respiratory functions … among patients with MND with a higher 10-year average exposure to all [pollutants].”
The team concluded that air pollution “contributes both to the risk of developing MND and to disease prognosis after … diagnosis.”
“These results highlight the public health importance of improving air quality to reduce the risk of neurodegenerative diseases and to improve the outcome of patients with these diseases,” the researchers wrote.
About the Author
