Prolonged exposure to air pollution has been associated with a higher risk of developing serious neurodegenerative diseases such as Amyotrophic Lateral Sclerosis (ALS), according to researchers from the Karolinska Institutet in Sweden. The findings were published in JAMA Neurology.
Motor neuron diseases (MNDs) are neurological conditions that cause the nerve cells responsible for voluntary movement to deteriorate, leading to muscle atrophy and paralysis. ALS is the most common form, making up approximately 85 to 90 percent of MND cases.
While the causes of these diseases remain largely unknown, environmental factors have been suspected as contributors. The recent study identifies air pollution as one possible factor influencing both the onset and progression of these diseases.
The research involved 1,463 recently diagnosed MND patients in Sweden. These individuals were compared with 1,768 siblings and over 7,000 matched controls from the general population. Researchers analyzed exposure levels to particulate matter (PM2.5, PM2.5-10, PM10) and nitrogen dioxide at participants' home addresses for up to ten years before diagnosis. Average annual pollutant levels were just above World Health Organization guidelines; peak values were much lower than those found in countries with severe air pollution.
The results indicated that long-term exposure to air pollution—even at relatively low levels typical for Sweden—was linked with a 20 to 30 percent increased risk of developing MND. Individuals living in areas with higher air pollution experienced more rapid motor and pulmonary decline after diagnosis. They also faced a greater risk of death and an increased likelihood of requiring invasive ventilator support.
"Our results suggest that air pollution might not only contribute to the onset of the disease, but also affect how quickly it progresses," said Caroline Ingre, adjunct professor at the Department of Clinical Neuroscience at Karolinska Institutet.
When focusing specifically on ALS patients within their sample group, researchers observed similar patterns regarding disease risk and progression.
The team noted that while their study demonstrates an association between air pollution and MNDs like ALS, it does not clarify underlying mechanisms or establish causation. Prior studies suggest that air pollution may lead to inflammation and oxidative stress in the nervous system.
This research was based on Swedish registry data and received funding from organizations including the US Center for Disease Control and Prevention, the Swedish Research Council, and Karolinska Institutet.
