Jin Wu, a scientist from the Institute of Environmental Medicine, emphasizes that although pollution levels in Sweden are lower than in many other countries, the link between air pollution and nervous system diseases remains evident. "This underscores the need to improve air quality," he noted.
Motor neuron diseases are serious neurological disorders in which nerve cells responsible for voluntary movements gradually lose their functionality, ultimately leading to muscle atrophy and paralysis. Amyotrophic lateral sclerosis is the most common type of this disease, accounting for about 85-90% of all cases.
Environmental Factors
While the exact causes of these diseases remain unclear, it is believed that environmental factors play a significant role. The new study confirms that air pollution may be one of these factors.
The study involved 1,463 people in Sweden who had recently been diagnosed with motor neuron diseases. These participants were matched with 1,768 of their siblings, as well as more than 7,000 control participants from the general population. The researchers analyzed levels of particulate matter (PM2.5, PM2.5–10, PM10) and nitrogen dioxide at the participants' residences over the 10 years preceding the diagnosis.
The average annual levels of pollutants slightly exceeded the recommended values of the World Health Organization, while peak levels were significantly lower than in countries with high pollution levels.
Increased Risk of Up to 30%
Long-term exposure to polluted air, even at relatively low levels typical for Sweden, is associated with a 20-30% increased risk of motor neuron diseases. Moreover, residents of areas with higher pollution levels experienced more rapid declines in motor and lung functions after diagnosis, as well as an increased risk of death and the need for invasive ventilation.
"Our results suggest that air pollution may not only contribute to the onset of diseases but also accelerate their progression," claims Caroline Ingre, adjunct professor at the Department of Clinical Neurology at the Karolinska Institute.
Data analysis focusing solely on ALS patients showed a similar trend as in the overall motor neuron disease group.
Inflammation and Oxidative Stress
Researchers note that while this study does not establish the mechanisms of the connection, previous work suggests that air pollution can trigger inflammatory processes and oxidative stress in the nervous system. Since this study was observational, causality cannot be confirmed.
The research was based on data from Swedish registries and was supported by several organizations, including the U.S. Centers for Disease Control and Prevention (CDC), the Swedish Research Council, and the Karolinska Institute.
