New research suggests that long-term exposure to air pollution may not only increase the risk of developing motor neurone disease (MND), but also worsen outcomes for patients after diagnosis, including faster disease progression and shorter survival.
The research, which took place in Sweden, is one of the largest and most detailed studies to investigate this link. It tracked 1,463 patients with newly diagnosed MND, comparing them to over 7,300 population controls and nearly 1,800 sibling controls to account for genetic and shared environmental factors.
Using high-resolution spatiotemporal models, the researchers examined detailed residential exposure data for multiple air pollutants over periods of up to 10 years before diagnosis.
The analysis found a consistently higher risk of MND among people exposed to elevated levels of fine particulate matter (PM2.5), coarse particulate matter (PM2.5–10 and PM10) and nitrogen dioxide (NO₂). The strongest associations were seen with longer-term exposure, particularly over a 10-year period, suggesting cumulative effects of poor air quality.
The study also found that people with MND who had higher long-term exposure to air pollution before diagnosis experienced worse clinical outcomes. These included an increased risk of death and a greater likelihood of requiring invasive ventilation. Patients exposed to higher levels of particulate matter showed a faster decline in motor and respiratory function after diagnosis, although no clear association was seen with bulbar function, which affects speech and swallowing.
The researchers – drawn from a variety of medical and academic institutions in Sweden – say their findings help clarify previously mixed evidence on the relationship between air pollution and MND. Earlier studies have produced inconsistent results, potentially due to differences in sample size, exposure measurement and study design. By contrast, this study drew on a large national dataset, high-resolution air quality data and repeated clinical assessments, allowing the team to examine multiple pollutants, exposure windows and disease outcomes in detail.
The authors note that the biological mechanisms behind the findings are not yet fully understood, but suggest that air pollution may interact with known genetic risk factors for MND through pathways linked to oxidative stress and neuroinflammation. They highlight the need for future studies to explore whether pollution-related risks differ between people with and without known MND-related genetic mutations.
The authors conclude that reducing long-term exposure to air pollution could play a role in lowering the burden of MND and improving outcomes for patients, while calling for further research to confirm the findings and explore underlying mechanisms.
Lead author Dr. Jing Wu said: ‘Our results suggest that air pollution, even at the relatively low levels typical of Sweden, may play a role in both the development and the progression of this devastating disease.’
Commenting on the research, Dr Brian Dickie, Chief Scientist, MND Association, said: ‘This is a well performed study indicating an association between long-term exposure to higher air pollution levels and a small, but notable, increased risk of developing MND, as well as faster disease progression, although these observations were not consistent across all subtypes of MND.
‘It is important to stress that ‘correlation’ does not mean ‘causation’ – and indeed, findings from previous research on the effects of air pollution have been inconsistent. The researchers are therefore cautious with their interpretation of the results, acknowledging that potential confounding factors, together with a lack of some additional data, prevent strong conclusions being made. For example, key information on the delay between symptom onset and diagnosis, which is known to be strongly linked to rate of disease progression, was not available.
‘We know that the vast majority of cases of MND are likely to occur through a combination of potentially many genetic, environmental and lifestyle factors. Scandinavian countries are known to have particularly high proportion of some genetic risk factors for MND within the population but, unfortunately, genetic data was not available for this study. These results point to the importance of integrating genetic information into future epidemiology studies, if we are to make genuine and significant inroads in understanding the causes of MND.’
The full research can be read here.
Photo: Milad Fakurian / unsplash
Leave a Reply