Air pollutants and amyotrophic lateral sclerosis in a population-based registry: investigating disease susceptibility, progression and survival

Objective: to investigate the association between long-term exposure to fine particulate matter (PM2.5) and nitrogen oxides (NOx) with ALS risk, progression, and survival. Methods: We conducted a population-based study in Lombardy, Italy. A case-control analysis included 161 incident ALS cases (2011-2014) and 161 age-, sex-, and province-matched controls. Average residential exposures to PM2.5 and NOx over the 20 years before diagnosis were estimated using European Monitoring and Evaluation Programme data and analysed with conditional logistic regression. A retrospective cohort of 135 ALS cases was used to assess associations with disease progression (ΔFS) and mortality using logistic and Cox regression models, adjusting for demographic and lifestyle factors. Results: Higher PM2.5 exposure in the 20 years preceding diagnosis was associated with increased ALS risk (adjusted OR per 5 µg/m³ increase 1.19; 95% CI 1.01-1.40), with consistent findings across sensitivity analyses. NOx was not associated with ALS incidence. In contrast, NOx exposure in the 5 years before diagnosis was marginally associated with increased mortality (adjusted HR 1.12; 95% CI 1.00-1.26), whereas PM2.5 was not. Neither pollutant was significantly associated with disease progression rate. Conclusions: Long-term PM2.5 exposure was associated with higher ALS risk, while NOx showed a modest association with mortality. These findings support a role of air pollution in ALS susceptibility and highlight the need for integrated environmental prevention strategies to mitigate the burden of neurodegenerative diseases.