Association of long-term outdoor air pollution exposure with incidence of Parkinson's disease, multiple sclerosis and motor neuron diseases: a systematic review and meta-analysis.

Authors

Alexandra Z Tien-Smith, Shazia Absar, Clare Best Rogowski, Veronica Phillips, Zorana Jovanovic Andersen, Christiaan Bredell, Kwan Wai Fung, Lucy Hong, Magdalena Szybka, James Woodcock, Carol Brayne, Haneen Khreis, Annalan M D Navaratnam

Published in

Environment international. Pages 110377. Jun 20, 2026. Epub Jun 20, 2026.

Abstract

Parkinson's disease (PD), multiple sclerosis (MS) and motor neurone disease (MND) are progressive and debilitating diseases that are increasing in prevalence globally. Some primary studies show an increased risk from long-term outdoor air pollution exposure, while others contradict this association.
A systematic review and meta-analysis were undertaken to assess the associations of long-term (≥1 year) outdoor air pollution exposure with PD, MS and MND incidence. We searched eight databases for publications up to July 2025. Primary case-control, cohort, cross-sectional or ecological studies investigating the association between long-term air pollution exposure and adult (>18 years old) PD, MS, or MND incidence were included. Meta-analyses were carried out using random-effects models with assessment of heterogeneity, meta-bias and shape of the exposure-response functions. PROSPERO (CRD42023417961).
Of 42 papers included, 26, 3 and 3 were meta-analysed for PD, MS, and MND outcomes, respectively. 19 studies from North America, 12 from Europe and 10 from Asia were meta-analysed. For every 5 μg/m³ and 15 μg/m³ increase of Particulate Matter 2.5 (PM_2.5) and PM₁₀ concentration, estimated (95% Confidence Interval) PD risk was 10% (1.10; 1.03-1.19) and 18% (1.18; 1.01-1.38), respectively but effects varied across settings (Prediction Interval: 0.80-1.52 for PM_2.5 and 0.41-3.36 for PM₁₀), with the largest estimated risk for PM_2.5 in Asia (1.19; 1.01-1.41). There was no clear evidence that PM_2.5 (1.01; 0.77-1.32) or nitrogen dioxide (NO₂, 0.98, 95% CI: 0.95-1.01) were associated with MS risk or PM_2.5 with MND risk (1.07, 95% CI: 0.86-1.33).
This systematic review reports increased PD risk from long-term PM_2.5 and PM₁₀ exposure. No association was observed for MS and MND from a very limited evidence base. The neurodegenerative diseases investigated here are rare and therefore alternatives to insufficiently powered cohort studies are needed to strengthen the evidence on risk.

PMID:
42420066
Bibliographic data and abstract were imported from PubMed on 09 Jul 2026.

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