Ultrafine particle exposure linked to dementia mortality
Each 10,000 particles/cm³ increase in outdoor ultrafine particle concentrations was associated with higher dementia mortality (hazard ratio 1.22, 95% CI 1.17–1.27).
Epidemiology
Researchers analyzed data from 2.1 million adults living in Montreal and Toronto in the Canadian Census Health and Environment Cohorts from 2001 to 2019. They assigned estimates of outdoor ultrafine particle concentrations and particle size to residential postal codes using three-year moving averages. National death records provided causes of death.
Over 19 million person-years, researchers identified 20,560 deaths from neurodegenerative diseases. Higher particle concentrations were associated with higher dementia mortality, with stronger associations after adjustment for particle size. Models also adjusted for sociodemographic factors and co-pollutants. Associations were positive across all dementia subtypes and largest for vascular dementia. Researchers found no association with mortality from Parkinson’s disease or amyotrophic lateral sclerosis.
Why it matters
The findings suggest that reducing exposure to these unregulated pollutants could help mitigate neurodegenerative mortality, particularly from dementia.
Caveats
This observational study cannot establish causation. Exposure estimates reflected outdoor concentrations at residential postal codes, rather than individual exposure measurements.
The paper
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Arman Ganji, Junshi Xu, Marianne Hatzopoulou, Scott Weichenthal,McGill University
Epidemiology · 5 Oct 2026
