Canadian Census Health and Environment Cohort records for 2.1 million adults in Montreal and Toronto were linked to vital statistics and to high-resolution residential estimates of ultrafine particle number concentration and size, 2001-2019. Over 19 million person-years and 20,560 neurodegenerative deaths, each 10,000 particle/cm3 increase was associated with dementia mortality (HR 1.22, 95% CI 1.17-1.27), largest for vascular dementia (HR 1.49, 1.27-1.76). No association was seen with Parkinson's disease or amyotrophic lateral sclerosis mortality.
Why it is interesting: Ultrafine particles are unregulated, and the association here is specific to dementia rather than to neurodegenerative mortality in general.