Airborne fine particulate matter (PM2.5) was associated with dementia development in a recent cohort study published in JAMA Internal Medicine. 

“Higher residential PM2.5 levels, especially from agriculture and wildfires, were associated with higher rates of incident dementia, providing further evidence supporting PM2.5 reduction as a population-based approach to promote healthy cognitive aging,” lead author Boya Zhang, PhD, University of Michigan School of Public Health, Ann Arbor, Michigan, and co-authors said. “These findings also indicate that intervening on key emission sources might have value, although more research is needed to confirm these findings.”

Researchers examined data from the Health and Retirement Study (HRS) from January 1, 1998, to December 31, 2016, and included participants who were 50+ years old, had had at least 2 interviews, and were free of dementia at their first interview. A spatiotemporal prediction model was used to estimate total PM2.5 at participants’ residential addresses by using measurements from the Environmental Protection Agency’s (EPA) regulatory networks, 300+ geographic covariates documenting factors like transportation, population density, emission, and vegetation, and “spatial correlations to predict concentrations for each 2-week period at any location in the US between 1999 and 2016.” Researchers used a validated algorithm of respondent-based cognitive testing and proxy respondent reports to measure incident dementia. 

A total of 27,857 participants were included, with a mean age of 61 years and made up of 56.5% women. Of these, 15% developed dementia during a mean follow-up of 10.2 years. Higher concentrations of pollution, except for dust, were connected to greater rates of dementia (HR, 1.08 per IQR; 95% CI, 1.01-1.17). The strongest associations between pollution and greater risk of dementia were agriculture (HR, 1.13; 95% CI, 1.01-1.27) and wildfires (HR, 1.05; 95% CI, 1.02-1.08).

“These findings also indicate that intervening on key emission sources might have value, although more research is needed to confirm these findings,” authors concluded.