A study of more than 1.6 million people in California found a direct correlation between exposure to wildfire smoke and increased dementia risk.
The research, published in the JAMA Neurology scientific journal, used electronic health record data between January 2008 to December 2019 among members of the Kaiser Permanente Southern California system, which serves 4.7 million people in the state. The study focused on people aged 60 years old or older but excluded people who had a dementia diagnosis before cohort entry.
The study found that people exposed to fine particulate matter PM2.5 from wildfires had an 18% increase in the odds of a dementia diagnosis, compared with an only 1% increase in people exposed to non-wildfire PM2.5. The most at-risk subjects were less than 75 years old, were from racially minoritized subgroups, and those living in high-poverty census tracts.
“As the climate changes, interventions focused on reducing wildfire PM2.5 exposure may reduce dementia diagnoses and related inequities,” the researchers said.

It’s not the first time wildfire smoke has been linked to neurological hazards. University of New Mexico Health Sciences researchers published a study in 2021 that found people inhaled microscopic particles from woodsmoke which worked their way into the bloodstream and reached the brain. The particles put people at risk for neurological problems ranging from premature aging and various forms of dementia to depression and even psychosis.
READ MORE: Researchers find that wildfire smoke poses neurological hazards
“Past research has consistently identified an association between long-term PM2.5 exposure and incident dementia, with varying magnitudes of association depending on study context, outcome ascertainment, and exposure averaging period,” researchers from the JAMA study said. “These results align with prior research consistently demonstrating that individual-level and area-level social determinants compound the risk of adverse health outcomes associated with climate-driven environmental exposures.”
Examples of how socioeconomic inequalities can exacerbate health issues from wildfire smoke include lower-quality housing increasing smoke infiltration and lack of air filtration systems to improve air quality during extreme smoke events.
“Future studies may wish to explicitly study these factors as effect modifiers,” the researchers said.

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