Wildfire smoke may increase dementia risk, study finds

A new US study finds that wildfire smoke is worse for brain health than other forms of air pollution and even increases the risk of dementia.

The findings, reported Monday at the Alzheimer’s Association’s international conference in Philadelphia, came as millions of people spent the weekend under air quality warnings due to wildfires that have sent smoke across the western U.S., including a massive wildfire in California that has grown to more than 900,000 acres.

It’s fine particulate matter, or PM 2.5 – tiny particles about 30 times smaller than the diameter of a human hair that can be inhaled deep into the lungs and enter the bloodstream. This pollution – from traffic, factories and fires – can cause or worsen heart and lung diseases, and the new study adds to evidence that it may also play a role in dementia.

Researchers tracked health data on 1.2 million older adults in Southern California between 2009 and 2019. They used air quality measurements and other data to estimate three years of household exposure to PM 2.5 from wildfire smoke and other sources.

The study found that the odds of a new dementia diagnosis increased by about 21 percent for every 1-microgram increase in wildfire particle concentration. That compared with a 3 percent increased risk for every 3-microgram jump in non-wildfire particles, researchers from the universities of Washington and Pennsylvania concluded.

It’s not clear why there would be a difference. But with the increase in wildfires, more research is needed, said Maria Carrillo, chief science officer for the Alzheimer’s Association. That’s especially because the risk of Alzheimer’s, the most common form of dementia, is higher for people with lower incomes, who may have a harder time avoiding unhealthy air, she said.

Health warnings urge people to stay indoors when air quality is poor, but “there are many people who don’t have the option to stay home or work outside,” she noted.

The study adds to a growing body of research on the negative effects of wildfire smoke on human health. A study published in June linked more than 50,000 premature deaths in California to wildfire smoke exposure over the past decade. Other studies have linked wildfire smoke exposure to increased risks of heart attacks and premature births.

The Associated Press contributed to the reporting