Research shows things such as exercise, a healthy diet and limited alcohol consumption can help protect someone from developing dementia. Avoiding air pollution can now be added to the list. Researchers from the University of Washington found people with long-term exposure to fine particulate air pollution where they live had a higher risk of dementia compared to people in areas with cleaner air.
Scientists reviewed data from a large study on air pollution from the early 1970s in the Puget Sound region of Washington and another large study on risk factors for dementia in that area that began in 1994. By comparing the overlapping data they were able to identify a link between air pollution and dementia.
What they found was a small increase in the levels of fine particulate pollution, 2.5 micrometers or smaller (PM2.5), averaged over a decade was associated with a greater risk of dementia for people living in the affected area.
"We found that an increase of 1 microgram per cubic meter of exposure corresponded to a 16% greater hazard of all-cause dementia,” said lead study author Rachel Shaffer. "There was a similar association for Alzheimer's-type dementia."
The study looked at more than 4,000 Seattle area residents and the results were published in the journal Environmental Health Perspectives. Researchers identified more than 1,000 people who had been diagnosed with dementia at some point since the Adult Changes in Thought (ACT) Study began in 1994.
When someone was diagnosed with dementia the researchers compared the average pollution exposure leading up to their diagnosis. Others in the study were then compared to that individual over the 10 years before they reached the same age as the new dementia patient.
That’s how researchers were able to determine how just 1 microgram per cubic meter of additional pollution leads to a 16% higher risk of a dementia diagnosis. For comparison, 1 microgram per cubic meter is the difference in PM2.5 pollution in 2019 that was found between Pike Street Market in downtown Seattle and the nearby residential area of Discovery Park.
"We know dementia develops over a long period of time. It takes years—even decades—for these pathologies to develop in the brain, and so we needed to look at exposures that covered that extended period," Shaffer said. "We had the ability to estimate exposures for 40 years in this region. That is unprecedented in this research area and a unique aspect of our study. "
"How we've understood the role of air pollution exposure on health has evolved from first thinking it was pretty much limited to respiratory problems, then that it also has cardiovascular effects, and now there's evidence of its effects on the brain," said researcher Lianne Sheppard.