UMich researchers find link between air pollution and dementia risk - The Michigan Daily

UMich researchers find link between air pollution and dementia risk

According to a University of Michigan-involved study published in August for the American Medical Association journal JAMA Internal Medicine, developing dementia may be linked to exposure to certain kinds of air pollution. Dementia is an umbrella term for multiple diseases, including Alzheimer’s Disease, Lewy body dementia and Vascular Dementia, all of which involve a decline in cognitive abilities. Research suggests that one in 10 Americans over the age of 65 have some form of dementia.

The study focused on PM2.5 pollutants — inhalable particles that are 2.5 micrometers or smaller — emitted from nine different sources including agriculture, traffic and energy production.

In an interview with The Michigan Daily, Boya Zhang, the study’s lead author and a U-M epidemiology research fellow, said the researchers chose to focus on the effects of PM2.5 pollutants because these smaller particles have been shown to have a greater impact on overall health.

“The PM2.5 has such an impact (compared to) other particle sizes because the 2.5 (micrometers) is smaller than other particles, which means that they can go deeper into your body,” Zhang said.

Sara Adar, associate professor in the School of Public Health and a member of the research team, explained how the exisiting theories on how air pollution can negatively impact brain health intersected with their study.

“One (theory) is that when you breathe in air pollution, our body tries to fight back using inflammation, and that inflammation can really cause damage throughout the body that can ultimately cause problems for the brain,” Adar said. “There’s also the idea that some of these really small particles … are small enough that they can actually get up through your olfactory bulb straight up through your nose into your brain.”

According to Zhang, previous work has already established that PM2.5 can have a negative impact on health. However in this particular study, the research team wanted to determine which sources of PM2.5 pollutants were most strongly associated with dementia.

“Air pollution has long been known to have negative health effects, (but) previously, (research) mainly focused on things like cardiovascular disease,” Zhang said. “During recent years, maybe a decade ago, studies have begun to learn more that air pollution may have some bad effects on your brain… We wanted to go deeper and see if PM from different sources would have different impacts.”

The researchers looked at data from 27,857 people who were a part of the Health and Retirement Study, a longitudinal survey of Americans over 50, and used a model to estimate total 10-year exposure to PM2.5 pollutants from all nine sources. The results showed that higher levels of PM2.5 exposure were generally associated with developing dementia, with PM2.5 pollutants from agricultural and wildfire sources being the most strongly linked to dementia.

Adar said she hopes the study will not only help individuals be more informed about the risks of PM2.5 exposure, but will also provide valuable insight to policymakers about the effects of different pollution sources. She noted that the study’s conclusions involved participants who were breathing in pollutant levels compliant with federal law.

“One thing that’s kind of interesting to think about is that these associations that we observed were all at levels that are generally less than our current National Ambient Air Quality Standards,” Adar said. “So, you know, it’s not just like the highest of all high exposures, this is a continuous response that we see.”

Because of the study’s observational design, it does not prove that PM2.5 pollutants cause dementia, just that they are correlated in the data the researchers looked at. However, the research team said if the relation was proven to be causal, the study’s findings would suggest that about 188,000 new cases of dementia per year in the U.S. could be caused by PM2.5 exposure.

Hannah White, vice president of the U-M chapter of the Youth Movement Against Alzheimer’s, said conducting research and raising awareness about genetic, environmental and socioeconomic risk factors related to dementia is important to help communities try to combat dementia.

“Dementia cases are projected to increase by about threefold over the next 30 years or so,” White said. “Dementia is extremely relevant now, and it’s only going to become more relevant. And what’s most important is that we know how to engage with this issue because so many of our community members in every single community will experience it.”

Daily Staff Reporter Nadia Taeckens can be reached at taeckens@umich.edu.