Air pollution could impact the cognitive function of older men more than previously thought — even from short-term exposure and at concentrations below World Health Organization guidelines for what's considered safe to breathe, a new study suggests. 

Despite the cognitive decline of older adults being a popular topic of research, our understanding of the short-term impacts of polluted air on cognitive function is still limited. The study, published Monday in Nature Aging, adds to our knowledge of the harmful effects of fine particulate matter on brain function, said Xu Gao, an assistant professor with the School of Public Health at Peking University in Beijing and corresponding author of the study. 

"Researchers have been working on this topic by analyzing associations with long-term exposure to air pollutants, up to a year or even longer," he told The Academic Times. "But there are several air pollution [surges] across a year, so our interest is in whether short-term exposure to air pollutants — maybe a couple of weeks — could also impair cognitive function." 

The researchers studied a cohort of 954 older white men in the greater Boston area who participated in the Normative Aging Study conducted by the U.S. Department of Veterans Affairs. Cognitive function was measured with tests over several appointments, providing researchers a total of 2,551 medical visits to analyze. The participants' performance in the tests was measured against local levels of fine particulate matter — no more than 2.5 micrometers in diameter, small enough to cross the lung barrier and enter the bloodstream — on the day of each visit and a period of four weeks prior to it. As a group, participants exposed to elevated air pollution up to 28 days before their appointment scored worse on cognitive tests. 

Significantly, the researchers also found this effect at fine particulate levels below ambient air pollution guidelines set by WHO at 10 micrograms of particulate matter per square meter. "In our figures, we found increased risk of cognitive decline [above] 0 microgram, which means there is no safe levels of [particulate matter]," Gao explained.

"Even under concentrations usually considered safe to the public, cognitive function is still under threat," he continued. "So, this is quite important, and it led to the next question: How can we prevent this short-term effect of air pollution? We have a hypothesis that air pollution may lead to cognitive impairment by inducing inflammation." 

The study suggests that nonsteroidal, inflammation-reducing pain medications, such as aspirin, could limit the cognitive effects of short-term air pollution. "We did an analysis based on the use of [anti-inflammatory] drugs in the normative aging study and found that more than 50% of the people took these kinds of drugs, and those people were suffering much less from cognitive impairment than the people who did not take the drugs." 

But the researchers did not have access to detailed information about the participants' non-steroidal anti-inflammatory drug use and could not draw firm conclusions. "We cannot recommend people to use an [anti-inflammatory] drug directly to protect from air pollution's effects," Gao said. Rather, he encouraged people who are already on such a pain medication regimen to think of possible protection from air pollution as an additional benefit. 

"The most important findings of our study are that short-term air pollution is harmful, and that air pollution below levels previously believed to be safe [is] still harmful to your cognitive function," he emphasized. 

The research has other limitations as well. "We used air pollution levels from a monitor based at Harvard University at the city level — not personal exposure of the participants to air pollution," Gao explained. "It's kind of a surrogate for personal exposure, but it cannot reflect the true personal exposure of these participants. They could be exposed to indoor air pollutants such as smoking and secondhand smoke, and other [sources] like forest fires that we cannot predict." 

In the coming year, the researchers will analyze a large cohort of Chinese men and women within a larger age range, and with more information about their use of anti-inflammatory drugs, Gao said: "This could be a very good cross-validation of our findings." 

The study, "Short-term air pollution, cognitive performance and nonsteroidal anti-inflammatory drug use in the Veterans Affairs Normative Aging Study," published May 3 in Nature Aging, was authored by Xu Gao, Peking University and Columbia University; Brent Coull, Xihong Lin and Joel Schwartz, Harvard T.H. Chan School of Public Health; Pantel Vokonas, Boston University School of Medicine; Avron Spiro III, Boston University School of Medicine; Lifang Hou, Northwestern University; and Andrea A. Baccarelli, Columbia University.