Even Short-Term Pollution May Threaten Brain Health
— Can a common drug protect against poor air quality?
by Judy George, Senior Staff Writer, MedPage Today May 3, 2021
Short-term exposure to airborne pollution was tied to lower cognitive function, but people who used non-steroidal anti-inflammatory drugs (NSAIDs) showed less impairment.
Even small increases in fine particulate matter (PM2.5) in the Boston area weeks before cognitive testing were associated with consistently worse cognitive performance in older men, reported Xu Gao, PhD, of Peking University in Beijing, China, and co-authors in Nature Aging.
“Our study is the first one that demonstrates that exposure to PM2.5, even just over a few weeks, can impair cognitive performance. We also found that even when PM2.5 was at the levels below that are usually considered hazardous the adverse effect still existed, suggesting that there is no safe zone for PM2.5,” Gao told MedPage Today.
“However, these adverse effects were lessened in people taking NSAIDs, like aspirin,” he continued. “But this finding should be validated with clinical trials or real-world data analyses with detailed drug use information because NSAIDs have side effects.”
PM2.5 includes particles 2.5 microns in diameter or less, noted Joanne Ryan, PhD, and Alice Owen, PhD, both of Monash University in Melbourne, Australia, in an accompanying editorial.
“They are so small that they can penetrate deep into the lungs and circulatory system, causing adverse health effects,” they wrote. Evidence suggests exposure to ambient air pollution over several years may be a risk factor for dementia: high levels of PM2.5 have been associated with cognitive decline and smaller brain volume.
Most previous studies considered only long-term exposure and generally high levels of pollution, Ryan and Owen pointed out. It’s remained unclear how air quality might affect general cognition:
“The results of the current study are especially important because they provide some of the first evidence that even relatively low-level, short-term increases in PM2.5 are detrimental for thinking and memory, as well as global cognition in older adults,” they wrote.
Other studies also have investigated NSAIDs as a potential treatment for cognitive dysfunction and dementia, but most, like the ASPREE trial of daily aspirin, did not show an effect. “The study by Gao et al., found no association between NSAID use — predominantly aspirin — and cognitive performance, which aligns with findings from the ASPREE trial,” Ryan noted.
“Their findings about the potential effect modification of NSAIDs, however, are quite intriguing,” she told MedPage Today.
“This could indicate that NSAIDs may help protect cognitive function when exposed to other external factors that trigger an inflammatory response, like pollution.
It’s an interesting observation that warrants further investigation, in particular to ensure the findings are not just an artifact of the sample or chance association.”
In their study, Gao and colleagues included 954 white men (mean age 69) in Greater Boston who were part of the Veterans Affairs Normative Aging Study from 1995 to 2012.
Most participants were obese or overweight; about 64% of participants were former smokers and 31% were never smokers. None had a history of stroke. More than 75% of participants used NSAIDs, most taking aspirin only.
The researchers assessed cognitive performance with a composite global cognitive function score and the Mini-Mental State Examination (MMSE) over several visits, comparing results to PM2.5 levels on the day of each visit and 7, 14, 21, and 28 days earlier.
Compared with the lowest quartile of 28-day average PM2.5 concentration, the second, third, and fourth quartiles were associated with 0.378, 0.376, and 0.499 unit decreases in global cognitive function score; 0.484, 0.315, and 0.414 unit decreases in MMSE score; and 69%, 45%, and 63% greater odds of low MMSE score (score of 25 or less), respectively (all P<0.05).
Findings for black carbon, a component of PM2.5 and a tracer of vehicle traffic, followed similar patterns.
Among NSAID non-users, the second, third, and fourth quartiles of 28-day average PM2.5 concentration were associated with decreases of 0.889, 0.987, and 1.416 in global cognitive function score compared with the lowest quartile. Among NSAID users, those decreases were 0.267, 0.252, and 0.292, respectively.
Likewise, NSAID non-users showed decreases of 0.938, 0.868, and 0.894 in MMSE score; NSAID users showed decreases of 0.347, 0.144, and 0.237. Non-users had 131%, 210%, and 128% greater odds of a low MMSE score; for NSAID users, those odds were 59%, 16%, and 44%.
“At this early stage, we need to be very cautious in not over-interpreting the data,” the editorialists observed. Men who use NSAIDs may be different than ones who don’t — they may have better access to healthcare or health literacy, for example — and observational studies can’t tease apart those differences, they noted.
“We cannot say people should take NSAIDs to specifically protect them from air pollution but for people who are now using them, we can say they may have additional benefits,” Gao said.
“Our study was conducted in a male-only elderly population, and more studies in different races and females are required,” he added. “Taking NSAIDs may be a solution, but definitely is not the final answer to the threats of air pollution. Changing our policies of air pollution towards a more restrictive manner is still warranted.”
Judy George covers neurology and neuroscience news for MedPage Today, writing about brain aging, Alzheimer’s, dementia, MS, rare diseases, epilepsy, autism, headache, stroke, Parkinson’s, ALS, concussion, CTE, sleep, pain, and more. Follow
This work was supported by the National Institute of Environmental Health Sciences. The Veterans Affairs Normative Aging Study is supported by the U.S. Department of Veterans Affairs and is a component of the Massachusetts Veterans Epidemiology Research and Information Center.
The researchers and the editorialists declared no competing interests.
Source Reference: Gao X, et al “Short-term air pollution, cognitive performance and nonsteroidal anti-inflammatory drug use in the Veterans Affairs Normative Aging Study” Nature Aging 2021; DOI: 10.1038/s43587-021-00060-4.