Long-term exposure to air pollution has many health consequences, including accelerating brain aging and increasing the risk of dementia. Now, new research suggests that short-term exposure to polluted air, even in amounts that are generally considered “acceptable”, can affect the mental abilities of the elderly.
Scientists studied 954 men, a mean age of 69, who lived in the greater Boston area. The men were tested multiple times at the start of the study and over the next 28 days using the Mini-Mental State Examination (MMSE), a widely used test of cognitive ability. The test includes simple questions like "What year is this?" and “What time of the year is it?” and requires tasks such as counting down by seven out of 100. Answering fewer than 25 of the 30 questions correctly indicates mild dementia.
During the month, the researchers measured the air content of so-called PM 2.5, soot particles and other fine dust particles with a diameter of up to 2.5 micrometers, which are small enough to get into the lungs and into the bloodstream. There is no safe level of PM 2.5, but the Environmental Protection Agency considers air acceptable if it is below 12 micrograms per cubic meter. During the test period, Boston PM 2.5 levels averaged 10.77.
A higher PM 2.5 was consistently associated with lower test scores. In weeks with the highest air pollution, the men in the MMSE were 63 percent more likely to get less than 25 points than in weeks with the lowest air pollution. The study in Nature Aging was adjusted for age, B.M.I., coronary artery disease, diabetes, alcohol consumption, smoking, high blood pressure and other factors.
Dr. Andrea A. Baccarelli, senior writer and professor of environmental science at Columbia Mailman School of Public Health, said these short-term effects could be reversible. “When air pollution goes down,” he said, “the brain restarts and goes back to normal. However, when these episodes are repeated, they cause long-term brain damage. "
"Some of these particles come from natural sources – sea salt, for example soil and pollen," added Dr. Baccarelli added. "We'll never be completely free of them. But the man-made ones are much worse. The good news is that we've got to a point where we have the technology to reduce air pollution even further."
In what the researchers called "fascinating," they found that men who took NSAIDs – aspirin and other nonsteroidal anti-inflammatory drugs – were partially protected from the negative cognitive effects of pollution. They speculate that NSAIDs might decrease the inflammatory response to pollutants in the brain and nervous system.
"This is an impressive study," said Robert M. Bilder, professor of psychiatry and psychology at the University of California at Los Angeles, who was not involved in the work. However, the study is an observational study and not a randomized study, which is why it does not prove cause and effect. In addition, it was only done on older white men, many of whom were overweight or had smoked in the past. "Given the identified perceptual risks of PM and other environmental threats, and particularly given its disproportionate impact on racial and ethnic minority communities," he said, "we urgently need research beyond the study of white men."
Dr. Bilder pointed out that “The study reveals a potentially important interaction between NSAID use and exposure to environmental risks. We need controlled clinical trials and more basic research to specify the mechanisms by which the NSAIDs can work. "
Dr. Baccarelli agreed. "I would like to do a randomized study to see if there is any real benefit," he said. At the moment, “anything that promotes a healthy lifestyle helps protect against air pollution. Eating a healthy diet helps. Exercise helps. But I wouldn't tell anyone to take aspirin to protect against air pollution. "
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