Alzheimer’s, dementia, slurred speech… A study published in The Lancet Planetary Health, Thursday, March 10, associates air pollution with reduced cognitive performance: the more a person is exposed to polluted air, the more their mental functions will be affected.
To arrive at this result, researchers from the National Institute of Health and Medical Research (Inserm), the University of Rennes and the School of Advanced Studies in Public Health analyzed data from more than 61,000 French people aged over 45. These participants are part of the French Constances epidemiological cohort and were randomly recruited from the Health Insurance lists. The researchers established a score for their cognitive performance based on tests measuring memory, fluency in oral expression (verbal fluency) and ability to make decisions (executive functions).
Then the researchers overlaid these results with so-called “exposure” maps that estimate the concentration of pollutants at each participant’s home address. In this study, three pollutants were taken into account: fine particles (PM2.5), nitrogen dioxide (NO2) and soot carbon. “We focused on these three pollutants because they are associated with or come from car traffic, explains Bénédicte Jacquemin, research fellow at Inserm and co-author of the study. Scientific evidence in all areas of health shows that these pollutants are probably the most harmful to health. »
A “modifiable” risk factor
According to the study, not only is exposure to higher concentrations of pollutants significantly associated with a lower level of cognitive performance, but each pollutant acts differently on this performance. “The most impacted abilities are verbal fluency and executive functions, says Bénédicte Jacquemin. Nitrogen dioxide and PM2.5 particles act more on verbal fluency, while soot carbon has a greater impact on executive functions. »
For the most exposed participants, the researchers found a difference ranging from 1 to almost 5% in the cognitive performance score compared to the less exposed participants. “Five percent on an individual level doesn’t have a strong impact, explains the researcher. But our results are very important at the population level because almost everyone is exposed to a higher level of air pollution than recommended by the WHO. »
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