Traffic-related air pollutants decrease cognitive performance

The harmful effects of air pollutants on health even at low levels of exposure are well documented. Recent research has notably suggested that in addition to increasing the risk of developing cardiovascular and pulmonary diseases, air pollutionair could accelerate cognitive decline, one of the warning symptoms of a neurodegenerative pathology such as Alzheimer’s disease and other dementias.

For some years, the air pollution is thus recognized as a “modifiable” risk factor for dementiathat is to say on which it is possible to act via changes in the regulations governing the tolerated levels of pollution. 40% of dementia cases could thus be avoided or delayed. However, no study has so far looked simultaneously at several types of pollutants and their potential respective effects on the different areas of cognition.

Researchers from Inserm, the University of reindeer 1 and the School of Advanced Studies in Public Health (EHESP) at Irset have studied how the level of exposure to atmospheric pollutants impacts performances cognitive. The results of the study suggest a link between exposure to higher concentrations of pollutants and a lower level of cognitive performance, a link which differs according to the pollutants. They are published in The Lancet Planetary Health.

Make exposure cards

A study that revealed that a decline in cognitive performance could occur from the age of 45 based on data from more than 61,000 participants from the cohort epidemiological constantsaged 45 and over.

All took part in a series of tests measuring their cognitive performance in three main areas of cognition: Memory, the fluency of oral expression (or verbal fluency) and the ability to make decisions. The researchers established a cognitive performance score for each of the tests, taking into account the sex, age and level of study of each participant.

To measure each participant’s exposure to pollution, the research team used so-called “exposure” maps that estimate the concentration of pollutants at the home address. These maps take into account several variables such as the density of the road traffic or the proximity of the residence to the roads. Three pollutants linked to road traffic were considered in the context of the study: fine particles diameter less than 2.5 microns (PM2.5), dioxidenitrogen (NO2) and carbon soot.

Air pollution affects cognitive performance

By crossing the results of the cognitive tests with the level of exposure to the three air pollutants, the study indicates that exposure to greater concentrations of these pollutants would be significantly associated with a lower level of performance in the three cognitive domains studied. For the most exposed participants, the researchers found a difference ranging from 1 to nearly 5% in the score of cognitive performance compared to less exposed participants.

” The abilities most affected are verbal fluency and executive functionssays Bénédicte Jacquemin, the Inserm researcher who led this work. Nitrogen dioxide and PM2.5 particles have a greater impact on verbal fluency, while carbon soot has a greater impact on executive functions. »

She concludes: The next step in our research is to observe the evolution over time of the cognitive functions of these adults, in order to see if exposure to pollution is also associated with a decline in cognitive functioning over time, a decline that may reflect the first signs of dementia, both from Alzheimer’s disease than other forms of dementia in the elderly. »