Traffic noise – the enemy of our brains

© CC-BY-NC-ND: Wissam Wahbeh

A new study shows that adolescents exposed to road traffic noise suffer memory and concentration deficits.

Noise is a stress factor for a large part of the population. It also affects our brains, and several scientific studies have already demonstrated the impact of air traffic noise on mental performance. However, we know very little about the effects of road traffic noise. As part of a project funded by the Swiss National Science Foundation (SNSF), Martin Röösli, professor of environmental epidemiology at the Swiss Tropical and Public Health Institute in Basel, investigated the effects of long-term exposure to road traffic noise on the brains of adolescents. In an article recently published in the journal Environmental Research*, he demonstrates that exposure to road traffic noise at home affects their cognitive performance.

Memory and attention affected

To study the effects of long-term exposure to traffic noise, the scientist spent a year charting the cognitive performance of a group of 900 adolescents between the ages of 10 and 17 who experienced different noise level from road traffic at home. He used questionnaires and tests to evaluate their cognitive performance at the start and finish of the study, then measured the difference between the two results. His study – according to the scientist one of the very few to investigate the effects of chronic noise over a certain period – shows that exposure to road traffic noise at home slightly reduces two cognitive parameters: memory and attention.

Specifically, each time average traffic noise rose by 10 dB – equivalent to a doubling of the perceived sound level – representational memory, a type of memory that involves images, was reduced by 0.27 points. In addition, ability to maintain concentration was reduced by 0.13 points. But what do these reductions actually signify? “To get an idea of what they mean, we can compare the difference in cognitive performance between the start and end of the study with the difference in the cognitive performance of different secondary school levels, for example between level B and level A or between level A and upper secondary level”, the researcher explains. The decline in representational memory recorded in the course of the study was equivalent to one third of the difference observed between two school levels, while the reduction in ability to concentrate consistently was roughly the same as the difference observed between two school levels.

Likely impact through sleep

The study also provides a clue as to why this may be. “The noise probably affects the cognitive performance of the adolescents because it disturbs their sleep”, Martin Röösli suggests. He found that noise had a bigger effect on the mental performance of young people whose bedroom looked out onto a busy road.

Admittedly, he is at pains to point out that the effects highlighted by this study are slight and need confirmation. During a previous study involving younger children living in Sao Paolo with higher noise levels, however, the researcher was able to demonstrate that road traffic noise had a much higher impact on cognitive performance.