Traffic noise may impair children’s cognitive development: study

Traffic noise intruding on schools may have a detrimental impact on the development of memory and attention in elementary students, a new study finds.

The study, published on Thursday in PLoS Medicine, determined that the progression of working memory, complex working memory and attention over the course of a year was slower in students who attended schools in Barcelona, Spain, that suffered from outdoor noise.

“Our study supports the hypothesis that childhood is a vulnerable period during which external stimuli such as noise can affect the rapid process of cognitive development that takes place before adolescence,” co-author Jordi Sunyer, a researcher at the Barcelona Institute for Global Health, said in a statement.

During a 12-month period from 2012 to 2013, Sunyer and his colleagues said they observed 2,680 children between 7 and 10 years old at 38 schools in Barcelona.

The children completed four cognitive tests, assessing their memory, attention and development, according to the study.

Over that yearlong study period, the authors also took noise measurements in front of all 38 participating schools, as well as at their playgrounds and inside classrooms.

The authors found that a 5-decibel increase in outdoor noise levels resulted in working memory development that was 11.4 percent slower than average and complex working memory development that was 23.5 percent slower than average.

They defined working memory as “the system that allows us to hold information in the mind and manipulate it over a short period of time.” Complex working memory, on the other hand, is used to “continuously and effectively process information stored in the working memory,” the authors stated.

Exposure to the same 5-decibel rise in outdoor noise levels also led to attention capacity development that was 4.8 percent slower than average, according to the study.

The researchers observed stark differences in the impacts of noise increases inside and outside the classroom.

While outdoor noise was associated with poorer student performance on all tests, children exposed to higher average classroom noise levels performed worse only on the attention test and not on the working memory tests.

But when children were exposed to greater fluctuations in noise levels inside the classroom, then they performed worse on all tests, according to the study.

That finding could indicate that “noise peaks” indoors might be more disruptive to children’s neurodevelopment than average volume levels, explained lead author Maria Foraster, a researcher at the Barcelona Institute for Global Health.

“This is important because it supports the hypothesis that noise characteristics may be more influential than average noise levels, despite the fact that current policies are based solely on average decibels,” Foraster said in a statement.

The authors also estimated average noise levels at each participant’s home by using a 2012 road traffic noise map produced by the city of Barcelona.

Different from their observations at schools, however, they said they found no association between residential noise and cognitive development.

“This could be because noise exposure at school is more detrimental as it affects vulnerable windows of concentration and learning processes,” Foraster said, acknowledging, however, that the estimates may have been less accurate than the measurements taken at school.

Nonetheless, the authors called for further studies on road traffic noise in other populations, stressing the importance in determining whether such findings can be extrapolated to other urban environments.