Students crossing crosswalk from busy road outside school

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BARCELONA — Children who attend schools near noisy roads are more likely to be slower learners, according to new research. Scientists say loud traffic harms working memory — a ‘mental sketchpad’ essential for retaining information.

Memory isn’t the only area of cognitive development to suffer. The study shows noisy roadways also have a detrimental affect on a child’s ability to pay attention in class, which could lead to poorer grades.

“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,” says study co-author Jordi Sunyer, a researcher from the Barcelona Institute for Global Health (ISGlobal) in Spain, in a statement.

The findings, are based on 2,680 pupils aged seven to ten at 38 schools across the city.

Participants underwent mental tests four times over a period of 14 months to check working and complex working memory and attentiveness. The skills are vital for learning and academic success and develop rapidly in pre-adolescence.

Attention includes processes such as selecting specific stimuli or focusing on a single task for a prolonged period. Working memory is the system that allows us to hold details in the mind and manipulate them over a short spell. When we need to continuously and effectively process them we use what is known as complex working memory.

The more traffic noise, the worse students performed

The field work was carried out from January 2012 to March 2013. Noise measurements were taken in front of participating schools, in playgrounds and inside classrooms. Afterwards progression of working memory, complex working memory and attention was worse in students at schools with higher levels of traffic noise.

A 5 dB (decibel) increase in outdoor levels resulted in working and complex working memory that was 11.4 and 23.5 percent slower than average, respectively. Similarly, exposure to an additional 5 dB of outdoor traffic noise resulted in attention capacity development that was 4.8 percent slower than average.

Higher outdoor average noise level and greater fluctuations were both associated with poorer performance on all tests.

Inside the classroom, greater fluctuations were also linked with slower progress over the course of the year on all cognitive tests. Those exposed to higher average classroom noise levels over the course of the year did worse on attention, but not working memory.

“This finding suggests noise peaks inside the classroom may be more disruptive to neurodevelopment than average decibel level,” explains lead author Maria Foraster. “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.”

Busy roadways linked to poorer health in adults, but children less studied

The research took into account traffic-related air pollution and sociodemographics. It has implications for noise policies to protect school environments. An increasing number of epidemiological studies in adults have linked it to illnesses in adults, but little is known about the effects in children.

The researchers also used the 2012 road traffic noise map of the city of Barcelona to estimate the average noise level at each participant’s home. In this case, however, no association was observed 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,” adds Foraster. “On the other hand, although noise measurements were taken at the schools, noise levels at the children’s homes were estimated using a noise map that may be less accurate and, in any case, only reflected outdoor noise. This, too, may have influenced the results.”

The study adds to evidence on the effects of transportation on children’s cognitive development. They have been observed at schools exposed to aircraft noise as well as at schools exposed to traffic-related air pollution. The findings are of public health relevance given the number of children around the world who are exposed to road traffic noise in schools.

Researchers are calling for further studies on road traffic noise in other populations to determine if the findings can be extrapolated to other cities and settings. They did not measure past noise exposure in their population which could affect the scores.

But 98 percent of the children had attended the same school for at least a year and noise levels were generally steady over time.

The study is published in the journal PLoS Medicine.

South West News Service writer Mark Waghorn contributed to this report.

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