Boys and girls with more exposure to pollution and less to green spaces are at higher risk for ADHD

An international team of researchers, led by Matilda van den Bosch from the Barcelona Institute for Global Health (ISGlobal) and the University of British Columbia, Canada, analyzed the possible associations between exposure to vegetation, air pollution and noise in the early years of life with the later incidence of attention deficit disorder. hyperactivity (ADHD).

The study used administrative data from 37,000 births in Vancouver between 2000 and 2001 and ADHD cases retrieved from hospital records, doctor appointments and prescriptions.

The results, published in the journal International Environmentindicate that boys and girls who live in areas with higher air pollution by PM2.5 particles and with scarcity of green spaces could have even 62% higher risk of developing ADHD.

Boys and girls who live in areas with the highest air pollution from PM2.5 particles and a shortage of green spaces may be up to 62% more likely to develop ADHD.

On the contrary, those who live in zgreener and less polluted areas have a 50% less risk to develop the disorder.

ADHD is one of the most prevalent neurodevelopmental disorders, affecting around 5-10% of the child and adolescent population. The aim of the study was to evaluate the joint effects of the three exposures (vegetation, pollution and noise) in relation to this disorder.

The percentage of green space in the neighborhood of the participants was estimated with a new and accurate satellite metric, while the residential levels of two air pollutants – nitrogen dioxide (NOtwo) and PM2.5 particles– as well as levels of noisewere estimated using available exposure models.

Statistics to estimate risk

Finally, the possible associations between the three environmental exposures and ADHD were evaluated using a statistical model that made it possible to determine the risk ratios.

The scientific team was able to identify 1,217 cases of ADHD, which is equivalent to 4.2% of the total study population. Analysis of green spaces revealed that participants who lived in areas with a higher percentage of vegetation had a lower risk of ADHD. More specifically, the results show that a 12% increase in the percentage of vegetation was associated with a 10% reduction in the risk of ADHD.

Regarding air pollution, the opposite association was seen with PM2.5: participants with greater exposure to fine particulates had a higher risk of ADHD (every 2.1 microgram increase in PM2 levels, 5 translated into an increase of 11 % in the risk of ADHD).

No associations were found for the rest of the environmental exposures evaluated: neither for NO2 nor for noise.

Joint effects of PM2.5 and vegetation

The results are consistent with previous studies, which found associations between green spaces and air pollution, respectively, with ADHD. However, most research conducted to date has focused on evaluating single exposures and has rarely evaluated the joint effects of multiple environmental exposures.

“We have observed that children who live in greener neighborhoods with low air pollution have a substantially lower risk of suffering from ADHD. It is an environmental inequality where, in turn, children living in areas with more pollution and less green face a disproportionately greater risk,” explains Van den Bosch.

“These associations are especially relevant because exposures occur in the early years of life, a crucial period for brain development in which children are especially vulnerable. More importantly, these exposures are modifiable, which means that the results must be taken into account for healthier urban planning”, he adds.

“Our findings also show that the associations between PM2.5 and ADHD were attenuated with residential green spaces and vice versa, as if the beneficial effects of vegetation and the harmful effects of PM2.5 cancel each other out,” he explains. Weiran Yuchiresearcher at the University of British Columbia (Canada) and first author of the study.

Reference:

Yuchi W. et al. “Neighborhood environmental exposures and incidence of attention deficit/hyperactivity disorder: a population-based cohort study”. International Environment. 2022

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