Lead researcher Talat Islam of the Keck School of Medicine of the University of Southern California, Los Angeles, says psychosocial stress appears to enhance the lung-damaging effects of traffic-related pollution in children.
Islam and colleagues administered a stress questionnaire -- the Perceived Stress Scale -- to the parents of nearly 1,400 children ages 10-12. The children were assessed for lung function and other respiratory health outcomes.
Hispanic and Asian parents had relatively higher levels of perceived stress than white parents, while stress was higher among children whose parents had an annual income of $30,000 or less, low education, lack of health insurance and lack of a home air conditioner.
The researchers did not observe any statistically significant associations between parental stress alone and lung function levels in children, but they found that as levels of traffic-related pollution increased among children who grew up in high-stress households, lung function decreased.
The study, published in the American Journal of Respiratory and Critical Care Medicine, found in high-stress households, children had on average a 4.8 percent lower lung volume and 4.5 percent lower flow in the larger airways for each 22 parts per billion increase in total oxides of nitrogen.
"Based on the emerging data we expected to see a modifying effect of stress," Islam says in a statement. "However, we were surprised by the magnitude of effect."