There may be a reason that children's asthma rates are so high in urban areas. Youngsters with stressed-out parents and exposure to air pollution have a higher risk of asthma, according to a study in the journal Proceedings of the National Academy of Sciences.
Air pollutants can cause an inflammatory response in the airways, which is a primary feature of asthma.
"The new study raises some questions about why stress-plus-pollution leads to worse problems than either alone," says Harold J. Farber, M.D., an associate professor of the pediatric pulmonary section at Baylor College of Medicine and Texas Children Hospital, in Houston, and the author of "Control Your Child's Asthma." "Why is it that this combination is somewhat more toxic than either alone?"
In the United States, about 22 million people -- including 6 million children -- have asthma. City-dwelling children have about a 22 to 45 percent higher risk of developing asthma than their peers living elsewhere.
In the new study, a research team led by Rob S. McConnell, M.D., a professor of preventive medicine at the Keck Institute of Medicine at the University of Southern California in Los Angeles, tracked 2,497 children from the region. The children were ages 5 to 9 and had no history of asthma or wheezing.
Children with stressed-out parents who lived around high levels of traffic-related pollution were at a higher risk of developing asthma during the three-year study period than children without stressed parents. Stressed parents tend to have children who report more stress too, but the researchers did not measure the children's stress levels. Parents were considered stressed if they said their lives were unpredictable, uncontrollable, and overwhelming. Health.com: Tips for staying hopeful when you have breast cancer
Air pollutants can cause an inflammatory response in the airways, which is a primary feature of asthma. Stress may increase a person's susceptibility to air pollutants by lowering immune system function or affecting the autonomic nervous system, which helps regulate breathing, the authors say.
The study helps to pinpoint the children most at risk for the respiratory disorder, says Farber, who was not involved in the new research.
"It also reinforces basic things, like parental stress and traffic-related pollution are bad things for children and things that we need to decrease our children's exposure to," he says, noting that this is easier said than done. "Managing stress and pollution are important, and if two things occur together, it's important to be on top of them." Health.com: How to have a healthy, stress-free summer
What's more, parental stress also seemed to exacerbate the effect of maternal smoking during pregnancy, according to the study. Children who had stressed-out parents and were exposed to cigarette smoke during pregnancy were two to three times more likely to develop asthma than children exposed to cigarette smoke alone. Stress and low socioeconomic conditions (such as not finishing high school) on their own did not increase a child's risk of developing asthma.
If your child develops any signs or symptoms of asthma -- such as a chronic cough or wheezing -- get it checked out as soon as possible, Farber advises. "If you think your child may be predisposed to asthma, don't live near a freeway; if you do live near a freeway, get on top of your stress and look at stress management programs and/or moving." Health.com: Simple changes to improve your mind, mood, and outlook
Neil Schachter, M.D., the director of respiratory care at Mount Sinai Medical Center, in New York City, and the author of "The Good Doctor's Guide to Colds and Flu," agrees.
"Stress alone does not provoke or make asthma worse, unless it is in conjunction with other known risk factors such as traffic-related air pollution," he says. "If a child lives in the country and is not exposed to air pollution, parental stress does not make it worse." Health.com: Change one thing, change your life: A primer for improving your mood
Dr. Schachter's advice? "Go green where you can," he says. "Use a home air cleaner to remove small particles that are in the air. You may not be able to control the outdoor air quality on your own, but you can try and control your indoor air quality by banning smoking inside the house and choosing green cleaning products, which do not contain harsh chemicals that can affect indoor air quality."
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