The findings, reported in the journal Pediatrics, add to evidence that smoking bans in workplaces, restaurants and bars have produced health benefits. But until now, most research has focused on adults.
In the current study, researchers found that children and teenagers who lived in U.S. counties with smoke-free laws were no less likely to have asthma than kids in counties without such laws.
Kids with asthma were, however, less likely to report persistent problems with wheezing and nighttime coughing bouts when they lived in smoke-free counties.
The findings, based on a national government health survey, do not prove that smoke-free laws, per se, are the reason for the benefit.
But the researchers were able to account for a number of factors that might explain the link, including race and family income. (Minority children, especially in urban areas, have an increased risk of asthma.) And they still found a connection between the smoking bans and a reduced risk of persistent asthma symptoms.
“One finding alone does not prove ‘truth,'” said Dr. Gregory Connolly, director of the Tobacco Control Research Program at the Harvard School of Public Health and one of the researchers on the study. “But we’re pretty close to it.”
Connolly said the findings back up a recent study showing that after Scotland banned smoking in workplaces and enclosed public spaces in 2006, children’s hospital admissions for asthma declined.
That study joined earlier ones suggesting health benefits in adults. A 2009 U.S. government study, for example, found that after the city of Pueblo, Colorado, banned smoking in workplaces and public places, heart attack hospitalizations dropped 41 percent in the 18 months after the law went into effect.
“I think the key thing is, when we pass policies like this, we are often criticized for not having measurements of the effects,” Connolly said. With the current findings and the earlier studies, he said, “you’re linking policies directly with health effects.”
For their investigation, Connolly and his colleagues examined data from a U.S. government health survey conducted between 1999 and 2006. Parents of 8,800 children between the ages of 3 and 15 answered questions about asthma diagnoses and symptom severity.
Overall, 10 percent of the children currently had doctor-diagnosed asthma, and 21 percent lived in a county with at least one law banning smoking in workplaces, restaurants or bars.
Among kids with asthma, 12 percent of those living in a county without public smoking bans had persistent wheezing symptoms, chronic nighttime cough or were on medication to control wheezing. That figure was 8 percent for kids in smoke-free counties.
When the researchers weighed other factors, like family income, race and whether mothers smoked during pregnancy, children with asthma living in smoke-free counties were one-third less likely to have persistent symptoms than those in other counties.
One criticism of smoke-free laws had been that by limiting smoking in public areas, the policies might drive parents to smoke more often at home, putting their kids at greater risk from secondhand smoke.
But the current study and the Scottish one suggest that might not be the case. Connolly said smoke-free laws might be beneficial, in part, because they alter the “social norms,” or acceptability, of smoking.
Since the time of the study, more U.S. states, counties and cities have launched anti-smoking laws. An estimated three-quarters of Americans are now covered by some form of smoke-free law, Connolly said.
But he added that worldwide, many regions do not have such bans, and evidence of health benefits might encourage wider adoption of smoke-free laws.
“I think our findings will ultimately help more children breathe cleaner air, not only in the U.S. but, even more importantly, worldwide,” Connolly said.
By Amy Norton