WEDNESDAY, Sept. 15 (HealthDay News) -- Laws that ban smoking in workplaces and public settings seem to show a fringe benefit: Scottish researchers report that such legislation is linked with a decline in hospital admissions for childhood asthma.

Researchers have long known that exposure to tobacco smoke increases the incidence and severity of asthma, and that children are especially vulnerable.

While other studies have looked at the effects of smoking bans on all ages, and have taken into account on-the-job exposure, "ours is the first study to have looked at a subgroup of the population [children], who do not have occupational exposure," said lead researcher Dr. Jill Pell, the Henry Mechan Professor of Public Health at the University of Glasgow.

In March of 2006, the Smoking, Health and Social Care Act was passed in Scotland. It banned smoking in all enclosed public places and in workplaces.

For the study, Pell and her colleagues identified all the hospital admissions for asthma among children under the age of 15 from January 2000 through October 2009.

The investigators found a total of 21,415 admissions for asthma. Before the smoking law passed, admissions were increasing, on average, by 5.2 percent per year.

After the law passed, there was a reduction, on average, of 18.2 percent each year, relative to the rate on the day the law went into effect.

"The evidence from Scotland is that legislation has an effect that extends beyond the locations that are covered by the restrictions," Pell said. "In Scotland there has been an increase in voluntary bans in the home and a resultant reduction in exposure to secondhand smoke among children. It is clear that legislation has a more general effect on smoking attitudes and behaviors."

She is confident the same effects are already occurring in the United States as well, as smoking bans have been passed.

In the Scottish study, the decline in admissions for asthma was seen in both preschool and school-age children.

When the legislation was first discussed, some feared that the bans in public and workplaces might cause home smoking to increase. But there's no evidence of that, she said. Instead the laws seem to have been followed by an increase in voluntary restriction of smoking at home.

The study was supported by a grant from NHS Health Scotland.

"The findings are a confirmation of the beneficial effect of reducing the exposure of children to environmental tobacco smoke," said Dr. E. Rand Sutherland, chief of the division of pulmonary and critical care medicine at National Jewish Health, in Denver.

"The study also suggests, importantly, that children [and not just adults] can be the beneficiaries of smoke-free policies which target the workplace and public spaces," he added.

In the United States, more than 200,000 episodes of childhood asthma each year have been blamed on parental smoking, some research has found.

More information

To learn more about secondhand smoke and children, visit the American Academy of Pediatrics.