For children with asthma, reducing exposure to environmental tobacco smoke greatly decreases their chances of an asthma flare-up, hospital admission or emergency room visit, a study shows.

"We found this to be true when the child's exposure (to second-hand smoke) decreased, even if the decrease did not mean completely eliminating their exposure," Dr. Lynn B. Gerald, of University of Arizona in Tucson told Reuters Health. "Any reduction in environmental tobacco smoke exposure seems to greatly benefit these children."

Gerald's team documented the association between changes in environmental tobacco smoke exposure and childhood asthma-related illness in 290 asthmatic children enrolled in a clinical trial of supervised asthma therapy. The average age of the children was 11 years and 80 percent had moderate persistent asthma.

At the start of the study, 28 percent of caregivers reported that the child was exposed to second-hand smoke in the home and 19 percent reported exposure to smoke outside the home only. At a follow-up interview, 74 percent of caregivers reported no change in the child's exposure to second-hand smoke, 17 percent reported less exposure, and 9 percent reported increased exposure.

According to a report in the medical journal Chest, children who had any decrease in exposure to second-hand smoke over the course of 1 year had fewer episodes of poor asthma control, made fewer respiratory-related trips to the emergency room and were less apt to be hospitalized than children who had the same or increased exposure to second-hand smoke.

"We were not surprised by the findings but we were surprised by the magnitude of the benefit that decreasing smoke exposure appeared to have," Gerald told Reuters Health.

She said doctors can use this information as another "teaching point" for caregivers and parents of children with asthma.

Given that the majority of second-hand smoke exposure in the home is due to parents smoking, "the most effective environmental tobacco smoke reduction strategy may be to provide smoking cessation interventions to parents and possibly other household members," Gerald and her colleagues conclude.