NEW YORK (Reuters Health) -- Cigarette smokers with asthma who quit smoking see significant improvement in their lung function as early as one week after quitting, a study shows. Kicking the habit also reduces inflammation in the airways.

"This demonstrates that there is a reversible component to the harmful effects of smoking on the airways in asthma," the study investigators note in the American Journal of Respiratory and Critical Care Medicine.

"The degree of the improvement in lung function noted in the smokers with asthma after quitting was much greater than we expected," Dr. Neil C. Thomson told Reuters Health. In fact, he and his colleagues say, the improvement "far exceeds" that seen with high doses of steroids.

Thomson, from the University of Glasgow, Scotland, and his associates assessed lung function and airway inflammation in 11 asthmatics who continued to smoke and 10 asthmatics who quit for six weeks. They were smoking 10 or more cigarettes per day and had a smoking history of more than 10 pack-years and had reduced lung function.

The lung function of the "quit" group improved "by a considerable degree" within one week of stopping smoking, the researchers report.

Their "asthma control score" also improved with smoking cessation but this did not translate into an improvement in daily asthma symptoms recorded by subjects up to two months after quitting.

The quitters also showed a reduction in airway inflammation six weeks after smoking cessation compared with those who continued to smoke. "Our research," Thomson told Reuters Health, "has shown that smokers with asthma obtain clinically important improvements in lung function and airway inflammation shortly after stopping smoking. These results help emphasize the importance of smoking cessation for adults with asthma."

Of the 10 asthmatic smokers who successfully quit smoking, five did so using nicotine patches, one used acupuncture and four quit without any aid.