Clinical Citations: What are the short-term effects of smoking cessation on asthma?

Perhaps surprisingly, limited published data exist on the effects of smoking cessation on symptoms, lung function, and corticosteroid responsiveness in smokers who have asthma. However, in a prospective controlled study, Scottish researchers found that 6 weeks af-ter smoking cessation, patients with asthma had significant improvement in lung function and a decrease in sputum neutrophil count compared with patients who continued to smoke.

Criteria for recruits included the American Thoracic Society definition of asthma; baseline forced expiratory volume in 1 second (FEV₁) of 85% or less of the predicted value; 15% or more reversibility of FEV₁ after nebulized albuterol; and smoking history of at least 10 pack-years. The study included 32 persons with asthma; 21 opted for smoking cessation, while 11 chose to continue smoking.

At 6 weeks, a comparison of smokers and quitters showed a mean difference in FEV₁ of 407 mL (P = .040), and the proportion of sputum neutrophils was reduced by 29 (P = .039). The total cutaneous vasoconstrictor response score to topical beclometasone improved after smoking cessation--the mean difference was 3.56 (P = .042). No change was noted in airway corticosteroid responses after smoking cessation.

The authors say that their results indicate that there is a reversible component to the adverse effects that smoking has on the airways in persons with asthma. The improvement in lung function could be the result of the elimination of the acute bronchoconstrictor effects of cigarette smoke, or it could be the result of the reduction in the proinflammatory effects of smoking.