Bronchial reactivity to methacholine in ten non-obstructive heavy smokers before and up to one year after cessation of smoking.

We studied non-specific bronchial reactivity to methacholine (MCh) before and during 1 year after cessation of smoking in four female and six male "smoke resistant" heavy cigarette smokers without severe respiratory symptoms or airways obstruction. The patients had smoked an average of 33 cigarettes a day since age 16. A standardized test of non-specific bronchial reactivity to methacholine was performed prior to cessation and 1 week, 1, 6 and 12 months after cessation of smoking proven by a decrease to normal COHb. Before cessation only two subjects showed a greater than or equal to 15% decrease of FEV1 after inhalation of 0.1% MCh which is compatible with bronchial hyperreactivity. Already 1 week after cessation there was a significant increase in FEV1 and VC to values around 100% of predicted. Bronchial reactivity was judged to decline after 1 month of non-smoking in four subjects but was unchanged in the others, and there was no statistically significant decrease of bronchial reactivity in the group of 10 after a 12-month smoke-free period.