Effects of multiple attempts to quit smoking and relapses to smoking on pulmonary function

The effect of intermittent smoking on pulmonary function was assessed among participants in the Lung Health Study, 5887 adult smokers with evidence of early chronic obstructive pulmonary disease (COPD), followed up for 5 year s. The mean annual rate of loss in FEV1% of predicted after year 1 was smal lest for those who quit at some point during the first year of the study an d stayed quit (-0.33%/year, +/-0.05%), intermediate for those who smoked in termittently during the study (-0.58%/year, +/-0.05%) and greatest for thos e who continued to smoke throughout the study (-1.18%/year, +0.03%). Surpri singly, those who made several attempts to quit smoking had less loss of lu ng function at comparable cumulative doses of cigarettes than those who con tinued to smoke. Quitting smoking for an interval followed by relapse to sm oking appeared to provide a measurable and lasting benefit in comparison to continuous smoking; In this early COPD population not only quitting smokin g but attempts to quit smoking can prevent some loss of lung function. Thes e results provide some encouragement to exsmokers who relapse on their way to complete cessation. J CLIN EPIDEMIOL 51;12:1311-1326, 1998. (C) 1998 Els evier Science Inc.