Multiple attempts to stop smoking, even with relapses, reduced loss of pulmonary function
Question What are the effects of multiple failed attempts to stop smoking on pulmonary function of adults?
Design
Retrospective analysis of a cohort of participants involved in a randomised controlled trial (Lung Health Study), with annual follow up for 5 years.
Setting
10 clinical centres in North America.*
Participants
5887 adults aged 35–60 years, who smoked and had evidence of early chronic obstructive pulmonary disease (ie, had an FEV1/FVC [forced expiratory volume at 1 sec/forced vital capacity] interval of ≤70%, and an FEV1 of 55–90% of predicted normal).
Assessment of risk factors
Smoking status was assessed at baseline and at 5 annual visits thereafter. Participant reports of abstinence were confirmed by salivary cotinine concentrations (<20 ng/ml) or if nicotine substitution therapy was used, by CO concentrations (<10 ppm in end tidal expired air). Participants were classified as sustained quitters (verified non-smokers at the first follow up visit, who remained abstinent at all subsequent follow up visits, and who recalled no …
