• David H Au, Christopher L Bryson, Jason W Chien, Haili Sun, Edmunds M Udris, Laura E Evans, and Katharine A Bradley.
• Health Services Research and Development, VA Puget Sound Health Care System, 1660 S. Columbian Way (152), Seattle, WA 98108, USA. dau@u.washington.edu
• J Gen Intern Med. 2009 Apr 1; 24 (4): 457463457-63.

BackgroundSmoking cessation has been demonstrated to reduce the rate of loss of lung function and mortality among patients with mild to moderate chronic obstructive pulmonary disease (COPD). There is a paucity of evidence about the effects of smoking cessation on the risk of COPD exacerbations.ObjectiveWe sought to examine whether smoking status and the duration of abstinence from tobacco smoke is associated with a decreased risk of COPD exacerbations.DesignWe assessed current smoking status and duration of smoking abstinence by self-report. Our primary outcome was either an inpatient or outpatient COPD exacerbation. We used Cox regression to estimate the risk of COPD exacerbation associated with smoking status and duration of smoking cessation.ParticipantsWe performed a cohort study of 23,971 veterans who were current and past smokers and had been seen in one of seven Department of Veterans Affairs (VA) primary care clinics throughout the US.Measurements And Main ResultsIn comparison to current smokers, ex-smokers had a significantly reduced risk of COPD exacerbation after adjusting for age, comorbidity, markers of COPD severity and socio-economic status (adjusted HR 0.78, 95% CI 0.75-0.87). The magnitude of the reduced risk was dependent on the duration of smoking abstinence (adjusted HR: quit < 1 year, 1.04; 95% CI 0.87-1.26; 1-5 years 0.93, 95% CI 0.79-1.08; 5-10 years 0.84, 95% CI 0.70-1.00; > or = 10 years 0.65, 95% CI 0.58-0.74; linear trend <0.001).ConclusionsSmoking cessation is associated with a reduced risk of COPD exacerbations, and the described reduction is dependent upon the duration of abstinence.

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