COPD-related morbidity and mortality after smoking cessation: status of the evidence
The evidence base for the benefit of quitting smoking as regards morbidity and mortality outcomes in patients with moderate-to-severe chronic obstructive pulmonary disease (COPD) is limited.
The present article is a review of the existing literature. A systematic literature search in medical databases was performed until March 2006, and subsequently until September 1, 2007. The outcomes examined were COPD-related morbidity and mortality (including all-cause mortality) in COPD patients in connection with smoking cessation.
A total of 21 and 27 published articles on morbidity and mortality, respectively, were identified and reviewed. For both outcomes, only a few of the studies included patients with severe COPD. Most of the studies reported a beneficial effect of smoking cessation compared with continued smoking, whereas a few found no improvement. Methodological problems, including small study sizes, poor data quality, possibility of reverse causality and incomplete ascertainment of cause of death, limit interpretation of some of the studies.
The evidence as a whole supports the conclusion that, even in severe chronic obstructive pulmonary disease, smoking cessation slows the accelerated rate of lung function decline and improves survival compared with continued smoking.
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Forced expiratory volume in one second (FEV
1) decline expressed as a percentage of the decline in 100% of continuing smokers in those studies for which this measure was available. All but one of these studies show a relative reduction in FEV 1decline.
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Relative risk (RR)/hazard ratio (HR)/mortality rate (MR) ratio of mortality due to chronic obstructive pulmonary disease after smoking cessation (▪) compared with continuing smoking (▴; RR 1.0).
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Risk of all-cause mortality after smoking cessation expressed as a percentage of the risk in 100% of continuing smokers. The majority of these studies show a reduction in risk. #: females alone.