Smoking cessation affects the natural history of COPD

Cigarette smoking is the most commonly encountered and readily identifiable risk factor for COPD. However, it is not clear which quantitative factors related to smoking influence the prognosis of COPD patients.

A total of 204 patients with a long-term history of smoking were enrolled into this study and followed up for 5 years. Patients were divided into "death" or "survival" groups based on follow-up results and "quitting-smoking" or "continuing-smoking" groups based on whether they gave up smoking.

Patients in the death group had a longer smoking time, lower prevalence of quitting smoking, later onset of COPD symptoms, older age at quitting smoking, lower forced expiratory volume in one second (FEV₁) % predicted, and lower ratio of FEV₁/forced vital capacity. Age, age at quitting smoking, and FEV₁% predicted were independently associated with mortality from COPD. Compared to the continuing-smoking group, the quitting-smoking group had a lower mortality rate, longer course of COPD, earlier onset of COPD symptoms, and lower residual volume percent predicted. During the 5-year follow-up, 113 deaths were recorded (quitting-smoking group: n=92; 40 deaths; continuing-smoking group: n=112; 73 deaths). The mortality risk remained significantly higher in the continuing-smoking group than the quitting-smoking group (log-rank test, 13.59; P=0.0002).

Smoking time may be related to the mortality rate from COPD. Smoking cessation has the greatest capacity to influence the natural history of COPD.