Bai J, et al. - 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. In this present study, performed on patients with a long-term history of smoking, it was demonstrated that smoking time may be related to the mortality rate from COPD. Furthermore, it was noted that smoking cessation had the greatest capacity to impact the natural history of COPD.