Study objectives: The health-related quality of life of smokers without COPD and that of ex-smokers has not been defined. If abnormal, the role of small airways disease and that of cough and phlegm have never been evaluated. Therefore, the aim of the study was to explore whether the differences in quality of life between smokers and ex-smokers could be explained by cough and phlegm, differences in pulmonary function tests, or exercise capacity.
Design: Observational, prospective.
Setting: Pulmonary and Critical Care Division, COPD Center at St. Elizabeth's Medical Center.
Population: In 36 smokers, 21 ex-smokers (stopped smoking for > 20 years), 19 never-smokers with normal FVC and FEV(1) values, and 41 patients with COPD (FEV(1) 38 +/- 11% predicted [mean +/- SD]), the St. George's Respiratory Questionnaire (SGRQ), pulmonary function tests, and a 6-min walk distance (6MWD) were performed.
Results: The total SGRQ scores were worse in current smokers (15 +/- 15) than in ex-smokers (6 +/- 4) or never-smokers (4 +/- 3) [p < 0.05]. As expected, the worst score was seen in COPD (50 +/- 15). After correcting for cough and phlegm, the difference in SGRQ scores between smokers and ex-smokers disappeared. In current and ex-smokers, the SGRQ score was associated with the exposure to pack-years smoking history (r = 0.45, p < 0.01, and r = 0.83, p < 0.0001, respectively) but independent of lung function or exercise parameters (6MWD).
Conclusions: In smokers without COPD, the abnormal SGRQ score is due to the noxious effect of cigarette smoke, resulting in cough and phlegm, independent of its physiologic effects.