Respiratory symptoms, lung function, and mortality in a screening center cohort

Numerous studies have documented the effects of smoking and reduced pulmonary function on all-cause mortality. The effects of respiratory symptoms are less well studied. This paper examines the joint effects of respiratory symptoms, lung function, and smoking using 11-year mortality data on 698 subjects aged 25 years and older. Copies of death certificates were obtained for all 120 confirmed deaths, and cause of death was coded by a nosologist using the rules of the international Classification of Diseases, Ninth Revision. Symptoms of cough/phlegm, wheeze, and dyspnea were significantly associated with all-cause mortality in separate univanate analyses. On a cause-specific basis, these associations appeared to hold for chronic obstructive pulmonary disease, lung cancer, and vascular disease. Further analysis indicated that, for both smokers and nonsmokers, the presence of chronic cough and/or sputum production was related to mortality only in the presence of wheezing. In addition, among smokers, the presence of both cough/phlegm and wheeze was significantly associated with mortality only among subjects with low initial lung function. Although the limited number of deaths and the nonrandom nature of the cohort limit the generalizability of our findings, it seems clear, based on these results and other published studies, that symptoms of cough, phlegm, and/or wheeze have important adverse health implications even in the absence of smoking and reduced lung function. More studies using common methodological approaches are needed.