Background: FEV1 is regarded as the most significant correlate of survival in COPD and is used as a measure of disease severity in the staging of COPD. Recently, however, the categorization of patients with COPD on the basis of the level of dyspnea has similarly been reported to be useful in the prediction of health-related quality of life and improvement in exercise performance after pulmonary rehabilitation.
Study objectives: We compared the effects of the level of dyspnea and disease severity, as evaluated by airway obstruction, on the 5-year survival rate of patients with COPD.
Design and methods: A total of 227 patients with COPD were enrolled in a 5-year, prospective, multicenter study in the Kansai area of Japan, involving 20 divisions of respiratory medicine from various university and city hospitals.
Results: After 5 years, 183 patients were available for the follow-up examination (follow-up rate, 81%). The 5-year cumulative survival rate among patients with COPD was 73%. The effect of disease staging, based on the American Thoracic Society (ATS) guideline as evaluated by the percentage of predicted FEV1, on the 5-year survival rate was not significant (p = 0.08). However, the level of dyspnea was significantly correlated to the 5-year survival rate (p < 0.001). The Cox proportional hazards model revealed that the level of dyspnea had a more significant effect on survival than disease severity based on FEV1.
Conclusions: The categorization of patients with COPD on the basis of the level of dyspnea was more discriminating than staging of disease severity using the ATS guideline with respect to 5-year survival. Dyspnea should be included as one of the variables, in addition to airway obstruction, for evaluating patients with COPD in terms of mortality.