Background: The American Thoracic Society recently recommended that chronic obstructive pulmonary disease be staged on the basis of the percentage of predicted FEV1.
Objective: To examine 1) the relation between the American Thoracic Society system for staging chronic obstructive pulmonary disease and health-related quality of life and 2) the effect of self-reported comorbid conditions on health-related quality of life.
Design: Cross-sectional study.
Setting: Outpatient clinics of respiratory department of four hospitals and one primary health care center in Spain.
Patients: 321 consecutive male patients with chronic obstructive pulmonary disease.
Measurements: Functional respiratory impairment, FEV1, respiratory symptoms, and health-related quality of life. Respiratory symptoms and health-related quality of life were measured by using the Spanish version of the St. George's Respiratory Questionnaire and the Nottingham Health Profile.
Results: Patient scores on the St. George's Respiratory Questionnaire were moderately to strongly associated with disease staging (r = 0.27 to 0.51). Compared with reference values, values for health-related quality of life for patients with stage I disease were substantially higher on the St. George's Respiratory Questionnaire (6 and 34; P < 0.001) and values for impairment were significantly greater in stage I patients with comorbid conditions (19 and 36; P = 0.001). At least one concomitant chronic condition was found in 84% of study patients. Comorbid conditions only partly influenced the observed pattern of deterioration of health-related quality of life with worsening stages of disease.
Conclusion: Staging criteria for chronic obstructive pulmonary disease based on percentage of predicted FEV1 separated groups of patients with varying degrees of impairment in health-related quality of life. Contrary to expectations, even patients with mild disease showed substantially compromised health-related quality of life. Comorbid conditions influenced the relation between chronic obstructive pulmonary disease and health-related quality of life.