Determinants of different dimensions of disease severity in asthma and COPD - Pulmonary function and health-related quality of life

Objective: To identify determinants of pulmonary function and health-relate d quality of life (HRQOL) to better understand disease severity in patients with asthma and COPD, Design: Observational study. Setting, Dutch general practice. Patients: We studied 837 asthma patients and 231 COPD patients. Results: The association between pulmonary function and HRQOL was poor for asthma (beta = 0.10) and COPD (P = 0.19). Multivariately, in asthma, lower pulmonary function was associated with male gender, region of living, curre nt smoking, use of inhaled short-acting bronchodilators, longer duration of disease, and higher diurnal variation in peak expiratory flow. In COPD, lo wer pulmonary function was associated with male gender, use of inhaled bron chodilators, more days and nights disturbed by respiratory complaints, not wheezing, and bronchial hyperresponsiveness. Reduced HRQOL was associated m ost strongly with more clays and nights disturbed by respiratory complaints and dyspnea in both asthma and COPD, In asthma, additional associations we re found with younger age, lower educational level, region of living, comor bidity, use of inhaled bronchodilators and corticosteroids, wheezing, chron ic cough, sputum production, and bronchial hyperresponsiveness. In COPD, lo wer age, not smoking, chronic cough, and sputum production were associated with reduced HRQOL. Conclusions: Pulmonary function and HRQOL appear to highlight different asp ects of disease severity in asthma and COPD, Therefore, both measures shoul d be taken into account in order to get a complete picture of severity of d isease.