PHYSIOLOGICAL FACTORS THAT DETERMINE THE HEALTH-RELATED QUALITY-OF-LIFE IN PATIENTS WITH COPD

Study objective: To determine Phe physiologic factors that influence t he health-related quality of life (HRQL) in patients with stable COPD and to identify the factors that most influence HRQL. Methods: The Not tingham Health Profile (NHP) tvas used as a general HRQL measure and t he Chronic Respiratory Disease Questionnaire (CRQ) was used as a disea se-specific HRQL measure to investigate 132 patients with stable COPD, and measurements of HRQL were compared with physiologic measures. Res ults: Vital capacity, FEV(1), the ratio of the FEV(1) to the FVC, diff usion capacity for carbon monoxide, diffusion capacity corrected for a lveolar volume, lifetime cigarette consumption expressed as pack-years , and age were weakly correlated with several dimensions of both the N HP and the CRQ. Factor analysis reduced these variables to three facto rs. Two factors mainly referring to airflow limitation and diffusing c apacity were weakly correlated with several dimensions of both the NHP and the CRQ. Logistic regression analysis identified 4 independent pr edictors of HRQL: airflow limitation (odds ratio [OR]=0.59 to 0.69), d iffusing capacity (OR=0.75 to 0.82), pack-years (OR=1.20 to 1.23), and age (OR=2.13). The CRQ was more sensitive to impairment of HRQL than the NHP. Conclusions: The HRQL of patients with stable COPD is partly determined by airflow limitation, diffusing capacity, pack-years, and age. However, these factors could not predict the whole spectrum HRQL, and the contribution of these factors to HRQL was limited. Therefore, HRQL should be measured directly in addition to physiologic measures.