Health-related quality of life in COPD: why both disease-specific and generic measures should be used

Although research has consistently demonstrated that chronic obstructive pulmonary disease (COPD) impairs health-related quality of life (HRQL), little agreement has been evidenced regarding the factors identified as contributing to impaired HRQL. The aim was to study such factors using well established generic and specific HRQL instruments. The patients (n=68) were stratified by forced expiratory volume in one second (FEV1) to represent a wide range of disease severity. Pulmonary function, blood gases and 6-min walking distance test (6MWD) were assessed. HRQL instruments included: St George's Respiratory Questionnaire (SGRQ), Sickness Impact Profile (SIP), Hospital Anxiety and Depression Scale and Mood Adjective Check List. The strength of the impact of COPD on HRQL was represented along a continuum ranging from lung function, functional status (physical and psychosocial) to wellbeing. Although correlations between FEV1 versus SGRQ total and SIP overall scores (r=-0.42 and -0.32) were stronger than previously reported, multiple regression analyses showed that lung function contributed little to the variance when dyspnoea-related limitation, depression scores and 6MWD were included in the models. These three factors were important to varying degrees along the whole range of HRQL. Physiological, functional and psychosocial consequences of chronic obstructive pulmonary disease are only poorly to moderately related to each other. The present study concludes that a comprehensive assessment of the effects of chronic obstructive pulmonary disease requires a battery of instruments that not only tap the disease-specific effects, but also the overall burden of the disease on everyday functioning and emotional wellbeing.