Determinants of health-related quality of life in patients with chronic obstructive pulmonary disease

Background - The consequences of chronic obstructive pulmonary disease (COPD) on daily life, encapsulated by the term ''health-related quality of life'' (HRQL), are important in determining appropriate home care. There is a need to understand the relative contribution of respiratory impairment, physical disability, coping, age, and socioeconomic variables on HRQL. Methods - Patients with COPD were recruited on admission to a pulmonary rehabilitation centre. Respiratory impairment was assessed by lung function tests and physical disability was evaluated by a 12 minute walking test. HRQL was assessed by means of the St George's Respiratory Questionnaire (SGRQ) measuring ''symptoms'', ''activity'', and ''impact''. Because the SGRQ does not include a measure of ''well being'', this was taken from the medical psychological questionnaire for lung diseases. The COPD coping questionnaire and a questionnaire covering basic socioeconomic variables were also used. Results - One hundred and twenty six patients of mean (SD) age 65 (9) years and mean (SD) forced expiratory volume in one second (FEV(1)) 39 (9)% predicted were included. The scores on the SGRQ indicated severe impairment. Correlations were found between lung function parameters, 12 minute walking test, and the HRQL ''activity'' and ''impact'' components. Coping strategies were correlated with the ''activity'', ''impact'', and ''well being'' components. No correlations were found between age, socioeconomic variables, and HRQL. FEV(1), 12 minute walking test, and the coping strategies ''avoidance'' and ''emotional reaction'' were the best predictors of HRQL. Conclusion - In patients with COPD methods of improving physical performance and teaching adequate coping strategies should be considered in order to improve HRQL.