Outdoor activity and performance status as predictors of survival in hypoxaemic chronic obstructive pulmonary disease (COPD)

Abstract

Background: Performance status has been associated with survival in hypoxaemic chronic obstructive pulmonary disease (COPD) patients on long-term oxygen therapy. Objective: To determine whether self-reported outdoor activity and performance status are independent predictors of survival in hypoxaemic COPD patients on long-term oxygen therapy. Design, subjects and main measure: In a prospective design, survival over an eight-year period was studied in 226 Danish patients on long-term oxygen therapy. They were subdivided according to self-reported mobility (±outdoor activity) and World Health Organization (WHO) performance status (score 0-4). Results: A total of 148 patients (65.5%) reported outdoor activity. Compared to the immobile patients, those reporting outdoor activity had higher performance status, higher body mass index and lower duration of oxygen administration. In multivariate analyses adjusting for body mass index, gender and age, both poor performance status and lack of outdoor activity were associated with poor survival (p-levels 0.006 and 0.045, respectively). Lack of outdoor activity was associated with increased mortality (relative risk (RR) and 95% confidence interval of dying was 1.39 (1.01-1.91)) and significantly higher risk was found among those with age in the youngest tertile (less than 66.4 years), the relative risk of dying was 2.18 (1.20-3.95). Conclusions: This study shows that self-reported performance status and outdoor activity are independent predictors of survival in hypoxaemic COPD patients on long-term oxygen therapy. However, our study suggests that in the most elderly patients, outdoor activity does not predicting survival. Further studies are needed to determine whether interventions that facilitate outdoor activity (e.g., pulmonary rehabilitation) have an effect on survival in this group of patients.