Self-reported daily walking time in COPD: relationship with relevant clinical and functional characteristics

BACKGROUND Quantifying physical activity in chronic obstructive pulmonary disease (COPD) is important as physical inactivity is related to poor health outcomes. This study analyzed the relationship between patients' self-reported daily walking time and relevant characteristics related to COPD severity. METHODS Pooled analysis was performed on data from four observational studies on which daily walking time was gathered from a personal interview. Patients were classified as physically inactive if walking time was <30 min/day. Walking times were described and compared according to several markers of disease severity. RESULTS The mean daily walking time of 5,969 patients was 66 (standard deviation [SD] 47) min/day; 893 (15%) patients were inactive. A linear dose-response relationship was observed between walking time and the modified Medical Research Council (mMRC) dyspnea score, admissions, COPD assessment test (CAT), body mass index, airway obstruction, dyspnea, exacerbation (BODEx) index, and Charlson index (P<0.001). Daily walking times were lower in patients classified as Global Initiative for Chronic Obstructive Lung Disease (GOLD) B and D (P<0.001). Often, inactive patients had mMRC or Charlson index >3, post-bronchodilator forced expiratory volume in the first second <30% predicted, at least one hospitalization for COPD, classified as GOLD B or D, BODEx >4, and CAT score >30. CONCLUSION Lower self-reported walking times are related to worse markers of disease severity in COPD.