Objectively Measured Physical Activity as a COPD Clinical Trial Outcome

BACKGROUND: Reduced physical activity is common in COPD and is associated with poor outcomes. Physical activity is therefore a worthy target for intervention in clinical trials; however, trials evaluating physical activity have used heterogeneous methods. RESEARCH QUESTION: What is the available evidence on the efficacy and/or effectiveness of various interventions to enhance objectively measured physical activity in patients with COPD, taking into account the minimal preferred methodologic quality of physical activity assessment? STUDY DESIGN AND METHODS: In this narrative review, the COPD Biomarker Qualification Consortium (CBQC) task force searched three scientific databases for articles that reported the effect of an intervention on objectively measured physical activity in COPD. Based on scientific literature and expert consensus, only studies with >_ 7 measurement days and >_ 4 valid days of >_ 8 h of monitoring were included in the primary analysis. RESULTS: Thirty-seven of 110 (34%) identified studies fulfilled the criteria, investigating the efficacy and/or effectiveness of physical activity behavior change programs (n = 7), mobile or electronic-health interventions (n = 9), rehabilitative exercise (n = 9), bronchodilation (n = 6), lung volume reduction procedures (n = 3), and other interventions (n = 3). Results are generally variable, reflecting the large differences in study characteristics and outcomes. Few studies show an increase beyond the proposed minimal important change of 600 to 1100 daily steps, indicating that enhancing physical activity levels is a challenge. INTERPRETATION: Only one-third of clinical trials measuring objective physical activity in people with COPD fulfilled the preset criteria regarding physical activity assessment. Studies showed variable effects on physical activity even when investigating similar interventions.