Physical activity end-points in trials of chronic respiratory diseases: summary of evidence

BACKGROUND: Physical activity contributes to improving respiratory symptoms. However, validated end-points are few, and there is limited consensus about what is a clinically meaningful improvement for patients. This review summarises the evidence to date on the range of physical activity end-points used in COPD, asthma and idiopathic pulmonary fibrosis (IPF) whilst evaluating their appropriateness as end-points in trials and their relation to patients’ everyday life. METHODS: Trials reporting physical activity end-points were collected using Citeline's database Trialtrove; this was supplemented by searches in PubMed. RESULTS: The daily-patient-reported outcome (PRO)active and clinical visit-PROactive physical activity composite end-points appeared superior at capturing the full experience of physical activity in patients with COPD and were responsive to bronchodilator intervention. Time spent in moderate-to-vigorous physical activity is a recently validated end-point for IPF that correlates with exercise capacity and quality of life. Step count appears the best available physical activity measure for asthma, which consistently declines with worse disease status. However, evidence suggests a time lag before significant improvement in step count is seen which may reflect the impact of human behaviour on physical activity. CONCLUSIONS: Physical activity represents a challenging domain to accurately measure. This is the first review evaluating physical activity measures used specifically within the respiratory field. Whilst physical activity can be effectively captured using PROactive in patients with COPD, this review highlights the unmet need for novel patient-focused end-points in asthma and IPF which would offer opportunities to develop efficacious medicines with impact on patients’ therapeutic care and quality of life.