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Physical activity trajectories and their determinants in COPD: A cohort study

Background: A mean annual decline in physical activity (PA) of 450 steps/d approximately has been reported in patients with COPD but it is not known if the evolution is the same for all patients. Aims: To identify PA trajectories and their determinants using a hypothesis-free approach. Methods: We pooled data from the PROactive initial validation (NCT01388218) study and the usual care arm of the Urban Training study (NCT01897298), including an objective measure of PA at baseline and 12 months. We identified clusters of individual PA trajectories (steps/d), using a k-means approach and compared baseline sociodemographic, interpersonal, clinical and psychological characteristics across clusters. Results: Based on 293 COPD patients (mean (SD) 68 (8) y, 82% male, FEV1 58% pred), we identified three distinct PA trajectories: inactive (59%), improvers (17%) and decliners (24%) (Fig 1). Being in the inactive group was associated with a lower proportion of patients still working and a worse general status (lower lung function, exercise capacity and quality of life, and higher dyspnoea and depression score) at baseline. While improvers and decliners were very similar in their baseline characteristics, improvers showed a significant reduction in weight during follow-up compared to decliners. Conclusions: The natural course of PA in patients with COPD was heterogeneous and one group improved PA over time.