Longitudinal associations of physical activity with disease burden in people with COPD

Abstract

Physical activity levels are reduced in people with chronic obstructive pulmonary disease (COPD). The factors underpinning this, and its impact on individuals’ health, are complex. Our aim was to investigate whether within-person changes in physical activity are associated with subsequent health outcomes, encompassing six-minute walk distance, quadriceps strength, lung function, perceived fatigue (FACIT-F), and symptom burden (CAT). In this multicentre cohort study, 565 individuals with COPD (37% female; age 68±8 years; FEV 1 54±21%pred) were followed over two years, with study visits every six months. Physical activity was assessed using wearable devices (Axivity AX6 or DynaPort MoveMonitor MM+), capturing daily step count and movement intensity during walking. Linear mixed-effects models assessed the longitudinal changes in physical activity and health outcomes, and the associations of within-person changes in physical activity and subsequent health outcomes. Participants showed a significant annual decline of 229 (95%CI 132–326) steps/day. Correcting for baseline PA, each 1000-step annual decline was associated with a 5.13 m (95%CI 3.20–7.06) lower six-minute walk distance, 0.37%pred (95%CI 0.08–0.66) lower FEV 1 , and 0.47-point (95%CI 0.20–0.75) lower FACIT-F at the end of that year. Similar associations were observed for movement intensity as exposure. Only movement intensity was associated with functional quadriceps strength, with each 0.1 m·s −2 decline resulting in a 0.18 s (95%CI 0.35–0.01) slower five-times sit-to-stand performance. No associations were found with the CAT. Within-person decline in physical activity is associated with lower lung function, reduced exercise capacity, increased fatigue symptoms and lower functional quadriceps strength.