Sedentary time in people with obstructive airway diseases

Sedentary time (ST) and light-intensity physical activity (LIPA) are movement behaviours associated with important health outcomes, but are not widely explored in respiratory diseases. We aimed to describe their volume and/or accumulation patterns in moderate-severe COPD, bronchiectasis and severe asthma using the accurate postural-based accelerometer activPAL, contrasting these values with a non-respiratory population. We also sought to test the cross-sectional associations of these behaviours with disease characteristics by diagnostic group, and as a combined label-free disease group.

Results
Adults with COPD (n = 64), bronchiectasis (n = 61), severe asthma (n = 27), and controls (n = 61) underwent cross-sectional measurements of volume and/or accumulation patterns of ST and LIPA. The prevalence and characteristics, and associations with exercise capacity, health-status, airflow-limitation, dyspnoea, systemic inflammation and exacerbations were analysed.
ST volumes in COPD were higher than that of bronchiectasis and severe asthma. Values in bronchiectasis and severe asthma were similar to each other and controls (≈8.9 h/day). Their accumulation patterns were also significantly better than in COPD, but similar if not worse compared to controls. LIPA volumes in bronchiectasis and severe asthma were also higher than those of COPD (p < 0.05) and controls. In bronchiectasis and COPD, lower levels/better patterns of ST accumulation, as well as higher LIPA volume were associated with better clinical characteristics. These associations may be mediated by airflow limitation.

Conclusions
The discordance between engagement in ST volume versus ST patterns highlights the importance of accounting for both these different yet complementary metrics. ST and LIPA are low-intensity activities associated with important clinical characteristics in people with chronic respiratory diseases.