Physical activity and exercise capacity in severe asthma: key clinical associations

Background: Physical inactivity and sedentary time are distinct behaviors that may be more prevalent in severe asthma, contributing to poor disease outcomes. Physical activity and sedentary time in severe asthma however have not been extensively examined. Objective: We aimed to objectively measure physical activity and sedentary time in people with severe asthma compared with age-matched control participants, describing the associations of these behaviors with clinical and biological outcomes. We hypothesized that people with severe asthma would be less active and more sedentary. In addition, more activity and less sedentary time would be associated with better clinical outcomes and markers of systemic and airway inflammation in people with severe asthma. Methods: Adults with severe asthma (n = 61) and sex- and age-matched controls (n = 61) underwent measurement of lung function, exercise capacity, asthma control, health status, and airway and systemic inflammation. Physical activity and sedentary time were measured using an accelerometer. Results: The severe asthma and control groups were matched in terms of age and sex (32 [53%] females in each group). Individuals with severe asthma accumulated less minutes per day in moderate and higher intensity activity, median (IQR) 21.9 (12.9-36.0) versus 41.7 (29.5-65.2) (P < .0001) and accumulated 2,232 fewer steps per day (P = .0002). However, they engaged in more light-intensity physical activity. No differences were found for sedentary time. In a multivariate regression model, steps per day were strongly and independently associated with better exercise capacity in participants with severe asthma (coefficient, 0.0169; 95% CI, 0.008-0.025; P < .001). Conclusions: People with severe asthma perform less moderate and vigorous activity than do controls. Higher levels of activity and lower levels of sedentary time are associated with better exercise capacity, asthma control, and lower levels of systemic inflammation.