Short-term effects of air pollution and weather on physical activity in patients with chronic obstructive pulmonary disease (COPD)

Introduction: Patients with chronic obstructive pulmonary disease (COPD) accumulate low levels of physical activity. How environmental factors affect their physical activity in the short-term is uncertain. Aim: to assess the short-term effects of air pollution and weather on physical activity levels in COPD patients. Methods: This multi -center panel study assessed 408 COPD patients from Catalonia (Spain). Daily physical activity (i.e., steps, time in moderate-to-vigorous physical activity (MVPA), locomotion intensity, and sedentary time) was recorded in two 7-day periods, one year apart, using the Dynaport MoveMonitor. Air pollution (nitrogen dioxide (NO2), particulate matter below 10 mu m (PM10) and a marker of black carbon (absorbance of PM2.5: PM2.5ABS), and weather (average and maximum temperature, and rainfall) were estimated the same day (lag zero) and up to 5 days prior to each assessment (lags 1-5). Mixed-effect distributed lag linear regression models were adjusted for age, sex, weekday, public holidays, greenness, season, and social class, with patient and city as random effects. Results: Patients (85% male) were on average (mean +/- SD) 68 +/- 9 years old with a post-bronchodilator forced expiratory volume in 1 s (FEV1) of 57 +/- 18% predicted. Higher NO2, PM10 and PM2.5ABS levels at lag four were associated with fewer steps, less time in MVPA, reduced locomotion intensity, and longer sedentary time (e.g., coefficient (95% CI) of -60 (-105, -15) steps per 10 mu g/m3 increase in NO2). Higher average and maximum temperatures at lag zero were related to more steps and time in MVPA, and less sedentary time (e.g., +85 (15, 154) steps per degree Celsius). Higher rainfall at lag zero was related to fewer steps and more sedentary time. Conclusion: Air pollution affects the amount and intensity of physical activity performed on the following days in COPD patients, whereas weather affects the amount of physical activity performed on the same day.