Background: Physical inactivity is common in stable chronic obstructive pulmonary disease (COPD) and independently predicts poor outcomes. Longitudinal assessments of physical activity in outpatients with COPD, covering periods of stability and exacerbations, have not been evaluated previously.
Methods: Patients with clinically stable COPD and a history of two or more clinical exacerbations in the preceding 12 months were recruited. Physical activity was measured using a triaxial accelerometer worn continuously on the nondominant wrist. Mean minutes per day of higher level physical activity was the primary outcome variable. Symptom-defined exacerbations were assessed using the 14-item Exacerbations of Chronic Pulmonary Disease Tool (EXACT) daily dairy. Clinically reported exacerbations were also captured. Minutes per day of higher level physical activity during exacerbation and nonexacerbation days were compared, using a mixed model analysis.
Measurements and main results: Seventeen patients were monitored for 135 ± 18 days. Nine were male with a mean age of 63 ± 12 years and mean FEV1 of 52 ± 20%. Fifteen patients had 27 symptom (EXACT)-defined exacerbations, including 9 that were also clinically reported. Patients spent fewer minutes per day at a higher level physical activity level during exacerbation days than nonexacerbation days: 131 ± 14 versus 157 ± 14 minutes (P < 0.0001). The greatest reduction in physical activity was during the first week of the exacerbation; activity remained low for approximately 2 weeks after exacerbation resolution.
Conclusions: Physical activity decreased significantly during exacerbations. Reduction in activity occurs early during an exacerbation and persists for about 2 weeks after symptomatic recovery.