No impact of exacerbation frequency and severity on the physical activity decline in COPD: a long-term observation

INTRODUCTION: COPD exacerbations are associated with a concomitant profound reduction in daily physical activity (PA). Thereby, exacerbation frequency and severity may have an amplifying effect. Whether the reduced level of PA returns to the level prior to exacerbation or has a sustained negative impact on activity behavior over time is unclear. METHODS: The number of steps per day over 1 week, as a measure of daily PA, was assessed annually in a cohort of patients with COPD. Exacerbation frequency and severity were documented. Uni- and multivariate mixed effect models were used to investigate associations between change in number of steps per day (dependent variable) and exacerbations. Stratification by possible confounders was performed. RESULTS: One hundred and eighty one COPD patients (median [quartile] age 64 [59/69] years, 65% male, median [quartiles] FEV(1) % pred. 46 [33/65]) suffered a total of 273 exacerbations during the observation period (median [quartiles] follow-up time of 2.1 [1.6/3.1] years). Neither the frequency nor the severity of exacerbations was significantly related to the overall decline in PA over time. Stratification by different possible confounders such as age, sex and disease severity did not yield a subgroup in which exacerbations enhance the decrease in PA over time. CONCLUSION: The drop in PA during the phase of an acute exacerbation seems not to be a lasting phenomenon leading to a fundamental change in activity behavior. TRIAL REGISTRATION: www.ClinicalTrials.gov, NCT01527773