Abstract
BACKGROUND: The relationships between physical activity (PA) and exercise performance and systemic biomarkers in persons with chronic obstructive pulmonary disease (COPD) have not been well characterized. The impact of PA promotion on biomarkers reflecting myocardial stress, systemic inflammation, and muscle injury is unclear. METHODS: This secondary analysis used 3 previously published studies in persons with COPD (2 examined a PA intervention that promoted community-based walking for 3 months) to explore these relationships. PA (daily step counts) and exercise performance (6-minute walk test [6MWT]) were assessed. Serum N-terminal pro-β-type natriuretic peptide (NT-proBNP), the soluble receptor for advanced glycation end products (sRAGE), and muscle-type creatine kinase (CKMM) were assayed at baseline and 3 months. General linear models examined associations between PA/exercise performance and systemic biomarkers at baseline and the effect of the PA intervention on change in biomarkers. RESULTS: Participants included 366 U.S. Veterans: 98% male, mean age 70±8 years, and forced expiratory volume in 1 second percentage predicted 59±21%. Lower baseline NT-proBNP, but not sRAGE or CKMM, was associated with higher daily step count (-0.95pg/ml per 1000 steps/day, p=.060) and higher 6MWT distance (-0.80pg/ml per 100 meters, p=.001). Change in daily step count, but not 6MWT, was significantly greater in the intervention (789±1864) compared to the control group (-174±1448; p=.002). The PA intervention had no significant impact on change in the systemic biomarkers. INTERPRETATION: Exercise performance is associated with NT-proBNP in persons with COPD. A 3-month community-based walking intervention is not associated with myocardial stress or muscle injury as assessed by NT-proBNP and CKMM, respectively. Clinical Trial Registration: NCT01772082 and NCT02099799.