Pain in Veterans with COPD: Relationship with Physical Activity and Exercise Capacity

Background: Pain is a common but underappreciated symptom experienced by people with Chronic Obstructive Pulmonary Disease (COPD). The relationships between pain and physical activity (PA) and exercise capacity are poorly understood. Methods: This retrospective secondary analysis included three cohorts of Veterans with COPD and objective measures of PA (daily step counts) and exercise capacity (6-minute walk test [6MWT] distance) who participated in longitudinal studies evaluating PA. Pain was assessed using the Bodily Pain (BP) domain of the Veterans RAND-36. In two cohorts, participants were randomly assigned to a web-based, pedometer-mediated PA intervention which has previously been demonstrated to improve PA. Results: Three-hundred and seventy-three (373) unique study participants were included in this analysis. Eighty-three percent (n=311) of the population reported at least mild pain and/or at least a little bit of interference due to pain at baseline. Cross-sectionally, greater BP was associated with lower 6MWT distance (β=0.51; 95% CI 0.20, 0.82; p=0.0013). Longitudinally, worsening BP was associated with a decline in 6MWT distance (β=0.30; 95% CI 0.03, 0.58; p=0.0312). There was no association between baseline BP and baseline daily step counts, baseline BP and change in PA, or change in BP and change in PA. Compared to usual care, our PA intervention improved BP scores (β=6.17; 95% CI 1.84, 10.45; p=0.0054). BP scores did not affect the impact of the intervention on daily step counts.Conclusion: Pain is highly prevalent and significantly associated with lower exercise capacity among Veterans with COPD. Worsening pain co-occurred with decline in exercise capacity but not PA. Our intervention reduced pain, although pain did not affect the impact of the intervention on PA.