Physical Activity in Overlap Syndrome of COPD and Obstructive Sleep Apnea: Relationship With Markers of Systemic Inflammation.

Abstract

Low physical activity (PA) is associated with poor health outcomes in chronic obstructive pulmonary disease (COPD). Overlap syndrome (OVS), the co-occurrence of COPD and obstructive sleep apnea (OSA), is highly prevalent. Little is known about PA in OVS, and its relationship with markers of systemic inflammation. We studied 256 persons with stable COPD, 61 (24%) of whom had OVS, who were well characterized in two previous PA studies. PA was directly assessed with the Omron HJ-720ITC pedometer. C-reactive protein (CRP) and interleukin-6 (IL-6) were assayed from peripheral blood. Linear regression models, adjusting for age and forced expiratory volume in 1 second (FEV1) % predicted, assessed daily step counts and CRP and IL-6 levels in OVS, compared to COPD alone. Linear regression models, adjusting for age, FEV1 % predicted, and coronary artery disease, assessed the relationships between PA and CRP and IL-6 in those with OVS versus those with COPD alone. Compared to COPD alone, persons with OVS walked 672 fewer steps per day (95% CI -1,317 to -28, P = .041). Those with OVS had significantly higher levels of CRP and IL-6 compared to COPD alone. In OVS, each 1,000 fewer steps walked was associated with a 0.875 ng/mL (95% CI 0.767 to 0.997) increase in IL-6, independent of lung function. Persons with OVS have significantly lower levels of PA and higher levels of inflammatory biomarkers, compared to COPD alone. Lower PA is significantly associated with higher IL-6 levels in OVS.