Inflammation biomarkers in OSA, COPD and COPD/OSA overlap syndrome.

STUDY OBJECTIVES: The coexistence of obstructive sleep apnea (OSA) and chronic obstructive pulmonary disease (COPD) in a single individual, also known as overlap syndrome (OVS), is associated with higher cardiovascular risk and mortality than either OSA or COPD alone. However, the underlying mechanisms remain unclear. We hypothesized that patients with OVS have elevated systemic inflammatory biomarkers relative to patients with either disease alone which could explain greater cardiovascular risk observed in OVS.

METHODS: We included 255 participants in the study, 55 with COPD alone, 100 with OSA alone, 50 with OVS, and 50 healthy controls. All participants underwent a home sleep study, spirometry, and a blood draw for hs-CRP and total blood count analysis. In a randomly selected subset of 186 participants, inflammatory protein profiling was performed using Bio-Rad Bio-Plex Pro Human Cytokine 27-Plex Assays. Biomarkers level differences across groups were identified using a mixed linear model.

RESULTS: Levels of Interleukin 6 (IL-6), high-sensitivity C-reactive protein (hs-CRP) and granulocyte colony stimulating factor (G-CSF), were higher in OVS and COPD participants when compared with healthy controls and OSA participants. Furthermore, OVS participants had higher circulating levels of leukocytes and neutrophils than COPD, OSA and controls.

CONCLUSIONS: COPD and OVS are associated with higher systemic inflammation relative to OSA and healthy controls. This work proposes the potential utilization of IL-6, G-CSF, and hs-CRP as screening biomarkers for COPD in patients with OSA. Inflammatory pathways may not fully explain the higher cardiovascular risk observed in OVS, indicating the need for further investigation.