Oxidative Stress and Inflammation Biomarker Expression in Obstructive Sleep Apnea Patients

Obstructive Sleep Apnea Syndrome (OSAS) is a respiratory sleep disorder characterised by repeated episodes of partial or complete obstruction of the upper airway during the night. This obstruction usually occurs with a reduction (hypopnea) or complete cessation (apnea) of the airflow in the upper airways with the persistence of thoracic-diaphragmatic respiratory movements. During the hypopnea/apnea events, poor alveolar ventilation reduces the oxygen saturation in the arterial blood (SaO₂) and a gradual increase in the partial arterial pressure of carbon dioxide (PaCO₂). The direct consequence of the intermittent hypoxia is an oxidative imbalance, with reactive oxygen species production and the inflammatory cascade's activation with pro and anti-inflammatory cytokines growth. Tumour necrosis factors, inflammatory cytokines (IL2, IL4, IL6), lipid peroxidation, and cell-free DNA have been found to increase in OSAS patients. However, even though different risk-related markers have been described and analysed in the literature, it has not yet been clarified whether specified inflammatory bio-markers better correlates with OSAS diagnosis and its clinical evolution/comorbidities. We perform a scientific literature review to discuss inflammatory and oxidative stress biomarkers currently tested in OSAS patients and their correlation with the disease's severity and treatment.