Identification of Biomarkers of Obstructive Sleep Apnea.

Obstructive sleep apnea (OSA) is a highly prevalent disorder characterized by recurrent upper airway obstruction during sleep, resulting in intermittent hypoxia, sleep fragmentation, oxidative stress, systemic inflammation, endothelial dysfunction, and metabolic disturbances. Untreated OSA is associated with an increased risk of cardiovascular disease, diabetes mellitus, stroke, impaired quality of life, and all-cause mortality. Despite the availability of polysomnography as the reference diagnostic method, current diagnostic approaches have limited accessibility and do not adequately reflect disease burden or predict treatment response.

The primary objective of this study is to identify and validate blood biomarkers associated with the presence, severity, and treatment response of OSA. The investigators hypothesize that selected circulating proteins, inflammatory mediators, oxidative stress markers, and metabolic profiles can improve the screening, diagnosis, risk stratification, and monitoring of patients with OSA.

A total of 120 adults will undergo standardized clinical evaluation and overnight polysomnography. Participants diagnosed with moderate-to-severe OSA will be randomly assigned to either immediate or delayed initiation of positive airway pressure (PAP) therapy, whereas participants without OSA will serve as the control group. Blood samples will be collected at predefined study visits to evaluate changes in candidate biomarkers before and during treatment.

The study will investigate a broad panel of biomarkers representing inflammatory pathways, endothelial dysfunction, oxidative stress, and metabolomic alterations using validated laboratory techniques, including multiplex immunoassays, enzyme-linked immunosorbent assays (ELISA), and metabolomic analyses. Changes in biomarker profiles will be evaluated in relation to OSA severity and response to PAP therapy.

The results of this study are expected to improve the understanding of the biological mechanisms underlying OSA and facilitate the development of novel biomarker-based approaches for screening, diagnosis, disease monitoring, and personalized management of patients with obstructive sleep apnea.

Inclusion criteria

• Participants with obstructive sleep apnea (OSA):

• Age 18 to 65 years.
• Moderate or severe obstructive sleep apnea confirmed by overnight polysomnography (apnea-hypopnea index [AHI] ≥15 events/hour).
• Willing and able to provide written informed consent.
• Willing to undergo repeated blood sampling and study assessments.
• Willing to use positive airway pressure (PAP) therapy and accept random assignment to immediate or delayed treatment.
• Control participants:

• Age 18 to 65 years.
• No obstructive sleep apnea (AHI <5 events/hour on overnight polysomnography).
• Willing and able to provide written informed consent.
• Willing to undergo study assessments and blood sampling.

Exclusion criteria

• Mild obstructive sleep apnea (AHI 5 to <15 events/hour).
• Central sleep apnea.
• Previous treatment for obstructive sleep apnea within the previous 3 months.
• Body mass index (BMI) ≥40 kg/m².
• Severe cardiovascular disease.
• Severe kidney disease or impaired renal function.
• Significant liver disease.
• Chronic inflammatory, autoimmune, or rheumatic disease.
• Active cancer or other condition associated with systemic inflammation.
• Chronic respiratory diseases, including asthma or chronic obstructive pulmonary disease.
• Respiratory infection within 4 weeks before enrollment.
• Major surgery or significant injury within the previous 3 months.
• Chronic rhinosinusitis.
• Current treatment with systemic corticosteroids, immunosuppressive drugs, cytotoxic drugs, chronic anti-inflammatory medications, or other medications that may influence inflammatory biomarkers.
• Pregnancy or any condition that, in the opinion of the investigators, would make participation unsafe or interfere with interpretation of the study results.