The Relationship Between Chronic Intermittent Hypoxia and MASLD and Fibrosis in Obstructive Sleep Apnea Patients

Background/Objectives: Obstructive sleep apnea (OSA) causes recurrent apneas/hypopneas and intermittent oxygen desaturation during sleep. Chronic intermittent hypoxia (CIH) may be linked to metabolic dysfunction-associated steatotic liver disease (MASLD) and fibrosis through metabolic dysfunction. This study evaluated the relationship between OSA severity/hypoxemia indices and MASLD and fibrosis assessed by transient elastography. Methods: We prospectively enrolled 400 adults evaluated for suspected OSA at a respiratory disease outpatient clinic in Rize, Türkiye. All patients underwent overnight polysomnography. The apnea–hypopnea index (AHI), oxygen desaturation index (ODI), mean SpO2, and mean of each participant’s minimum SpO2 values were recorded. MASLD and fibrosis were assessed in the same individuals using FibroScan, with CAP (controlled attenuation parameter) and LSM (liver stiffness measurement) values recorded. OSA severity was categorized by AHI, and multivariable logistic regression was used to identify independent associations. Results: MASLD was present in 76% and fibrosis in 34.5% of patients. Patients with fibrosis had higher AHI (13.8 8.2–35.2) and ODI (11.5 4.5–33.2) and lower minimum SpO2 (p < 0.001). In multivariable models, BMI (OR 1.09; p < 0.001) and metabolic syndrome (OR 3.34; p < 0.001) were independently associated with MASLD, while BMI (OR 1.02; p < 0.001), metabolic syndrome (OR 2.03; p = 0.015), and ALT (OR 1.02; p = 0.032) were independently associated with fibrosis. Conclusions: MASLD and fibrosis were associated with OSA severity and hypoxemia before multivariable adjustment. However, after adjustment for obesity-related factors, liver outcomes were primarily explained by BMI and metabolic syndrome. Liver assessment should be considered in patients with OSA, particularly in those with high BMI and metabolic syndrome.