Abstract
Background/Objectives: Metabolic dysfunction-associated steatotic liver disease (MASLD) often coexists with obstructive sleep apnea (OSA) due to overlapping metabolic risk factors. Whether continuous positive airway pressure (CPAP) influences hepatic outcomes in MASLD remains uncertain. This systematic review, using updated criteria for MASLD, evaluated the effects of OSA treatment on liver and metabolic outcomes. Methods: PubMed, Web of Science, and CINAHL were searched for randomized controlled trials (RCTs) and observational studies in adults with MASLD and OSA treated with CPAP, lifestyle interventions, pharmacotherapy, or surgery. Outcomes included liver stiffness, fat content, enzymes, fibrosis scores, HbA1c, lipids, and anthropometrics. Risk of bias was assessed with RoB 2 (RCTs) and ROBINS-I (non-randomized studies) and certainty of evidence with GRADE. Results: Eight studies (three RCTs, five observational; n = 1006; 73.5% male) met criteria. Studies evaluated CPAP for from 4 weeks to 3 years, with adherence ≥ 4 h/night in most. CPAP produced modest, inconsistent reductions in alanine aminotransferase and aspartate aminotransferase, small improvements in HbA1c and triglycerides, and minimal changes in liver stiffness, steatosis, weight, or anthropometrics. No RCT demonstrated significant improvement in fibrosis or steatosis. Risk of bias was low in one RCT, "some concerns" in two, and moderate in observational studies; one study had serious confounding risk. Conclusions: CPAP may modestly improve liver enzymes and select metabolic parameters in MASLD with OSA, but evidence for salutary effects on steatosis, fibrosis, and body composition is limited. Level of evidence was low due to methodological limitations, heterogeneity, and imprecision. High-quality, longitudinal trials are needed.