Efficacy of CPAP Therapy on Liver Steatosis and Insulin Resistance in Fatty Liver Patients With Obstructive Sleep Apnea: A 4-Year Follow-Up Cohort Study.

Metabolic dysfunction-associated steatotic liver disease (MASLD) and obstructive sleep apnea (OSA) are comorbid conditions that synergistically increase cardiovascular risk through systemic inflammation and insulin resistance. While continuous positive airway pressure (CPAP) is the standard treatment for OSA, its efficacy in improving hepatic steatosis and insulin resistance in patients with concurrent MASLD remains unclear. This study aims to characterize metabolic profiles in patients with MASLD stratified by OSA severity and evaluate the longitudinal effects of CPAP therapy on hepatic steatosis and insulin resistance. This retrospective cohort study screened 2429 adults and analyzed 321 patients with computed tomography-confirmed MASLD who underwent polysomnography (PSG) at a tertiary center. Participants were stratified by OSA severity by using the apnea-hypopnea index (AHI). The 4-year longitudinal trajectories of hepatic steatosis were evaluated by employing the hepatic steatosis index (HSI) and those of insulin resistance were investigated by using the triglyceride-to-high-density lipoprotein cholesterol (TG:HDL) ratio and triglyceride-glucose (TyG) index. Moreover, the effects of CPAP therapy on these metabolic indicators were assessed. Compared with other participants, those with severe OSA (AHI ≥ 30) exhibited a significantly higher prevalence of elevated HSI at baseline (p < 0.001) and consistently higher longitudinal levels of HSI, TG:HDL, and TyG over the four-year follow-up. CPAP therapy significantly attenuated insulin resistance in the severe OSA cohort, as reflected by its reduced prevalence of elevated TyG relative to that of the nonuser cohort (27.4% vs. 31.9%, p = 0.043). Longitudinal assessment further identified that CPAP users maintained significantly lower TyG-body mass indices during the first-second year (135.7 vs. 146.6, p = 0.025) and second-third year (133.6 vs. 146.0, p = 0.036) intervals, indicating a sustained metabolic benefit. In conclusion, severe OSA significantly exacerbates metabolic dysfunction in patients with MASLD, necessitating PSG for accurate diagnosis. Long-term CPAP therapy effectively improves insulin resistance specifically in severe OSA cases. Therefore, routine OSA screening and CPAP intervention based on OSA severity are strategies for improving metabolic prognosis in patients with MASLD.