Impact of long-term continuous positive airway pressure on liver fat in male obstructive sleep apnea patients with fatty liver

Obstructive sleep apnea (OSA) is an established factor in the pathogenesis and exacerbation of fatty liver disease. However, randomized controlled trials have failed to demonstrate decreases in liver fat content in OSA patients by continuous positive airway pressure (CPAP) performed for several months. The aim of this study is to investigate the impact of long-term CPAP therapy on liver fat content in OSA patients with fatty liver. Liver fat content in 61 male OSA patients was evaluated by computed tomography performed because of abdominal obesity before and after CPAP initiation. At baseline, there were 25 participants with fatty liver. Their apnea–hypopnea index and percent sleep time with oxygen saturation < 90% were greater than those in the 36 participants who did not have fatty liver (52.3 vs. 41.8/h and 30.4 vs. 14.8%, respectively). The average therapy duration was 31 months. In the analysis of the entire participant group, liver fat content did not change after CPAP therapy. In those without fatty liver, liver fat content increased accompanied by increases in BMI, whereas in the participants with fatty liver, liver fat content decreased despite stable BMI, abdominal fat distribution, and insulin resistance. In male OSA patients with abdominal obesity, decreases in liver fat content were observed after long-term CPAP therapy only when fatty liver was present at baseline. This implies that there are some conditions, such as OSA-related hypoxemia and others, which may exacerbate fatty liver and that fatty liver may improve with CPAP therapy.