Abnormal aminotransferase levels in obese patients prompted this group to investigate changes in serum aminotransferase levels in 40 obese patients with obstructive sleep apnoea who, on polysomnography and clinical symptoms, were candidates for treatment with nasal CPAP (continuous positive airway pressure). Patients who had an excessive intake of alcohol, hepatitis B antigen, hepatitis C antibody, or autoimmune disease were excluded. Serum aminotransferase levels were measured in the afternoon and morning, before and after nasal CPAP. Before treatment with CPAP aminotransferase levels increased after sleep (p=0.006). After the first night of nasal CPAP overnight mean increases in aminotransferase levels were less marked (p=0.0003). 35% of patients had abnormal aminotransferase levels (>1.5 times upper limit of normal) initially. In these patients changes in aminotransferase levels were significantly greater (p<0.0001). Improvements in aminotransferase levels were maintained after 1 month (p=0.0006) and 6 months of CPAP.

Recurrent apnoea and hypoxaemia may aggravate hepatic dysfunction in these patients, as indicated by release of aspartate aminotransferase. CPAP may therefore prove to be a useful method of preventing some complications of obstructive sleep apnoea such as hepatic dysfunction and cirrhosis.