Obstructive sleep apnea (OSA) and non-alcoholic fatty liver disease (NAFLD) are both common diseases related to metabolic diseases with potential cardiovascular consequences and liver complications respectively. Though studies show OSA may take part in the progression of hepatic steatosis, the independent contribution of OSA on liver fat accumulation is unknown. It is hypothesized that nocturnal intermittent hypoxia from OSA is the main driver of NAFLD in non-obese OSA patients. This study is to assess the effect of OSA on NAFLD in non-obese patients.

Inclusion Criteria:

• aged 18 years or more

Exclusion Criteria:

• underlying cause of liver disease
• history of excessive alcoholic consumption (more than 30 g/day for men and 20 g/day for women)
• secondary causes of hepatic steatosis (such as chronic use of systemic corticosteroids)
• positive hepatitis B surface antigen, anti-hepatitis C virus antibody, or histological evidence of other concomitant chronic liver diseases.

It is proposed to recruit consecutive patients who have been referred to the Respiratory Clinic at the Prince of Wales Hospital with clinical suspicion of sleep-disordered breathing. In order to invite subjects without symptoms of sleep apnea, collaboration with the Jockey Club School of Public Health and Primary Care, CUHK, to engage healthy volunteers.