BACKGROUND AND AIMS Sarcopaenia is associated with advanced nonalcoholic fatty liver disease (NAFLD). However, the impact of the muscle mass categorised by muscle quality on fibrosis progression remains unclear.

METHODS A total of 292 patients with biopsy-proven NAFLD who underwent serial vibration-controlled transient elastography assessments at least 1 year from baseline were selected. The skeletal muscle area (SMA) was determined on abdominal computed tomography (CT) at the third lumbar vertebra level and categorised to normal-attenuation muscle area (NAMA), low-attenuation muscle area (LAMA) and intermuscular adipose tissue (IMAT) using a muscle quality map. These SMAs were normalised by the height squared to obtain the skeletal muscle index (SMI).

RESULTS At baseline, as the histological fibrosis stage increased, SMI_NAMA decreased and SMI_LAMA increased (p for trend = 0.014 and p for trend <0.001, respectively), which was not significant after adjustment for age, sex and obesity. During a median follow-up of 41 months, fibrosis progression was detected in 48 out of 292 patients, and higher SMI_LAMA quartiles independently increased the risk of fibrosis progression in a dose-dependent manner (hazard ratio [HR] per quartile: 1.41; 95% confidence interval [CI], 1.04-1.91). The highest quartile of SMI_LAMA increased the risk of fibrosis progression by 3.25 times compared to the lowest quartile of SMI_LAMA (95% CI, 1.18-8.90). SMI_NAMA quartiles were not associated with the risk of fibrosis progression.

CONCLUSION Increased low-quality muscle mass, but not decreased normal-quality muscle mass, as assessed by a muscle quality map in CT, predicts fibrosis progression in patients with NAFLD.