Adverse muscle composition is a significant risk factor for all-cause mortality in NAFLD

BACKGROUND & AIMS: Adverse muscle composition (MC) (i.e., low muscle volume and high muscle fat) has previously been linked to poor functional performance and comorbidities in non-alcoholic fatty liver disease (NAFLD). In this study we aimed to investigate associations of all-cause mortality with liver fat, NAFLD, and MC in the UK Biobank imaging study. METHODS: Magnetic resonance images of 40,174 participants were analyzed for liver proton density fat fraction (PDFF), thigh fat-free muscle volume (FFMV) z-score, and muscle fat infiltration (MFI) using the AMRA® Researcher. Participants with NAFLD were sex-, age-, and BMI-matched to participants without NAFLD with low alcohol consumption. Adverse MC was identified using previously published cut-offs. All-cause mortality was investigated using Cox regression. Models within NAFLD were crude and subsequently adjusted for sex, age, BMI (M1), hand grip strength, physical activity, smoking, alcohol (M2), and previous cancer, coronary heart disease, type 2 diabetes (M3). RESULTS: A total of 5,069 participants had NAFLD. During a mean (±SD) follow-up of 3.9 (±1.4) years, 150 out of the 10,138 participants (53% men, age 64.4 [±7.6] years, BMI 29.7 [±4.4] kg/m(2)) died. In the matched dataset, neither NAFLD nor liver PDFF were associated with all-cause mortality, while all MC variables achieved significance. Within NAFLD, adverse MC, MFI and FFMV z-score were significantly associated with all-cause mortality and remained so in M1 and M2 (crude hazard ratios [HRs] 2.84, 95% CI 1.70–4.75, p <0.001; 1.15, 95% CI 1.07–1.24, p <0.001; 0.70, 95% CI 0.55–0.88, p <0.001). In M3, the relationship was attenuated for adverse MC and FFMV z-score (adjusted HRs 1.72, 95% CI 1.00–2.98, p = 0.051; 0.77, 95% CI 0.58–1.02, p = 0.069) but remained significant for MFI (adjusted HR 1.13, 95% CI 1.01–1.26, p = 0.026). CONCLUSIONS: Neither NAFLD nor liver PDFF was predictive of all-cause mortality. Adverse MC was a strong predictor of all-cause mortality in individuals with NAFLD. IMPACT AND IMPLICATIONS: Individuals with fatty liver disease and poor muscle health more often suffer from poor functional performance and comorbidities. This study shows that they are also at a higher risk of dying. The study results indicate that measuring muscle health (the patient's muscle volume and how much fat they have in their muscles) could help in the early detection of high-risk patients and enable targeted preventative care.