Anthropometric Measures and Mortality Risk in Individuals With Metabolic Dysfunction-Associated Steatotic Liver Disease (MASLD): A Population-Based Cohort Study.

Background/aims: As the primary anthropometric measure in metabolic dysfunction-associated steatotic liver disease (MASLD), waist circumference (WC) may more accurately reflect the visceral fat distribution than body mass index (BMI). This study aimed to compare the prognostic value of BMI, WC and WC-related indices including waist-hip ratio (WHR), body shape index (BSI) and weight-adjusted-waist index (WWI) in individuals with MASLD.

Methods: The study population was derived from four large-scale cohorts: the National Health and Nutrition Examination Survey (NHANES 2017-2020 and NHANES III), the Kailuan Cohort and the UK Biobank Cohort. We evaluated the mortality risk across these measures using multivariate Cox proportional hazards regression and restrictive cubic spline.

Results: The Pearson correlation coefficient of WC with hepatic steatosis and fibrosis was better than that of BMI. WC [Quartile 4 vs. Quartile 1: HR (hazard ratio) = 1.48 (95% confidence interval (CI) 1.13-1.93)] and WC-related indices [Quartile 4 vs. Quartile 1: WHR HR = 3.21 (95% CI 2.36-4.37); BSI HR = 3.22 (95% CI 2.48-4.17); WWI HR = 4.72 (95% CI 3.36-6.62)], but not BMI [obesity vs. lean: HR = 0.90 (95% CI 0.72-1.12)], indicated a significant mortality risk gradient among individuals with MASLD. The finding was consistent across sex and racial/ethnic subgroups, with external validation supporting the WC-related indices. MASLD and fibrosis prevalence showed a dose-dependent pattern across WC-related index quartiles. Notably, low BMI and high WC-related indices portended the highest mortality risk.

Conclusions: WC and WC-related indices are better parameters in prognosticating MASLD than BMI. The BMI-related 'obesity paradox' may be a misnomer resulting from the use of an incorrect metric. WC should be measured more routinely among individuals with MASLD.