BACKGROUND & AIMS Metabolic dysfunction-associated steatotic liver disease (MASLD) has become a major cause of chronic liver disease globally, particularly among young adults. We aimed to analyze all-cause and disease-specific mortality in young adults with MASLD.

METHODS In this nationwide cohort study, we analyzed data from the Korean National Health Insurance Service, focusing on individuals aged 20 to 39 years who underwent health screenings between 2009 and 2012. The participants were categorized into two groups: those with MASLD and those without steatotic liver disease (SLD). SLD was defined by a fatty liver index ≥30. Mortality risk was analyzed via Cox proportional hazards models.

RESULTS A total of 5,699,047 participants were included in the study, 25.4% of whom had MASLD. During a median follow-up of 10.6 years (interquartile range, 9.5-11.2), all-cause death occurred in 11,706 (0.8%) participants in the MASLD group and in 19,611 (0.5%) in the non-SLD group. Young adults with MASLD had a significantly greater risk of all-cause mortality than those without steatosis (adjusted hazard ratio [aHR], 1.15; 95% CI 1.12-1.19). The MASLD group also had an increased risk of mortality related to cardiovascular disease, liver cancer, and liver disease, whereas the risk of extrahepatic cancer-related mortality did not significantly differ between the two groups. Compared to men with MASLD, women with MASLD had higher risks of all-cause, cardiovascular, extrahepatic cancer, and liver disease-related mortality, although the risk of liver cancer-related mortality was similar between the sexes.

CONCLUSION Young adults with MASLD are at a significantly increased risk of all-cause and disease-specific mortality. These findings underscore the importance of early detection and intervention to mitigate the long-term outcomes of MASLD in young adults.

IMPACT AND IMPLICATIONS Global increases in obesity among adolescents and young adults are driving an increase in the prevalence of metabolic dysfunction-associated steatotic liver disease (MASLD) in these populations. In this nationwide cohort study, young adults with MASLD were found to have a significantly greater risk of all-cause mortality, as well as mortality related to cardiovascular disease, liver cancer, and liver disease than those without steatosis. Therefore, early detection and timely intervention for MASLD in young adults are crucial to improving clinical outcomes and reducing the global burden of the disease.