Impact of Fatty Liver Index on Cardiovascular Disease and Mortality across Alcohol Consumption Levels in Young Adults

The fatty liver index (FLI) is widely used as a surrogate marker for metabolic dysfunction-associated steatotic liver disease, but its predictive value among individuals who consume alcohol remains uncertain. We aimed to investigate the association between FLI and the risk of cardiovascular disease (CVD) and mortality in young adults by alcohol consumption status.

Using the Korean National Health Information Database, we identified 6,487,686 individuals aged 20-39 years who underwent health examinations between 2009 and 2012. FLI was calculated using body mass index, waist circumference, triglycerides, and γ-glutamyl transferase, and categorized as <30, 30-59, or ≥60. Alcohol consumption was classified as non-drinking, mild, moderate, or heavy using sex-specific thresholds. Risks of CVD-including myocardial infarction (MI) and stroke-and all-cause mortality were evaluated using multivariable Cox proportional hazards models.

During a mean follow-up of 13.3 years, 49,399 MI, 29,842 stroke, and 53,330 deaths were identified. The risk of CVD and mortality increased stepwise across higher FLI categories in all alcohol consumption groups. Compared with participants with FLI <30, the adjusted hazard ratios (95% confidence intervals [CIs]) for composite outcome among those with FLI ≥60 were 1.72 (95% CI, 1.67 to 1.77) in non-drinkers, 1.41 (95% CI, 1.38 to 1.43) in mild drinkers, 1.19 (95% CI, 1.15 to 1.24) in moderate drinkers, and 1.20 (95% CI, 1.12 to 1.30) in heavy drinkers. The association was strongest among non-drinkers (P for interaction <0.0001).

FLI is a useful and practical indicator for predicting CVD and mortality in young adults, regardless of alcohol intake, with the highest predictive performance in non-drinkers.