ABSTRACT Background and Aims Metabolic dysfunction–associated steatotic liver disease (MASLD) is an increasing public health concern, particularly among young adults. Although smoking has been implicated in hepatic steatosis, large‐scale longitudinal evidence remains limited. Methods We analyzed data from the Korean National Health Insurance Service, including 3 496 144 adults aged 20–39 years who underwent health examinations between 2004 and 2007 and were followed through 2022. Hepatic steatosis was assessed using the Fatty Liver Index (FLI), a validated surrogate marker, and categorized as < 30, 30–59, or ≥ 60. Smoking exposure was evaluated at baseline according to smoking amount, duration, and pack‐years. Cox proportional hazards models were used to estimate adjusted hazard ratios (HRs) and 95% confidence intervals (CIs). Results Smoking was associated with an increased risk of incident FLI‐defined hepatic steatosis across multiple exposure metrics. Among men, smoking ≥ 20 cigarettes/day was associated with the highest risk of FLI ≥ 60 (HR 1.41, 95% CI 1.40–1.43), whereas 10–19 years of smoking was associated with an HR of 1.15 (95% CI 1.14–1.15). Among women, 10–19 years of smoking was associated with a 49% higher risk of FLI ≥ 60 (HR 1.49, 95% CI 1.43–1.56). Associations were generally stronger among participants with BMI < 25 kg/m 2 or alcohol intake < 25 g/day. Risk estimates varied according to FLI threshold. Conclusions Smoking was independently associated with an increased risk of FLI‐defined hepatic steatosis in young adults. These findings support smoking prevention and cessation strategies as potential measures to reduce early‐onset steatotic liver disease.
Jee et al. (Thu,) studied this question.