Transitions from Combustible to Noncombustible Tobacco Use and Liver Outcomes in Steatotic Liver Disease

Background/Aims: In adults with steatotic liver disease (SLD), the hepatic impact of transitioning between combustible cigarettes (CCs) and noncombustible nicotine or tobacco products (NNTPs) remains unclear. We examined CC-NNTP transitions and liver-related events (LREs). Methods: From the Korean National Health Insurance Service, 502,198 adults with SLD and at least one cardiometabolic risk factor completing health screenings during both 2012-2013 and 2019-2020 were followed through December 2023. Seven mutually exclusive groups were defined by CC status and NNTP use; the primary outcome was LRE, including hepatocellular carcinoma and liver cirrhosis. Cox proportional hazards regression, propensity-score matching (PSM), and counterfactual mediation analysis were performed. Results: Among 502,198 participants (mean age 57.9 years; 65.6% male), 2,549 LREs occurred over a median 3.0-year follow-up. Compared with never-smokers, continuous CC smokers without NNTP use had the highest LRE risk (aHR, 1.51; 95% confidence interval (CI), 1.34-1.70), followed by CC initiators (1.45; 1.17-1.79) and CC quitters (1.28; 1.12-1.46) without NNTPs. CC quitters with NNTP use showed a lower LRE risk than continuous CC smokers without NNTP use in the full cohort (aHR, 0.65; 95% CI, 0.43-0.99), but this association was not statistically significant under PSM (aHR, 0.65; 95% CI, 0.39-1.09). Within-group PSM of NNTP versus nonuse was nonsignificant across all CC categories. Conclusions: CC cessation was associated with lower LRE risk than continued CC smoking, even among those who transitioned to NNTPs. However, NNTP use showed no independent protective association, supporting complete tobacco/nicotine abstinence as the preferred goal.