Combined use of alternative tobacco products and liver function: findings from the Korea National Health and Nutrition Examination Study 2019–2022

Non-cigarette tobacco or nicotine products (NCTNPs) have been developed as healthier alternatives to conventional cigarettes; however, their safety, particularly regarding liver health, has not been sufficiently studied due to their short market tenure. Additionally, research on multiple use of different kinds of tobacco products remains limited. This study aims to evaluate the association of multiple tobacco product use with liver function. A cross-sectional study was conducted using data from the Korea National Health and Nutrition Examination Survey (KNHANES), 2019–2022. A total of 19,374 adults were classified into five groups based on their ever use of cigarettes (cigs), e-cigarettes (e-cigs) and heated tobacco products (HTPs): non-users of any product (non-users) and cigarette smokers who also used either no other product (cigs only), e-cigs but not HTPs (cigs + e-cigs), HTPs but not e-cigs (cigs + HTPs), or both e-cig and HTPs (triple users). Participants’ liver function was assessed by serum aspartate (AST) and alanine aminotransferase (ALT) levels. Linear regression models adjusting for participants’ demographics and health-related variables were constructed and further stratified by sex and body mass index (BMI) status. Multiple use of tobacco products was associated with greater serum ALT levels. Compared to non-users, triple users tended to have the greatest ALT levels (β = 1.57, p = < 0.001), followed by cigs + e-cigs users (β = 1.09, p = 0.044) and cigs +HTPs users (β = 1.00, p = 0.035) in the fully adjusted model. The association was more clearly seen in males, showing similar patterns with the results from total participants. In the BMI-stratified model, the association was observed only among triple users with normal BMI status (β = 2.11, p = 0.003). Additional use of HTP was related to higher serum ALT levels, especially in males, possibly due to increased nicotine absorption from HTP use.