Tobacco exposure, Cotinine, Non-alcoholic fatty liver disease, Fatty liver index, NHANES, Diseases of the digestive system. Gastroenterology, RC799-869

Abstract Background The correlation between serum cotinine and fatty liver index (FLI) needs further investigation for the early identification, prevention, and treatment of metabolic dysfunction-associated steatotic liver disease (MASLD). Methods Data from the NHANES database spanning from March 2017 to 2018 was used to perform the population-based study to assess the relationship between serum cotinine and FLI. A variance estimation strategy was applied to address the data volatility. To examine the correlation between serum cotinine and FLI, a weighted multivariate logistic regression model was used. Initial normality assessment through the Kolmogorov-Smirnov test indicated non-normal distribution. Median and interquartile range were employed for description of non-normally distributed measurement data, and group comparisons were made using the Kruskal-Wallis H test. Proportions were used for ordinal data description and comparisons, with the chi-square test used for categorical data. Smooth curve fittings and generalized additive models were used to explore the non-linear relationship between serum cotinine and FLI. Results Finally, 2350 subjects (mean age: 49.83 ± 18.30, 1135 males and 1215 females) were selected for analysis. After adjusting for confounders, serum cotinine showed positive correlation with FLI in adults (β = 0.009, 95% CI: 0.003 to 0.014, P = 0.001). Additionally, individuals in the unexposed and passively exposed groups had lower FLI compared to those in the actively exposed group (β = -3.041, 95% CI: -4.728 to -1.353, P