Association between the alanine aminotransferase/aspartate aminotransferase ratio and new-onset non-alcoholic fatty liver disease in a nonobese Chinese population: a population-based longitudinal study

BACKGROUND: The alanine aminotransferase (ALT)/aspartate aminotransferase (AST) ratio has been considered an alternative marker for hepatic steatosis. However, few studies have investigated the association of the ALT/AST ratio with non-alcoholic fatty liver disease (NAFLD) in nonobese people. METHODS: A total of 12,127 nonobese participants who were free of NAFLD participated in this study. The participants were divided into quintiles of the ALT/AST ratio. Multiple Cox regression models were used to explore the association of the ALT/AST ratio with new-onset NAFLD. RESULTS: During the five-year follow-up period, 2147 individuals (17.7%) developed new-onset NAFLD. After adjusting for all non-collinear covariates, the multiple Cox regression analysis results showed that a higher ALT/AST ratio was independently associated with new-onset NAFLD in nonobese Chinese (adjusted hazard ratios [aHRs]: 2.10, 95% confidence intervals: 1.88, 2.36). The aHRs for NAFLD across increasing quintiles of the ALT/AST ratio were 1, 1.63 (1.30, 2.04), 2.07 (1.65, 2.60), 2.84 (2.33, 3.48) and 3.49 (2.78, 4.39) (P for trend< 0.001). The positive association was more significant among people with high blood pressure, high blood lipids and hyperglycaemia, as well as in men. Additionally, the regression spline showed that the saturation effect of the ALT/AST ratio on NAFLD risk was at 0.93 in this study population, which was 1.22 in males and 0.89 in females. CONCLUSIONS: In nonobese Chinese individuals without NAFLD at baseline, the increase in the ALT/AST ratio is closely associated with the risk of new-onset NAFLD. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12944-020-01419-z.