The study examined the relationship between the ALT/HDL-C ratio (the ratio of the enzyme alanine aminotransferase to high-density cholesterol) and non-alcoholic fatty liver disease (NAFLD) in 1,592 Chinese adults aged 40 to 70 years. The prevalence of NAFLD in this group was 61.1%. The results showed that each increase in the ALT/HDL-C ratio was associated with a 79% higher likelihood of NAFLD, with a non-linear relationship between these variables observed. The association was significantly stronger in women (289% increase in odds) than in men (66% increase), while no significant association was found in those over 60 years of age. The ALT/HDL-C ratio demonstrated better predictive ability (area under the curve 0.710) compared to individual ALT or HDL-C values. The authors conclude that ALT/HDL-C is a promising biomarker to improve NAFLD risk stratification in middle-aged adults, particularly women, although its utility in the elderly population may be limited.