The results of this cross-sectional study, which included 6,591 participants, showed that the ALI levels in the AHF and NAFLD groups were considerably higher than the control group. Multiple linear regression models, analyzing ALI as both a continuous and quartile variable, revealed a positive correlation between ALI and both CAP and LSM levels. A positive smooth curve fit was observed in the relationship between ALI, CAP, and LSM levels, with threshold effect inflection points at 88.287 and 98.420, respectively. Monitoring ALI can help identify those at risk for NAFLD due to systemic inflammation and nutritional imbalances. Maintaining ALI within a desirable range may lower the prevalence of NAFLD. Significant evidence for the primary prevention of NAFLD is provided by this study.
Upon review, this study represents the first NHANES investigation to examine the connection between ALI and hepatic steatosis and fibrosis. ALI has been frequently utilized as a predictive tool for various malignancies in previous studies. A cohort study of 425 individuals revealed that ALI could serve as a prognostic indicator for both overall survival (OS) and cancer-specific survival (CSS)among hepatocellular carcinoma patients after hepatectomy (10). In a single-center retrospective study involving 65 individuals, the ALl index demonstrated superior prognostic predictive capability relative to OS among patients with advanced HCC after hepatectomy (23). A single-center retrospective study of 98 individuals found that ALI could be employed as a novel prognostic marker in patients with advanced HCC treated with immunotherapy (24). This study identified significant correlations between ALI and hepatic steatosis and hepatic fibrosis. Apart from cancerous diseases, ALI is widely used for other diseases. A cohort study comprising 1440 individuals discovered an inverse J-shaped nonlinear association between elevated ALI and all-cause mortality among stroke patients (21). A study including 3,888 participants established a significant association between ALI and long-term all-cause cardiovascular mortality among type 2 diabetes patients (25) A cross-sectional study of 15,681 individuals found that ALI was significantly associated with long-term all-cause mortality among hypertensive patients(26). Furthermore, it was determined that the use of the independent prognostic factor - can predict reoperation rates after bowel resection surgery in Crohn's disease patients.
The effect of ALI on NAFLD may stem from the involvement of multiple pathophysiological mechanisms, including lipid metabolism disorders (27), oxidative stress (28), and inflammatory response (29).ALI, a composite index, integrates BMI, albumin levels, and NLR, effectively reflecting the patient's systemic inflammation level and nutritional metabolism. Obesity triggers excessive accumulation of adipose tissue in the body, leading to abnormal release of free fatty acids due to disordered lipid metabolism. These free fatty acids are transported to the liver through the circulatory system, resulting in fat accumulation in the liver and promoting the progression of NAFLD (30). Excessive fat accumulation induces oxidative stress in the liver which triggers an inflammatory response and eventually leads to liver fibrosis (31). Albumin is a major protein synthesized in the liver that reflects hepatic cell damage and apoptosis. Its levels are closely associated with liver function and metabolic status (32). Higher neutrophil counts serve as markers for persistent destructive inflammation processes while lower lymphocyte counts indicate relatively deficient immune regulation and impaired immunity (33). Albumin, a key protein synthesized in the liver, serves as an indicator of hepatocyte damage and apoptosis. It is closely linked to liver function and nutritional status(34). A higher neutrophil count is a marker of a persistent, destructive, and non-specific inflammatory process, while a lower lymphocyte count indicates relative immunodeficiency and compromised immunity(35). The NLR combines neutrophil and lymphocyte counts to provide a comprehensive assessment of the body's immune status and inflammatory response. NLR is considered an independent predictor of major morbidity, mortality, and long-term survival in NAFLD-related liver fibrosis(36).