Age Impacts Ability of Aspartate–Alanine Aminotransferase Ratio to Predict Advanced Fibrosis in Nonalcoholic Fatty Liver Disease

Background and Aim: While histological differences have been reported between pediatric and adult nonalcoholic fatty liver disease (NAFLD), potential age-related changes in serum transaminases and liver histology remain largely unexplored. Our study sought to investigate the clinical and histological characteristics of NAFLD across age. Methods: This was a prospective cross-sectional study of 502 biopsy-proven NAFLD patients. Clinical data were evaluated and compared among different age groups; group A (ages 18–44), B (ages 45–64), and C (≥ages 65). Results: 34.9, 56.0, and 9.1 % of the cohort were distributed among group A, B, and C, respectively. While the prevalence of nonalcoholic steatohepatitis (NASH) was comparable across age groups, the prevalence of advanced fibrosis increased with age (p = 0.000). Although the mean ALT progressively decreased with age; 87, 64, 56 U/L in group A, B, and C, respectively (p = 0.000), there was no difference in mean AST (p = 0.939) across age. The AST:ALT ratio (AAR) progressively increased from 0.7, 0.9, and 1.1 in group A, B, and C, respectively (p = 0.000). In group C, an AAR ≥1 was found in 74 and 40 % of patients with and without advanced fibrosis. Conclusion: With advancing age, ALT levels progressively declined while AST levels remained stable, leading to a higher AAR. Although higher AAR is often used as a surrogate measure of advanced fibrosis, advancing age can also contribute to increased AAR. In fact, an AAR ≥1 was found in significant number of elderly patients without advanced fibrosis. Consequently, an increased AAR may be a function of decreasing ALT with age in addition to progressive fibrosis.