Changing aetiology of liver dysfunction in the new generation of a hepatitis B and C-endemic area: cross-sectional studies on adolescents born in the first 10 years after universal hepatitis B vaccination

Background/Aim: Geographical variation in viral hepatitis infection complicates various levels of liver diseases. This study elucidates the changing aetiology of alanine transaminase elevation (ALT levels > 40 IU/L) in a previously hepatitis-endemic township. Design/Methods: Five cross-sectional screenings were performed on teenagers born from 1984 to 1993. We examined hepatitis B surface antigen (HBsAg), anti-hepatitis C virus (anti-HCV), ALT and body mass index, and additionally checked hepatitis B envelope antigen (HBeAg) for positive HBsAg and HCV RNA for positive anti-HCV. Teenagers with ALT elevation underwent an ultrasonography examination. Results: This study enrolled 1788 (93.7%) of 1909 students, discovering individual prevalence of HBsAg (6.3%), anti-hepatitis B core (anti-HBc) (15.5%), anti-HCV (2.2%), overweight (22.4%), obesity (12.8%) and ALT > 40 IU/L (3.7%). HBsAg and anti-HBc prevalence declined with trends, while obesity increased with trends (P < 0.001). Among 66 ALT-elevated teenagers, prevalence percentages of risk factors were HBsAg (22.7%), anti-HCV (1.5%), obesity (45.5%), HBsAg with obesity (7.6%) and anti-HCV with obesity (3.0%). Additionally, obesity showed predominance (85.7%) among aetiologies of teenagers with fatty livers (60.9%). The independently associated factors of ALT elevation included being male (odds ratio, 2.18; 95% confidence interval, 1.21-3.93), HBsAg (4.25; 1.06-17.13), HBeAg (7.24; 1.64-31.9), HCV RNA (29.03; 5.8-145.29) and obesity (16.5; 8.79-30.98). Conclusion: In place of viral hepatitis, obesity is becoming the major aetiology of abnormal liver function among the young generation in a previously hepatitis-endemic area.