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.