The risk factors for ultrasound-diagnosed non-alcoholic fatty liver disease among adolescents.

INTRODUCTION: Non-alcoholic fatty liver disease (NAFLD) is garnering increasing interest and acceptance as one of the most important causes of chronic liver disease. The aim of this study was to investigate the risk factors for NAFLD among selected adolescent students in Hualien City, Taiwan.

MATERIALS AND METHODS: A stratified random sampling scheme was carried out among 1724 adolescent students aged 12 or 13 years old in Hualien City. In total, 220 students (normal: overweight: obese = 97:48:75) agreed to join the study. They underwent physical examination, laboratory tests and ultrasonography examination of the liver. Diagnosis of NAFLD in this study was based on sonographic evidence of a fatty liver and testing negative for serum HBsAg and anti- HCV antibody.

RESULTS: Of the 220 participants, 4 were excluded because they tested positive for HBsAg or anti-HCV antibody. NAFLD was detected in 86 (39.8%) out of the 216 subjects. The rate of NAFLD in the adolescents increased progressively from 16.0% in the normal group to 50.5% in the overweight group, and 63.5% among the obese subjects. Compared to their normal counterparts, adolescents with NAFLD had a significantly higher weight, body mass index (BMI), waist circumference, levels of alanine aminotransferase (ALT), triglyceride and nonhigh- density-lipoprotein (non-HDL) cholesterol. However, among the participants with NAFLD, only 20 (23.3%) showed ALT abnormality but there was an increasing trend of ALT abnormality as the severity of fatty liver increased. In addition, the higher ALT, Homeostasis model assessment- insulin resistance (HOMA-IR), cholesterol, triglyceride, and non-HDL levels and lower HDL-C as the severity of fatty liver increased. In a stepwise logistic regression analysis, the most significant factor associated with the presence of NAFLD was weight category. When compared with their normal counterparts, overweight and obese adolescents had a 4.14 and 5.98 times the risk of having NAFLD, respectively. Elevated ALT was the second most important factor as adolescents with elevated ALT were more likely to have NAFLD (odds ratio = 3.32, 95% CI: 1.16 to 9.50). Non-HDL cholesterol level was the third most important factor associated with NAFLD with a 3.81-fold increase in risk incurred for every l n (1 mg/dL) increment.

CONCLUSIONS: Obesity, ALT abnormality and elevated non-HDL-cholesterol are risk factors for NAFLD in adolescents. However, only 23.3% of the adolescents with NAFLD showed an abnormality for ALT. Therefore, ALT alone is not a sufficient indicator; and it is recommended that ultrasonography of the liver should be part of the routine health examination of obese adolescents.