Association of body mass index with serum alanine aminotransferase in Chinese adolescents: a school-based cross-sectional study

BACKGROUND: Numerous studies have consistently demonstrated that high body mass index (BMI) is related to elevated serum alanine aminotransferase (ALT) among adults, but little is known about the association regarding adolescents, especially in China. In this study, we aimed to investigate the association between BMI and ALT activity among Chinese adolescents. METHODS: A school-based cross-sectional study was performed among nine high schools in Shenzhen, China between February 2017 and June 2018. A generalized linear-regression model adjusting for age and gender was conducted, and bivariate correlation analysis between ALT and BMI was also performed. RESULTS: A total of 7,271 adolescents aged from 9 years to 17 years were enrolled. Height, weight, BMI, and ALT were higher among boys than among girls (all P < 0.001). The mean (standard deviation) of serum ALT levels was 14.26 (14.77) U/L. In the entire BMI range, the BMI−ALT correlation was stronger for boys (Spearman's r = 0.396, P < 0.001) and adolescents of 14 years−17 years (r = 0.356, P < 0.001) than for girls (r = 0.203, P < 0.001) and adolescents of 9 years−13 years (r = 0.221, P < 0.001), respectively. Serum ALT increased rapidly and followed a linear pattern from the point of BMI ≥20.5 kg/m(2), and each increase of 1 kg/m(2) in BMI range above 20.5 kg/m(2) was averagely correlated with an increase of 2.71 U/L in ALT levels (P < 0.001). CONCLUSIONS: We found a significant BMI−ALT relationship. BMI at 20.5 kg/m(2) may be a cut-off for evaluating serum ALT. BMIs ≥27.1 kg/m(2) for boys and ≥24.9 kg/m(2) for girls were linked to an elevated ALT activity for Shenzhen adolescents.