Prevalence of Elevated Alanine Aminotransferase Among US Adolescents and Associated Factors: NHANES 1999–2004

Background & Aims: Nonalcoholic fatty liver disease (NAFLD) is a common cause of liver disease in children and adolescents. The majority of studies of NAFLD in children have been in select populations of the clinically obese. Study aims were to estimate the prevalence of elevated alanine aminotransferase (ALT, as a marker of NAFLD) in a general contemporary adolescent population and to identify leading risk factors for ALT elevation (>30 U/L). Methods: We analyzed data of adolescent participants (aged 12-19 years; N = 5586) in the National Health and Nutrition Examination Survey 1999-2004, a representative sample of the civilian noninstitutionalized US population. Results: The prevalence of elevated ALT levels (>30 U/L) was 7.4% among white adolescents, 11.5% among Mexican American adolescents, and 6.0% among black adolescents. Elevated ALT levels were prevalent in 12.4% of male subjects compared with 3.5% of female subjects. Multivariable associations with elevated ALT levels were found for sex (odds ratio [OR] male vs female, 7.7; 95% confidence interval [CI], 3.9-15.1), ethnicity (OR black vs white, 0.6; 95% CI, 0.3-1.3; OR Mexican American vs white, 1.6; 95% CI, 1.0-2.6), waist circumference (OR per 1 SD, 1.4; 95% CI, 1.0-2.0), and fasting insulin level (OR per 1 SD, 1.6; 95% CI, 1.2-2.1). Age, C-reactive protein levels, and triglyceride levels were also positively and socioeconomic position inversely associated with elevated ALT levels. The magnitude of associations were similar across ethnic groups. Conclusions: ALT level is associated with waist circumference and insulin resistance even in a young population. These characteristics could be utilized to identify adolescents who may benefit from screening for NAFLD, offering an opportunity to prevent disease progression at an early age.