Age, sex, and ethnic variations in serum insulin concentrations among U.S. youth: findings from the National Health and Nutrition Examination Survey 1999-2002.

OBJECTIVE Distributions of serum concentrations of insulin among adolescents and young adults are poorly understood in the U.S. The objective of this study was to describe the distribution of serum insulin across demographic characteristics of U.S. adolescents and young adults. RESEARCH DESIGN AND METHODS A total of 1,791 male and female subjects aged 12-19 years who participated in the National Health and Nutrition Examination Surveys for 1999-2002 were included in the analyses. RESULTS Among male participants, serum concentrations of insulin increased from age 12 to 14 years before decreasing. Among female participants, concentrations were highest at age 13 years before decreasing steadily through age 19 years. Among participants aged 12-17 years but not those aged 18-19 years, females had higher mean log-transformed concentrations than males (P, Wald, F = 0.038 and 0.125, respectively) after adjusting for age and ethnicity. After adjusting for age and BMI percentile, mean log-transformed concentrations were higher in African-American females aged 12-17 years than in white or Mexican-American participants. No significant ethnic differences were found among female participants aged 18-19 years or male participants aged 12-19 years. Concentrations of insulin increased strongly with increasing levels of BMI. CONCLUSIONS These results provide detailed information about serum concentrations of insulin in a representative sample of U.S. adolescents and young adults and may be useful to monitor future trends of this risk factor for diabetes and cardiovascular disease.