Distribution of HbA(1c) levels for children and young adults in the U.S.: Third National Health and Nutrition Examination Survey.

OBJECTIVE To describe the distribution of HbA(1c) levels among children and young adults in the U.S. and to evaluate the effects of age, sex, race/ethnicity, socioeconomic status, parental history of diabetes, overweight, and serum glucose on HbA(1c) levels. RESEARCH DESIGN AND METHODS We analyzed HbA(1c) data from the Third National Health and Nutrition Examination Survey, 1988-1994, for 7,968 participants aged 5-24 years who had not been treated for diabetes. After adjusting for the complex sample design, we compared the distributions of HbA(1c) in subgroups and developed multiple linear regression models to examine factors associated with HbA(1c). RESULTS Mean HbA(1c) level was 4.99% (SD 0.50%) and varied from 4.93% (95% CI +/-0.04) in non-Hispanic whites to 5.05% (+/-0.02) in Mexican-Americans to 5.17% (+/-0.02) in non-Hispanic blacks. There were very small differences among subgroups. Within each age- group, among men and women, among overweight and nonoverweight subjects, and at any level of education, mean HbA(1c) levels were higher in non-Hispanic blacks than in non-Hispanic whites. After adjusting for confounders, HbA(1c) levels for non-Hispanic blacks (5.15%, 95% CI +/-0.04) and Mexican-Americans (5.01%, +/-0.04) were higher than those for non-Hispanic whites (4.93%, +/-0.04). CONCLUSIONS These data provide national reference levels for HbA(1c) distributions among Americans aged 5-24 years and show statistically significant racial/ethnic differences in HbA(1c) levels that are not completely explained by demographic and health-related variables.