Survey Results

Survey Items: Survey instrument item number for children 10-11 years: C4,C5; for children 12-17 years: C5,C6
Variable name in public use file: BMICLASS (derived)

Denominator: Children age 10-17 years

Numerator: Underweight (less than 5th percentile); Normal weight (5th to 84th percentile); Overweight (85th to 94th percentile); Obese (95th percentile or above)

Revisions and Changes: There have been no substantive changes to this measure since 2016.

Additional Notes: Assessment of body mass index (BMI) in children and teenagers is approached differently than for adults. Because growth patterns differ, BMI in youth is age and gender specific. BMI-for-age categories are: Underweight - Less than the 5th percentile; Healthy weight - 5th percentile to less than the 85th percentile; Overweight - 85th to less than the 95th percentile; Obese - Equal to or greater than the 95th percentile. Additional information about BMI-for-age is available from the CDC website. The child's age in months is used to calculate BMI-for-age. However, since the NSCH reports age only in years, all children were assumed to be at the midpoint of their age-year for this calculation. In the NSCH, BMI is based on parents' recollection of the selected child's height and weight. Responses to these questions about child's current height and weight were not independently verified (e.g., measurement, health records, etc.). A study comparing parent-reported height and weight estimates from the 2003 NSCH with results of physical measurement from the National Health and Nutrition Examination Survey (NHANES) revealed that parents typically overestimate height and underestimate weight of children younger than 10 years of age. (Lara J. Akinbami, Cynthia L. Ogden. (2009) Childhood Overweight Prevalence in the United States: The Impact of Parent-reported Height and Weight. Obesity 17:1574-1580); therefore BMI for children under 10 years of age is not reported in this measure.

Treatment of Unknown Values: Missing values may be due to non-response (i.e. a skipped item) or a “don’t know” response. The way these items are handled can vary by measure. For NPMs and NOMs, having missing values for all items in an indicator will lead to the case being given a missing value on the overall measure. For some other measures, if there is a missing value on any of the items, the case will be set to missing. How missing values are handled is documented in the "Additional notes" field above when required.
Missing values are not included in the denominator when calculating prevalence estimates and weighted population counts displayed in the Interactive Data Query results table. In the majority of cases, the proportion of missing values is less than 2%. Exceptions are noted in the form of a Data Alert at the bottom of a results table. The exclusion of these values does not change the prevalence estimates (%) and only marginally affects the weighted population counts (Pop. Est.). To learn about the impact of the missing values on the population count estimates, click here.

History and Development:
About NSCH
The National Survey of Children’s Health (NSCH), funded and directed by the Health Resources and Services Administration’s (HRSA) Maternal and Child Health Bureau (MCHB), is designed to provide annual national and state-level information on the health and well-being of children ages 0-17 years in the United States. The U.S. Census Bureau administers the survey, oversees the sampling, and produces a final data set of survey results. HRSA’s Maternal and Child Health Bureau (MCHB) develops survey content in collaboration with the U.S. Census Bureau and a Technical Expert Panel. The Technical Expert Panel consists of experts in survey methodology and children’s health, federal and state stakeholders, clinicians and researchers. In 2016, the NSCH underwent a significant redesign which combined content from both the NSCH and the National Survey of Children with Special Health Care Needs (NS-CSHCN). Further information on that redesign can be found in “The Design and Implementation of the 2016 National Survey of Children’s Health”.
The NSCH is conducted as a household survey, and one child per household is selected to be the subject for the detailed age-specific questionnaire. The respondent to this questionnaire is a parent or guardian who is living in the home and has knowledge of the sampled child. Survey participants complete either web-based or self-administered paper-and-pencil questionnaires. Data from the NSCH is used for scientific research, federal policy and program development, and state-level planning and performance reporting. Information is collected on factors related to the health and well-being of children, including access to and utilization of health care, receipt of care in a medical home, systems of care for CSHCN, family interactions, parental health, school and after-school experiences, and neighborhood characteristics.
More information about the survey can be found in the “About the National Survey of Children’s Health” section of this website and HRSA’s MCHB website.