Survey Results

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

Denominator: Children age 10-17 years

Numerator: Children who are underweight (less than 5th percentile); Children who are at a healthy weight (5th to 84th percentile); Children who are overweight or obese (85th percentile or above)

Revisions and Changes: In 2018 this measure did not change from the 2017 NSCH.

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: The Health Resources and Services Administration's (HRSA) Maternal and Child Health Bureau (MCHB) funds and directs the National Survey of Children's Health (NSCH), and 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. The U.S. Census Bureau conducts the survey, oversees the sampling, and produces a final data set of survey results. Respondents' cognitive understanding of the survey questions was assessed during the pretest phase of the survey redesign (in 2015) and reassessed after the 2016 survey; subsequent revisions were made. Previously validated questions and scales are used when available. The manuscript "The Design and Implementation of the 2016 National Survey of Children's Health" provides detailed information about the redesign of the NSCH, administration of the first redesigned survey (2016), and the sampling and administration changes for the 2017 and 2018 NSCH. Prior to 2016, the NSCH and the National Survey of Children with Special Health Care Needs were each conducted three times as interviewer-assisted telephone surveys using random digit dial sampling. In 2016, the two surveys were combined into a single annual self-administered questionnaire. Due to decline in the number of households with landline telephones, the NSCH now utilizes an addressed based sampling method to select participating households, thus all invitations are sent by mail. Participants may choose to complete the survey either online using a secure website or a mailed paper version of the survey. All final data components are verified by the Census Bureau, HRSA/MCHB and CAHMI/DRC staff prior to public release. 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.