The GROWTHCH file contains the public release data from three NHANES and two NHES surveys used in the development of the 2000 CDC growth charts for the United States. It does not include other data that were used to create the growth charts, such as the length data from the Pediatric Nutrition Surveillance System (PedNSS), national birth weight from the National Birth Certificate Data, Wisconsin and Missouri Birth Length, and head circumference data from the Fels Longitudinal Study (http://www.med.wright.edu/lhrc/fels.html). The GROWTHCH file includes body measures data on weight, length, height, and head circumference. The only other omission is the variable “Age in Days.” This variable was omitted from the file even though it was used in the construction of the growth charts. This was done to ensure survey participant confidentiality.
Below is a summary table of the number of sample persons and age ranges selected from each of the NHES and NHANES surveys used to develop the growth charts. The different surveys covered different age groups in the population so the age ranges vary by survey. Sample persons were not excluded from the surveys based on any medical, safety, or other exclusion criteria.
Survey years, sample size and age ranges in each survey
|Number of sample persons
|Age in months of sample persons
||72 – 145.9
||144 – 217.9
||12 – 305.9
||6 – 305.9
||2 – 305.9
Protocol and Procedure
Body measures were collected by trained health technicians. The health technicians were assisted by a recorder during the body measurement examination. These anthropometric procedures were developed based on published recommendations for standardized anthropometric techniques (for general guidelines on the body measurement procedures, please refer to the Anthropometric Standardization Reference Manual, Lohman et al, 1988).
The NHANES III measurement techniques for weight, recumbent length, stature, and head circumferences were based on procedures used in the previous NHES surveys; and either the same or comparable measuring equipment was used across the five surveys.
NHANES III Anthropometric Procedures Video (Centers for Disease Control and Prevention) illustrates the NHANES III anthropometry methodology. The NHANES III video is available in VHS and DVD format upon request and may also be viewed on the NHANES website.
Quality Assurance & Quality Control
All NHES and NHANES surveys had strict quality assurance protocols although there was some variation between surveys. See documentation for specific surveys for more information.
Two different flags exist for low birth weight (LBW) with SAS names LBWFLAG1 and LBWFLAG2. Of the five NCHS surveys, birth certificate information existed only for NHANES III. All observations where the birth certificate indicated the birth weight was below 2500 grams were flagged in LBWFLAG1. All three NHANES surveys contained reported birth weight of the child. For these surveys, all subjects where the reported birth weight was less than 2500 grams were flagged in LBWFLAG2. For NHANES III, these two indicators differed in about 2% of the cases.
1It is possible that a subject’s measurements could be extreme for more than one body measure (say weight and BMI). We created a flag if the subject was indicated on any of the three body measures.
Modified Recumbent Lengths for NHANES III
We modified the final NHANES III variables to correct the recumbent lengths of 15 of the subjects by subtracting 23.1 centimeters to correct for incorrect procedures of one technician. The sequence numbers (SEQN) of these 15 subjects are (17350, 1936, 18423, 6939, 1133, 15844, 1768, 13630, 13510, 3327, 6672, 8517, 20377, 13749, and 18556).
The user needs to be aware that the statistical weights, pseudo-PSU, and pseudo-strata are those from the five original surveys. Any analysis needs to take this into account.