For surviving children born in the three to five years before the survey, HWWAZWHO (HW71) reports the difference between the child's weight and the median weight of a reference population of the same age and sex, expressed in units equal to one standard deviation of the reference population's distribution. An anthropometry measure expressed in reference standard deviation units is also known as a Z-score. HWWAZWHO values are reported in units equal to 100 times the Z-score, to preserve two decimal places without requiring the use of a decimal point. Dividing HWWAZWHO by 100 will yield a child's weight-for-age Z-score (WAZ) value.
Low child weight-for-age, or "underweight," is a composite indicator of acute and/or chronic malnutrition. The WHO Global Database on Child Growth and Malnutrition [URL omitted from DDI.] considers a weight-for-age Z-score (WAZ) between -2 and -3 to represent moderate malnutrition, and WAZ below -3 to represent severe malnutrition.
Reference populations used to generate HWWAZWHO draw from the WHO Multicenter Growth Reference Study (MGRS) [URL omitted from DDI.] released in 2006, which defined new standard anthropometry curves using a globally diverse reference population intended to reflect healthy growth conditions. For DHS samples that preceded WHO MGRS release, DHS retroactively calculated weight-for-age Z scores using WHO MGRS reference data.
Prior to the WHO MGRS, DHS anthropometry reference populations drew from 1978 U.S. CDC National Center for Health Statistics (NCHS) international growth reference [URL omitted from DDI.] data, which was the previous international standard reference. The DHS variable HWWAZNCHS (HW8) reports the child's weight-for-age Z-score value using the NCHS/CDC 1978 reference population. DHS has continued to release versions of all child anthropometric variables using NCHS/CDC 1978 reference populations, to preserve comparability with samples preceding the 2006 WHO MGRS release.
HWWEIGHT (HW2) reports the child's weight as measured by DHS personnel. KIDAGEMO (HW1) reports the child's age in months at the time of measurement.