For surviving children born in the three to five years before the survey, HWHAZNCHS (HW5) reports the difference between the child's height and the median height 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. HWHAZNCHS 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 HWHAZNCHS by 100 will yield a child's height-for-age Z-score (HAZ) value.
Low child height-for-age, or "stunting," is an indicator of chronic malnutrition. The WHO Global Database on Child Growth and Malnutrition [URL omitted from DDI.] considers a height-for-age Z-score (HAZ) between -2 and -3 to represent moderate chronic malnutrition, and HAZ scores below -3 to represent severe chronic malnutrition.
Reference populations used to generate HWHAZNCHS draw from 1978 U.S. CDC National Center for Health Statistics (NCHS) international growth reference [URL omitted from DDI.] data. This reference was considered standard by WHO until the 2006 release of the WHO Multicenter Growth Reference Study (MGRS), which generated new standard anthropometry curves using a globally diverse reference population intended to reflect healthy growth conditions. DHS has continued to release anthropometric variables using NCHS/CDC 1978 reference populations, to preserve comparability with samples preceding the 2006 WHO MGRS release.
DHS has also created anthropometric Z-score variables using WHO MGRS 2006 reference populations. The variable HWHAZWHO (HC70) uses WHO MGRS 2006 reference populations to generate height-for-age Z-scores. This variable was generated for all DHS samples including the necessary anthropometric measurements, including those preceding 2006.
HWHEIGHT (HW3) reports the child's length or height as measured by DHS personnel. See this variable and HWHTHOWMEAS (HW15) for specifics on child length/height measurement. The related variable KIDAGEMO (HW1) reports the child's age in months at the time of measurement.
The complementary DHS variable HWHTAPCT (HW4) reports the child's height-for-age percentile within the same reference population used in HWHAZNCHS. The complementary DHS variable HWHTAPCTRM (HW9) reports the child's height-for-age as a percentage of the median of the same reference population. Unlike z-scores, percentiles do not allow comparison across age and sex and cannot assess longitudinal change in growth status; users are advised to consult anthropometry literature [URL omitted from DDI.] for further discussion.