Prevalence of wasting among under 6-month-old infants in developing countries and implications of new case definitions using WHO growth standards: a secondary data analysis

Abstract

Objectives: To determine wasting prevalence among infants aged under 6 months and describe the effects of new case definitions based on WHO growth standards.

Design: Secondary data analysis of demographic and health survey datasets.

Setting: 21 developing countries.

Population: 15 534 infants under 6 months and 147 694 children aged 6 to under 60 months (median 5072 individuals/country, range 1710-45 398). Wasting was defined as weight-for-height z-score <-2, moderate wasting as -3 to <-2 z-scores, severe wasting as z-score <-3.

Results: Using National Center for Health Statistics (NCHS) growth references, the nationwide prevalence of wasting in infant under-6-month ranges from 1.1% to 15% (median 3.7%, IQR 1.8-6.5%; ∼3 million wasted infants <6 months worldwide). Prevalence is more than doubled using WHO standards: 2.0-34% (median 15%, IQR 6.2-17%; ∼8.5 million wasted infants <6 months worldwide). Prevalence differences using WHO standards are more marked for infants under 6 months than children, with the greatest increase being for severe wasting (indicated by a regression line slope of 3.5 for infants <6 months vs 1.7 for children). Moderate infant-6-month wasting is also greater using WHO, whereas moderate child wasting is 0.9 times the NCHS prevalence.

Conclusions: Whether defined by NCHS references or WHO standards, wasting among infants under 6 months is prevalent in many of the developing countries examined in this study. Use of WHO standards to define wasting results in a greater disease burden, particularly for severe wasting. Policy makers, programme managers and clinicians in child health and nutrition programmes should consider resource and risk/benefit implications of changing case definitions.

Figure 1

Country prevalence of wasting (<−2 weight-for-height z-score) as defined by National Center for Health Statistics (NCHS) growth references (striped) and WHO growth standards (shaded). Countries are ordered by increasing infant under-6-month wasting prevalence (NCHS). Boxed comments (ie, ‘Famine’, ‘Humanitarian emergency’) refer to the ‘integrated food security phase classification, IPC’ – see Methods section. (A) Wasting prevalence among infants aged from 0 to under 6 months. (B) Wasting prevalence among children aged from 6 to under 60 months.

Figure 2

Scatter plot of country prevalence of (A) severe and (B) moderate wasting (weight-for-height z-score <−3 and ≥−3 to <−2 respectively), as diagnosed using either National Center for Health Statistics (NCHS) or WHO growth norms. Regression and identity lines are shown. Each country survey is represented by one filled and one unfilled circle.

Figure 3

Difference in WHO and National Center for Health Statistics (NCHS) −2 and −3 z-score cut-offs. Arrows on the figure show median length/height at different ages for boys (using WHO growth standards).