In the absence of actual plasma zinc values to estimate zinc deficiency, stunting has sometimes been used as a proxy. To test the validity of this practice in a middle-income country without widespread helminths or malaria, data were analyzed from children less than 5 years of age in Azerbaijan.
Data came from a nationally representative nutrition survey conducted in 2012-2013. Stunting was defined using the 2006 WHO standards, and plasma zinc concentration was measured using inductively coupled plasma optical emission spectrometry. In addition to bivariate analysis, multivariate models took into account potential confounders. Calculation of all measures of precision accounted for the clustered and stratified sampling.
In 1,009 children, plasma zinc and height/length-for-age z-score were marginally correlated (Pearson correlation=0.062, p=0.05); however, the difference in the prevalence of zinc deficiency did not differ substantially according to the presence of stunting (relative risk=0.86, p=0.56). Stunting only identified 14.4% of 117 children with zinc deficiency (95% CI: 8.5, 23.5). On the other hand, 83.2% of 890 children without zinc deficiency were also not stunted (95% CI: 78.9, 86.7). In different logistic regression models with several demographic (age, sex, urban/rural residence, household wealth, mother’s education), health (diarrhea and/or lower respiratory infection in the past 2 weeks), and nutrition variables (wasting, anemia, iron deficiency, vitamin A deficiency), stunting was among the most weakly associated with zinc deficiency (odds ratios 0.9 – 1.2).
At least in Azerbaijani children, stunting is not an accurate proxy for zinc status and cannot be used to identify zinc deficient children.