Micronutrient deficiencies among preschool-aged children and women of reproductive age worldwide: a pooled analysis of individual-level data from population-representative surveys

Abstract

Background: Micronutrient deficiencies compromise immune systems, hinder child growth and development, and affect human potential worldwide. Yet, to our knowledge, the only existing estimate of the global prevalence of micronutrient deficiencies is from over 30 years ago and is based only on the prevalence of anaemia. We aimed to estimate the global and regional prevalence of deficiency in at least one of three micronutrients among preschool-aged children (aged 6-59 months) and non-pregnant women of reproductive age (aged 15-49 years).

Methods: In this pooled analysis, we reanalysed individual-level biomarker data for micronutrient status from nationally representative, population-based surveys. We used Bayesian hierarchical logistic regression to estimate the prevalence of deficiency in at least one of three micronutrients for preschool-aged children (iron, zinc, and vitamin A) and for non-pregnant women of reproductive age (iron, zinc, and folate), globally and in seven regions using 24 nationally representative surveys done between 2003 and 2019.

Findings: We estimated the global prevalence of deficiency in at least one of three micronutrients to be 56% (95% uncertainty interval [UI] 48-64) among preschool-aged children, and 69% (59-78) among non-pregnant women of reproductive age, equivalent to 372 million (95% UI 319-425) preschool-aged children and 1·2 billion (1·0-1·4) non-pregnant women of reproductive age. Regionally, three-quarters of preschool-aged children with micronutrient deficiencies live in south Asia (99 million, 95% UI 80-118), sub-Saharan Africa (98 million, 83-113), or east Asia and the Pacific (85 million, 61-110). Over half (57%) of non-pregnant women of reproductive age with micronutrient deficiencies live in east Asia and the Pacific (384 million, 279-470) or south Asia (307 million, 255-351).

Interpretation: We estimate that over half of preschool-aged children and two-thirds of non-pregnant women of reproductive age worldwide have micronutrient deficiencies. However, estimates are uncertain due to the scarcity of population-based micronutrient deficiency data.

Funding: US Agency for International Development.

Figure 1:. Prevalence of single or two or more micronutrient deficiencies in preschool-aged children aged 6–59 months (A) and non-pregnant women aged 15–49 years (B)

Results shown for datasets containing at least five of six sentinel micronutrients. Exact age ranges varied by dataset and are specified in the appendix (pp 19–22). Sample sizes and deficiency cutoffs used are in table 1 and in the appendix (pp 19–22). For both women and children, the dataset from Guatemala did not include folate and the dataset from Cameroon did not include vitamin D. For women, the survey in Pakistan measured folate but the data were not included here, and the surveys in Ecuador, Ethiopia, Malawi, and Bangladesh did not measure vitamin D. For children, the survey from Mexico did not measure folate, from the UK did not measure zinc, and from Viet Nam did not measure vitamin B₁₂.

Figure 2:. Estimated prevalence of three core micronutrient deficiencies (2003–19) in preschool-aged children 6–59 months (A) and women aged 15–49 years (B)

Direct survey results, survey results that were adjusted for one unmeasured micronutrient, and regional and global estimates are shown. Error bars show 95% uncertainty intervals. Exact age ranges varied and are listed in the appendix (pp 19–22). Sample sizes are also listed in the appendix (pp 19–22). Core micronutrients for children are iron, zinc, and vitamin A, and the median year of data collection was 2013. Core micronutrients for women are iron, zinc, and folate, and the median year of data collection was 2013.