According to United Nations Children's Fund (UNICEF) data, 21.3% of children under the age of five in the world had undernutrition in 2019, which represents 144 million individuals.1 The latest data available for Brazil reported a prevalence of 6.95% of stunting in 2007.1 Undernutrition has been identified to be negatively associated with child development, while other studies have shown that nutritional interventions, especially in locations where undernutrition is endemic, have a positive effect on child development.2–5 Among the three main World Health Organization (WHO) child growth standards (length/height-for-age, weight-for-age, weight-for-length, weight-for-height), child linear growth (crude height or height-for-age z) score [HAZ]) is the one with the greatest amount of evidence on the negative impact on child development.6 Chronic malnutrition, expressed by this indicator, has been associated in recent decades with impaired neuronal growth and poor development of brain connections.7 The effect of acute malnutrition, however, is much less studied, having a different explanatory model for its impact on child development.4

More than 250 million children under the age of 5 years in low- and middle-income countries (LMICs) may not reach their full developmental potential, as estimated in 2015.8 Children's development is an essential determinant of later life educational performance and human capital outcomes.9–11 Therefore, factors that impair child development can have effects on the individual across the life course and may jeopardize development at the population level in LMICs. World Health Organization (WHO) stated that childhood stunting is one of the most important impediments to human development.12

The World Health Organization's Nurturing Care Framework for Early Childhood Development and literature report multiple factors to be associated with suboptimal development, including poverty, low maternal education, toxic stress exposure, low birth weight, poor child growth, and suboptimal breastfeeding, besides inadequate nutrition.4,13–16 However, few large, population-based studies have examined the relationship of nutritional risk factors with child development outcomes, particularly in the context of rough climates regions such as Ceará and studies that evaluated the effect of undernutrition on the development of Brazilian children under 5 years of age are exceedingly rare. Although the prevalence of child undernutrition has dramatically declined, in Semiarid climatic regions as Ceará, it may have persisted, as this type of climate has been associated in different parts of the world with an increased risk of food insecurity, which in turn is associated with child malnutrition.17

To fill in the gaps in this literature, the authors aimed to assess the prevalence of undernutrition in a semiarid region of Brazil and to explore the relationship of undernutrition and short duration of breastfeeding with communication, gross-motor, fine-motor, problem-solving and personal-social development scores through a cross-sectional population-based study of children 0-66 months of age residing in Ceará, Brazil.

The study included a cross-sectional population-based sample of 3,566 children from 3,200 households. A summary of the study population characteristics is presented in Table 1. The authors found that 8.2%, 3.0%, 2.1%, and 3.6% of children were stunted, underweight, or wasted, at the time of the interview, respectively. The mean child age was 31.8 ± 23.1 months, and the sample was equally distributed between males and females. The mean maternal education was 4.4 ± 2.8 years, and the mean monthly family income was 1090.4 (∼ 280 USD) ±1017.9 Reais per household.

The relationship of undernutrition and breastfeeding practices with child development outcomes, adjusted for all factors of Table 1, is presented in Tables 2 and 3. In multivariate analysis, all studied factors were associated with a higher prevalence of child development impairment in at least one of the assessed domains. WAZ was the factor with the strongest effect, with an adjusted odds ratio (AOR) of 4,14 (2,26–7,58), p < 0.001, followed by WHZ (AOR 3,04 (1,47–6,25), p = 0.003), HAZ (AOR 2,2 (1,34–3,59), p = 0.004), and breastfeeding for up to two months compared to more than six months (AOR 2,08 (1,38–3,12), p = 0.001). All three undernutrition indicators were associated with all development domains, except for the gross motor domain.

The authors conducted a population-representative cross-sectional study of 3566 children aged 0–66 months of age in Ceará, in the semiarid region of Brazil. The authors estimated the prevalence of undernutrition in the given setting, 8.2% (CI 95% 7.3–9.3) for stunting, 2.1% (CI 95% 1.7–2.6) for wasting and 3.0% (CI 95% 2.5–3.6) for underweight. The authors also found that undernutrition and a short duration of breastfeeding were associated with a higher prevalence of impaired child development.

Although the general data on the prevalence of stunting in Brazil in 2007, the last available according to UNICEF, is 6.95%, the previous PESMIC study performed in Ceará, Brazil, the same state of this study, found a prevalence of 13.0%, and the present study reveals a drop of 37% in ten years in Ceará.1,29 However, it is still 16% higher than the general Brazilian prevalence of 2007, which suggests the existence of concentrations of child malnutrition in specific regions. Reduction in stunting is one of the Global Nutrition Targets 2025 from WHO, and the target is a reduction of 40% in the number of children under five who are stunted, and to achieve this objective directed actions will be necessary.12 Brazil experienced a fall of almost 37% in stunting that can be linked to changes in the socioeconomic factors, as improvements in the purchasing capacity of families through successive increases in the minimum wage and expansion of “Bolsa Família”, the main Brazilian cash-transfer program,30 a rise in maternal education,31 as well as to care factors, namely improvements in the coverage of maternal and child health services.32 The semiarid climate, and the food insecurity associated with it, may contribute to the higher prevalence found in Ceará.

The authors contribute to the robust literature that points out that child linear growth is associated with development outcomes. A prior study conducted among children in Tanzania determined that HAZ and WAZ were linearly associated with cognitive, communication, and motor domains.4,28 In Brazil, although the prevalence of undernutrition is now lower, as compared to other LMICs, the authors still found significant associations of child anthropometric measures with development outcomes. It is proposed that the factors which lead to linear growth faltering can simultaneously affect child development through several mechanisms. It is important to emphasize that the explanatory models of the effect of chronic and acute malnutrition on child development have differences. First, undernutrition can lead to deficits in neuronal growth and the generation of connections between brain regions associated with motor functioning and learning, this effect being more associated with chronic malnutrition, stunting.33 Second, acute malnutrition can be associated with the existence of infections and diarrheal conditions, which can lead to nutritional deficiency due to malabsorption, excessive loss of nutrients, and poor distribution of micronutrients, which impacts the availability of essential substrate for child development.34 Finally, malnourished children may also have difficulty engaging in activities that stimulate development.35 Child undernutrition can exist in contexts where other risk factors for child development accumulate, such as poverty, low educational level and adverse experiences.36 In the study's analysis, the authors adjusted the results for these overlapping determinants, finding less confounded effects of undernutrition on child development.

The authors also identified that decreased breastfeeding time was associated with a higher prevalence of any developmental delay with a gradient in this association, with a lower time reflecting a higher prevalence. The protective effect of breastfeeding for child development is already well established, and the effect appears to last as long as for the first six years of life, as found in the present study's results.37,38 Some may argue that children breastfed in the first hour are healthier, but in this study, the authors adjusted the analysis for birth weight, the same technique used in the studies that found a reduction in mortality and morbidity.

This study has a few limitations. First, the design of the study does not allow for analysis of child development trajectories over time, nor does direct determination of causal relationships and recall bias can impact information in older children. Second, the authors used the ASQ-3, which although being a validated highly suitable populational screening tool, it is less accurate for the detection of changes in child development than other more complex techniques. Further, while the study was designed to be population representative of children living in a semiarid setting, the present study's findings may not be generalizable to children in other contexts. Finally, the authors did not assess parenting, which may contribute to undernutrition and poor child development.

Overall, the authors found that undernutrition and breastfeeding are associated with development outcomes among Brazilian children. As a result, integrated nutritional programs may improve child development outcomes. The effect of the results was independent of income, maternal education, and exposure to toxic stress, and the two did not interact. The authors also highlight that the interventions targeting child nurturing should not only focus on food supply but to stimulate sensory and motor stimulation practices with children who are beneficiaries of income transfer programs.

Fundação Cearense de Apoio ao Desenvolvimento Científico e Tecnológico. Edital CHAMADA 07/2013 - PPSUS CE - FUNCAP/SESA/MS/CNPq. Número do auxílio 13506703-0.

Fundação Cearense de Apoio ao Desenvolvimento Científico e Tecnológico. Edital Jovens Doutores – Edital n° 02/2017.