Stunted growth
Stunted growth, also known as stunting or linear growth failure, is defined as impaired growth and development manifested by low height-for-age. Stunted growth is often caused by malnutrition, and can also be caused by endogenous factors such as chronic food insecurity or exogenous factors such as parasitic infection. Stunting is largely irreversible if occurring in the first 1000 days from conception to two years of age. The international definition of childhood stunting is a child whose height-for-age value is at least two standard deviations below the median of the World Health Organization's Child Growth Standards. Stunted growth is associated with poverty, maternal undernutrition, poor health, frequent illness, or inappropriate feeding practices and care during the early years of life.
Among children under five years of age, the global stunting prevalence declined from 26.3% in 2012 to 22.3% in 2022. It is projected that 19.5% of all children under five will be stunted in 2030. More than 85% of the world's stunted children live in Asia and Africa. Once stunting occurs, its effects are often long-lasting. Stunted children generally do not recover lost height, and they may experience long-term impacts on body composition and overall health.
Health effects
Stunted growth in children has the following public health impacts:- Greater risk for illness and premature death
- Delayed cognitive development, and poor school performance
- Reduced intelligence quotient
- Future risk of obesity
- Women of shorter stature have a greater risk for complications during childbirth due to their smaller pelvis and are at risk of delivering a baby with low birth weight
- Stunted growth can be passed to the next generation, known as the "intergenerational cycle of malnutrition"
On a societal level, stunted individuals may have physical and/or cognitive delays, affecting their performance in their careers. Stunting can therefore limit economic development and productivity, and it has been estimated that it can affect a country's GDP by up to 3%.
Stunting is prevalent in the Global South and has severe consequences, including increased risk of infections and death. The global percentage of stunted growth decreased from 33% to 22.3% between 2000 and 2022. The largest drop took place in Asia, from 37.1% in 2000 to 28.2% in 2012 and 22.3% in 2022. Despite global progress, the prevalence of child stunting was greater than 30% in 28 countries in 2022.
Causes
In many publications, the causes for stunting are considered very similar, if not the same, as the causes for malnutrition in children. However, some contradict this notion. Recent evidence suggests that stunting may not be taken as a synonym for malnutrition, but as the natural condition of human height in non-Westernized societies.Almost all stunting occurs within the 1,000-day period that spans from conception to a child's second birthday, which constitutes a window of opportunity for growth promotion. The recognition of prenatal factors underlines the intergenerational aspects of growth, and the need for early interventions. The three main causes of stunting in South Asia, and probably in most developing countries, are poor feeding practices, poor maternal nutrition, and poor sanitation. A recent risk assessment analysis for 137 developing countries found that the leading risk factors for stunting were fetal growth restriction followed by unimproved sanitation and diarrhea. It was estimated that 22% of stunting cases were attributable to environmental factors, while 14% were attributable to child nutrition. In addition, looking at trends from 1970 to 2012 for 116 countries, women's education, gender equality, and finally, the quantity and quality of foods available at the country level have been instrumental in reducing stunting rates, while income growth and governance have played facilitating roles.
Feeding practices
Inadequate complementary child feeding and a general lack of vital nutrients besides pure caloric intake are some causes of stunted growth. Children need to be fed diets that meet the minimum requirements in terms of frequency and diversity to prevent undernutrition. Exclusive breastfeeding is recommended for the first six months of life and nutritious food alongside breastfeeding for children aged six months to two years old. Prolonged exclusive breastfeeding is associated with undernutrition because breast milk alone is nutritionally insufficient for children over six months old. Breastfeeding for a long time with inadequate complementary feeding leads to growth failure due to insufficient nutrients, which are essential for childhood development. The relationship between undernutrition and prolonged duration of breastfeeding is mostly observed among children from poor households with uneducated parents, as they are more likely to continue breastfeeding without meeting the minimum dietary diversity requirement.Maternal nutrition
Poor maternal nutrition during pregnancy and breastfeeding can lead to stunted growth of children. Proper nutrition for mothers during the prenatal and postnatal period is important for ensuring healthy birth weight and healthy childhood growth. Prenatal causes of child stunting are associated with maternal undernutrition. Low maternal BMI predisposes the fetus to poor growth leading to intrauterine growth retardation, which is strongly associated with low birth weight and size. Women who are underweight or anemic during pregnancy are more likely to have stunted children, which perpetuates the intergenerational transmission of stunting. Children born with low birth weight are more at risk of stunting. However, the effect of prenatal undernutrition can be addressed during the postnatal period through proper child feeding practices.Maternal undernutrition increases the risk of stunting at 2 years of age. Based on data from 19 birth cohorts from low and middle income countries, 20% of stunting is attributed to being born small-for-gestational-age. Further, an estimated 33% of stunting at 2 years was attributed to fetal growth restriction and preterm birth in 2011 in developing countries, and 41% in South Asia. Restricted pre- and postnatal growth are in turn important determinants of short adult height, increasing the likelihood of the next generation experiencing stunted growth.
Sanitation
One notable contribution to stunted growth is a lack of sanitation—an example of this is countries where public defecation is practiced. The ingestion of high quantities of fecal bacteria by young children through putting soiled fingers or household items in the mouth leads to intestinal infections. This affects children's nutritional status by diminishing appetite, reducing nutrient absorption, and increasing nutrient loss.Research on a global level has found that the proportion of stunting that could be attributed to five or more episodes of diarrhea before two years of age was 25%. Since diarrhea is closely linked with water, sanitation, and hygiene, this is a good indicator of the connection between WASH and stunted growth. To what extent improvements in drinking water safety, toilet use and good handwashing practices contribute to reducing stunting depending on how bad these practices were prior to interventions.
Environmental enteropathy
The condition termed environmental enteropathy is proposed as an immediate causal factor of childhood stunting. This is an asymptomatic small intestinal disorder characterized by chronic gut inflammation, reduced absorptive surface area, and disruption of intestinal barrier function. This small bowel disorder can be attributed to sustained exposure to intestinal pathogens caused by fecal contamination of food and water. Recent evidence confirmed a causal relationship between stunted growth and environmental enteropathy in children. Several studies are also underway to examine the link between this condition and stunted growth. The exact parthenogenesis of environmental enteropathy causing linear growth failure is unclear, but it is hypothesized that a chronic inflammatory state and impaired absorption associated with this condition may inhibit bone growth and affect linear growth during the early years of life.Diagnosis
Growth stunting is identified by comparing measurements of children's heights to the World Health Organization 2006 growth reference population: children who fall below the fifth percentile of the reference population in height for age are defined as stunted, regardless of the reason. The lower than fifth percentile corresponds to less than two standard deviations of the WHO Child Growth Standards median.As an indicator of nutritional status, comparisons of children's measurements with growth reference curves may be used differently for populations of children than for individual children. The fact that an individual child falls below the fifth percentile for height for age on a growth reference curve may reflect normal variation in growth within a population: the individual child may be short simply because both parents carried genes for shortness and not because of inadequate nutrition. However, if substantially more than 5% of an identified child population have height for age that is less than the fifth percentile on the reference curve, then the population is said to have a higher-than-expected prevalence of stunting, and malnutrition is generally the first cause considered.