Stunted Growth
Stunted Growth
Linear growth or height is influenced by genetic factors, environmental factors, and medical conditions. The National Center for Health Statistics (NCHS) has developed age- and gender-specific growth charts for health professionals to track children’s height over time. Height is converted to height-for-age, often expressed as a percentile. Children growing between the fifth and ninety-fifth percentiles are considered to be growing within normal limits.
Children whose height is below the fifth percentile may be classified as stunted or of short stature. Stunting, defined as height-for-age that is more than two standard deviations below the NCHS or World Health Organization (WHO) International Growth Reference, serves as a general indicator of a child’s nutritional status over long periods of time. Growth stunting is a gradual process that occurs in response to chronic biological insults, including malnutrition and infectious diseases, during periods of linear bone growth. It often begins in utero and extends through the first two years. Childhood stunting is closely associated with poverty and is often used as a population-based indicator to compare nutritional adequacy across countries. Without environmental changes, such as adoption, stunting can lead to a permanent reduction in growth. Thus, children who experience stunting early in life are often shorter during childhood and adulthood than peers who had adequate early growth.
The term short stature (SS) usually refers to children whose height is compromised by medical problems, such as Turner’s syndrome, growth hormone deficiency, renal insufficiency, or Prader-Willi syndrome. The term idio-pathic short stature (ISS) is used when there is no apparent explanation for a child’s short stature. ISS can include children with short familial stature or a constitutional/maturational delay in development.
STUNTING
In the absence of adequate nutrients, a child’s body conserves energy by limiting weight gain and then by limiting linear growth. Cross-sectional and longitudinal studies from multiple countries have found associations between stunting and children’s health and development, caused by underlying factors such as malnutrition and infections. The consequences associated with early stunting include metabolic changes, depressed immune function, morbidity, mortality, delayed motor skills, delayed and irregular school attendance, low cognitive scores, and poor academic achievement. Adults with a history of stunting are at risk for obesity, reduced glucose tolerance, coronary heart disease, hypertension, and osteoporosis, as well as decreased work performance and productivity, thereby limiting economic capacity. In settings in which stunting is prevalent, the economic capacity of the entire society may be diminished.
The United Nations Standing Committee on Nutrition estimated that in 2004 approximately 148 million preschool children (27 percent under five years of age) in developing countries were stunted. Malnutrition is a serious global concern, and in some countries rates of stunting among children exceed 50 percent. In 2000, 70 percent of stunted children were from Asia, primarily South Central Asia, and 24 percent were from sub-Saharan Africa.
The primary causes of stunting are nutrient deficiencies and infection. Recent evidence has shown that cow’s milk intake is linked to linear growth, primarily by stimulating insulin-like growth factor (IGF-1). Although several nutrients have been linked to stunting, including protein, iron, zinc, copper, calcium, and vitamins D, A, and C, supplementation trials have not yielded clear findings, with the exception of 2002 meta-analysis by Brown et al. showing small but significant effects of zinc supplementation on linear growth. Intestinal infections can lead to stunting by reducing the absorption of nutrients. In environments with poor hygienic conditions, frequent infections can directly impact metabolism, particularly during infancy when nutritional demands are high and complimentary foods are introduced.
Caregiving practices can influence stunting through feeding patterns, food choices, and household stress. In food-insecure households, families may rely on foods low in macro- and micronutrients. When food is readily available, stunting rates are low. Stunting related to nutrient deficiencies can be minimized by exclusive breastfeeding for the first six months of life, as recommended by the WHO. However, in much of the world, complimentary foods are introduced before six months, often with liquids and cereals that are low in nutrients. If animal-source foods are not available, it can be difficult to provide sufficient nutrients for adequate growth. Finally, there is some evidence that severe family stress can result in diminished linear growth.
Stunting can continue into later childhood, adolescence, and adulthood, generally as an extension of prior stunting. Latin America has high rates of stunting in middle and late childhood, particularly in economically depressed areas. Although malnourished girls may have extended growth periods due to delayed menarche, they generally remain shorter than peers due to past stunting. Growth during adolescence does not typically compensate for earlier stunting.
Catch-up growth is defined as growth that is greater in velocity than expected. Although catch-up growth typically occurs during periods of rapid growth in infancy and toddlerhood, it can occur in middle childhood, particularly if there are nutritional or environmental improvements. There is recent controversy about the promotion of catch-up growth, as rapid weight gain has been linked with metabolic syndrome later in life.
Historically, stunting has been addressed through nutrition supplement programs, with inconsistent success in reducing stunting and increasing linear growth. Supplementation, combined with psychosocial stimulation, can also lead to improvements in cognitive performance into early adulthood.
In Peru, where food availability is adequate and stunting is primarily caused by dietary patterns, a randomized controlled trial of a nutrition education intervention from birth found that feeding practices and dietary intake improved, and the stunting rate was reduced by two-thirds among children eighteen months of age.
Economic progress has also been linked with decreased stunting rates. For example, Southeast Asia has seen a significant decrease since 1990 corresponding with economic improvements. National factors such as energy availability, female literacy, safe water rate, amount of economy derived from agriculture, and gross national product largely explain stunting prevalence within nations.
SHORT STATURE
The health and developmental consequences of SS/ISS are generally less severe than stunting, depending on the underlying causes. Although early studies raised concerns about the emotional well-being of SS/ISS children, recent studies with adequate comparison groups have not found difficulties in emotional well-being or self-image related to SS/ISS.
INTERVENTION AND TREATMENT
Children with growth hormone deficiency have been treated effectively with recombinant growth hormone. Growth hormone therapy (GHT) has been approved for treatment of children with ISS, but it is expensive and requires injections six or seven times a week until adult height is achieved. A 2003 Cochrane review by Jackie Bryant, C. Cave, and R. Milne found nine randomized controlled trials of GHT among children with ISS, most with only short-term effects. Although GHT can contribute to short-term increases in height (ranging from 0 to 0.7 standard deviations per year), children with ISS will be shorter than peers in adulthood. There is debate on the merits of GHT among children with ISS, particularly because treatment with GHT does not appear to alter children’s quality of life. More research is needed to examine the long-term consequences of GHT, including adult stature, quality of life, and costs.
There have been concerns regarding the relation between long-acting stimulations given to children with attention-deficit/hyperactivity disorder and children’s growth. Although most studies have found no long-term negative effects on children’s height, the findings are not consistent and there are some data suggesting diminished gains in height after four years of treatment.
OTHER CONDITIONS
Severe dieting and anorexia nervosa result in inadequate weight gain (including weight loss) and may alter the sex hormones and menarche. However, there is not a clear relation between anorexia nervosa and stunting/SS. Growth history, timing of onset (before or after puberty), and duration of anorexia nervosa can impact nutritional status and growth outcomes, but have not been studied systematically.
In summary, stunting occurs early in life and can have lifelong consequences on cognition, academic performance, work capacity, and economic potential. Ensuring adequate nutrition and care through the promotion of breastfeeding; access to nutrient-rich food, including cow’s milk; and developmentally and culturally appropriate feeding practices may be effective strategies to prevent stunting.
SEE ALSO Body Mass Index; Child Development; Development; Disease; Hypertension; Malnutrition; Nutrition; Obesity; Undereating; World Health Organization
BIBLIOGRAPHY
Branca, Francesco, and Marika Ferrari. 2002. Impact of Micronutrient Deficiencies on Growth: The Stunting Syndrome. Annals of Nutrition and Metabolism 46 (suppl. 1): 8–17.
Brown, Kenneth H., Janet M. Peerson, Juan Rivera, and Lindsey H. Allen. 2002. Effect of Supplemental Zinc on the Growth and Serum Zinc Concentrations of Prepubertal Children: A Meta-analysis of Randomized Controlled Trials. American Journal of Clinical Nutrition 75: 1062–1071.
Bryant, Jackie, C. Cave, and R. Milne. 2003. Recombinant Growth Hormone for Idiopathic Short Stature in Children and Adolescents. Cochrane Database of Systematic Reviews (4): CD004440.
Frongillo, Edward A., Mercedes de Onis, and Kathleen M. Hanson. 1997. Socioeconomic and Demographic Factors are Associated with Worldwide Patterns of Stunting and Wasting of Children. Journal of Nutrition 127: 2302–2309.
Lee, Mary M. 2006. Idiopathic Short Stature. New England Journal of Medicine 354: 2576–2582.
Milman, Anna, Edward A. Frongillo, Mercedes de Onis, and Ji-Yun Hwang. 2005. Differential Improvement among Countries in Child Stunting is Associated with Long-term Development and Specific Interventions. Journal of Nutrition 135: 1415–1422.
Penny, Mary E., Hilary M. Creed-Kanashiro, Rebecca C. Robert, et al. 2005. Effectiveness of an Educational Intervention Delivered through the Health Services to Improve Nutrition in Young Children: A Cluster-Randomised Controlled Trial. Lancet 365: 1863–1872.
United Nations System: Standing Committee on Nutrition. 2004. Fifth Report on the World Nutrition Situation: Nutrition for Improved Development Outcomes. Geneva, Switzerland:Author. http://www.unsystem.org/scn/Publications/html/RWNS.html.
Margo A. Candelaria
Maureen M. Black