The international growth standard for children and adolescents project: environmental influences on preadolescent and adolescent growth in weight and height.

This review has two aims. The first is to identify important environmental influences on the growth of children aged 1 to 9 years and of adolescents, defined as those aged 10 to 19 years. The second is to identify possible environmentally based criteria for the selection of individuals and populations for data collection in the development of an international growth reference for these age ranges. There are many common environmental influences on the growth of children between the ages of 1 and 19 years; the examination and description of these forms the main body of this review. Subsequently, environmental factors influencing adolescent growth only are considered. In both cases, possible selection criteria are put forward. The most important inclusion criteria for both preadolescence and adolescence are good nutrition, lack of infection, and socioeconomic status that does not constrain growth. Additionally, low birthweight, catchup growth, breastfeeding, and early adiposity rebound have impacts on growth and/or body composition into puberty. Exclusion of children born at low birth and/or experiencing catch-up growth could be most realistically operationalized if populations in which secular trends in growth were either completed or minimal were selected. Although an effect of hypoxia on child and adolescent growth, independent of nutrition, is small at most, many high-altitude populations have high prevalances of low birthweight and should be excluded on this basis. Since all populations are exposed to pollutants, contaminants, and toxicants in varying degrees, they cannot be realistically excluded from the sample frame. However, it may be desirable to exclude populations that are habitually exposed to extremely high levels of environmental pollution, including air pollution, and those living in close proximity to toxic waste. It is impossible to exclude populations and individuals on the basis of their exposure to aflatoxin contamination of food. However, exclusion on the basis of low socioeconomic status or poverty may well act as a proxy for this. There are a small number of populations that show extreme patterns of growth in body size and proportion in preadolescence and adolescence, and these should be excluded from the sample frame.