Researchers suggest an alternative growth chart more suitable for children from poor countries.
Researchers found different growth patterns for children aged below 15 in Ethiopia, India, Peru and Vietnam. Doctors can use this information to help children in poorer countries thrive.
Scientists sometimes use models and growth charts to estimate how a child is expected to grow over time. Scientists use these growth charts to present their data in picture form and to show how things change over time. They say growth charts made for children in rich countries may not be suitable for children in poorer countries because living conditions are different.
In this study, the researchers wanted to model growth for children aged up to 15 in developing countries, and at the end draw the most suitable growth chart.
They used data from a study that examined poverty and health in children in Ethiopia, India, Peru and Vietnam. They extracted growth information like height and weight, collected every 3 to 4 years, over 15 years from 2002 to 2016.
They tested and compared different models that could best represent children’s growth in poor countries.
The researchers observed that growth among the children differed across gender and by country. Boys were generally taller but did not grow as fast as girls. This means girls would reach their ‘tallest’ height earlier than boys, even though boys eventually grew past the girls’ height.
The researchers also said shorter children generally grew faster than taller children. Vietnamese children were the tallest, followed by Ethiopians, and lastly Indians and Peruvians. By the age of 15, the average child’s height was 172 cm in Ethiopia, 170 cm in India, 171 cm in Peru and 174 cm in Vietnam.
They said Ethiopian children reached adult height earlier than Indian children, but later than Peruvian children. Ethiopian and Vietnamese children grew at almost the same rate.
The researchers said average height increased with age. Boys aged 1, 5, 8, and 15 were taller than girls, while only at an age of 12 were girls taller than boys for all the countries.
In the end, the researchers recommended a model that produced a growth chart in which height did not increase with age continuously, with no change at a certain age.
The researchers, who were based in Ethiopia and South Africa, said the differences they observed among the children could be due to their living conditions.
Background: Modelling the growth curve of height has a significant role in understanding the growth trajectories over time and generated mathematical functions that depict the expected height of children at a particular age. However, modelling the mathematical growth functions for physical height is not well studied in low- and middle-income countries. Modelling and identifying nonlinear growth curves that adequately describe the growth trajectories in low- and middle-income countries were the aims of this study.
Methods: The data were obtained from the Young Lives study. Longitudinal measures of height from infancy to middle-adolescence were collected from low- and middle-income countries. A number of nonlinear growth trajectories were studied through the family of three-parameter nonlinear mixed-effects models.
Results: This study examined the performances of different growth curves for the height growth trajectories. The Logistic curve was chosen among the three-parameter nonlinear growth curves for modelling the growth trajectories from infancy to middle-adolescence. Gender and country have significant effects on the three parameters of growth curves. Males had higher asymptotic height and a lower rate of growth than females. Females reached asymptotic height earlier and shorter at asymptotic height than males. Children with low asymptotic height grow faster than those with higher asymptotic height. Compared to Ethiopian children, Indian and Peruvian children had lower asymptotic height, but Vietnamese children had higher asymptotic height. Ethiopian children approached adult height earlier than Indian children, but later than Peruvian children. However, there was no significant difference in the rate of growth between Ethiopian and Vietnamese children.
Conclusions: This study concludes that the Logistic growth curve was found to be the best growth curve to describe the height growth trajectories. Children in Ethiopia, India, Peru and Vietnam showed different growth parameters. Further enhancements may be attained with the incorporation of other plausible covariates.
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