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Non-linear law-like relationship between weight & height of infants & pre-school children
K R Sundaram1, R K Ahuja, T K Jena
1Department of Biostatistics, All India Institute of Medical Sciences, New Delhi.
Insights
This study models infant and preschooler growth using a non-linear equation, finding nutritional status significantly impacts maturation rates and growth patterns. Malnourished children exhibit delayed growth compared to well-nourished peers.
Area of Science:
- Pediatric Nutrition
- Biostatistics
- Growth Modeling
Background:
- Childhood growth patterns are influenced by nutrition and sex.
- Accurate modeling is crucial for understanding developmental trajectories.
- Previous models may not fully capture nuances in growth across nutritional statuses.
Purpose of the Study:
- To apply a non-linear growth model to weight (w) and height (h) data of 1177 infants and preschool children.
- To analyze the impact of nutritional status and sex on growth parameters.
- To determine the goodness-of-fit for the proposed non-linear equation.
Main Methods:
- Utilized a non-linear equation: log w - 0.008 h = a - be^(-kl).
- Employed the modified Gauss-Newton Method for fitting the equation.
- Used the BMDP 03R program for data analysis.
- Data comprised 1177 infants and preschool children from Ballabhgarh.
Main Results:
- The non-linear model demonstrated a good fit across both sexes and all nutritional groups.
- The nutritional index ('a') was similar between sexes but decreased with malnutrition severity.
- The maturation index ('k') was higher in boys and normal nutrition groups, with slower decay in malnourished children.
- Asymptotic growth attainment was delayed in malnourished girls compared to boys.
Conclusions:
- The non-linear model effectively describes growth in infants and preschoolers.
- Nutritional status is a key determinant of growth rate and maturation.
- Growth delays associated with malnutrition highlight the need for nutritional interventions.
Abstract:
A non-linear equation of the type log w - 0.008 h = a - be-kl for weight (w) and height (h) of 1177 infants and pre-school children from the Rural Health Centre area in Ballabhgarh was fitted by modified Guass-Newton Method using BMDP 03R program. On applying the non-linear model to the data of the present study it was found that the curve was a good fit in both sexes and also in all nutritional groups. The value of 'a' (the nutritional index) was almost the same in boys and girls but it was higher in case of children with normal nutrition (0.37) and lower in children with malnutrition (0.34 in Grade I, 0.32 in Grade II and 0.28 in Grades III & IV). The exponential term 'k' (index of maturation) was higher in boys compared to that of girls and higher in those with normal nutrition than with malnutrition. It was found that the rate of decay of the exponential term was slower in those with malnutrition compared to those with normal nutrition. While no difference was observed in the asymptotic value i.e., the rate at which infants reach the shape of older children, between boys and girls with normal nutrition (19 and 20 months respectively), it was delayed by 5 to 8 months in girls compared to boys with malnutrition. In the total sample, the Ehrenberg's index attained the asymptotic value at 20 months in boys and at 35 months in girls and at 27 months in the combined sample.