Establishing anthropometric growth references for school-going children aged 3–13 years in southern Thailand using GAMLSS

The growth and nutritional status of children are critical to national prosperity and sustainable development. Developing population-specific growth centiles is therefore essential for promoting the health and well-being of children in Lower Southern Thailand. This study aimed to develop sex-specific growth centile references for children aged 3–13 years using anthropometric measures and Generalized Additive Models for Location, Scale, and Shape (GAMLSS) and to compare these regional references with the WHO growth reference. This cross-sectional study sampled 2170 children (1081 boys, 1089 girls) across seven provinces of Lower Southern Thailand using multistage stratified random sampling. Centiles for height-for-age, weight-for-age and BMI-for-age were fitted using Generalized Additive Models for Location, Scale, and Shape (GAMLSS), with distribution families selected by information criteria. Boys had a mean height of 125.4 ± 15.7 cm and mean weight of 27.2 ± 11.2 kg; girls had a mean height of 124.9 ± 16.8 cm and mean weight of 27.1 ± 11.4 kg. Height and weight centiles rose smoothly with age; BMI centiles increased more markedly from 8 to 9 years onward, particularly in the upper tail. The 50th centile showed slightly lower growth in both boys and girls from approximately age 4, as compared to the WHO growth references. Among children aged 5–13 years, stunting was more prevalent in girls (2.6%) than boys (2.2%) and obesity was similar between sexes (2.1%); both were lower than estimates obtained using the WHO 2007 growth reference. These centiles provide a descriptive, population-specific reference which supplements, rather than replaces, the WHO growth references which are the primary standard for clinical assessment and international comparison. They may facilitate descriptive surveillance, secular trend monitoring, and regional health planning.