Pubertal Growth Spurt Characteristics of Vietnamese Urban Schoolchildren: Population and Individual Level Analysis Using SITAR

Pubertal growth spurt characteristics vary substantially across populations, but no study has characterized these parameters in Vietnamese children using the SITAR (SuperImposition by Translation And Rotation) framework, despite Vietnam rapid ongoing nutritional transition. We fitted sex specific SITAR models to longitudinal height data from 15,491 children (9,047 boys, 6,444 girls, 2018 to 2025) to estimate population and individual age at peak height velocity (APHV) and peak height velocity (PHV), and used multivariable linear mixed effects and logistic regression models to identify prepubertal predictors of pubertal timing and intensity. Population mean APHV was 12.2 years in boys and 9.2 years in girls, with PHV of 9.3 and 7.0 cm/year, respectively. This is earlier than previously reported Korean, Colombian, Ethiopian and US cohorts. Individual variability in pubertal timing was nearly twice as large in girls as in boys. After multivariable adjustment, higher baseline BMI-for-age z-score independently predicted earlier pubertal timing in both sexes, whereas height-for-age z-score and prepubertal height velocity showed opposite direction associations (earlier timing in boys but later timing in girls). A significant secular trend toward earlier puberty was observed in girls (~1 year per decade) but not in boys. Logistic models predicting early pubertal timing achieved acceptable discrimination in boys (AUC=0.76) and modest discrimination in girls (AUC=0.70). This first SITAR-based characterization study reveals earlier pubertal timing in these Vietnamese urban schoolchildren than comparator populations, pronounced sex-specific associations between prepubertal BMI status and height status, and a marked secular trend in earlier puberty in girls warranting further surveillance. Keywords: puberty, growth spurt, SITAR, peak height velocity, adolescent growth, Vietnam, BMI, secular trend