Body mass index and the duration of the pubertal growth spurt in Vietnamese urban children
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Background
Higher childhood body mass index (BMI) is linked to earlier and less intense pubertal growth spurts, but whether it also changes the spurt duration is rarely studied, especially in Vietnam and Southeast Asia.
Methods
We used previously fitted Superimposition by Translation and Rotation (SITAR) growth curves for 8,018 boys and 5,491 girls in a multicity Vietnamese cohort. For each child we derived two duration measures from their own predicted velocity curve, a full width at half maximum (FWHM) measure and a threshold free growth quartile duration, and tested associations with prepubertal BMI z score before and after adjusting for pubertal timing and peak height velocity.
Results
FWHM was identifiable in 99.9% of boys but only 18.0% of girls, and identifiable girls had systematically lower BMI, indicating informative missingness. Growth quartile duration was available for nearly all boys and 94.9% of girls. Higher BMI predicted shorter unadjusted duration in both sexes (p < 0.001 to p = 0.037). After adjustment, in boys, the association weakened but stayed significant. In girls, growth quartile duration reversed direction and remained significant (0.0052 years per unit BMI z score, p = 0.004), with a significant BMI by sex interaction (p = 0.007). Functional principal component analysis confirmed these findings independent of any single model parameter.
Conclusion
Pubertal growth spurt duration responds to BMI differently by sex once timing and intensity are accounted for. Full width based duration measures should be checked against each child’s own available age range before use, particularly in girls.
