Abstract
ABSTRACTBackgroundAn inverse association between childhood body mass index (BMI; in kg/m2) and pubertal timing is well established for girls. Among boys, studies are scarce and the results inconclusive.ObjectiveWe aimed to determine the association between childhood BMI and age at peak height velocity (PHV) in boys.DesignWe collected height and weight measurements between 6.5 and 22 y of age for boys born 1945–1961 (original cohort; n = 31,971; mean ± SD childhood BMI: 15.74 ± 1.41; age at PHV: 14.06 ± 1.11 y) and 1981–1996 (replication cohort; n = 1465; childhood BMI: 16.47 ± 2.06; age at PHV: 13.71 ± 1.08 y) attending schools in Gothenburg, Sweden, and examined at mandatory military conscription. Age at PHV was obtained from curve-fitting of measured heights with the use of a modified Infancy-Childhood-Puberty model.ResultsIn the original cohort, childhood BMI was inversely associated with age at PHV (P < 0.001) and a significant quadratic term for childhood BMI (P < 0.001) indicated the nonlinearity of this association. Via piecewise linear regression, we identified a threshold for the association at a childhood BMI of 18.42. A significant inverse association was observed below (β: −0.17 y/BMI unit; 95% CI: −0.18, −0.16 y/BMI unit) but not above (β: 0.02 y/BMI unit; 95% CI: −0.03, 0.06 y/BMI unit) this childhood BMI threshold. For every unit increase in childhood BMI, age at PHV was ∼2 mo earlier up to the childhood BMI threshold. Similar results were observed in the replication cohort, demonstrating a significant inverse association below (β: −0.16; 95% CI: −0.21, −0.11) but not above (β: −0.03; 95% CI: −0.11, 0.05) the childhood BMI threshold. The identified threshold was close to the cutoffs for overweight at 8 y of age, and childhood BMI was inversely associated with age at PHV below but not above the overweight cutoffs.ConclusionsThe present findings establish an inverse association between childhood BMI and pubertal timing in normal-weight but not overweight boys.
Highlights
The transition from childhood to adulthood through puberty is one of the milestones in human development
Childhood body mass index (BMI) was inversely associated with age at peak height velocity (PHV) in normal-weight but not overweight boys (Tables 3 and 4)
In the present study we demonstrate that prepubertal BMI is inversely associated with age at pubertal timing in normal-weight but not overweight boys in 2 population-based cohorts of boys born before and during the obesity epidemic
Summary
The transition from childhood to adulthood through puberty is one of the milestones in human development. An inverse association between childhood BMI (in kg/m2) and pubertal timing is well established and a systematic review of longitudinal studies recently confirmed that higher BMI at 7 and 8 y of age was associated with earlier menarche [1]. Objective: We aimed to determine the association between childhood BMI and age at peak height velocity (PHV) in boys. Similar results were observed in the replication cohort, demonstrating a significant inverse association below (β: −0.16; 95% CI: −0.21, −0.11) but not above (β: −0.03; 95% CI: −0.11, 0.05) the childhood BMI threshold. The identified threshold was close to the cutoffs for overweight at 8 y of age, and childhood BMI was inversely associated with age at PHV below but not above the overweight cutoffs. Conclusions: The present findings establish an inverse association between childhood BMI and pubertal timing in normal-weight but not overweight boys.
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