Period-specific changes in childhood body mass index and later externalizing behaviors: A longitudinal birth cohort...

Rapid early-life growth has been linked to adverse cardiometabolic outcomes, yet its association with behavioral risk remains unclear. We characterized period-specific rates of change in zBMI from birth through childhood and examined their associations with externalizing behaviors in early adolescence, including sex differences.

Data were drawn from 18,815 participants in the Taiwan Birth Cohort Study. Repeated height and weight measurements from birth to 9 years were used to derive age- and sex-standardized BMI z-scores (zBMI). Period-specific rates of change in zBMI were estimated via piecewise growth modeling and examined in relation to externalizing behaviors at age 12 using multiple linear regression.

Four periods of zBMI change were identified: infancy (0-12 months), toddlerhood (12-36 months), early to middle childhood (36-84 months), and late childhood (84-108 months). Higher rates of change during infancy and late childhood were associated with lower and higher levels of externalizing behaviors at age 12, respectively (B = -0.01, p < .01; B = 0.02, p < .05). After adjustment for attained zBMI at age 12, only the late-childhood association remained significant. Girls exhibited higher rates of change during toddlerhood and lower rates during early to middle childhood than boys, but associations with externalizing behaviors did not differ by sex.

Variations in rates of change in zBMI, particularly in late childhood, were associated with externalizing behaviors in early adolescence, underscoring the importance of period-specific patterns of zBMI change across childhood.