Objective: To identify childhood body mass index (BMI) trajectories and to describe their association with subsequent academic and cognitive outcomes.
Study design: Prospective cohort: Height and weight measured annually from 4 to 7 years. A mixture of regressions approach grouped children into BMI trajectories (n=1959 children; n=5754 BMI measures). Academic outcomes included teacher-rated progress and achievement. Cognitive outcomes measured by Kaufman's Assessment Battery for Children. Academic and cognitive outcomes were regressed according to BMI trajectories, controlling for family and individual covariates. Subjects drawn from Quebec Longitudinal Study of Child Development (Canada), a 1998 birth cohort (n=2120).
Results: Four clusters of BMI trajectories emerged: two healthy weight groups, one overweight group and one low weight group. Relative to healthy weight, belonging to the overweight or low weight clusters was negatively associated with cognitive and academic outcomes. With the exception of the low weight cluster, this relationship was insignificant in the adjusted model.
Conclusions: Results suggest that during childhood being overweight does not increase risk for poor educational outcomes. Instead, being underweight may the increase risk for poorer cognitive outcomes. Further group-based trajectory modeling (GBTM) for BMI development over time is needed to confirm results.