Sustained active transportation is associated with a favorable body mass index trajectory across the early school years: findings from the Quebec Longitudinal Study of Child Development birth cohort

Abstract

Objective: To determine the extent to which active transportation (AT) to and from school is associated with changes in body mass index (BMI) from kindergarten (6-year-olds) through grade 2 (8-year-olds).

Methods: The sample included 1170 children (50.4% of baseline participants) who were part of the Quebec Longitudinal Study of Child Development (QLSCD), a birth cohort established in 1998 in Quebec, Canada. Data were collected by trained interviewers using structured interviews and measuring height and weight in the home with the person most knowledgeable about the child's health. Relative weight was operationalized as age- and sex-adjusted BMI Z-scores.

Results: Growth curve analyses showed that using AT to and from school both when in kindergarten and in grade 1 was predictive of a lower BMI Z-score (coeff=-0.18, SE=0.09, p=0.05) in grade 1. Using AT to and from school in kindergarten, grade 1, and grade 2 was predictive of a lower BMI Z-score (coeff=-0.30, SE=0.098, p=0.003) in grade 2. No other covariates were predictive of relative weight across time, although having an overweight or obese mother was associated with a BMI Z-score of 0.39 (SE=0.07, p<0.001) across all time points.

Conclusion: Sustained AT is associated with more healthful trajectories of BMI across the early school years.