Associations between household income, height, and BMI in contemporary US schoolchildren

This paper evaluates the association between income and physical development in a nationally representative sample of contemporary US schoolchildren followed from kindergarten to eighth grade (average ages of 6-14). A generalized linear mixed modeling framework is used to evaluate height and body mass index (BMI) as both levels and annualized growth in a pooled sample. Contemporary US schoolchildren show income variation in height that is significant but modest at around .1cm (in kindergarten) to .4cm (eighth grade) increases per doubling of income. An exception is found for Hispanic children who show faster height velocity associated with higher income through childhood yielding a 1.0cm increase per doubling of income by the eighth grade. All groups except black males show a negative relationship between income and BMI that becomes stronger with age with an average .8kg/m(2) lower BMI per doubling of income by the eighth grade. These results are robust to the inclusion of baseline anthropometric controls. The analysis suggests that higher-income US schoolchildren enter mid-adolescence as taller but with lower proportional body mass relative to their lower-income counterparts.