National school lunch program for all.

摘要

I am responding to the April 2011 article by Hernandez et al entitled "National School Lunch Program Participation and Sex Differences in Body Mass Index Trajectories of Children From Low-Income Families." I believe the main exposure, participation in the National School Lunch Program, was incorrectly measured. Hernandez et al used parental reports of whether children received free or reduced-price lunches at school as a measure of participation in the National School Lunch Program. Eligibility for free and reduced-price meals is based on income and is an indirect measure of socio-economic status.