Author Affiliation: Eastern Michigan University, School of Health Sciences, Ypsilanti.
I am responding to the April 2011 article by Hernandez et al1 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 socioeconomic status.
Rainville AJ. National School Lunch Program for All. Arch Pediatr Adolesc Med. 2011;165(11):1051. doi:10.1001/archpediatrics.2011.181