Duke 2008 | ASHE | Equity and Efficiency in Health and Healthcare

Given the importance of education over the life course, there is a long economics literature exploring how health affects education. In particular, the recent rise in adolescent obesity has raised concerns that diabetes and depression may adversely affect education. If greater obesity leads to worse education outcomes, then the long-run consequences of obesity go well beyond the direct health effects. The link between health and education has been postulated to be that those in better health may have greater productive efficiency in education, or that there may be an unobserved third factor, such as the discount rate, that may be correlated with both. Estimating the relationship between health and education is therefore complicated by endogeneity. We use an instrumental variables approach to address the endogeneity. We use variation in genotype to predict variation in phenotype (obesity). Genetic information from specific genes linked to obesity in the biomedical literature provide strong exogenous variation in the body mass index, and thus can be used as instrumental variables. These genes predict swings in weight of between 5 and 20 pounds for persons between five and six feet tall. Genes that change the propensity of a person to be obese provide natural variation, as long as those genes are not correlated with other behavioral factors. We use additional genetic information to control for omitted variables correlated with both obesity and education outcomes. We analyze data from the National Longitudinal Study of Adolescent Health (Add Health). In Wave III of Add Health, a subset of 2,612 of the Add Health respondents (total of about 17,000) contributed DNA samples. Six genes identified from the DNA samples were chosen specifically because they are believed to be related to obesity and to have a relatively high prevalence in the population. Polymorphisms in these six genes have been linked to obesity through behavior (Blundell 1977; Hoebel et al., 1989). All affect how the central nervous system regulates satiation and eating behavior. Several pass all specification tests for good instruments; others were used to control for omitted variable bias. Our empirical work will test the null hypothesis that changes in obesity (measured either as continuous BMI or as threshold effects) have no effect on education outcomes, measured as GPA and obtaining a high school diploma. Results will be calculated separately for men and women. We will conduct a number of sensitivity checks, from different functional forms to different sets of instruments. This paper also shows the potential of using genetic information in social sciences. Genetic information holds great promise for social science research. Many large surveys now routinely collect biomarkers, including genetic information.