Jamie L. Lynch

Why are Educated Adults Slim — Causation or Selection?

More educated adults tend to have lower body mass index (BMI) and a lower risk of overweight and obesity. We contrast two explanations for this education gradient in BMI. One explanation is selection: adolescents with high BMI are less likely to plan for, attend, and complete higher levels of education. An alternative explanation is causation: higher education confers lifelong social, economic, and psychological benefits that help adults to restrain BMI growth. We test the relative importance of selection and causation using data from the National Longitudinal Survey of Youth, 1997 cohort (NLSY97), which tracks self-reported BMI from adolescence (age 15) through young adulthood (age 29). Ordinal regression models confirm the selection hypothesis that high-BMI adolescents are less likely to complete higher levels of education. Selection has primarily to do with the fact that high-BMI adolescents tend to come from socioeconomically disadvantaged families and tend to have low grades and test scores. Among high-BMI girls there is also some evidence that educational attainment is limited by bullying, poor health, and early pregnancy. About half the selection of high-BMI girls out of higher education remains unexplained. Fixed-effects models control for selection and suggest that the causal effect of education on BMI, though significant, accounts for only one-quarter of the mean BMI differences between more and less educated adults at age 29. Among young adults, it appears that most of the education gradient in BMI is due to selection.

Low Birth Weight and Parental Investment: Do Parents Favor the Fittest Child?

Do parents contribute to birth weight disparities in status attainment? This study uses a nationally representative sample of 8,550 children and 1,450 twins from the Early Childhood Longitudinal Study-Birth Cohort to investigate whether, as recent studies have suggested, parents favor healthier children. Children with poor health are found to receive fewer parental investments, including breast-feeding and quality parent-child interaction, but results from between- and within-family regression models, using low birth weight as a proxy for child health, find no evidence that parents compensate for or reinforce child health endowments. Instead, birth-weight disparities in parental investment are linked with observable family, maternal, and child sociodemographic characteristics. Our results shed new light on the broad spectrum of disadvantage faced by children with poor health, and raise doubts about the utility of human capital models to explain birth weight disparities in parental investment.

Health consequences of same and opposite-sex unions: partnership, parenthood, and cardiovascular risk among young adults

We use the National Longitudinal Survey of Adolescent to Adult Health to examine union and parenthood differences across same and opposite-sex couples in systolic and diastolic blood pressure (SBP and DBP), C-reactive protein (CRP), and abdominal adiposity (waist circumference) among partnered (dating, cohabiting, married) young adults ages 25–33. Relative to women dating men, women cohabiting with women reported lower DBP and were less likely to have high CRP. Mothers reported lower SBP and DBP than non-mothers, but were more likely to have high waist circumference if they lived with a biological or step-child. Among men, nonresidential fathers reported higher DBP than nonfathers, and married men were more likely to have high waist circumference than men dating an opposite-sex partner. Same-sex cohabitation was neither a risk factor nor a health resource for men. Although the sample sizes for same-sex couples are quite small compared with those for opposite-sex couples, this study provides initial insight that occupying a sexual minority status while partnered is associated with some health benefits and few or no health risks relative to those who are dating an opposite sex partner.