Ashlesha Datar

We examined the relationship between parent-perceived neighborhood safety and children's physical activity, sedentary behavior, body mass, and obesity status using 9 years of longitudinal data (1999–2007) on a cohort of approximately 19,000 US kindergartners from the Early Childhood Longitudinal Study. Children's height and weight measurements and parent perceptions of neighborhood safety were available in kindergarten and in the first, third, fifth, and eighth grades. Dependent variables included age- and gender-specific body mass index percentile, obesity status, and parent- or child-reported weekly physical activity and television-watching. Pooled cross-sectional and within-child longitudinal regression models that controlled for child, family, and school characteristics were fitted. Both cross-sectional and longitudinal models indicated that children whose parents perceived their neighborhoods as unsafe watched more television and participated in less physical activity, although the magnitude of this association was much weaker in longitudinal models. However, there was no significant association between parent-perceived neighborhood safety and children's body mass index.

Despite limited empirical evidence, there is growing concern that junk food availability in schools has contributed to the childhood obesity epidemic. In this paper, we estimate the effects of junk food availability on body mass index (BMI), obesity, and related outcomes among a national sample of fifth graders. Unlike previous studies, we address the endogeneity of the school food environment by controlling for children'sBMIat school entry and estimating instrumental variables regressions that leverage variation in the school's grade span. Our main finding is that junk food availability does not significantly increaseBMIor obesity among this fifth‐grade cohort despite the increased likelihood of in‐school junk food purchases. The results are robust to alternate measures of junk food availability including school administrator reports of sales during school hours, school administrator reports of competitive food outlets, and children's reports of junk food availability. Moreover, the absence of any effects on overall food consumption and physical activity further support the null findings forBMIand obesity.

OBJECTIVE: To analyze changes in BMI, according to gender and race/ethnicity, in a nationally representative cohort of children in the United States during their elementary and middle school years to identify critical periods of excess BMI gains. METHODS: The Early Childhood Longitudinal Study-Kindergarten Class monitored a nationally representative cohort of kindergarten students over 9 years (1998–2007). Height and weight measurements were available for 4240 white, 640 black, and 1070 Hispanic children in kindergarten and 1st, 3rd, 5th, and 8th grades. In each wave, we estimated the proportions of children with BMI values in each quartile of the Centers for Disease Control and Prevention reference-population distribution according to gender and race/ethnicity. We conducted nonparametric tests of differences in BMI distributions over time within racial/ethnic groups and across racial/ethnic groups in each wave. Piecewise linear growth models were estimated to test for specific time periods during which the largest gains in BMI percentiles occurred. RESULTS: Overall, nearly 40% of children started kindergarten with a BMI in the top quartile of the growth charts (BMI > 75th percentile). This proportion increased significantly during the elementary school years, and the largest gains were between 1st and 3rd grades (5.8 percentage points), but there was no further increase during middle school. Increases in BMI percentiles over time were most notable among Hispanic children and black girls. CONCLUSIONS: The early school years might be a critical time for excess BMI gains, even among children with normal BMI values at kindergarten entry.

This article tests whether parents reinforce or compensate for child endowments. We estimate how the difference in birth weight across siblings impacts specific parental investments: breast-feeding, well-baby visits, immunizations, and preschool attendance. Our results indicate that normal-birth-weight children are 5%–11% more likely to receive early childhood parental investments than their low-birth-weight siblings. Moreover, the presence of additional low-birth-weight siblings in the household increases the likelihood of investments such as well-baby visits and immunizations for normal-birth-weight children. These results suggest that parental investments in early childhood tend to reinforce endowment differences.

Objective To determine the effect of very low birth weight (VLBW; Methods We use data on dizygotic (DZ) and monozygotic (MZ) twins and singleton births from the first two waves of the Early Childhood Longitudinal Study—Birth Cohort (ECLS-B), a nationally representative dataset of children born in the US in 2001. We estimate the effects of VLBW and MLBW on children’s mental and motor development scores, weight-for-age, weight-for-length, weight-for-height, and length-for-age z-scores at 9 months and 2 years. We examine whether differences in outcomes within twin pairs are related to differences in their birth weights. The within-twins analysis is conducted on samples of DZ and MZ twins. For comparison, we also estimate birth weight effects on child outcomes from multivariate linear regression models using the full singleton and twins’ sample. We also estimate the effect of being small-for-gestational age (SGA; birth weight Results Evaluation of all births showed that VLBW and MLBW have large negative effects on mental development, motor development, and growth at 9 months and 2 years of age. However, results from within-twin models with DZ twins that control for shared maternal and environmental factors showed much less effect of birth weight on mental or motor development, but continued large effects on growth for the VLBW group. Within-twin models with MZ twins that control for shared maternal, environmental, and genetic factors showed statistically insignificant effects of birth weight on mental and motor development, but continued effects on growth. Similar patterns were found when examining the effects of SGA. Conclusions After controlling for the influence of maternal, environmental, and genetic factors, low birth weight has at most a small negative effect on children’s mental and motor development in their first 2 years of life. However, low birth weight is a major risk factor for children’s physical growth in the early years and there is no evidence of catch-up by age 2.

Estimates the causal effect of competitive food availability on children's body mass index and other food- and school-related outcomes using an instrumental variables approach on a national sample of children.

The theoretical and empirical literature on parental investment focuses on whether child-specific parental investments reinforce or compensate for a child's initial endowments. However, many parental investments, such as neighborhood quality and family size and structure, are shared wholly or in part among all children in a household. The empirical results of this paper imply that such household parental investments compensate for low endowments, as proxied by low birth weight.

OBJECTIVES. The objectives of this study were to examine the impact of postpartum hospital-stay legislation on newborns’ length of stay, neonatal readmissions, and 1-year mortality in California, and whether this legislation had differential impacts by demographics and complications during delivery or pregnancy.METHODOLOGY. This study used linked birth certificates, death certificates and hospital discharge records for all full-term, normal birth weight, and singleton-birth newborns during 1991–2000 in California (n = 662 753). Interrupted time-series analyses were used to examine changes in newborns’ length of stay and outcomes after 1 year, 2 years, and 3 years since the passage of postpartum laws. Multivariate linear and logistic regressions were estimated separately by maternal characteristics (race, education, age, and partity), delivery type, and complications during pregnancy or delivery.RESULTS. Length of stay increased by 9.5, 12, and 14 hours in years 1, 2, and 3, respectively, after the passage of the law. Increases were larger for newborns of white mothers, more educated mothers, mothers >35 years of age, primaparous mothers, cesarean deliveries, and Medicaid recipients, but there were no differences by pregnancy or delivery complications. The odds of neonatal readmission declined by 9.3%, 11.8%, and 19.7% in years 1, 2 and 3 after the law, respectively. The odds of infection-related readmissions declined by 21.5% and 30.3% in years 2 and 3, respectively. The odds of jaundice-related readmissions increased by 7% in year 1. There was no significant change in either the odds of readmission due to respiratory problems or the odds of 1-year mortality in the postlaw years. Demographic differences in the impact of the law on readmissions and mortality could not be detected because of lack of statistical power.CONCLUSIONS. Postpartum length of stay legislation was associated with increased length of stay among all births in California, with significant variation in the law’s impact across demographic groups. After the law’s passage, there was a significant decline in neonatal readmissions but not in 1-year mortality.