While children in nonparental care had higher BMIs at different intervals than children in parental care, when controlling for confounding variables, this difference was not significant.
Evidence Rating Level: 2
Study Rundown: Several observational studies have been published to demonstrate that children who receive nonparental childcare are at increased risk of obesity. The reasons for this are not entirely understood, but it is hypothesized that the association could be due to confounding variables or selection bias and not necessarily due to the effect of nonparental childcare itself. To address this gap in the literature, authors of this study sought to identify any significant relationship between nonparental childcare attendance and obesity in children while attempting to minimize the inherent bias of observational studies. Results showed that 48.7% of children studied were in nonparental childcare at 24 months of age. Amongst these children, 35.1% of them were considered overweight/obese with higher BMIs than controls upon entering kindergarten. Confounding variables were controlled for and analyzed using the individual fixed effect and instrumental variable (IV) analysis (defined below). Both of these measures revealed no significant effect of childcare on BMI. One limitation of this study is the fact that children were only followed until kindergarten entry; any impacts after this age was not be captured by this data. Another limitation is the possibility that the IV technique could be biased when there are sample size limitations. This study may alleviate concerns of parents regarding placement of their children in nonparental childcare. Results of future studies could help identify ways in which the limited resources available on obesity prevention can be allocated.
In-Depth [retrospective cohort]: Data was collected from the Early Childhood Longitudinal Study Birth (ECLS-B), which included 10,700 racially and socioeconomically diverse US children born in 2001 and followed for 6 years. Parents were surveyed about the different types childcare utilized. Previous studies had identified child’s age, gender, race/ethnicity, maternal age and weight, family socioeconomic status, household structure, and neighborhood level as confounders because they were all associated with the type of childcare attended and BMI levels. In order to control for these confounding variables, 2 quasi-experimental approaches were used in analysis: the individual fixed effect and the IV analysis. The individual fixed effect model controlled for all observed and unobserved time-invariant confounders, while IV analysis was used to see if semirandom childcare attendance caused by a third confounder variable might lead to an increase in BMI. At the age of 2 years, 48.7% of children were in nonparental childcare and 35.1% of children were obese/overweight at kindergarten entry. Furthermore, the average BMI z score at each wave of collection was significantly higher for children in nonparental care vs. children in parental care (p<0.05). However, when using the fixed effect and IV analysis to account for confounding variables, no effect on BMI z score was observed (fixed effect: p=0.62; IV: p=0.14).
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