In this study, we found that more hours in child care during the first 6 months of life was associated with an increased WFL z score at 1 year of age and increased BMI z score at 3 years of age. The association was limited to child care attendance in someone else’s home. Neither center-based child care nor care in the child’s own home by a nonparent was related to the adiposity outcomes.
The finding that care in someone else’s home was the only type of child care associated with our main outcomes raises the possibility that this setting may be a particularly obesigenic environment. In our questionnaires, we did not separate licensed family child care homes from other types of child care in someone else’s home, but it is possible that either setting could contribute to greater gain in adiposity. Family child care homes tend to be less regulated by the state than child care centers, especially regarding nutrition and physical activity, practices that may affect obesity.26,27
Consequently, family child care homes may provide less structure, which may not be an ideal setting for an infant. Family child care homes may have 1 or 2 infants and additional older children in care, which may mean less individual time for the infants, with longer exposure to restricted movement (eg, bouncy seat) and increased opportunities for inappropriate feeding practices (eg, early introduction of solid foods). We speculate that child care providers who care for a group of children of different ages, as in a family child care home, may also be more likely to advance infants beyond their developmental readiness to help match feeding of older children. Similarly, care by a family member, friend, or neighbor in that person’s home may allow for improper feeding of infants, and among them relatives in particular seem to be less likely to follow infant-feeding guidelines.21
This may be related to generational differences in feeding practices. In addition, without the support of other child care professionals, individuals caring for children in a home-based setting may be more isolated from other adults and consequently less likely to provide healthy nutrition and physical activity environments for children.
Our results are consistent with findings from a similar study of child care during infancy. Kim and Peterson21
found that infant care by a relative, in either the relative’s home or the child’s own home, compared with parental care, was associated with introduction of solid foods before 4 months of age and increased infant weight gain at 9 months of age.21
Our results extend those of Kim and Peterson21
by examining adiposity outcomes at older ages.
An alternative explanation for our findings is that families with some unmeasured attribute, itself related to adiposity, may be more likely to choose child care in someone else’s home for their infants. Additional adjustment for other potential confounding factors did not materially change our estimates, although we were limited to variables collected in the study.
In contrast to care in someone else’s home, child care centers serve a larger number of children and therefore may have multiple infants in care. Centers typically have a classroom devoted to infant care. This type of setting may allow child care providers to be more responsive to the individual needs of infants and therefore may be less likely to promote obesity. The child care center may also allow for increased movement and physical exploration by infants in a safe and protected environment. Our findings indicate that in addition to center-based care, care in the child’s own home by someone other than a parent was not related to development of adiposity. We speculate that a nanny or regular infant sitter in the child’s own home may be more likely to adhere to parental preferences for feeding and physical activity. Alternatively, having a nanny or regular baby-sitter may be a marker for families with more resources, which was not captured in the household income covariate used in our analyses.
If early child care is associated with later obesity, 1 question is what are the pathways by which this effect could occur? In this study, we found that potential mediators of breastfeeding, sleep, and television viewing slightly attenuated our estimates. For the 1-year adiposity outcome, breast-feeding duration seemed to drive the attenuation. When mothers return to work and their children enter child care, they often decrease breast-feeding frequency or discontinue it altogether.28
Consistent with this inference is the results of Kim and Peterson,21
who found that child care attendance that was initiated before 3 months of age and care by a relative at any age in infancy were associated with shorter breastfeeding duration. Longer duration of breastfeeding may protect against development of later obesity.29,30
Increased television viewing31–43
and shorter sleep duration44–46
are also linked to obesity in children. It is possible that certain child care settings differ from the family home in ways that allow for additional television viewing and shorter sleep durations. Little is known, however, about television use or children’s sleep patterns, duration of sleep, and quality of sleep in child care.
Our study has several limitations. First, the relatively high family income and education level of study participants may limit generalizability. In our sample, infants from birth to 6 months of age spent an average of 12.4 hours per week in care, which is lower than other infants from birth to 12 months of age in the United States who spent ~22 hours per week in care.47
This may be because of the sociodemographic characteristics of our sample. However, the greater number of hours may be explained, in part, by the older ages of the infants, because time in care increases with age.47
Second, “child care center” included Head Start Program48
centers as well as other centers. Head Start centers are required to meet specific federal nutrition and physical activity standards that are more stringent than state regulations for licensed child care centers. However, few Project Viva families were eligible to participate in the Head Start program, and consequently, it is unlikely that this issue affected our findings. Third, this study was based on observational data and was not a randomized, controlled trial. Finally, we were not able to consider all types of child care, including no child care, in the same model, because of collinearity of the exposure variables. In our analyses, we chose to examine the amount of time in each type of care separately, unadjusted for the other types of care.