Although such effects with regard to child care type have been rather mixed, there is some reason to suspect that heightened exposure to peers—such as often found in center-based child care—may be a salient stressor for young children . For instance, at abehavioral level, the replicated link between greater exposure to center-based child care and subsequently heightened levels of aggression in childhood has been shown to be at least partially explained by the typically higher levels of peer exposure faced by these children . That said, the potential effects of peer exposure on HPA axis functioning in infancy and toddlerhood are largely unknown. Indeed, some work has suggested that heightened peer exposure may be associated with lower levels of HPA activity. For instance, in their generative study of infants and toddlers, Watamura and colleagues found that toddlers who spent more time playing with their peers tended to show lower cortisol levels than their less social classmates. Of course, the direction of this relation remains unclear; for example, perhaps less physiologically stressed children choose to play more with peers . However, it nonetheless raises the possibility that peer exposure may provide valuable opportunities for young children to learn to negotiate such complex social contexts.With rare exception, the extant literature concerning child care and children’s early adrenocortical functioning has been based on rather small, homogeneous samples of children from middle- to upper income families. Informed by findings from studies of children’s behavioral outcomes, plastic grow bag there is increasing evidence to suggest that child care effects for children growing up in poverty may be quite different those for children from more affluent home families .
Accumulating findings indicate that the beneficial effects of high-quality child care may be comparatively more pronounced for children from high-risk contexts. For instance, some work has shown that greater exposure to high-quality child care , or even simply attending regular non-maternal care , may mitigate the detrimental effects of economic adversity or low levels of maternal education on children’s subsequent academic achievement. Similar buffering effects have been noted with respect to children’s language development, such that exposure to high-quality language environments in child care may mitigate the negative effects of low-quality language environments experienced at home . Related findings also extend to children’s social development. For example, contrary to the replicated finding that more extensive hours in child care are predictive of heightened levels of aggression , increasing evidence suggests that the opposite may be true for children from high-risk home environments. Greater hours in high-quality child care have been linked with lower levels of internalizing and externalizing behavior in samples of low-income children . Similarly, using data from a large Canadian sample, Côté and colleagues found that the prototypically positive relation between non-maternal care and aggression in childhood was evident only for children from middle- to upper class families. Indeed, although it failed to reach statistical significance, there was a descriptive indication that non-maternal care was associated with better socialoutcomes for low-income children. We and our colleagues have recently shown similar findings with respect to child care exposure and several outcomes in pre-kindergarten .
Specifically, we found that for children experiencing high levels of household chaos across early childhood, greater weekly hours in child care were predictive of comparatively fewer behavior problems. In particular, consistent with the idea of a buffering effect, greater child care exposure ameliorated the detrimental relation between household chaos and children’s social problems. We have also recently shown similar interactive relations with respect to children’s HPA axis functioning at 48 months of age ; specifically, using the same sample as in the present study, we found that the direction of the relation between child care exposure and children’s cortisol levels at 48 months varied as a function children’s broader environmental risk. For children from low-risk households, greater weekly hours of child care were predictive of higher cortisol levels. In contrast, for children facing substantial cumulative risks at home, greater hours of child care exposure were predictive of lower cortisol levels. Of note, and contrary to our hypotheses, is that other aspects of children’s experiences, such as caregiver responsivity and child care type, were unrelated to children’s cortisol level, irrespective of children’s home contexts. As such, the potential mechanisms underlying these relations remain unclear. Furthermore, this work was concerned with HPA axis functioning just prior to children’s transition to school in relation to their average child care experiences across early childhood. Although this represents an important development span, we know little about the extent to which similar conditional relations are evident much earlier in development. Also, unlike the elegant within-person designs adopted by prior work that has considered links between child care and children’s diurnal rhythms on child care versus non–child care days, our findings comprised only between-child analyses. Within person designs afford important methodological advantages.
Most notably, they strengthen the internal validity of one’s inferences by essentially treating each individual as his or her own control group. In so doing, this holds all possible time-invariant confounds constant.Informed by our prior work, we hypothesized that increases in child care exposure would be associated with contemporaneous increases in children’s cortisol levels for those facing low levels of environmental risk. In contrast, we hypothesized that this within-child relation of child care exposure and cortisol levels would be comparatively more negative for those experiencing higher levels of risk—possibly to the extent to which the conditional relation reverses direction, such that increases in child care are predictive of contemporaneous decreases in children’s cortisol levels. Given that our prior work showed evidence of a similar interaction effect at approximately 48 months of age , we expected this conditional relation to extend downwardly to children in toddlerhood. However, consistent with cross-sectional findings by others , we allowed for the possibility that the relation might be comparatively weaker in early infancy. In our prior work we have found little evidence of effects of child care type or caregiver responsivity with respect to 48-month cortisol. Yet, informed by prior studies by others , we nonetheless conjectured that the high-quality and center-based care might play a particularly important role in children’s cortisol levels for those from high-risk home environments. Finally, informed by that idea that peer relations may support optimal behavioral and physiological regulation for children in child care , we hypothesized that within-child increases in positive peer exposure would be associated with cotemporaneous decreases in children’s cortisol levels—perhaps, particularly so for children experiencing heightened levels environmental risk. Our hypotheses with respect to between-child differences in children’s child care experiences were substantively identical to the within-person representations above.The Family Life Project was designed to study young children and their families in two of the four major geographical areas of the United States with high poverty rates —eastern North Carolina and central Pennsylvania; specifically, 1,292 children whose families resided in one of the six counties at the time of the child’s birth were sampled. Lowincome families in both states and African American families in NC were oversampled. A comprehensive description of the sampling plan was provided by Vernon-Feagans and colleagues . The present analytic sample comprises the 1,155 children with child care data for at least one of the three points at which child care information was collected between the time children were 7 and 24 months of age. Those excluded from the analytic sample did not differ from the present sample with respect to race or family income or primary caregiver education level at 7 months.In the present study we focused on data collected across infancy and toddlerhood. Children’s mothers were interviewed regarding demographic and personal information when their children were approximately 2 months of age. The demographic data used to calculate economic adversity, pe grow bag as well as information about child care usage, were collected from mothers during interviews when their children were 7, 15, and 24 months of age. At the ages of 7, 15, and 24 months, saliva samples were collected from children during home visits to assess resting or “non- stimulated” cortisol levels. Saliva samples were collected after the data collectors had been in the home for at least 1 hour interviewing the primary caregiver and prior to conducting a number of assessments with children.
The modal time of collection was approximately 10:00 a.m. at each wave of collection; however, there was some variability. Within-child differences in saliva sampling times across the three home observation points, as well as between-child differences in the saliva sampling times were adjusted statistically in all models. We use the term resting given that no active, purposeful stimulation was present, and children were given ample time to return to baseline after the arrival of the research assistants . We cannot rule out, however, that our “resting” cortisol levels partly capture HPA axis stimulation due to the visit. Unstimulated whole saliva was collected using either cotton or hydrocellulose absorbent material and expressing the sample into 2-ml cryogenic storage vials using a needleless syringe or by centrifugation . Prior studies have indicated no differences in cortisol concentrations associated with the two collection techniques . Children’s saliva samples were immediately frozen at −20° C and subsequently stored at −80° C. Intra- and interassay coefficients of variability for cortisol were, on average, less than 10% and 15%, respectively. When children were in non-parental care for at least 10 hours per week, interactions between the child care caregiver and the child were rated for caregiver responsivity by independent raters.Salivary cortisol—All samples from the 7-, 15-, and 24-month assessments were assayed for salivary cortisol using a highly sensitive enzyme immunoassay US FDA 510k cleared for use as an in vitro diagnostic measure of adrenal function . The samples were assayed in duplicate, with the average of the duplicates was used in all analyses. We examined child temperature and use of medications as influences on child cortisol); no relations were evident, after adjusting for the time of day when the saliva sample was collected. Saliva collection times were included as both time varying and time-invariant control covariates. Child care quantity—Children’s primary caregivers provided the average hours per week that the child attended non-parental child care when the child was 7, 15, and 24 months old. non-parental caregiver responsivity—Traditional measures of child care quality, such as the Early Childhood Environment Rating Scale or the Observational Record of the Caregiving Environment were unavailable in these data. We thus used independent ratings of the non-maternal caregivers’ behavior toward the child, as scored with Home Observation Measure of the Environment scale , as a proxy for process quality in child care. Indeed, although the HOME Responsivity scale is not a measure of child care quality, per se—like the process quality measure used in the NICHD Study of Early Child Care and Youth Development —it taps the sensitivity and responsivity of the non-parental caregiver to the child’s needs in ways that are comparable across different types of child care. HOME scale observations were made when the child was 7, 15, and 24 months old. Informed by prior psychometric work , we fitted a series of confirmatory factor analytic models, based on 10 items tapping caregiver responsiveness and affection toward the child. We hypothesized that a single latent factor explained observed caregiver responsivity across the items within a given time point. Because items were scored dichotomously these models were fitted using a robust weighted least-squares estimator . Descriptions of the CFA models are provided in the online supporting materials on the Family Relations website. In short, the results discussed below are based on factor scores estimated from a longitudinal CFA, constrained for partial measurement invariance. Higher values reflect higher levels of caregiver responsivity. Child care type—Child care type was reported by independent observers during child care visits conducted when the target child was 7, 15, and 24 months of age . Child care peer exposure—The numbers of peers in the classroom were based on counts conducted by independent observers during child care visits at 7, 15, and 24 months of age. Cumulative risk—Informed by extensive prior work with these data , we created a cumulative-risk composite comprising seven variables— family income, maternal education, constant spouse/partner living in the home, hours of employment, occupational prestige, household density, and neighborhood noise and safety—that were measured across infancy and toddlerhood. As described in detail in the online supporting materials, we created a continuous cumulative-risk index by reverse scoring the positively framed variables, standardizing each risk measure, and averaging across the risks.