Objective To investigate whether the total amount of time in childcare through the first 3 years of life was associated with children's receptive vocabulary, externalising and internalising problem behaviours at age 4–5 years, and whether this association varied for different types of childcare.
Methods We used data from the prospective, population-based Longitudinal Study of Australian Children (n=3208–4066, depending on outcome). Parental reports of the time spent in different types of childcare were collected at face-to-face interviews at age 0–1years and at age 2–3 years. Children's receptive vocabulary was directly assessed in the child's home, and externalising and internalising behaviours were measured by questionnaire, completed by parents and teachers at age 4–5 years.
Results At 3 years of age, 75% of the sample spent regular time in the care of someone other than the parent. After adjustment, more time in childcare was not associated with children's receptive vocabulary ability but was associated with higher levels of parent-reported (β=0.10 (95% CI 0.00 to 0.21)) and teacher-reported (β=0.31 (0.19 to 0.44)) externalising problem behaviours and lower levels of parent-reported internalising problem behaviours (β=−0.08 (−0.15 to −0.00)). Compared with children who did not attend any type of childcare, children in centre-based care had higher parent-reported and teacher-reported externalising and lower internalising problem behaviours.
Conclusions More time in centre-based childcare (but not other types of care) through the first 3 years of life was associated with higher parent-reported and teacher-reported externalising problem behaviours, and lower parent-reported internalising problem behaviours but not with children's receptive vocabulary ability at school entry.
- child care
- child behaviour
- cognitive development
- early childhood development
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What is already known on this topic?
Many children now spend substantial periods of time in childcare during the first 3 years of their life.
Childcare during children's preschool years may be an important context for children's cognitive and socioemotional development.
Evidence regarding the developmental effects of the type and time spent in childcare for children younger than 3 years is equivocal.
What this study adds?
Time spent in childcare during the first 3 years of life was not associated with children's receptive vocabulary at school entry.
Time spent in childcare had small effects on higher levels of parent-reported and teacher-reported externalising problems and lower parent-reported internalising problems at school entry.
The effects were concentrated among children who experienced predominately centre-based care.
Due primarily to changes in labour market conditions over recent decades in rich and middle-income countries, children are spending increasing amounts of time in childcare during their first 3 years. Childcare is often referred to as the care of a child, by a person other than the child's parent. This can either be formal or informal care. Formal childcare refers to regulated, paid care away from the child's home including childcare centres (referred to henceforth as centre-based care) and family day care (carers paid to deliver care in their home for small groups of children). Informal childcare is non-regulated care in or away from the child's home and includes relative (eg, grandparents) and non-relative care (eg, friends).1 Childcare fulfils many roles including supporting labour force participation and providing an opportunity to foster children's socioemotional and cognitive development before they start school.2 However, there has been long-standing concern that early and long exposure to childcare may be harmful.3 ,4
Different types of childcare environments may be an important context for child development but arguments could be mounted that time spent away from parents may or may not harm children's development depending on the amount of time spent in those environments and the context within which it occurs. Indeed, the evidence is mixed as to whether time spent in childcare adversely affects children's later socioemotional and cognitive development. In terms of socioemotional outcomes, studies conducted in the USA revealed that more hours in childcare, particularly centre-based care was associated with poorer social-behavioural outcomes.5–7 A recent study in the UK also found that more time in centre-based care was associated with more behavioural difficulties.8 However, studies from Norway have shown little evidence that greater time in care is associated with children's externalising problems.9 ,10 There is inconclusive evidence regarding associations between the time spent in different types of childcare and children's cognitive outcomes. Some studies have found benefits of centre-based care on children's cognitive abilities at school entry,11 however this seems not to be the case in the Australian context.12
With an increasing number of children attending childcare and the potential role childcare may have in promoting the development of young children we used data from a contemporary, population-based Longitudinal Study of Australian Children (LSAC) to examine whether the total amount of time spent in all types of childcare through the first 3 years of life was associated with children's receptive vocabulary and externalising and internalising problem behaviours when children were aged 4–5 years. In subsequent analyses, the influence of the main type of childcare from 0 year to 3 years on children's development at 4–5 years was examined. It would have been ideal to measure the quality of childcare but directly observing quality in different types of childcare settings is not practical for most large population-based studies due to cost constraints. Moreover, research from the comprehensive National Institute of Child Health and Human Development study of early childcare suggests that quality, quantity and type of childcare have independent effects on children's development.6 ,13
Subjects and methods
Study design and sample
We examined data from the LSAC, a prospective, population-based study of young children's development. Study design and sample information for LSAC are detailed elsewhere.14 Briefly, LSAC used a two-stage cluster sampling design. The first stage selected Australian postcodes and the second stage sampled children within these postcodes. Postcodes were randomly selected and stratified by state/territory and urban/rural status to ensure a nationally representative sample. The Medicare database, which provides medical and hospital coverage for all Australian permanent residents was then used to randomly select infants born between March 2003 and February 2004 within each stratum. This method identified 8921 infants who were eligible to participate. Of these, 5107 infants were recruited into the study. Our analyses use the first three waves of data when children were 0–1 years, 2–3 years and 4–5 years of age. The study was approved by the Australian Institute of Family Studies Ethics Committee.
Detailed information concerning the time and type of childcare was obtained from face-to-face interviews with the study child's primary caregiver (97% mothers) at 0–1 year and again at 2–3 years. At each time point, the primary caregiver reported whether over the past 1 month the study child had been looked after at regular times during the week by anyone other than the parent living in the home. If the response was ‘yes’ then the regular type of care, the number of hours each week the child attended, and for how many months the child had been attending this care was ascertained for up to three different types of childcare arrangements.
The types of childcare were: (1) centre-based care (2) family day care (3) nanny or relative and (4) other informal childcare such as care by friends. We excluded a small proportion of children (n=218) enrolled in preschool/kindergarten, as in Australia, they are administratively classified as belonging to the education sector unlike childcare services.15 We calculated the time spent in each type of childcare as reported by parents at 0–1 year and 2–3 years as: Total Time (TT)=(total hours per week×4.3 weeks in a month)×(total months in childcare). The cumulative time was calculated as the sum of the time spent at the 0–1 year and 2–3 years time period (TT0–1+TT2–3). If a child did not attend childcare, a value of 0 was given. Children who did not attend any type of childcare across the 0–3 years period were classified into the ‘primary caregiver only’ category and were used as the reference group in all analysis. Our measure of time spent in childcare is similar with research from the US National Institute of Child Health and Human Development study that examined the developmental effects of cumulative time in childcare.7
Children's receptive vocabulary at age 4–5 years was directly assessed in the child's home using the well-validated Peabody Picture Vocabulary Test III—LSAC Australian Short Form.16 Raw scores were scaled according to a Rasch model to enable comparison of scores across waves. Children's externalising and internalising behaviours at age 4–5 years were assessed by the parent and teacher using the Strengths and Difficulties Questionnaire (SDQ).17 The SDQ contains five subscales, measuring prosocial behaviour, hyperactivity, emotional symptoms, conduct problems and peer problems of five items each. The conduct and hyperactivity subscales of the SDQ were summed to reflect externalising behaviours and the emotional and peer subscales were summed to reflect internalising behaviours.18 Childhood externalising behaviour problems are expressed in children's outward behaviour reflecting a child's negative reaction to his or her environment.19 ,20 These externalising problems may include disruptive, hyperactive and aggressive behaviours.19 Internalising behaviour problems primarily affect the child's internal psychological environment rather than the external environment.19 ,20 These internalising problems may include withdrawn, anxious and depressed behaviours.19 The score for externalising and internalising behaviours ranged in between 0 and 20, respectively, with higher scores indicating higher risk of behavioural problems.
Covariates were identified a priori, on the basis of directed acyclic graphs21 and from research evidence to be associated with the type and time in childcare and children's cognitive and socioemotional outcomes. Covariates included; the primary caregiver’s country of birth, education, employment; annual household income; economic hardship over the last year; geographical remoteness using the Accessibility and Remoteness Index of Australia22; family structure; number of siblings; child age, sex and birth weight; parental concern about the child's learning and development; number of children's books in the home; time spent reading to the child; whether the child undertook regular cost activities; the primary caregiver’s age, psychological distress using the Kessler 6 scale,23 and self-reported level of attachment and warmth towards the child.
To address attrition and item non-response in the present study, multiple imputation by chained equations was used to impute missing values.24 Imputed data sets were generated under the missing at random assumption that uses observed variables in the data set to predict missingness and estimate parameters.25 The imputation was conducted for the full sample, however, data were analysed only for children who had observed receptive vocabulary scores (n=4066), and parent-reported (n=3646) and teacher-reported (n=3208) externalising and internalising behaviour scores.26 The imputation model included all outcomes, exposures and covariates. Twenty imputed data sets were generated and the results of the imputed analyses were combined using Rubin's rules.27 Results using the complete-case data were not substantively different from the imputed analysis and would not change the conclusions of this study; therefore, we report the imputed results.
First we used multivariable linear regression to examine the overall association between the cumulative time from age 0 year to 3 years spent in all types of childcare and children's receptive vocabulary and parent-reported and teacher-reported externalising and internalising behaviours at age 4–5 years. To aid interpretability of the regression coefficients we present the results for the effect of increasing the time spent in any type of childcare by 1 day per week over the first 3 years of life. Second, we examined the association between the time spent in the main type of childcare from age 0 year to 3 years and receptive vocabulary and parent-reported and teacher-reported internalising and externalising behaviours at age 4–5 years. All analyses were conducted using Stata V.12.1 (Stata Corp, College Station, Texas, USA).
As shown in figure 1, the sample consisted of 4066 children with receptive vocabulary scores, 3646 and 3208 children with parent-reported and teacher-reported externalising and internalising behaviour scores at age 4–5 years, respectively. As shown in table 1, the majority of children had an Australian born primary caregiver (∼80%) and lived in a two-parent household (∼90%). About two-thirds of the primary caregivers had less than a bachelor's degree (∼64%) with an average weekly household income of $A1178–1210. At 3 years of age, 75% of the total sample spent regular time in the care of someone other than the parent. Approximately, 39% experienced some centre-based care, 21% nanny or relative care, 8% family day care and 6% other types of childcare. The mean number of hours per week spent in childcare at 0–1 years was 17.2 h (SD: 13.6) and 20.4 h (SD: 14.3) at 2–3 years (data not shown). On average, the total number of hours spent in childcare across the 3 years was 1024–1035 h (341.3–345.2 h/year) depending on outcome.
Cumulative exposure to childcare through the first 3 years of life
In unadjusted analyses, for each increase of 1 day per week in childcare, parent-reported and teacher-reported externalising problem behaviours increased by 0.07 (95% CI −0.02 to 0.16) and 0.25 (0.14 to 0.36) points, respectively (table 2). Parent-reported and teacher-reported internalising problem behaviours decreased by −0.07 (−0.14 to 0.00) and −0.07 (−0.15 to 0.01) points, respectively, and children's receptive vocabulary scores increased by 0.41 points (0.24 to 0.57). After adjustment, the association between the total amount of time in childcare and children's receptive vocabulary strongly attenuated (β=0.04 (−0.11 to 0.21)). In contrast, after adjustment, higher levels of parent-reported and teacher-reported externalising problem behaviours and lower parent-reported internalising problem behaviours were still observed, although the effects were small (table 2). Similar results were seen when examining the effects separately for children aged 0–1 year and 2–3 years (see online supplementary appendix A).
Main type of childcare
To determine whether the higher risk of externalising and lower risk of internalising problem behaviours observed with increasing time in childcare by 1 day per week depended on the type of childcare, we examined the association between main type of care and externalising and internalising problem behaviours by the four childcare categories (1) centre-based care (2) family day care (3) nanny or relative and (4) other compared with children who did not attend any type of childcare in the first 3 years of life. Table 3 shows that compared with children who did not attend any type of childcare through the first 3 years of life, children in centre-based care had higher parent-reported (β=0.45 (0.17 to 0.72)) and teacher-reported (β=0.50 (0.17 to 0.83)) externalising problem behaviours and lower parent-reported (β=−0.43 (−0.63 to −0.22)) and teacher-reported (β=−0.36 (−0.63 to −0.08)) internalising problem behaviours at 4–5 years. There was no association between any other types of childcare and children's externalising and internalising behaviours at 4–5 years. The patterns of results were similar when examining effects separately for children aged 0–1 year and 2–3 years (see online supplementary appendix B).
This study showed that more time in childcare through the first 3 years of life was associated with a small increase in parent-reported and teacher-reported externalising problem behaviours, and lower parent-reported internalising problem behaviours but no effect on receptive vocabulary at school entry. These data also suggest that the effect was concentrated among children who experienced predominately centre-based care. To our knowledge, this is the first study to have examined the developmental effects of the time spent in different types of childcare across multiple years using multiple informants from a contemporary, nationally representative birth cohort from a country that has a different social policy context for childcare than the USA, UK or Northern Europe.
Unlike previous research from the UK28 and USA29 this study found no evidence of an association between the amount of time in childcare and children's cognitive abilities. However, results are consistent with findings from an Australian longitudinal study that revealed time in childcare was not associated with children's rate of growth in receptive vocabulary from 4 years to 8 years.30 A possible explanation for the contradictory findings between countries may be that different cognitive domains of child development were used. For example, in our study, the number of words the child understands (receptive vocabulary) was assessed. In contrast, Loeb et al29 examined US children's reading ability, letter and word recognition, vocabulary and comprehension. It may be that time in childcare does not influence children's simple word recognition skills but does influence more complex literacy based skills that require exposure to text and reading activities.
In our study, after adjusting for time spent in the main childcare arrangement, centre-based care was associated with lower levels of parent-reported and teacher-reported internalising problems. One possible explanation for lower levels of internalising problem behaviours may be that interactions with peers before starting school may lead to lower internalising problems. Children in centre-based care have more opportunity for same-age peer interactions than children in other types of care, including parental care, that may help them develop conflict-resolution and cooperativeness skills31 that help in reducing anxiety-based and withdrawn behaviour.
The present study also found that centre-based care was associated with higher externalising problem behaviours at 4–5 years. These results are consistent with prior studies from the USA6 ,7 ,32 ,33 and UK8 but in contrast with Norwegian studies that showed quantity of childcare during the first 4½ years of life had little influence on children's externalising behaviour.9 ,10 One possible explanation for the contradictory results from studies conducted in the USA, UK and Australia compared with Norway may relate to the high level of government investment in childcare,3 family-friendly policies including long-paid parental leave entitlements34 and generally higher quality childcare arrangements in Nordic countries.3 ,10
A limitation of the present study is that we could not capture the quality of childcare for all children. The LSAC used carers’ reports to obtain information about the quality of childcare provided to children participating in the study. Where quality information was obtained it was only for children who spent eight or more hours per week in childcare and our goal in the present study was to characterise the developmental effects of childcare on the whole population experiencing childcare environments. A further limitation is that information concerning the time and type of childcare was obtained from interviews with the child's primary caregiver at two points in time: 0–1 year and 2–3 years. We therefore had to assume that childcare arrangements were consistent over the periods being reported.
In conclusion, there was no evidence that the total amount of time in childcare through the first 3 years of life was associated with children's receptive vocabulary. However, children who spent more time in childcare, particularly centre-based care had higher externalising problems and lower internalising problems around the age of school entry. Although, the effects identified in this study were small, they may have important implications at the population level due to the large proportion of children who spend significant amounts of time in childcare on a regular basis. For example, research has shown that the effects of extensive childcare influence the child and their classroom peers with little or no exposure to such care.35 With more children experiencing childcare in their preschool years and government commitment in supporting healthy, early child development, greater public investment in family (eg, paid parental leave) and childcare policies may help reduce any negative consequences of time spent in childcare.
The authors used data from the Longitudinal Study of Australian Children (LSAC), which was conducted in partnership between the Department of Families, Housing, Community Services and Indigenous Affairs (FaHSCIA), the Australian Institute of Family Studies (AIFS) and the Australian Bureau of Statistics (ABS). The findings reported in this article are those of the authors and should not be attributed to FaHCSIA, the AIFS or the ABS. The authors thank Dr Alyssa Sawyer for her comments and suggestions on earlier versions of this manuscript.
This web only file has been produced by the BMJ Publishing Group from an electronic file supplied by the author(s) and has not been edited for content.
Files in this Data Supplement:
- Data supplement 1 - Online supplement
Contributors AG: corresponding author designed the study, performed the analyses, interpreted the data, drafted the initial manuscript and approved the final manuscript as submitted. MNM: contributed to the design and interpretation of the study, provided statistical advice, reviewed the manuscript and approved the final manuscript as submitted. SRZ: contributed to the design and interpretation of the study, reviewed the manuscript and approved the final manuscript as submitted. MGS: contributed to the design and interpretation of the study, reviewed the manuscript and approved the final manuscript as submitted. JL: contributed to the design and interpretation of the study, reviewed and revised the manuscript and approved the final manuscript as submitted.
Competing interests AG is supported by a Faculty of Health Sciences, University of Adelaide postgraduate award and a Healthy Development Adelaide and Channel 7 Children's Research Foundation supplementary scholarship award. JL is supported by an Australia Fellowship from the National Health and Medical Research Council of Australia (570120). MNM is supported by funds from the Australia Fellowship awarded to JL. The researchers are independent of the funding body.
Ethics approval Australian Institute of Family Studies Ethics Committee.
Provenance and peer review Not commissioned; externally peer reviewed.
Data sharing statement The authors of the present manuscript cannot share data directly with other researchers. The LSAC data is owned by the Australian Government Department of Family and Community Services and governed by the Privacy Act, the Health Insurance Act, the Crimes Act, the Commonwealth Protective Security Manual, the Australian Communications – Electronic Security Instruction and the National Health Act. The data is publicly accessible. For more information regarding data access the LSAC Data Manager should be contacted: http://www.growingupinaustralia.gov.au/data/dataaccess.html.