Influence of childcare attendance on the development of two-year-olds in a Brazilian birth cohort study

Background: The first years of life are the most important for human development, which is influenced by diverse factors, such as childcare attendance. Yet, little is known about the longitudinal influence of childcare in diverse domains of development. The aim of the present study was to assess the development and to measure potential influences of childcare attendance in two-year-olds from the 2015 Pelotas (Brazil) Birth Cohort Study. Methods: The present study used longitudinal data from the 2015 Pelotas Birth Cohort. Childhood development at two-year-olds was assessed throughout INTER-NDA (INTERGROWTH-21st Neurodevelopment Assessment). Childcare attendance was measured at ages 1 and 2 years old and categorized as: a) never went to childcare; b) attended some childcare (either at 12 or 24 months); c) always attended childcare (both 12 and 24 months). Demographic, socioeconomic, health, and child stimulation variables were considered as confounders. Crude and adjusted analysis of childcare attendance and early childhood development were performed using linear regression. Results: Among the 3,870 infants included in the analyses, around 2/3 never went to childcare. In the crude analyses, any exposure to childcare was positively associated with development, except for in the motor domain. It was also perceived a trend positive association and higher mean values for the always category. In the adjusted analyses only children who always went to childcare had higher development scores in the total (β: 0.17, 95% CI: 0.06; 0.28), cognitive (β: 0.10, 95% CI:-0.003; 0.21) and language (β:0.10, 95% CI:-0.003; 0.21) domains, even after adjustment for stimulation variables. Conclusions: This study suggests that childcare may help improve early childhood development. The association was particularly strong for the total global development domain, even after adjusting for stimulation, but there was no association with motor development. Considering the low prevalence of children in childcare, and that it may

support child development it is recommended to improve childcare opportunities in early childhood.

Background
The most important period for growth and development are the first years of life, which have a major impact on future health (1). Child development is an interactive and maturational process, with the environment affecting multiple domains of development, including motor, language, cognitive, socio-emotional and self-regulation skills (2).
Recent evidence suggest that, in low and middle income countries, about 80 million children at ages 3 and 4 years, experienced low cognitive and/or socio-emotional development in 2010 (3). A more recent study, including data from over 330,000 children from 63 low and middle-income countries, found that a quarter of the children were suspected to have developmental delay (4). Thus, strategies to promote adequate development such as nurturing care, physical health, adequate early learning opportunities, and security and safety are critical in these countries (5).
A large body of work has considered how childcare environments can influence developmental outcomes. A review showed that most early education and care programs, based on care centers, had positive short-term effects and small positive long-term effects on cognitive development (6). Yet, the literature in low and middle-income countries is scarce, especially considering a longitudinal and/or dose-response of the childcare in the infant development.
Considering the 4th Goal of the Sustainable Development Goals, which include: "by 2030, ensure that all girls and boys have access to quality early childhood development, care and preprimary education so that they are ready for primary education" (7), it is important to understand the role of childcare for early child development (ECD), especially in middle-income countries. The aim of this study was to investigate the association between childcare attendance from birth to 2 years and development at 2 years in a large population based cohort study in Brazil.

Study design and population
We analyzed data from the 2015 Pelotas (Brazil) Birth Cohort Study. Pelotas is a city in southern Brazil, with around 340,000 inhabitants. All hospital-delivered children live born in Pelotas between 1 January and 31 December 2015, whose mother lived in the urban area of the city, were eligible for the study (8). From the 4,333 eligible live births, 4,275 were assessed at birth (response rate 98.7%). All these children and their mothers were invited to follow-up measures at 3, 12 and 24 months. Further information about the 2015 Pelotas Birth Cohort is available elsewhere (8,9).

years follow-up
In the 2 years follow-up, the interviews were conducted at a research clinic, with a followup rate of 95.4%. Mothers answered a questionnaire (updating previous information about the child's and mother's health, household characteristics, diseases, child activities, among other topics). All procedures were done by female interviewers trained and retrained during the data collection phase. Written informed consent was obtained for participation in all phases of the study.  (10). It consists of 53 items that are directly administered, concurrently observed and caregiver reported.
INTER-NDA was designed to be free from cultural biases and is based upon objective reporting of the child's performance on cognition, expressive and receptive language, gross and fine motor skills, behavior, attention and social-emotional reactivity. This instrument presents Interclass coefficient ranges between 0.75 and 0.83 (p < 0.001) and a moderate agreement with the Bayley Scales of Infant Development III (k = 0.72, p < 0.001), a well-established child development assessment, measuring cognition, language skills, motor skills and adaptive behavior from 1 to 42 months. The validation tests were perfomed in Oxford, United Kingdom, with eighty-one children aged 23-28 months old (11).
Assessment of children who did not present any serious physical or neural disability precluding them doing the INTER-NDA assessment was conducted by trained interviewers, not experts in neurodevelopment, when children went to the clinic (excluding the phone interviews), or in the family's home. Age-adjusted scores were calculated for cognition, receptive language, motor domains and global development (mean of the domains combined). The adjustment considers a mean of 0 and a standard deviation of 1.

Childcare attendance
Childcare outside the home was measured using interview data from the 1 and 2-year follow-ups. In the 1 year follow-up, mothers were asked about who took care of their children from birth to 1 year, and children receiving any external childcare in that period were identified. At 2 years, mothers reported whether children were currently attending external childcare. Those who responded "no", were also asked if the child attended any external childcare since 1 year, although they were not currently in childcare.
For our analyses, childcare attendance reported at ages 1 and 2 years was categorized in three mutually exclusive categories as: a) never went to childcare; b) attended some childcare (either at 1 or at 2 years only); c) always (both 1 and 2 years).
In the 2-years follow-up, mothers were asked if they read or told stories to their child (yes/no), if the child visited the house of other people in the past week (yes/no), went to the park or some square in the last week (yes/no), and also if the child participated in the PIM (Primeira Infância Melhor) programme, a government home visitation programme that aims to enhance ECD in vulnerable households with young children.

Statistical analysis
The analyses were conducted using Stata 16.0 in five steps: (a) descriptive analyses of children and their mothers were conducted for the entire cohort and compared with those with valid outcome data; (b) description of the participants, according to childcare attendance; (c) description of the participants according to child development; (d) crude analysis of the relationship between the outcomes and childcare attendance; (e) adjusted analysis of the relationship between the outcomes and childcare attendance.
For the first two stages (a and b), chi-squared tests were used. In steps c, d and e, linear regression models were used. For step e, adjusted analyses were conducted including all covariates at the same time as model I. Model II also included variables related to ECD stimulation. Statistical significance was set at 5%, and 95% confidence intervals are provided.

Results
Of the 4,275 children from the original cohort, 3,870 had developmental data at age 2 years and were included in the analyses. Their mothers were mostly 21-30 years old, had 9-11 years of education and about 10% presented depression symptoms. In addition, about 15% of the children were born pre-term and 10% were low birth weight. Half of the children were stimulated through storytelling by their parents, almost 60% went to park or square, more than 4/5 went to other people houses and about 10% participate in PIM program, in the 2 yearsfollow-up (Table 1).  Table 2 indicates that boys, children with low birth weight, mothers tended to be older, richer, more educated and with no depression symptoms, were the ones who attended more external childcare. In addition, children who were stimulated through storytelling, taken to park or square and did not participate in the PIM attended more in external childcare.  Table 3 shows that boys presented a smaller mean of total, cognitive and language measures. Children of mothers older than 30 presented a lower mean of total development score compared to children of younger mothers. Income and maternal education presented a positive relationship with the outcomes, in which sons of richer and more educated mothers presented higher scores of development except for the motor domain. Mother's depression symptoms presented a negative relationship with cognitive and language domains. Children born pre-term and with low birth weight presented lower means in the four outcomes. Children, whose parents read stories, take them to the park and to other people houses presented higher means in all outcomes, except motor in the ones who went to the park. Participation in PIM was negatively associated with cognitive and language domains. Table 3 Association between early childhood development at 2 years and sample characteristics (N = 3870).  Table 4 presents crude and adjusted analyses of the association between childcare attendance and child development. In the crude analyses, children who attended childcare centers at any point in life presented higher means in all the outcomes, except the motor domain. Besides that, the effect was higher for those who always went to childcare, compared to those who never went. In the adjusted analyses, in the model I only the category of the ones who always went to childcare presented higher means of the outcomes compare to the children who never went, except the motor domain. Also in the crude and adjusted model I, the total, cognitive and language domains presented a positive trend raise in the outcomes. The model II, which included stimulation, presented the same pattern of association than the model I, even though the association for cognitive and language was borderline. Only the total development presented a trend positive association between childcare and the outcome.

Discussion
The present study showed that the children more exposed to childcare, present better scores of total development, also in the cognitive and language domains. These results remained even after adjustment for several confounders, including parents' stimulation, which is an important influencer of the ECD.
Total development was associated with all independent variables, except for maternal age, maternal depression and child participation in PIM. The present study also shows that children of older mothers are more likely to be in center-based care, in agreement with another study (14). This may explain the association with mothers' age and total development. Although mother depression symptoms was not associated with total development, cognitive and language domains were negatively associated with this condition. Some studies show that children of depressed mothers show poorer socioemotional and cognitive outcomes (15,16), with maternal depression leading to compromised interaction patterns and reduced child stimulation. Besides, the negative association found between PIM participation and child development outcomes in this study may be due to the program focusing on vulnerable families with children at elevated risk for developmental delay (17).
In the crude analysis, any influence of childcare was positively associated with total, cognitive and language, but the motor domain. Similar results, indicating that children who went to centre-based childcare present better development are encounter in the literature (6,14). After adjustment, only the children who always went to childcare had higher means in the development measures, except in the motor domain. Considering the time of exposure to the child in the center-based care, one study has shown that the early care was associated with better cognitive outcome than informal care at ages 3, and 5 years (14). However, a systematic review about early childhood care and cognitive development has shown that the relation between early beginning and longer duration with the cognitive development it still inconsistent (6).
This association pattern remained after adjustment for child stimulation, which is one of the most important "interventions" related to the development. Several studies show that the stimulation, here presented as parents' storytelling, going to park/square and other people houses, and PIM participation, is a positive influence in the child development (3,18). This indicates that the childcare exposure may be a great opportunity of stimulating development, even if the child is not stimulated at home, but if they both co-occur, the improvement appears to be better.
Childcare attendance was not associated with motor domain. This findng migh be related to the type of intervention provided in childcare centers. Previous studies have shown a positive relation between childcare and motor development, but it is not conclusive (19).
It appears that only childcare center, with interventions focused on movement activities, can import motor development (20).
In Brazil, one of the aims of the National Plan of Education (NPE) is expanding the provision of early childhood education centers to achieve at least 50% of children up to three years (21). In the present study, about 2/3 of boys and girls never went to childcare.
This proportion is low, considering the aim of the government, but is higher than the prevalence of childcare attendance in the country (23.2%) and in the city of Pelotas (22.0%) (22). Despite the benefit of childcare centers for children's development, each child has his own individuality and particularity, which could not be fully understood since the activities in the center are organized for groups. Besides that, even though there are appropriate formation and preparation, the childcare caregivers do not have the same intimate relationship with the children as do parents or relatives and this can affect the capacity to interpret children signs and needs (23).
Some limitations of the study were the smaller sample size than the whole cohort sample, but in general, they did not differ. In addition, the information regarding to type of childcare and amount of time the children spent in them were not used.

Conclusions
Childcare attendance is a good strategy for improving ECD, even after adjustment for diverse characteristics, including parent's stimulation at home, and must be encouraged in this age. Only motor development not shown any association with childcare attendance.
Considering that more than half of the samples never attend to childcare, it is important to advise parents about its relevance. In this sense, to improve this numbers, some intervention by the local governance, like the rise in public childcare facilities numbers and/or vacancies are suggested.

Consent for publication
Not applicable.
The dataset supporting of this article are available upon request to the corresponding author.

Competing interests
The authors declare that they have no competing interests.

Funding
The study used data from the 2015 Pelotas Birth Cohort study and was carried out by the