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. 2024 Nov 28;14:29550. doi: 10.1038/s41598-024-81343-9

Group childcare has a positive impact on child development from the Japan Environment and Children’s Study

Keita Kanamori 1,2,, Tomohisa Suzuki 3, Chiharu Ota 1,3,4; The Japan Environment and Children’s Study Group
PMCID: PMC11605057  PMID: 39609593

Abstract

This study aimed to investigate the impact of early group childcare on child development using data from the Japan Environment and Children’s Study. This prospective cohort study enrolled participants between January 2011 and March 2014. The Ages and Stages Questionnaires (ASQ)-3 was used to obtain data regarding group childcare and other factors. The participants were divided into two groups: the early childcare group (exposed group) and the non-early childcare group (control group). The ASQ-3 scores in all five domains, i.e., communication, gross motor skills, fine motor skills, problem-solving, and personal-social skills, were compared. A total of 39,894 participants were included in this study. The exposed and control groups comprised 13,674 and 26,220 participants, respectively. The number of participants with the ASQ-3 values below the cut-off value did not differ significantly between the two groups in any of the five domains at six months of age. However, the number of participants with the ASQ-3 values below the cut-off values was significantly lower in the exposed group for all five domains at three years of age. The difference between the two groups, especially in terms of communication and personal-social skills, increased with age.

Supplementary Information

The online version contains supplementary material available at 10.1038/s41598-024-81343-9.

Keywords: Communication, Development, Early childcare, Group childcare, Personal-social skills, Toddlers

Subject terms: Health care, Medical research, Neurology, Risk factors

Introduction

A healthy and positive environment nurtures the physical, cognitive, emotional, and social development of infants1. With parents increasingly participating in the labor market and recognizing the beneAfits of education and care beyond the family for very young children, the attendance of children at childcare centers under the age of three is increasing across Organization for Economic Cooperation and Development (OECD) countries2. Previous studies have reported positive effects of attending kindergarten or preschool for child development310. National Institute of Child Health and Human Development Early Child Care Research Network showed that cumulative experience in center-based care was associated with better outcomes to cognitive and language development after adjusting for child care quality6. In addition, group childcare and early educational intervention reduce the rates of motor4,5, cognitive3,57,9,10, psychosocial5,7, and communication impairment4,6,911, as well as aggression8,10. Furthermore, advanced cognitive ability, language skills, and pre-academic outcomes have been associated with higher-quality child care3,6,10. On the other hand, most previous studies on this topic were conducted in North America6,7,1013 and European countries (including The Netherlands3, Germany4,9, Australia5, and the United Kingdom)14, which have a long history of early education and care. Although Nakamichi et al. showed the Japanese data about the relationship between child-centered teaching attitudes in childcare centers and the socio-emotional development of Japanese toddlers15, no large-scale birth cohort study has examined the effects of early group childcare on childhood development in Japan. Consequently, debates in Japan regarding how the early utilization of group childcare impacts development of children persist. The environment surrounding infants varies greatly depending on the country and culture. Moreover, factors such as home environment, family structure, attitude towards childcare, and the willingness of the father to participate in childcare also play a role in the development of the child. The Ministry of the Environment has conducted the Japan Environment and Children’s Study (JECS), a large-scale, nationwide epidemiological study involving about 100,000 mother-child pairs across Japan. The aim of JECS is to identify the impact of environmental factors on the health and development of children. The study was launched in January 2011. During the first three years, about 100,000 expectant mothers were recruited, and their biological samples, such as blood and urine, were collected during pregnancy and at childbirth. Afterward, the children are followed through questionnaire surveys until they reach the age of 1316. Several studies from JECS revealed the association between environmental changes and the child health such as maternal Mediterranean diet and allergy in offspring17 or heavy metal exposure and Kawasaki disease18 and so on. Further Several studies from JECS focused on outcomes related to child development19,20. However, there have been no publications from JECS study and other Japanese large-cohort studies focusing on the group childcare. In the present study, we sought to investigate whether early group childcare facilitates child development from JECS. If a large-scale study in our country, with its distinct cultural context from that of Western countries, demonstrates that early group childcare positively impacts child development, or at least shows no negative effects, this could alleviate concerns and psychological burdens for parents who require early group childcare. Furthermore, such findings could actively encourage parents to participate in work and social activities, benefiting not only the parents but society.

Methods

Participants and the study protocol

This prospective cohort study, which utilized data from the JECS, was based on the jecs-ta-20,190,930 dataset. The JECS protocol21 was reviewed and approved by the Institutional Review Board on Epidemiological Studies of the Ministry of Environment and the Ethics Committees of all participating institutions (Ethical Number: 100910001). All procedures and experiments were commenced after obtaining written informed consent from the participants. All experiments were performed in accordance with relevant guidelines and regulations.

To ensure the generalizability and applicability of the results of JECS to the Japanese population, the Regional Centers were selected to cover wide geographical areas. Pregnant women from the following regions in Japan were enrolled in the JECS between January 2011 and March 2014: Hokkaido, Miyagi, Fukushima, Chiba, Kanagawa, Toyama, Koshin, Aichi, Kyoto, Osaka, Hyogo, Tottori, Kochi, Fukuoka, South-Kyushu, and Okinawa. The regions cover in total 19 prefectures. The study locations exhibit diverse levels of urbanization and land development, ranging from urban and suburban to rural areas, and from agricultural and fishery to commercial and industrial uses. Information regarding the following factors was obtained via a questionnaire survey for caregivers: the Ages and Stages Questionnaires (ASQ)-3 scores (six months and three years old), participation in group childcare (six months, one, two, and three years old), sex, participation in enrichment lessons (three years old), screen time (three years old), time spent with family (three years old), family structure (two and a half years old), educational background of the parents, neurodevelopmental disorders in the mother, family income, and occupation of the mother (one years). Enrichment lessons included swimming, sports (e.g., gymnastics), dance, music, abacus, painting, handicrafts, preschool classes, and cram schools. Participants with incomplete questionnaire items regarding the use of childcare facilities, those already using childcare facilities at six months of age, and those with inconsistent childcare facility usage between the ages of one and three years were excluded. The jecs-ta-20,190,930 dataset comprises 104,062 records. The number of live births was 100,303; however, 60,409 records were excluded after applying the aforementioned exclusion criteria. Thus, the remaining 39,894 mother-child pairs were analyzed in this study (Supplementary Fig S1 online).

Measurements

This survey examined the utilization of group childcare at the ages of six months, one year, two years, and three years. The exposure variable was the utilization of group childcare among 1–3-year-old children. The exposed group comprised children who received group childcare from six months to one year of age until three years of age. Children who did not receive group childcare at any of these time points were included in the control group. The primary outcome measure was the number of patients with the ASQ-3 values less than the cut-off value at three years of age. The ASQ-3 is a tool designed to screen for developmental delay in children aged 1–66 months. The ASQ-3 comprised 30 items divided into five developmental domains: communication, gross motor skills, fine motor skills, problem-solving, and personal-social skills. Mezawa et al. reported the following cut-off values for three years of age in their study: 29.95 for communication, 39.26 for gross motor, 27.91 for fine motor, 30.03 for problem-solving, and 29.89 for personal-social skills22. These cut-off values were used in the present study. In the study by Mezawa et al., data from 439 children in a birth cohort were used to identify the score distribution, establish cut-off scores, and calculate the instrument’s internal consistency. Data were also collected from 491 outpatients to examine the test-retest reliability and concurrent validity. Cronbach’s alpha for each subscale on each questionnaire ranged from 0.45 to 0.89. Test-retest reliability was greater than 0.75 for the subscales on almost all questionnaires. Concurrent validity was also acceptable when compared to the Japanese version of the Denver Developmental Screening Test II22.

Statistical analyses

The participants were divided into two groups: the early childcare group (exposed group) and the non-early childcare group (control group). The number of participants with the ASQ-3 scores below the cut-off value at three years of age was analyzed using Pearson’s chi-square test. Multiple logistic regression analysis was also performed. The outcome of the multiple regression analysis was the number of participants with the ASQ-3 scores below the cut-off value at three years of age. The explanatory variables included the main exposure factor of the use of childcare facilities, as well as other factors previously reported to be associated with development of children, such as enrichment lessons23, group childcare24, cohabitation with parents25, presence or absence of siblings and grandparents living together25,26, educational level of parents27, family income27, and occupation of mother25. Since screen time has already been suggested to be associated with development in other JECS report28, and factors such as the ASQ-3 score at six months of age, sex, and neurodevelopmental disorders in the mother were not environmental factors, they were included as covariates, but their p-values were not calculated. All statistical analyses were conducted using R (version 3.3.0+). A p-value of < 0.05 was considered statistically significant.

Results

A total of 39,894 children, comprising 20,098 boys and 19,796 girls, were included in this study. Table 1 presents the characteristics of the participants. The exposed and control groups comprised 13,674 and 26,220 participants, respectively (Table 1). The number of participants with the ASQ-3 values below the cut-off value in any of the five developmental domains did not differ between the two groups at six months of age: communication (0.7% vs. 0.8%, p = 0.367), gross motor (12.0% vs. 11.6%, p = 0.230), fine motor (6.1% vs. 6.0%, p = 0.768), problem-solving (12.4% vs. 12.2%, p = 0.674), and personal-social skills (4.7% vs. 4.6%, p = 0.440). In terms of child living environments such as parental socioeconomic status or child exposure to media devices, there are significant differences in parents’ education (for mothers, high school graduate or lower: 31.5% vs. 36.4%, p < 0.001, for fathers, high school graduate or lower: 44.3% vs. 40.8%, p < 0.001), family income (< 6 million yen: 66.4% vs. 79.0%, p < 0.001), mothers’ occupation (Full-time job: 59.0% vs. 7.0%, p < 0.001) between exposure and control groups. Interestingly, although control children spend significantly longer time with their family (5.27 ± 1.86 vs. 12.0 ± 3.10, p < 0.001), they are exposed to significantly longer time to the media devices (for game / phone, ≥ one hr/day: 7.9% vs. 13.1%, p < 0.001, for TV/DVD, ≥ one hr/day: 65.7% vs. 86.3%, p < 0.001). Furthermore, less children take enrichment lessons in exposure groups (7.5% vs. 17.8%, p < 0.001).

Table 1.

Characteristics of participants (n = 39,894).

Exposure
(n = 13,674)
Control
(n = 26,220)
P value
Boys (n, %) 7,054 (51.6%) 13,044 (49.7%) 0.001*
Low ASQ-3 at 6 mo (n, %)
 Communication 94 (0.7%) 203 (0.8%) 0.367
 Gross motor 1,643 (12.0%) 3,040 (11.6%) 0.230
 Fine motor 834 (6.1%) 1,576 (6.0%) 0.768
 Problem solving 1,690 (12.4%) 3,200 (12.2%) 0.674
 Personal-social 647 (4.7%) 1194 (4.6%) 0.440
Enrichment lessons (n, %) 1,019 (7.5%) 4,647 (17.8%) < 0.001*
Cohabitation with mother (n, %) 13,372 (99.7%) 25,814 (99.6%) 0.012*
Cohabitation with father (n, %) 12,601 (94.0%) 25,277 (97.5%) < 0.001*
Senior siblings (n, %) 7,765 (57.9%) 14,127 (54.5%) < 0.001*
Junior siblings (n, %) 2,186 (16.3%) 5,421 (20.9%) < 0.001*
Grandparents (n, %) 2,778 (20.7%) 5,412 (20.9%) 0.731
Other cohabitation (n, %) 995 (7.4%) 1,978 (7.6%) 0.472
Mother’s education (n, %) < 0.001*
 Junior high school 389 (2.9%) 1,049 (4.0%)
 High school 3,750 (27.6%) 8,408 (32.4%)
 College of technology 284 (2.1%) 293 (1.1%)
 Vocational school 3,671 (27.1%) 5,299 (20.4%)
 Junior college 2,218 (16.4%) 5,345 (20.6%)
 University 2,970 (21.9%) 5,350 (20.6%)
 Graduate school 283 (2.1%) 223 (0.9%)
Father’s education (n, %) < 0.001*
 Junior high school 903 (6.7%) 1,434 (5.5%)
 High school 5,077 (37.6%) 9,135 (35.3%)
 College of technology 302 (2.2%) 569 (2.2%)
 Vocational school 2,818 (20.9%) 4,500 (17.4%)
 Junior college 317 (2.3%) 512 (2.0%)
 University 3,537 (26.2%) 8,436 (32.6%)
 Graduate school 543 (4.0%) 1,278 (4.9%)
NDD of mother (n, %) 6 (0.0%) 15 (0.1%) 0.748
Family income (n, %) < 0.001*
 < 2 million yen 626 (4.9%) 1,048 (4.3%)
 2 to < 4 million yen 3,781 (29.4%) 9,045 (37.4%)
 4 to < 6 million yen 4,131 (32.1%) 9,018 (37.3%)
 6 to < 8 million yen 2,629 (20.4%) 3,224 (13.3%)
 8 to < 10 million yen 1,104 (8.6%) 1,091 (4.5%)
 10 to < 12 million yen 340 (2.6%) 419 (1.7%)
 12 to < 15 million yen 145 (1.1%) 174 (0.7%)
 15 to < 20 million yen 91 (0.7%) 98 (0.4%)
 ≥ 20 million yen 31 (0.2%) 59 (0.2%)
Occupation of mother (n, %) < 0.001*
 Housework 618 (4.6%) 20,608 (79.8%)
 Unemployed 213 (1.6%) 1,071 (4.1%)
 Student 55 (0.4%) 14 (0.1%)
 Full-time job 8,002 (59.0%) 1,799 (7.0%)
 Part-time job 3,956 (29.2%) 1,306 (5.1%)
 Self-employed/family business 500 (3.7%) 685 (2.7%)
 Side job 19 (0.1%) 218 (0.8%)
 Others 206 (1.5%) 136 (0.5%)
Game / Phone (n, %) < 0.001*
 No screen times 7,303 (53.5%) 12,153 (46.4%)
 < 1 h 5,266 (38.6%) 10,610 (40.5%)
 1 to < 2 h 879 (6.4%) 2,463 (9.4%)
 2 to < 4 h 182 (1.3%) 806 (3.1%)
 ≥ 4 h 22 (0.2%) 146 (0.6%)
TV / DVD (n, %) < 0.001*
 No screen times 265 (1.9%) 277 (1.1%)
 < 1 h 4,415 (32.4%) 3,315 (12.7%)
 1 to < 2 h 6,320 (46.4%) 10,992 (42.1%)
 2 to < 4 h 2,413 (17.7%) 9,286 (35.5%)
 ≥ 4 h 216 (1.6%) 2,261 (8.7%)
Time spent with family (hr / day) 5.27 ± 1.86 12.0 ± 3.10 < 0.001*

Continuous variables: mean ± standard deviation. ASQ, Ages and Stages Questionnaires; NDD, neurodevelopmental disorder.

The number of participants with the ASQ-3 values below the cut-off value was significantly lower in the exposed group for all five domains at three years of age: communication (2.1% vs. 5.7%, p < 0.001), gross motor (3.8% vs. 5.0%, p < 0.001), fine motor (7.0% vs. 8.4%, p < 0.001), problem-solving (5.6% vs. 8.9%, p < 0.001), and personal-social skills (1.7% vs. 5.1%, p < 0.001) (Table 2). This tendency was also observed in the multiple logistic regression analysis in group childcare: communication (β = -0.989, p < 0.001), gross motor (β = -0.452, p < 0.001), fine motor (β = -0.331, p < 0.001), problem-solving (β = -0.519, p < 0.001), and personal-social skills (β = -1.184, p < 0.001) (Table 3). Figure 1(a)–(e) depict the transition in the average the ASQ-3 score. The difference between the two groups increased with age. This difference was particularly evident in terms of communication (Fig. 1a) and personal-social (Fig. 1e) skills. Multiple logistic regression analysis revealed that the number of children with the ASQ-3 scores below the cut-off value in all five domains was significantly lower among children participating in enrichment lessons: communication (β = -0.349, p < 0.001), gross motor (β = -0.206, p = 0.008), fine motor (β = -0.412, p < 0.001), problem-solving (β = -0.297, p < 0.001), and personal-social skills (β = -0.347, p < 0.001). Furthermore, cohabitation with siblings, irrespective of their seniority: communication (β = -0.037, p < 0.50), gross motor (β = -0.450, p < 0.001), fine motor (β = -0.409, p < 0.001), problem-solving (β = -0.176, p < 0.001), and personal-social skills (β = -0.369, p < 0.001) or juniority: communication (β = -0.097, p = 0.16), gross motor (β = -0.391, p < 0.001), fine motor (β = -0.154, p = 0.004), problem-solving (β = -0.214, p < 0.001), and personal-social skills (β = -0.240, p = 0.002), decreased the number of participants with the ASQ-3 values below the ASQ-3 cutoff value in four domains, except for communication.

Table 2.

The number of below the cut-off in ASQ-3 at three years of age, n = 39,894.

Exposure
(n = 13,674)
Control
(n = 26,220)
Odds ratio Log odds ratio P value
Communication (n, %) 288 (2.1%) 1,498 (5.7%) 0.35 − 1.03 < 0.001*
Gross motor (n, %) 516 (3.8%) 1,317 (5.0%) 0.75 − 0.27 < 0.001*
Fine motor (n, %) 957 (7.0%) 2,186 (8.4%) 0.82 − 0.20 < 0.001*
Problem solving (n, %) 750 (5.6%) 2,317 (8.9%) 0.61 − 0.50 < 0.001*
Personal-social (n, %) 232 (1.7%) 1,323 (5.1%) 0.32 − 1.13 < 0.001*

ASQ, Ages and Stages Questionnaires.

Table 3.

Multiple logistic regression analysis.

Communication β Std. error t P value
Group childcare − 0.989 0.103 − 9.588 < 0.001*
Enrichment lessons − 0.349 0.085 − 4.091 < 0.001*
Cohabitation with mother − 0.164 0.380 − 0.431 0.66
Cohabitation with father − 0.263 0.150 − 1.759 0.07
Senior siblings − 0.037 0.056 − 0.662 0.50
Junior siblings − 0.097 0.071 − 1.376 0.16
Grandparents − 0.230 0.083 − 2.768 0.006*
Other cohabitation 0.002 0.128 0.015 0.98
Mother’s education − 0.112 0.018 − 6.158 < 0.001*
Father’s education 0.017 0.016 1.068 0.28
Family income − 0.038 0.025 − 1.482 0.13
Occupation of mother − 0.017 0.020 − 0.856 0.39
Time spent with family − 0.013 0.010 − 1.315 0.18
ASQ-3 at 6 mo − 0.034 0.003 − 12.037
Boys − 1.093 0.060 − 18.343
NDD of mother 1.309 0.751 1.743
Game / Phone 0.119 0.032 3.717
TV / DVD 0.278 0.033 8.516
Gross motor
Group childcare − 0.452 0.094 − 4.799 < 0.001*
Enrichment lessons − 0.206 0.078 − 2.649 0.008*
Cohabitation with mother − 0.221 0.359 − 0.616 0.53
Cohabitation with father − 0.087 0.144 − 0.605 0.54
Senior siblings − 0.450 0.054 − 8.395 < 0.001*
Junior siblings − 0.391 0.073 − 5.344 < 0.001*
Grandparents 0.109 0.074 1.470 0.14
Other cohabitation − 0.161 0.121 − 1.324 0.18
Mother’s education 0.011 0.018 0.615 0.53
Father’s education 0.020 0.015 1.321 0.18
Family income − 0.058 0.024 − 2.407 0.01*
Occupation of mother − 0.021 0.020 − 1.079 0.28
Time spent with family − 0.029 0.010 − 2.902 0.004*
ASQ-3 at 6 mo − 0.043 0.003 − 15.587
Boys − 0.398 0.052 − 7.605
NDD of mother 1.474 0.635 2.321
Game / Phone − 0.065 0.035 − 1.845
TV / DVD 0.040 0.031 1.285
Fine motor
Group childcare − 0.331 0.074 − 4.504 < 0.001*
Enrichment lessons − 0.412 0.068 − 6.044 < 0.001*
Cohabitation with mother − 0.042 0.315 − 0.132 0.89
Cohabitation with father 0.025 0.114 0.217 0.82
Senior siblings − 0.409 0.043 − 9.613 < 0.001*
Junior siblings − 0.154 0.054 − 2.844 0.004*
Grandparents − 0.047 0.061 − 0.782 0.43
Other cohabitation 0.047 0.092 0.512 0.60
Mother’s education − 0.075 0.014 − 5.395 < 0.001*
Father’s education 0.001 0.012 0.052 0.95
Family income − 0.056 0.019 − 2.943 0.003*
Occupation of mother − 0.021 0.016 − 1.351 0.17
Time spent with family − 0.041 0.008 − 5.123 < 0.001*
ASQ-3 at 6 mo − 0.031 0.002 − 13.774
Boys − 1.203 0.046 − 26.080
NDD of mother 0.708 0.756 0.936
Game / Phone 0.053 0.026 2.049
TV / DVD 0.189 0.025 7.560
Problem solving
Group childcare − 0.519 0.075 − 6.893 < 0.001*
Enrichment lessons − 0.297 0.065 − 4.548 < 0.001*
Cohabitation with mother − 0.296 0.293 − 1.010 0.31
Cohabitation with father 0.006 0.120 0.046 0.96
Senior siblings − 0.176 0.043 − 4.102 < 0.001*
Junior siblings − 0.214 0.056 − 3.830 < 0.001*
Grandparents − 0.046 0.061 − 0.759 0.44
Other cohabitation − 0.047 0.096 − 0.495 0.62
Mother’s education − 0.060 0.014 − 4.278 < 0.001*
Father’s education 0.002 0.012 0.165 0.86
Family income − 0.052 0.019 − 2.703 0.007*
Occupation of mother − 0.016 0.015 − 1.053 0.29
Time spent with family − 0.026 0.008 − 3.271 0.001*
ASQ-3 at 6 mo − 0.032 0.002 − 14.440
Boys − 0.796 0.043 − 18.354
NDD of mother 1.040 0.629 1.655
Game / Phone 0.090 0.026 3.508
TV / DVD 0.228 0.025 9.016
Personal-social skills β Std. error t P value
Group childcare − 1.184 0.111 10.679 < 0.001*
Enrichment lessons − 0.347 0.089 3.895 < 0.001*
Cohabitation with mother − 0.494 0.348 − 1.418 0.15
Cohabitation with father − 0.052 0.169 − 0.307 0.75
Senior siblings − 0.369 0.059 − 6.209 < 0.001*
Junior siblings − 0.240 0.076 − 3.164 0.002*
Grandparents 0.014 0.084 0.164 0.87
Other cohabitation − 0.165 0.135 − 1.225 0.22
Mother’s education − 0.084 0.019 − 4.338 < 0.001*
Father’s education 0.021 0.017 1.261 0.20
Family income − 0.034 0.027 − 1.283 0.20
Occupation of mother 0.012 0.020 0.573 0.56
Time spent with family − 0.011 0.010 − 1.067 0.28
ASQ-3 at 6 mo − 0.039 0.003 − 12.771
Boys − 1.320 0.067 − 19.678
NDD of mother 0.879 1.031 0.853
Game / Phone 0.115 0.034 3.390
TV / DVD 0.315 0.035 9.034

ASQ, Ages and Stages Questionnaires; NDD, neurodevelopmental disorder.

Fig. 1.

Fig. 1

Progression of the ASQ-3. This line chart illustrated the progression of mean the ASQ-3 scores as age increases. The continuous solid line corresponded to the ASQ-3 of the exposed group, while the dashed line represented the ASQ-3 of the control group.

Discussion

The present study demonstrated that early group childcare had a positive effect on child development at three years of age. Previous studies have shown that early group childcare has positive effects on child development; however, the items showing positive effects differed among studies: motor4,5, cognitive3,57,9,10, psychosocial5,7, and communication impairment4,6,911. Few reports discuss the negative aspects of early group childcare on child development. However, Caniato et al. reported no significant association between the duration of kindergarten and speech disorders5. Additionally, Stich et al. found that the impact on speech skills was smaller compared to the impact on motor skills, cognition, memory, and concentration9. There were several probable reasons for such discrepancies in results. First, the studies had different sample characteristics, including variations in demographics such as socioeconomic status, geographic location, and age groups. Second, the methods and assessment tools used to measure child development could influence the results. Additionally, the quality of childcare might vary between facilities, which was likely to have a significant impact on child development. Some reports have emphasized the importance of not only utilizing group childcare but also ensuring the provision of high-quality care3,6,10. These factors underscore the complexity of assessing the effects of early group childcare on child development, suggesting that while there are general positive effects, specifics can vary based on numerous variables. To clarify the overall impact, it is crucial to continue accumulating reports from diverse regions, subjects, and study designs. A positive impact was observed in all five developmental domains in the present study. However, this effect was most evident in the domains of communication, including speech skills and personal-social skills. Early group childcare encourages children to learn how to relate to others through interactions with other children and adults other than their family members. Furthermore, physical movements, such as playing with their peers, lead to improvements in motor skills.

Most studies on this topic were conducted in the United States and European countries. Given the impact of regional differences and customs on child development, the present study is novel and socially impactful in that it was conducted in Japan using large-scale data. In Japan, there is a growing societal need for professional childcare for children under the age of three years15. In reviewing cross-cultural similarities and differences in parenting, it is evident that cultural variations exist in many aspects, including physical caregiving, cognitive stimulation, warmth, control and monitoring, and discipline, all of which may influence child development29. For instance, Western parents tend to express warmth through physical affection, such as hugging, kissing, and frequently saying “I love you.” In contrast, Asian parents are more likely to demonstrate warmth by attending to their children’s educational needs and providing instrumental support30. Cultural differences are also observed in the amount of physical contact between parents and their infants. While infants in many Western cultures often sleep alone, not only in separate beds but also in separate rooms, parents and children in Japan are commonly found sharing the same space both during the day and at night31. In a recent national survey, 44.6% of children under the age of three years attended a childcare center32. According to OECD data, significant disparities exist among countries regarding the utilization of daycare for children under the age of three, with Japan ranking 15th out of 33 countries for which data is available2. Although the same report indicates a correlation between childcare or school attendance rates for children aged under the age of three and maternal employment status, in Scandinavian countries such as Denmark and Belgium, high childcare rates are observed despite varying maternal employment rates2. These differences may be attributed to varying motivations for early education, early socialization practices, and cultural backgrounds across countries. Traditionally in Japan, from around the 1960s, there was a widespread belief that mothers should focus on child-rearing until their children reached the age of around three years old33. Although the Ministry of Health, Labour and Welfare announced in 1998 that there is no rational basis for this idea33, and there has been a shift away from this perspective, there is often debate in Japan regarding how the early utilization of group childcare affects development of children. Our current study utilized a large cohort conducted in Japan, allowing us to demonstrate that the utilization of childcare facilities positively influences children’s development by the age of three. We considered that our findings provide crucial evidence to challenge and correct the traditional misconceptions that have persisted in our country.

Early group childcare did not demonstrate a uniformly positive impact on children across all aspects in the present study. Borge et al. reported that aggression was significantly more common in children aged 2–3 years who were receiving care from their own mothers than in those attending group daycare34. However, Belsky et al. and Vandell et al. reported that greater exposure to center care resulted in a higher incidence of teacher-reported externalizing problems at ages 12 and 1513,14. The present study only included children of up to three years of age. Moreover, other factors, such as mother-child attachment formation or physical aggression and behavioral problems in children, were not evaluated.

Multiple logistic regression analysis revealed that engagement in enrichment lessons and cohabitation with siblings decreased the number of participants with the ASQ-3 values below the cut-off value. Kajiume et al. reported that participation in enrichment lessons was associated with later occupational success35. Schlaug et al. reported that music training resulted in long-term enhancement of visual-spatial, verbal, and mathematical performance in children36. Interaction with diverse people plays an important role in the development of social skills in children. Thus, providing children with opportunities to gain various social experiences plays an important role in enhancing their development. Therefore, educational institutions and communities must value diversity and offer opportunities for children to engage in various experiences.

This study has some limitations. First, participants were recruited from the general population, and participation was voluntary, potentially introducing selection bias towards parents with higher health literacy. Second, The ASQ was indeed a developmental screening tool completed by caregivers, rather than a comprehensive assessment tool administered by trained professionals, which may have led to differences in scores between evaluators. Third, in this study, we analyzed data compiled from questionnaires utilized in JECS. Thus, the questionnaire used in our research was not created by the researchers. Therefore, the items in the survey were not perfect, even by the authors. For example, they include neurodevelopmental disorders of the mother, but not the father. Finally, this study targeted pregnant women recruited between 2011 and 2014, and the data used were collected approximately a decade ago. We acknowledge that there may be a discrepancy between the data and current circumstances.

Conclusion

Early group childcare has a positive effect on child development, especially on communication and personal-social skills. Thus, it is important to expose children to various social experiences to enhance their development.

Electronic supplementary material

Below is the link to the electronic supplementary material.

Acknowledgements

The authors thank participants, Research Coordinators, doctors, the staff and medical editor at Tohoku University, and Editage (www.editage.com) for English language editing.

Abbreviations

ASQ

Ages and Stages Questionnaires

JECS

Japan Environment and Children’s Study

OECD

Organization for Economic Cooperation and Development

Author contributions

K.K. conceived and designed the study, collected the data, drafted the initial manuscript, carried out the initial analyses, and reviewed and revised the manuscript. T.S. critically reviewed the data analyses and the manuscript. C.O collected the data and critically reviewed and revised the manuscript. All authors are responsible for reported research and have participated in the concept and design, analysis and interpretation of data, drafting and revising of the manuscript, and approved the final manuscript as submitted and agreed to be accountable for all aspects of the work.

Funding

This study was funded by the Ministry of the Environment, Japan. The findings and conclusions of this article are solely the responsibility of the authors and do not represent the official views of the Japanese Ministry of the Environment. The Ministry of the Environment, Japan had no role in the design and conduct of the study.

Data availability

Data are unsuitable for public deposition due to ethical restrictions and legal framework of Japan. It is prohibited by the Act on the Protection of Personal Information (Act No. 57 of 30 May 2003, amendment on 9 September 2015) to publicly deposit the data containing personal information. Ethical Guidelines for Medical and Health Research Involving Human Subjects enforced by the Japan Ministry of Education, Culture, Sports, Science and Technology and the Ministry of Health, Labour and Welfare also restricts the open sharing of the epidemiologic data. All inquiries about access to data should be sent to: jecs-en@nies.go.jp. The person responsible for handling enquiries sent to this e-mail address is Dr Shoji F. Nakayama, JECS Programme Office, National Institute for Environmental Studies.

Declarations

Competing interests

All the authors have no conflicts of interest to disclose.

Footnotes

A list of authors and their affiliations appears at the end of the paper.

Publisher’s note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Contributor Information

Keita Kanamori, Email: kanamori.keita.q5@dc.tohoku.ac.jp.

The Japan Environment and Children’s Study Group:

Michihiro Kamijima, Shin Yamazaki, Yukihiro Ohya, Reiko Kishi, Nobuo Yaegashi, Koichi Hashimoto, Chisato Mori, Shuichi Ito, Zentaro Yamagata, Hidekuni Inadera, Takeo Nakayama, Tomotaka Sobue, Masayuki Shima, Seiji Kageyama, Narufumi Suganuma, Shoichi Ohga, and Takahiko Katoh

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Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Supplementary Materials

Data Availability Statement

Data are unsuitable for public deposition due to ethical restrictions and legal framework of Japan. It is prohibited by the Act on the Protection of Personal Information (Act No. 57 of 30 May 2003, amendment on 9 September 2015) to publicly deposit the data containing personal information. Ethical Guidelines for Medical and Health Research Involving Human Subjects enforced by the Japan Ministry of Education, Culture, Sports, Science and Technology and the Ministry of Health, Labour and Welfare also restricts the open sharing of the epidemiologic data. All inquiries about access to data should be sent to: jecs-en@nies.go.jp. The person responsible for handling enquiries sent to this e-mail address is Dr Shoji F. Nakayama, JECS Programme Office, National Institute for Environmental Studies.


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