2024 年 29 巻 p. 18
Background: Social relationships are essential in maintaining the physical and mental health of mothers and their children. However, there is limited evidence on how social support provided to the mother during pregnancy could impact child development. Herein, we examined whether maternal social support levels during pregnancy was associated with the risk of developmental delay in 3-year-old children.
Methods: Overall, 68,442 mother-child pairs completed questionnaires on maternal social support during pregnancy and development delay in 3-year-old children. The maternal social support level was evaluated using four items. The risk of development delay was evaluated using the Japanese version of the Ages and Stages Questionnaire-3 (ASQ-3) with five domains of communication, gross motor, fine motor, problem-solving, and personal-social. Odds ratios (OR) and 95% confidence intervals (CI) were calculated using logistic regression according to the quintiles of maternal social support levels after adjusting for potential confounding factors.
Results: Social support during pregnancy was associated with a lower risk of development delay at 3 years of age. Beneficial effects were detected in all domains of the ASQ-3 (p for trend <0.001). Multivariable ORs (95% CIs) for the highest versus lowest quartiles of maternal social support level were 0.57 (0.50–0.65) for communication, 0.49 (0.43–0.55) for gross motor delay, 0.58 (0.53–0.64) for fine motor delay, 0.56 (0.51–0.62) for problem-solving delay, and 0.52 (0.45–0.60) for personal social delay. The associations remained unchanged when stratified by maternal education level, paternal education level, living with children, household income, and postpartum depression.
Conclusion: Maternal social support during pregnancy was inversely associated with the risk of developmental delay at 3 years of age.
Individual’s social and organized connections, such as family, neighborhood networks, and marital relationships may improve the individuals’ health and quality of life [1]. The presence of trusted acquaintances fostered high social support in the community to raise their children among mothers in post-disaster communities [2].
Pregnancy, inherently accompanied by physical and emotional transformation, places a substantial demand on women’s psychological resilience. Social support such as emotional empathy from families and friends, treated neighborhoods could alleviate the challenges of this transition [3] and also positively influence the in-utero environment through glucocorticoid metabolism [4, 5]. Pregnant women with low social support were at an increased risk for mental health problems, such as depression, anxiety, and self-harm [6]. Social support buffered the association between stressful life events and depression during pregnancy among women [7].
Maternal social support during pregnancy was positively associated with child development at 2 to 3.5 years of age according to previous studies in the United States, Europe, and Canada [8–10]. However, the sample size was limited to approximately 700 to 1,600 [8–10] and potential confounding was not adjusted sufficiently [9, 10]. We therefore attempted to investigate the association between maternal social support during pregnancy and the risk of child development delay using the Japan Environment and Children’s Study (JECS) by assessing approximately 68,442 mother-child pairs.
We hypothesized that high levels of maternal social support during pregnancy would positively affect child development at 3 years of age, independent of maternal age, socioeconomic factors, gestational week, birth weight, and maternal postpartum depression.
The present study used data from the JECS. The JECS is a nationwide birth cohort study funded by the Ministry of the Environment, Japan. A total of 104,062 fetuses were registered across 15 Regional Centers (Hokkaido, Miyagi, Fukushima, Chiba, Kanagawa, Koshin, Toyama, Aichi, Kyoto, Osaka, Hyogo, Tottori, Kochi, Fukuoka, and South Kyushu/Okinawa) between January 2011 and March 2014. This study analyzed the jecs-ta-20190930 dataset, released in October 2019 and revised in November 2022. The JECS protocol was reviewed and approved by the Ministry of the Environment’s Institutional Review Board of Epidemiological Studies and the Ethics Committees of all participating institution. Written informed consent was obtained from all participants. The details of the JECS project have been described elsewhere [11, 12].
We used the data from questionnaires administered to mothers. Pregnant women completed self-reported questionnaires during their first, second and third trimesters. The questionnaire included questions regarding the mothers’ social support, socioeconomic status, medical history, and lifestyle factors. Additionally, mothers answered questionnaires regarding their children at 3 years of age.
Out of the registered 104,062 fetuses, a total of 100,303 live births were recorded. After excluding 1,891 multiple births, 98,412 singleton births remained. We next excluded unidentified and missing data of children’s sex (n = 18) and maternal age (n = 7); infants with eye (n = 60) and ear (n = 615) abnormalities; those with chromosomal abnormalities (n = 145); mother’s with mental disorders (n = 7,909); those with missing data on birth weight (n = 314), maternal social support during pregnancy (n = 3,226), and the Ages and Stages Questionnaire, third edition (ASQ-3) [13] at 3 years of age (n = 17,676).
We defined mothers with mental disorders as those suffering from depression, autonomic neuropathy, anxiety disorders, or schizophrenia assessed in the second half of pregnancy and at the childbirth or taking medication for these disorders assessed in the first and second half of pregnancy. Finally, 68,442 mother-child pairs were included in the analysis. (Fig. 1).
Flow chart of participant selection.
The primary exposure was maternal social support levels during pregnancy, which were evaluated using the following four items: [1] ‘Is there someone available to you who shows you love and affection?’ [2] ‘Is there someone you can count on to provide you with emotional support (talking about problems or helping you make difficult decisions)?’, [3] ‘How often do you have as much contact as you would like with someone you feel close to someone in whom you can trust and confide?’ and [4] ‘Number of friends/neighbors to whom you can talk casually about your concern?’. Questions 1, 2, and 3 were scored using a 5-point scale (0 = not always, 1 = sometimes, 2 = to a certain extent, 3 = almost always, 4 = always), and question 4 was scored using a 3-point scale (0 = none, 1 = 1–2 people, 2 = more than 3 people). Therefore, the total score for social support ranged from 0 to 14. To assess the internal consistency in these indicators to measure child development, we calculated the standardized Cronbach’s alpha (α = 0.74). We used categorical values (quintiles) for maternal social support. These questions were modified from the Social Support Questionnaire [14].
OutcomesThe ASQ-3 is composed of 21-age specific questionnaires for children ages 1 to 66 months to evaluate children’s development in 5 domains (communication, gross motor, fine motor, problem-solving, personal-social), with 6 questions result for each domain. Parents respond to these questions describing behavioral skills and abilities; “yes” (10 points), “sometimes” (5 points), or “not yet” (0 points). Parents may skip an item if they are not sure how to answer it or concerned about their poor child’s performance. If one or two scores were missing, the average score of the remaining items was substituted to calculate the overall score [15]. Following the recommended ASQ-3 procedures, modified age was used to determine the ASQ-3 for preterm infants (<37 weeks gestation). The cutoff scores (−2.0 standard deviation (SD)) were 29.95 for communication, 39.26 for gross motor, 27.91 for fine motor, 30.03 for problem-solving, and 26.89 for personal-social. These cutoff scores were based on previously validated cutoff scores for Japanese children [16]. We determined that children whose score was below the cutoff value were at risk for development delay.
Statistical analysesWe calculated the mean values (SD) and risk factor prevalence according to maternal social support levels during pregnancy. A logistic regression model was used to estimate odds ratios (ORs) and 95% confidence intervals (CIs) for social support quintiles. The lowest social support quintile was used as the reference for the analysis. The multivariable ORs (95% CI) were estimated after adjustment for maternal age (continues) and other covariates, including residential area (15 regional centers), maternal education (junior high school or high school, vocational school, junior college, university or graduate school, or missing), paternal education (junior high school or high school, vocational school, junior college, university or graduate school, or missing), household income (<4 million, ≥4 and <6 million, ≥6 and <8 million, ≥8 and <10 million and ≥10 million yen, or missing), living with other children (yes/no or missing), and living with a partner (yes/no or missing) in model 1, and further adjustment for gestational week (continuous), birth weight (continuous), postpartum depression evaluated by the Edinburgh Postnatal Depression Scale (EPDS score) (<9, ≥9, or missing) added in model 2. The reason for constructing model 2 was to adjust for potential confounding factors that may affect development after birth. Missing data for these confounding factors were included as categorical variables in the model. Tests for trends were conducted using the median value of each category of social support levels. We also used step-wise multiple linear regression to examine which factors other than social support score (continuous) was associated with the child development score (continuous).
All statistical analyses were performed using the SAS software (version 9.4; SAS Institute Inc., Cary, NC, USA).
Table 1 presents the mean values and proportions of maternal and child characteristics according to quintiles of maternal social support levels during pregnancy. The highest quintile of maternal social support level was less likely to have smoking, living with other children, and postpartum depression and more likely to have education, household income, living with a partner, and partner’s education (p value <0.001 for each).
| Quintiles of maternal social support | |||||
|---|---|---|---|---|---|
| Q1 | Q2 | Q3 | Q4 | Q5 | |
| N | 13919 | 11051 | 11502 | 19373 | 12597 |
| Maternal age (year ± SD) | 31.2 ± 5.2 | 31.3 ± 5.1 | 31.5 ± 4.9 | 31.6 ± 4.7 | 31.6 ± 4.6 |
| Pre-pregnancy body mass index (kg/m2 ± SD) | 21.4 ± 3.3 | 21.2 ± 3.2 | 21.1 ± 3.2 | 21.0 ± 3.0 | 21.0 ± 3.1 |
| Baby’s sex (boy, %) | 7193 (51.7) | 5564 (50.4) | 5860 (51.0) | 9984 (51.5) | 6507 (51.7) |
| Birth weight (g ± SD) | 3026 ± 405 | 3026 ± 412 | 3030 ± 416 | 3027 ± 403 | 3033 ± 402 |
| Gestational week (weeks ± SD) | 38.8 ± 1.5 | 38.9 ± 1.5 | 38.8 ± 1.5 | 38.9 ± 1.5 | 38.9 ± 1.5 |
| Maternal smoking during pregnancy, n (%) | |||||
| Never | 7719 (55.5) | 6377 (57.7) | 6979 (60.7) | 12355 (63.8) | 8338 (66.2) |
| Quit before pregnant | 3427 (24.6) | 2648 (24.0) | 2747 (23.9) | 4416 (22.8) | 2790 (22.2) |
| Quit after pregnant | 2048 (14.7) | 1499 (13.6) | 1322 (11.5) | 2004 (10.3) | 1131 (9.0) |
| Current smoking | 609 (4.4) | 452 (4.1) | 382 (3.3) | 498 (2.6) | 274 (2.2) |
| Missing | 116 (0.8) | 75 (0.7) | 72 (0.6) | 100 (0.5) | 64 (0.5) |
| Maternal education, n (%) | |||||
| High school or less | 5912 (42.5) | 4092 (37.0) | 3881 (33.7) | 5485 (28.3) | 3113 (24.7) |
| Vocational school | 3171 (22.8) | 2572 (23.3) | 2661 (23.1) | 4636 (23.9) | 2855 (22.6) |
| Junior college | 2360 (17.0) | 2137 (19.3) | 2311 (20.1) | 4107 (21.2) | 2877 (22.8) |
| University or graduate school | 2436 (17.5) | 2225 (20.1) | 2613 (22.7) | 5099 (26.3) | 3719 (29.5) |
| Missing | 40 (0.3) | 25 (0.2) | 36 (0.3) | 46 (0.2) | 33 (0.3) |
| Paternal education, n (%) | |||||
| High school or less | 6757 (48.6) | 4915 (44.5) | 4790 (41.6) | 7248 (37.4) | 4466 (35.5) |
| Vocational school | 2445 (17.6) | 2025 (18.3) | 2158 (18.8) | 3717 (19.2) | 2345 (18.6) |
| Junior college | 626 (4.5) | 480 (4.3) | 522 (4.5) | 865 (4.5) | 520 (4.1) |
| University or graduate school | 3939 (28.3) | 3547 (32.1) | 3948 (34.3) | 7329 (38.4) | 5206 (41.3) |
| Missing | 152 (1.1) | 84 (0.8) | 84 (0.7) | 114 (0.6) | 60 (0.5) |
| Income, n (%) | |||||
| <4 million yen | 5881 (42.3) | 4258 (38.5) | 4111 (35.7) | 6311 (32.6) | 3933 (31.2) |
| ≥4 and <6 million yen | 4167 (29.9) | 3420 (31.0) | 3723 (32.4) | 6349 (32.8) | 4127 (32.8) |
| ≥6 and <8 million yen | 1835 (13.2) | 1623 (14.7) | 1753 (15.2) | 3264 (16.9) | 2288 (18.2) |
| ≥8 and <10 million yen | 661 (4.8) | 632 (5.7) | 745 (6.5) | 1445 (7.5) | 978 (7.8) |
| ≥10 million yen | 413 (3.0) | 387 (3.5) | 473 (4.1) | 948 (4.9) | 651 (5.2) |
| Missing | 962 (6.9) | 731 (6.6) | 697 (6.1) | 1056 (5.5) | 620 (4.9) |
| Living with partner, n (%) | |||||
| Yes | 12753 (91.6) | 10206 (92.4) | 10761 (93.6) | 18241 (94.2) | 11806 (93.7) |
| No | 1109 (8.0) | 798 (7.2) | 695 (6.0) | 1071 (5.5) | 750 (6.0) |
| Missing | 57 (0.4) | 47 (0.4) | 46 (0.4) | 61 (0.3) | 41 (0.3) |
| Living with other children, n (%) | |||||
| Yes | 7777 (55.9) | 6106 (55.3) | 6163 (53.6) | 10073 (52.0) | 6683 (53.1) |
| No | 6085 (43.7) | 4898 (44.3) | 5293 (46.0) | 9239 (47.7) | 5873 (46.6) |
| Missing | 57 (0.4) | 47 (0.4) | 46 (0.4) | 61 (0.3) | 41 (0.3) |
| Postpartum depression, n (%) | |||||
| EPDS score <9 | 11534 (82.9) | 9880 (89.4) | 10476 (91.1) | 18089 (93.4) | 11994 (95.2) |
| EPDS score ≥9 | 2318 (16.7) | 1129 (10.2) | 983 (8.6) | 1211 (6.3) | 567 (4.5) |
| Missing | 67 (0.5) | 42 (0.4) | 43 (0.4) | 73 (0.4) | 36 (0.3) |
Table 2 shows the ORs (95% CI) for developmental delay in 3-year-old children according to the quintiles of maternal social support level during pregnancy. The higher social support was associated with a lower risk of child developmental delay at 3 years of age. The multivariable OR (95%CI) for the highest versus lowest quantities of maternal social support levels were 0.57 (0.50–0.65) for communication (p for trend <0.001), 0.49 (0.43–0.55) for gross motor delay (p for trend <0.001), 0.58 (0.53–0.64) for fine motor delay (p for trend <0.001), 0.56 (0.51–0.62) for problem-solving delay (p for trend <0.001), and 0.52 (0.45–0.60) for personal social delay (p for trend <0.001).
| Quintiles of maternal social support | p for trend | |||||
|---|---|---|---|---|---|---|
| Q1 | Q2 | Q3 | Q4 | Q5 | ||
| N | 13919 | 11051 | 11502 | 19373 | 12597 | |
| Communication | ||||||
| Cases | 760 | 444 | 434 | 639 | 345 | |
| OR (95%CI) | 1.00 | 0.73 (0.64–0.82) | 0.68 (0.60–0.77) | 0.59 (0.53–0.66) | 0.49 (0.43–0.56) | <0.001 |
| Adjusted OR (95%CI) 1 | 1.00 | 0.75 (0.66–0.84) | 0.71 (0.63–0.80) | 0.64 (0.57–0.71) | 0.54 (0.47–0.61) | <0.001 |
| Adjusted OR (95%CI) 2 | 1.00 | 0.78 (0.69–0.88) | 0.75 (0.66–0.85) | 0.68 (0.60–0.75) | 0.57 (0.50–0.65) | <0.001 |
| Gross motor | ||||||
| Cases | 831 | 520 | 497 | 778 | 391 | |
| OR (95%CI) | 1.00 | 0.78 (0.69–0.87) | 0.70 (0.63–0.79) | 0.64 (0.58–0.71) | 0.49 (0.44–0.56) | <0.001 |
| Adjusted OR (95%CI) 1 | 1.00 | 0.79 (0.71–0.89) | 0.72 (0.65–0.81) | 0.67 (0.61–0.75) | 0.52 (0.46–0.59) | <0.001 |
| Adjusted OR (95%CI) 2 | 1.00 | 0.77 (0.69–0.86) | 0.70 (0.62–0.78) | 0.64 (0.57–0.70) | 0.49 (0.43–0.55) | <0.001 |
| Fine motor | ||||||
| Cases | 1395 | 905 | 834 | 1290 | 690 | |
| OR (95%CI) | 1.00 | 0.80 (0.74–0.87) | 0.70 (0.64–0.77) | 0.64 (0.59–0.69) | 0.52 (0.47–0.57) | <0.001 |
| Adjusted OR (95%CI) 1 | 1.00 | 0.82 (0.75–0.89) | 0.72 (0.66–0.79) | 0.67 (0.62–0.73) | 0.56 (0.50–0.61) | <0.001 |
| Adjusted OR (95%CI) 2 | 1.00 | 0.84 (0.77–0.92) | 0.75 (0.68–0.82) | 0.70 (0.65–0.76) | 0.58 (0.53–0.64) | <0.001 |
| Problem-solving | ||||||
| Cases | 1377 | 811 | 831 | 1232 | 654 | |
| OR (95%CI) | 1.00 | 0.72 (0.66–0.79) | 0.71 (0.65–0.78) | 0.62 (0.57–0.67) | 0.50 (0.45–0.55) | <0.001 |
| Adjusted OR (95%CI) 1 | 1.00 | 0.74 (0.67–0.81) | 0.73 (0.66–0.80) | 0.64 (0.59–0.70) | 0.53 (0.48–0.58) | <0.001 |
| Adjusted OR (95%CI) 2 | 1.00 | 0.76 (0.69–0.83) | 0.76 (0.69–0.83) | 0.68 (0.62–0.74) | 0.56 (0.51–0.62) | <0.001 |
| Personal-social | ||||||
| Cases | 643 | 381 | 346 | 542 | 265 | |
| OR (95%CI) | 1.00 | 0.74 (0.65–0.84) | 0.64 (0.56–0.73) | 0.60 (0.53–0.67) | 0.44 (0.38–0.51) | <0.001 |
| Adjusted OR (95%CI) 1 | 1.00 | 0.76 (0.67–0.86) | 0.66 (0.58–0.76) | 0.63 (0.56–0.70) | 0.48 (0.41–0.55) | <0.001 |
| Adjusted OR (95%CI) 2 | 1.00 | 0.79 (0.69–0.90) | 0.70 (0.61–0.80) | 0.67 (0.60–0.76) | 0.52 (0.45–0.60) | <0.001 |
OR, odds ratio; CI, confidence interval.
Model 1: Adjusted for regional centers, maternal age, maternal education, paternal education, household income, living with children, and living with a partner.
Model 2: Adjusted further for gestational weeks, birth weight, and postpartum depression.
According to the stepwise multiple regression analysis, social support during pregnancy, as well as gestational week, household income were positively associated with child development while maternal age and postpartum depression was inversely associated with it consistently for all of the ASQ-3 domains (Table 3).
| β | Std. error | P value | |
|---|---|---|---|
| Communication | |||
| Social support | 0.278 | 0.014 | <0.001 |
| Maternal age | −0.127 | 0.009 | <0.001 |
| Postpartum depression | −1.672 | 0.144 | <0.001 |
| Gestational week | 0.428 | 0.027 | <0.001 |
| Maternal education | 1.105 | 0.095 | <0.001 |
| Paternal education | 0.233 | 0.089 | 0.009 |
| Household income | 0.533 | 0.039 | <0.001 |
| Living with children | 0.136 | 0.084 | 0.105 |
| Gross Motor | |||
| Social support | 0.194 | 0.011 | <0.001 |
| Maternal age | −0.073 | 0.007 | <0.001 |
| Postpartum depression | −1.303 | 0.114 | <0.001 |
| Gestational week | 0.378 | 0.025 | <0.001 |
| Birth weight | 0.229 | 0.044 | <0.001 |
| Paternal education | −0.169 | 0.067 | 0.012 |
| Household income | 0.179 | 0.030 | <0.001 |
| Living with children | 0.928 | 0.068 | <0.001 |
| Living with a partner | −0.292 | 0.140 | 0.036 |
| Fine motor | |||
| Social support | 0.350 | 0.016 | <0.001 |
| Maternal age | −0.092 | 0.011 | <0.001 |
| Postpartum depression | −2.468 | 0.175 | <0.001 |
| Gestational week | 0.584 | 0.033 | <0.001 |
| Maternal education | 0.894 | 0.115 | <0.001 |
| Paternal education | 0.372 | 0.108 | 0.005 |
| Household income | 0.479 | 0.048 | <0.001 |
| Living with children | 1.979 | 0.102 | <0.001 |
| Problem-solving | |||
| Social support | 0.285 | 0.014 | <0.001 |
| Maternal age | −0.121 | 0.009 | <0.001 |
| Postpartum depression | −2.038 | 0.149 | <0.001 |
| Birth weight | 0.107 | 0.033 | 0.063 |
| Gestational week | 0.421 | 0.058 | <0.001 |
| Maternal education | 0.514 | 0.098 | <0.001 |
| Paternal education | 0.239 | 0.092 | 0.009 |
| Household income | 0.357 | 0.040 | <0.001 |
| Living with children | 0.792 | 0.088 | <0.001 |
| Living with a partner | −0.474 | 0.183 | 0.010 |
| Personal-social | |||
| Social support | 0.257 | 0.013 | <0.001 |
| Maternal age | −0.202 | 0.009 | <0.001 |
| Postpartum depression | −2.234 | 0.139 | <0.001 |
| Birth weight | −0.123 | 0.054 | 0.021 |
| Gestational week | 0.475 | 0.031 | <0.001 |
| Maternal education | 0.500 | 0.091 | <0.001 |
| Paternal education | −0.255 | 0.085 | 0.003 |
| Household income | 0.586 | 0.037 | <0.001 |
| Living with children | 1.833 | 0.081 | <0.001 |
In this large prospective study of approximately 67,000 mother-child pairs, we found that higher social support during pregnancy was positively associated in a dose response fashion with a lower risk of child development delay at 3 years of age, independent of maternal age, socioeconomic factors, gestational week, birth weight, and maternal postpartum depression. Our study extended the findings from the previous smaller studies [8–10] with confirming the robust dose-response relation in all of ASQ-3 domains.
There are multiple possible mechanisms by which the social support during pregnancy has an impact on reducing child development delay. First, the experience of stressful life events such as money, employment problems and moving were associated with depression during pregnancy, but the social support during pregnancy buffer the association [7]. A meta-analysis of 64,449 pregnant from 67 studies showed that low social support was associated with psychological problems such as depression and anxiety during pregnancy [6]. Pregnant women with low social support may have an absence of people to confide in, to obtain important information or advice, and/or to alleviate the negative emotions under distressing situations [17]. Secondly, maternal social support, albeit after birth, was positively associated with psychological well-being and the better language acquisition environment at home for children [18]. We assumed that such a beneficial effect could be obtained by social support during pregnancy, too. Third, it is possible that social support received during pregnancy may improve mother’s psychological stress which can be transmitted to the baby through the placenta, though elevated levels of circulating glucocorticoids under the activated hypothalamic pituitary adrenal axis [4]. Such metabolic alternations may affect fatal brain development directly [3–5].
Our study had several limitations. First, the assessment of child development was based on the caregiver’s self-reports. Although ASQ-3 is a worldwide screening tool, it does not accurately cover all developmental aspects. Assessment of mother’s social-economic status and ACES (Adverse Childhood Experiences study) scores should be assessed at multiple time points as prenatal time and infancy other than 3 years of age. Second, nursery school attendance was not determined. Nursery schools afford children opportunities to interact with their peers, which may positively affect their development in low-income and ethnic minority groups [19].
In conclusion, the higher social support during pregnancy was associated with a lower risk of child development delay at 3 years of age. The further follow-up studies are necessary to elucidate the long-term impact of maternal social support during pregnancy on child development.
Ages and Stages Questionnaire-3
CIconfidence intervals
EPDSEdinburgh Postnatal Depression Scale
JECSJapan Environment and Children’s Study
ORodds ratios
SDstandard deviation
We are grateful to all JECS participants and all individuals involved in the data collection. Members of the JECS Group as of 2023: Michihiro Kamijima (principal investigator, Nagoya City University, Nagoya, Japan), Shin Yamazaki (National Institute for Environmental Studies, Tsukuba, Japan), Yukihiro Ohya (National Center for Child Health and Development, Tokyo, Japan), Reiko Kishi (Hokkaido University, Sapporo, Japan), Nobuo Yaegashi (Tohoku University, Sendai, Japan), Koichi Hashimoto (Fukushima Medical University, Fukushima, Japan), Chisato Mori (Chiba University, Chiba, Japan), Shuichi Ito (Yokohama City University, Yokohama, Japan), Zentaro Yamagata (University of Yamanashi, Chuo, Japan), Hidekuni Inadera (University of Toyama, Toyama, Japan), Takeo Nakayama (Kyoto University, Kyoto, Japan), Tomotaka Sobue (Osaka University, Suita, Japan), Masayuki Shima (Hyogo Medical University, Nishinomiya, Japan), Seiji Kageyama (Tottori University, Yonago, Japan), Narufumi Suganuma (Kochi University, Nankoku, Japan), Shoichi Ohga (Kyushu University, Fukuoka, Japan), and Takahiko Katoh (Kumamoto University, Kumamoto, Japan).
Ethics approval and consent to participateThe JECS protocol was approved by the Ministry of the Environment’s Institutional Review Board of Epidemiological Studies and the Ethics Committees of all participating institutions. Written informed consent was obtained from all the participants.
Consent for publicationNot applicable.
Availability of data and materialsData 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.
Competing interestNo interest to declare.
FundingThis study was funded by the Ministry of Environment, Japan. The findings and conclusions of this study are solely the responsibility of the authors and do not represent the official views of the government.
Author’s contributionsYI and SI were involved in the study design and data interpretation. YI, SI and YA analyzed the data. SI, TS and HI critically revised the manuscript. HI supervised the whole manuscript. All authors approved the final manuscript.
