Association of allergies in children younger than 3 years with levels of maternal intake of n-3 polyunsaturated fatty acids or fish during pregnancy: A nationwide birth cohort study, the Japan Environment and Children's Study

BACKGROUND

N-3 polyunsaturated fatty acids (PUFAs) have anti-inflammatory properties and are expected to prevent the onset of allergies. However, epidemiological studies investigating the relationship between child allergies and maternal intake of n-3 PUFAs or fish have yielded inconsistent results.

METHODS

Following exclusions from a dataset comprising 103,057 records from the Japan Environment and Children's Study, 72,105 participants were divided into five groups according to mothers' intake of n-3 PUFAs or fish during pregnancy to assess the risk of their children being diagnosed with allergy by 3 years old. Adjusted odds ratios (aORs) with 95% confidence intervals (CIs) for child allergies were calculated using multivariable logistic regression analyses with reference to the lowest intake group.

RESULTS

Levels of maternal intake of n-3 PUFAs or fish showed inverted associations (i.e., reduced risk) with the incidence of physician-diagnosed allergic rhinoconjunctivitis or parent-reported symptoms of current rhinitis with eye symptoms at different time points and the cumulative incidence from birth to 3 years of age. Inverted associations were also found for current wheeze at 1-<2 years of age and current eczema at 1-<2 and 0-<3 years of age. However, for food allergies, no significant associations were observed in the incidence in each group compared with the lowest intake group at any age.

CONCLUSIONS

The findings suggest that n-3 PUFA intake during pregnancy may reduce the risk of developing allergic diseases and symptoms in children. In addition, consumption of n-3 PUFAs or fish is very unlikely to increase the risk of allergy given that the results are from a country with high fish consumption.

TRIAL REGISTRATION

UMIN000030786 https://rctportal.niph.go.jp/detail/um?trial_id=UMIN000030786.

Maternal fermented food intake and infant neurodevelopment: The Japan Environment and Children's Study

BACKGROUND AND OBJECTIVES

Fermented foods play an important role in establishing intestinal bacterial flora, and the composition of the intestinal bacterial flora might be associated with neurodevelopment. This study investigated the association between maternal intake of fermented foods during pregnancy and early neuro-development in offspring.

METHODS AND STUDY DESIGN

Data were analyzed for 73,522 pregnant women participating in the Japan Environment and Children's Study. Their intake of four common fermented foods during pregnancy was assessed using a semi-quantitative FFQ. Neurodevelopment in their infants at 1 year of age was estimated using the Ages and Stages Questionnaires.

RESULTS

Multivariable logistic regression analysis showed that maternal intake of miso soup and fermented soybeans was each associated with a significantly reduced risk of delay in infant communication skills. Maternal intake of fermented soybeans and cheese was each associated with a significantly reduced risk of delay in fine motor skills in the third and fourth quartiles. For problem-solving, preventive associations were observed with maternal intake of fermented soybeans in the second and third quartiles and with maternal intake of cheese in the third and fourth quartiles. Maternal intake of yogurt was associated with a significantly reduced risk of delay in personal-social skills in the third and fourth quartiles, while that of cheese was associated with a reduced risk in the third quartile. No reductions in risk were observed for gross motor skills.

CONCLUSIONS

Our results suggest that fermented food intake during pregnancy may have beneficial associations with several areas of psychomotor development in children.

Maternal dietary intake of fish and child neurodevelopment at 3 years: a nationwide birth cohort-The Japan Environment and Children's Study

Background

Results on the association between fish intake during pregnancy and a reduction in neurodevelopmental delays in children have been inconsistent, with some reports finding an association and others finding none. Because neurodevelopmental delays are more pronounced at the age of 3 years, their association needs to be examined at this age.

Methods

After exclusion and multiple imputation from a dataset comprising 104,057 records from the Japan Environment and Children's Study, logistic regression analysis was conducted in quintiles to evaluate the association between maternal fish intake during pregnancy and child neurodevelopment at age 3 years in 91,909 mother-child pairs. The Food Frequency Questionnaire (FFQ), validated in the Japan Public Health Center-Based Prospective Study for the Next Generation, was used to assess maternal fish intake during pregnancy. The Ages and Stages Questionnaires-3 was used to assess children's neurodevelopment in five domains: communication, gross motor, fine motor, problem-solving, and personal-social.

Results

Consistently lower odds were found for the highest vs. lowest quintile for the domains of communication, fine motor, problem-solving, and personal-social but not gross motor skills, with adjusted odd ratios (95% confidence intervals) of 0.89 (0.80-0.998), 0.90 (0.83-0.97), 0.86 (0.80-0.94), 0.87 (0.77-0.98), and 1.04 (0.94-1.16), respectively. The trend for lower odds of symptoms of neurodevelopmental delays across quintiles of higher maternal fish intake were significant for fine motor, problem-solving, and personal-social but not communication or gross motor.

Conclusions

Fish consumption during pregnancy may be associated with a reduced risk of neurodevelopmental delay in 3-year-olds, particularly in the fine motor, problem-solving, and personal-social domains. Continued investigation after the age of 3 could further clarify the association.

Differences in health literacy related to gestational weight gain and children's birth weight according to maternal nativity status in the Japan Environment and Children's Study (JECS): a longitudinal cohort study

OBJECTIVES

We examined literacy related to healthy gestational weight gain (GWG) in immigrant and native Japanese mothers and determined whether it is associated with children's birth weight.

DESIGN

Longitudinal cohort study.

SETTING

As the baseline survey in the Japan Environment and Children's Study (JECS), mothers completed self-administered questionnaires distributed by hand during pregnancy. The self-administered questionnaires used in this study were distributed by mail 6 months after delivery. Children's birth weight, actual GWG and any complications during delivery were recorded by obstetricians collaborating with JECS.

PARTICIPANTS

Of 97 452 mothers who consented to participate in the JECS during pregnancy between January 2011 and March 2014, 67 953 were included in this study after exclusions for multiple births, multiple instances of consent by the same pregnant woman, miscarriages/stillbirths or withdrawal from the study within 3 years after participating. In total, 324 immigrant mothers and 963 native Japanese mothers were selected by propensity score matching for analysis.

PRIMARY AND SECONDARY OUTCOME MEASURES

Data were collected on maternal literacy related to healthy GWG at the baseline survey, and data on actual GWG and children's birth weight were collected by obstetricians. The associations of knowledge about healthy GWG and mothers' actual GWG with maternal nativity status were examined using a χ2 or Student's t-test.

RESULTS

More native Japanese mothers than immigrant mothers knew the appropriate GWG and reason the for needing to know this. Actual GWG was significantly higher among the immigrant mothers, but was within the recommended range. The low birthweight (LBW) incidence was significantly higher among the native mothers.

CONCLUSIONS

Immigrant mothers to Japan had less knowledge about appropriate GWG, but their actual GWG was appropriate and they delivered fewer LBW infants than native Japanese mothers. These findings may indicate the presence of other protective factors for pregnancy or delivery among immigrant mothers.

Maternal Dietary Vitamin D Intake during Pregnancy Is Associated with Allergic Disease Symptoms in Children at 3 Years Old: The Japan Environment and Children's Study

INTRODUCTION

Vitamin D plays an important role in the immune system, and postnatal vitamin D insufficiency is one of the risk factors for the development of allergic disease. However, the effects of women's vitamin D intake during pregnancy on the prevalence of allergic disease in their children remain controversial.

METHODS

From the Japan Environment and Children's Study, an ongoing nationwide birth cohort study, we obtained information on maternal dietary vitamin D intake determined using a food frequency questionnaire and parent-reported allergic disease symptoms based on the ISAAC questionnaire in children at 3 years of age.

RESULTS

From the full dataset of 103,060 pregnancies, we analyzed complete data for 73,309 mother-child pairs. The prevalence of current wheeze, current rhinitis, current rhino-conjunctivitis, current eczema, ever asthma, ever pollinosis, and ever atopic dermatitis in the children was 17.2%, 29.7%, 3.8%, 15.2%, 9.6%, 3.7%, and 11.0%, respectively. The ORs for current rhinitis were significantly lower in the 3rd, 4th, and 5th quintiles than in the 1st quintile after adjustment for various covariates and showed a linear association. The ORs for ever pollinosis were significantly lower in the 2nd, 3rd, and 4th quintiles than in the 1st quintile, showing a U-shaped curve. There was no clear association between mothers' dietary vitamin D intake and symptoms of asthma or atopic dermatitis in their 3-year-old children.

CONCLUSION

Maternal dietary vitamin D intake during pregnancy is associated with the ORs for nasal allergies in children at the age of 3 years. Further studies are warranted to evaluate the appropriate intake dose of vitamin D for pregnant women to prevent the development of nasal allergies in their children.

Galectin-4 Is Involved in the Structural Changes of Glycosphingolipid Glycans in Poorly Differentiated Gastric Cancer Cells with High Metastatic Potential

Gastric cancer with peritoneal dissemination is difficult to treat surgically, and frequently recurs and metastasizes. Currently, there is no effective treatment for this disease, and there is an urgent need to elucidate the molecular mechanisms underlying peritoneal dissemination and metastasis. Our previous study demonstrated that galectin-4 participates in the peritoneal dissemination of poorly differentiated gastric cancer cells. In this study, the glycan profiles of cell surface proteins and glycosphingolipids (GSLs) of the original (wild), galectin-4 knockout (KO), and rescue cells were investigated to understand the precise mechanisms involved in the galectin-4-mediated regulation of associated molecules, especially with respect to glycosylation. Glycan analysis of the NUGC4 wild type and galectin-4 KO clones with and without peritoneal metastasis revealed a marked structural change in the glycans of neutral GSLs, but not in N-glycan. Furthermore, mass spectrometry (MS) combined with glycosidase digestion revealed that this structural change was due to the presence of the lacto-type (β1-3Galactosyl) glycan of GSL, in addition to the neolacto-type (β1-4Galactosyl) glycan of GSL. Our results demonstrate that galectin-4 is an important regulator of glycosylation in cancer cells and galectin-4 expression affects the glycan profile of GSLs in malignant cancer cells with a high potential for peritoneal dissemination.

Relationship between prenatal checkup status and low birth weight: a nationwide birth cohort-the Japan Environment and Children's Study

PURPOSE

We investigated the association between prenatal checkup status and low birth weight (LBW). We also sought to identify the background factors of pregnant women that influence their attendance at prenatal checkups and consider measures that might prove useful in reducing the LBW rate.

METHODS

Using data from a large nationwide birth cohort study, the Japan Environment and Children's Study (JECS), the sample comprised 91,916 unique mother-infant pairs with singleton live births. The outcome variable was cases of LBW, and the exposure variable was prenatal checkup status (number of visits missed). Adjusted odds ratios (AORs) with 95% confidence intervals (CIs) were calculated by logistic regression analysis.

RESULTS

AORs (95% CIs) for cases of LBW were 1.57 (1.46-1.69) for 1 missed checkup, 2.40 (1.97-2.94) for 2 missed checkups, and 2.38 (1.46-3.88) for ≥3 missed checkups. A linear trend was also observed (P < .0001). Further analysis revealed that the main risk factors for missed checkups were divorced or widowed marital status, followed by negative attitude toward pregnancy, and single marital status, whereas protective factors were being employed and better mental health in mid-late pregnancy.

CONCLUSIONS

Our results suggest the importance of implementing various measures to promote regular attendance at prenatal checkups.

Impact of longer working hours on fathers' parenting behavior when their infants are 6 months old: The Japan Environment and Children's Study

Objective

Long working hours have been suggested to affect fathers' parenting behavior, but previously reported findings have been inconsistent. This study examined the association between the working hours and parenting behavior of fathers while accounting for other factors related to their parenting behavior, using data from the Japan Environment and Children Study (JECS), a large cohort study in Japan.

Methods

Data from 43,159 father-mother pairs were analyzed. The mother assessed the father's frequency of seven parenting behaviors at 6 months after delivery. Then, each behavior was classified into a high-engagement group (always and sometimes) or a low-engagement group (rarely and never). The father's weekly working hours was obtained from his responses and was classified into six levels.

Results

Logistic regression analysis showed that after adjustment for covariates, fathers' weekly working hours was inversely associated with the frequency of all parenting behaviors examined in this study (p for trend <0.0001). Compared with fathers working ≥0 to ≤40 h per week, those working >65 h per week showed the following adjusted odds ratios (95% confidence intervals) for low engagement in parenting behaviors: playing at home, 2.38 (2.08-2.72); changing diapers, 2.04 (1.89-2.20); and bathing the child, 2.01 (1.84-2.18).

Conclusion

This study suggests that the greater time constraints imposed by longer working hours constitute a major factor that discourages fathers from engaging in childrearing behavior. Intervention targeting long working hours could contribute to measures aimed at promoting high-engagement parenting behaviors among fathers.

Longitudinal study of the relationship between number of prior miscarriages or stillbirths and changes in quality of life of pregnant women: the Japan Environment and Children's Study (JECS)

BACKGROUND

Although a history of miscarriage or stillbirth has been reported to negatively affect quality of life (QOL) during the subsequent pregnancy, the association between the number of previous miscarriages or stillbirths and QOL, as well as trends in QOL during pregnancy, has not been clarified. This study sought to determine this association during early and mid- to late pregnancy.

METHODS

Data from 82,013 pregnant women who participated in the Japan Environment and Children's Study (JECS) from January 2011 to March 2014 were analyzed. In early and mid/late pregnancy, participants completed questionnaires and QOL was assessed using the Physical and Mental Component Summary (PCS and MCS, respectively) scores from the 8-item Short-Form Health Survey (SF-8). The pregnant women were divided into four groups according to number of previous miscarriages or stillbirths (0, 1, 2, and ≥ 3), and the PCS and MCS scores in early pregnancy and mid/late pregnancy were compared between group 0 and groups 1, 2, and ≥ 3. Generalized linear mixed models were used for analysis.

RESULTS

PCS score in early pregnancy was lower in group 1 (β =  - 0.29, 95% confidence interval [CI] - 0.42 to - 0.15), group 2 (β =  - 0.45, 95% CI - 0.73 to - 0.18), and group ≥ 3 (β =  - 0.87, 95% CI - 1.39 to - 0.35) than in group 0. Group 1 and group ≥ 3 showed a trend for increased PCS score during pregnancy (β = 0.22, 95% CI 0.07 to 0.37 and β = 0.75, 95% CI 0.18 to 1.33, respectively) compared with group 0.

CONCLUSIONS

PCS score in early pregnancy was lower with a more frequent history of miscarriage or stillbirth. However, in terms of changes in QOL during pregnancy, pregnant women with a history of miscarriage or stillbirth showed greater increases in PCS score during mid/late pregnancy than pregnant women with no history of miscarriage or stillbirth.

Association of infants' feeding pattern up to 2 years postpartum with mothers' mental and physical health: the Japan Environment and Children's Study

BACKGROUND

Exclusive breastfeeding, a longer breastfeeding duration, and interaction with the baby during lactation improve mothers' mental health. However, few studies have targeted women around 2.5 years after childbirth, when women are still considered to have been in a period of mental and physical health vulnerability. This study examined this aspect in a large cohort of mother-child pairs.

METHODS

Data were obtained from 85,735 mothers in an ongoing nationwide birth cohort study in Japan. Exposures were exclusive breastfeeding (yes/no), continued breastfeeding up to 2 years (yes/no), and interaction with the baby during feeding (yes/no). Outcomes were mothers' mental and physical health 2.5 years after childbirth measured using Mental and Physical Component Summary scores (MCS and PCS scores, respectively) from the 8-item Short-Form Health Survey. Generalized additive mixed model analysis was used to derive each estimate for the three exposures and their interactions, with each "no" answer as reference.

RESULTS

Exclusive breastfeeding and interaction with the baby during feeding were associated with MCS score increases of 0.28 (95%CI: 0.10-0.47) and 0.41 (95%CI: 0.29-0.54), respectively. However, no associations were found for continued breastfeeding up to 2 years and no interactions were identified. No significant differences were observed for PCS scores.

LIMITATIONS

All variables were measured using a self-administered questionnaire.

CONCLUSIONS

Continued exclusive breastfeeding until 6 months and interaction with the baby during feeding may help to promote mother's mental health 2.5 years after childbirth. These findings further strengthen the rationale for the World Health Organization's recommended lactation practices.

Association of soap use when bathing 18-month-old infants with the prevalence of allergic diseases at age 3 years: The Japan Environment and Children's Study

BACKGROUND

Atopic march is defined as the progression from atopic dermatitis (AD) during early life to other allergic diseases in later childhood. In a nationwide birth cohort study, the Japan Environment and Children's Study, we investigated the association of bathing habits, which are known to affect skin conditions, for infants with their later development of allergic diseases.

METHODS

Pregnant women who lived in 15 designated regional centers throughout Japan were recruited. We obtained information on bathing habits for their 18-month-old infants and the prevalence of allergic diseases when they were aged 3 years.

RESULTS

Data for 74,349 children were analyzed. Most 18-month-old infants were bathed or showered almost every day. When they were divided into four groups according to the frequency of soap use during bathing (every time, most of the time, sometimes, and seldom), the risk of AD later at age 3 was shown to increase in association with a decreasing frequency of soap use [most of the time: adjusted odds ratio (aOR) 1.18, 95% confidence interval (CI) 1.05-1.34; sometimes: aOR 1.72, 95% CI 1.46-2.03; seldom: aOR 1.99, 95% CI 1.58-2.50], compared with soap use every time during bathing at 18 months of age. Similar results were obtained for food allergy but not for bronchial asthma.

CONCLUSIONS

Frequent soap use when bathing 18-month-old infants was associated with a decreased risk of them developing allergic diseases at age 3. Further well-designed clinical studies are warranted to determine an effective bathing regimen for preventing the development of allergic diseases.

Extracellular vesicles released from ganglioside GD2-expressing melanoma cells enhance the malignant properties of GD2-negative melanomas

Exosomes (small extracellular vesicles: EVs) have attracted increasing attention from basic scientists and clinicians since they play important roles in cell-to-cell communication in various biological processes. Various features of EVs have been elucidated regarding their contents, generation and secretion mechanisms, and functions in inflammation, regeneration, and cancers. These vesicles are reported to contain proteins, RNAs, microRNAs, DNAs, and lipids. Although the roles of individual components have been rigorously studied, the presence and roles of glycans in EVs have rarely been reported. In particular, glycosphingolipids in EVs have not been investigated to date. In this study, the expression and function of a representative cancer-associated ganglioside, GD2, in malignant melanomas was investigated. Generally, cancer-associated gangliosides have been shown to enhance malignant properties and signals in cancers. Notably, EVs derived from GD2-expressing melanomas enhanced the malignant phenotypes of GD2-negative melanomas, such as cell growth, invasion, and cell adhesion, in a dose-dependent manner. The EVs also induced increased phosphorylation of signaling molecules such as EGF receptor and focal adhesion kinase. These results suggest that EVs released from cancer-associated ganglioside-expressing cells exert many functions that have been reported as a function of these gangliosides and regulate microenvironments, including total aggravation of heterogeneous cancer tissues, leading to more malignant and advanced cancer types.

Dietary Intake of Vitamin D during Pregnancy and the Risk of Postpartum Depressive Symptoms: The Japan Environment and Children's Study

Many recent clinical and epidemiological studies have demonstrated the effects of vitamin D on health, yet few studies have examined the association of dietary intake of vitamin D during pregnancy with postpartum depressive symptoms. This study examined this association in a large cohort of 74,840 pregnant women who are enrolled in the longitudinal Japan Environment and Children's Study. Dietary vitamin D intake during pregnancy (specifically after learning of the pregnancy to mid-late pregnancy) was determined using the Food Frequency Questionnaire. Postpartum depressive symptoms 1 mo after delivery were assessed using the Edinburgh Postnatal Depression Scale. Logistic regression analysis showed a reduced risk of postpartum depressive symptoms for all except the first quintile of vitamin D intake: second quintile (adjusted odds ratio [95% confidence interval]: 0.88 [0.82-0.94]), third (0.83 [0.78-0.89]), fourth (0.87 [0.81-0.93]), and fifth (0.90 [0.83-0.97]). Post-adjustment trend tests revealed a significant association between dietary vitamin D intake and postpartum depressive symptoms (p for trend=0.004). Our results revealed a higher vitamin D intake during pregnancy was associated with a lower risk of postpartum depressive symptoms 1 mo after delivery, suggesting the potential applicability of vitamin D in reducing postpartum depression.

Season of birth and atopic dermatitis in early infancy: results from the Japan Environment and Children's Study

BACKGROUND

Atopic dermatitis (AD) is reported to be more prevalent in children who were born in autumn than in spring. Here, we investigated how early the association between season of birth and eczema or AD can be observed in the postnatal period. We also examined whether specific prevalence outcomes for infant eczema and AD differed according to sex and maternal history of allergic disease in a large Japanese cohort.

METHODS

Using data of 81,615 infants from the Japan Environment and Children's Study, we examined the associations of birth month or season with four different outcomes-eczema at 1 month, 6 months, and 1 year of age and physician-diagnosed AD up to 1 year of age-using multiple logistic regression analysis. We also analyzed the effect of maternal history of allergic disease on these outcomes stratified by infant sex.

RESULTS

The risk of eczema at 1 month was highest in infants born in July. In contrast, infants born in autumn had higher risks of eczema at 6 months (adjusted odds ratio [aOR], 2.19; 95% confidence interval [CI], 2.10-2.30) and at 1 year (aOR, 1.08; 95% CI, 1.02-1.14) and of physician-diagnosed AD up to 1 year of age (aOR, 1.33; 95% CI, 1.20-1.47) compared with infants born in spring. Eczema and AD were more prevalent in infants with a maternal history of allergic disease, particularly boys.

CONCLUSIONS

Our findings suggest that the prevalence of AD is associated with the season of observation. Eczema is prevalent in infants born in autumn, and this phenomenon was observed in infants as young as 6 months old. The risk associated with being born in autumn was particularly clear in boys with a maternal history of allergic disease.

TRIAL REGISTRATION

UMIN000030786.

Omega-3 fatty acid intake during pregnancy and risk of infant maltreatment: a nationwide birth cohort - the Japan Environment and Children's Study

BACKGROUND

Intake of omega-3 polyunsaturated fatty acids (PUFAs) has favorable effects, including reducing violent and aggressive behaviors, but its association with infant maltreatment is unknown. We therefore tested the hypothesis that maternal intake of omega-3 PUFAs is associated with a lower risk of infant maltreatment.

METHODS

Participants were 92 191 mothers involved in the ongoing Japan Environment and Children's Study. Omega-3 PUFA intake during pregnancy was measured using a food frequency questionnaire. Infant maltreatment was assessed using a self-reported questionnaire administered at 1 and 6 months postpartum.

RESULTS

Analysis using the lowest quintile of intake as a reference revealed that the adjusted odds ratios (ORs) with 95% confidence intervals (CIs) for cases of 'hitting' decreased as quintiles increased, with values for the second to fifth quintiles of 0.93 (95% CI 0.77-1.13), 0.79 (95% CI 0.64-0.97), 0.78 (95% CI 0.64-0.96), and 0.72 (95% CI 0.59-0.89), respectively. Adjusted ORs (95% CIs) for 'shaking very hard' at 6 months were 0.87 (0.73-1.04), 0.81 (0.67-0.97), 0.73 (0.61-0.89), and 0.78 (0.65-0.94), respectively. Adjusted ORs for 'leaving alone at home' for the second to fifth quintiles were 0.92 (0.87-0.98), 0.91 (0.86-0.97), 0.94 (0.88-0.99), and 0.85 (0.80-0.90), respectively.

CONCLUSIONS

Higher maternal intake of omega-3 PUFAs during pregnancy was associated with fewer cases of hitting and violent shaking and leaving the child alone at home, implying a lower risk of infant maltreatment. Our results indicate the potential applicability of omega-3 PUFAs in reducing infant maltreatment.

Cesarean section and parenting stress: Results from the Japan Environment and Children's Study

BACKGROUND

Accumulating evidence suggests a long-term health risk of cesarean section for the mother and child, but few studies have examined the link between cesarean section and parenting stress. Here, we examined this association by exploiting a large dataset.

METHODS

Participants were 65,235 mothers participating in the Japan Environment and Children's Study, an ongoing nationwide birth cohort. Outcome variables were parenting stress assessed as total score and subscale scores (representing the difficult child, parental distress, and spouse factors) on the Japanese 19-item version of the Parenting Stress Index Short Form (J-PSI-SF). Exposures were the mode of delivery, the timing of the J-PSI-SF assessment (1.5, 2.5, and 3.5 years postpartum), and the interaction between them. Multivariate regression analysis was used to calculate adjusted β coefficients and standard error of the means (SEMs).

RESULTS

The J-PSI-SF total score was higher in the cesarean section group than in the vaginal delivery group (adjusted β = 0.24, SEM = 0.09). This increase was primarily due to higher scores for the difficult child factor (adjusted β = 0.18, SEM = 0.05) and not to higher scores for the parental distress or spouse factor.

CONCLUSIONS

Cesarean section was associated with higher parenting stress, especially in relation to the difficult child factor. Our results highlight the importance of paying particular attention to the mental health of both mother and child in the case of cesarean section.

Prevalence of infectious diseases in preterm infants: a 2-year follow-up from the Japan Environment and Children's Study

Evidence regarding the long-term risk of infections in preterm infants is lacking. In this study, we examined whether preterm infants developed various common childhood infections more frequently than full-term infants by the age of 2 years by analyzing data from a questionnaire completed by 67,282 mother-toddler pairs in a nationwide birth cohort study. Of the target population, 2885 (4.3%) were born prematurely. After covariate adjustment for maternal and children factors, lower respiratory tract infections appeared more frequent in preterm than in full-term infants at both 1 and 2 years (adjusted odds ratio [aOR] 1.21, 95% confidence interval [CI] 1.05-1.41, and aOR 1.27, 95% CI 1.11-1.46, respectively). However, there was no significant difference in the frequencies of lower respiratory tract infection between preterm and full-term infants after Palivizumab administration. The risk of other common infections, such as in the upper respiratory tract infection, otitis media, urinary tract infection, gastroenteritis, herpangina, hand-foot-and-mouth disease, chickenpox, influenza virus, and adenovirus infections, was not higher in preterm than in full-term infants after covariates adjustment for maternal and children factors. These findings suggest Palivizumab prophylaxis could reduce the frequencies of lower respiratory tract infection in preterm to the same level as in full-term infants.

Provision of educational events and subsequent questionnaire response rates in a large-scale birth cohort study from Japan

OBJECTIVES

We examined whether providing educational events for participants in a birth cohort study would increase the response rates of study questionnaires.

DESIGN

Birth cohort study.

SETTING

Questionnaires were distributed and returned by post twice in 1 year. We developed and implemented two educational sessions; a Baby Food lecture for mothers with children around 8 months old (analysis 1) and a Eurythmic session for mothers with children around 1 year and 8 months old (analysis 2). Mothers with children over the target ages were not invited (not-invited group). The invited participants were divided into three groups: those who did not apply to attend (not-applied group), those who applied but did not attend (applied group), and those who applied and attended (attended group).

PARTICIPANTS

The participants were 5379 mother-child pairs registered with the Toyama Regional Center of the Japan Environment and Children's Study (JECS).

OUTCOME MEASURE

The outcome measure was return of the JECS questionnaire for 1 year old sent out after the Baby Food lecture and the JECS questionnaire for 2 years old sent out after the Eurythmic session. The questionnaires were returned to us by post.

RESULTS

The response rate for the attended group of the Baby Food lecture was 99.7%, and the odds ratio (OR) was significantly higher for this group than for the not-invited group (crude OR 24.54; 95% confidence interval (CI) 3.42 to 176.13; analysis 1). After the exclusion of participants who had previously attended the Baby Food lecture, the response rate for the attended group of the Eurythmic session was 97.8%, and the OR was significantly higher for this group than for the not-invited group (adjusted OR 5.66; 95% CI 1.93 to 16.54; analysis 2).

CONCLUSION

Providing educational events that are appropriate to the age and needs of the participants may increase questionnaire response rates in birth cohort studies.

TRIAL REGISTRATION NUMBER

UMIN 000030786.

Factor structure of the Parenting Stress Index-Short Form used in the Japan Environment and Children's Study

The Parenting Stress Index-Short Form (PSI-SF) has been widely employed to assess parenting stress in a number of research and clinical trials. To date, no parenting stress studies in Japan have examined the factor structure, validity, and reliability of the PSI-SF. Therefore, this study aimed to evaluate the psychometric properties of this 19-item version as administered in a national cohort study, the Japan Environment and Children's Study, to two sample groups of mothers, those with a 1.5-year-old child and those with a 2.5-year-old child (n = 79,282 and 75,831, respectively). We performed exploratory factor analysis to re-examine the appropriate factor structure, confirmatory factor analysis to evaluate goodness of fit, and calculated Cronbach's α and Pearson's r coefficients to evaluate internal consistency and reproducibility over time, respectively. The results highlighted that a three-factor structure fit the instrument better than a two-factor structure, yielding better scores for the model fit indices and the α and r coefficients. In addition, the third factor identified in this study was strongly associated with having a relationship with and help from the husband. The findings suggest the importance of using a parenting stress scale with various factors to evaluate mothers' parenting stress.

Dietary intake of yogurt and cheese in children at age 1 year and sleep duration at age 1 and 3 years: the Japan Environment and Children's Study

Background

We previously reported that 1-year-old infants born to mothers who regularly consumed fermented food during pregnancy had a lower risk of sleep deprivation. However, it is not known if these positive effects are enhanced when infants themselves eat fermented foods or the long-term effects of such consumption. In this study, we examined the association between the frequency of fermented food intake during the child’s weaning period and sleep deprivation at age 1 and 3 years.

Methods

This birth cohort study used data from a nationwide, government-funded study called the Japan Environment and Children’s Study (JECS), covering 65,210 mother-child pairs. We examined the association between infants’ consumption of fermented foods at 1 year of age and sleep deprivation at 1 and 3 years of age.

Results

There was no association between yogurt or cheese intake and sleep duration at age 1; at age 3, there was no group difference, although a trend test showed that yogurt intake at age 1 was significantly associated with sleep duration at age 3. There was also no association between the frequency of cheese intake and inadequate sleep duration at age 3.

Conclusion

Frequency of children’s yogurt and cheese intake at age 1 was not associated with sleep duration at age 1 or 3. However, a trend test showed a significant association between the frequency of yogurt intake at age 1 and sleep duration at age 3.

Association between maternal fermented food consumption and child sleep duration at the age of 3 years: the Japan Environment and Children's Study

Background

Using cohort data from the Japan Environment and Children’s Study (JECS), we previously reported that the risk of sleep deprivation in 1-year-old children was reduced with a higher maternal intake of fermented foods, particularly miso. The present study, which evaluates children from the same cohort at 3 years of age, is a continuation of that work.

Methods

After applying exclusion criteria to 104,062 records in the JECS dataset, we evaluated 64,200 mother-child pairs in which the child was 3 years old. We examined the association of the dietary intake of fermented foods during pregnancy with child sleep duration < 10 h at the age of 3 years.

Results

Multivariable logistic regression analysis with the lowest quartile used as a reference revealed adjusted odds ratios (95% confidence intervals) for the second through fourth quartiles of 0.98 (0.90–1.06), 0.93 (0.85–1.01), and 0.85 (0.78–0.94) for cheese intake.

Conclusions

The consumption of fermented foods during pregnancy is associated with reduced risk of sleep deprivation in 3-year-old children, albeit in a limited way.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12889-022-13805-6.

Predictors of non-response to successive waves of surveys in the Japan Environment and Children's Study during the 3-year postpartum period: a longitudinal cohort study

OBJECTIVES

We examined changes in factors related to non-response to successive waves of the nationwide birth cohort study, the Japan Environment and Children's Study (JECS), during the first 3 years after childbirth.

DESIGN

Longitudinal cohort study.

SETTING

As the baseline survey, mothers completed self-administered questionnaires distributed by hand during pregnancy or 1 month after delivery. The self-administered questionnaires that we used in this study were then distributed by mail every 6 months until the children were 3 years old, for a total of six times.

PARTICIPANTS

Of 103 060 mothers who consented to participate in the JECS during pregnancy, 88 489 mothers were included in the study after excluding those with multiple births, miscarriages or stillbirths and those who withdrew from the study within 3 years after providing informed consent.

PRIMARY AND SECONDARY OUTCOME MEASURES

Data were collected at the baseline survey on participants' socioeconomic status, medical history, health status, health-related behaviours and their children's health conditions and living situations. The strength of the impact of related factors and the prediction of response status were examined and compared using binominal logistic regression analysis.

RESULTS

For all six follow-up questionnaire surveys, higher maternal age was strongly associated with providing a response. Factors that were strongly associated with mothers not providing a response were smoking after childbirth and having more children. The concordance rate of response status based on the presented model was about 70%, suggesting that the response status for the first 3 years after birth can be predicted from the information collected in the baseline survey.

CONCLUSION

By identifying predictors of non-response from information obtained in baseline surveys, researchers may be able to reduce non-response to successive survey waves by issuing reminders, reviewing data collection methods and providing appropriate financial and/or non-financial incentives.

Change in cholesterol level during pregnancy and risk of postpartum depressive symptoms: the Japan Environment and Children's Study (JECS)

OBJECTIVE

Women with postpartum depressive symptoms (PDS) are at higher risk of postpartum depression (PPD) and require further assessment. Emerging evidence indicates a relationship between the total cholesterol (TC) level of blood and PPD but the results are inconsistent. In this study, we investigated the possible association of change in serum TC levels during pregnancy with the risk of PDS in a Japanese population.

METHODS

We analyzed complete data on questionnaire responses and serum lipid profiles of pregnant women from 12 datasets obtained from the Japan Environment and Children's Study (n = 61,585 to n = 72,406; 103,063 pregnancies in total). TC was measured at 3 time points-during early pregnancy, during mid-late pregnancy, and after delivery-and we calculated changes in TC in 3 ways: by subtracting early pregnancy from mid-late pregnancy, subtracting mid-late pregnancy from delivery, and subtracting early pregnancy from delivery. These 6 factors were used as predictors to estimate the risk of PDS at 1 and 6 months after delivery.

RESULTS

In multivariable logistic regression analysis, point serum cholesterol level did not predict PDS at any time point except for during mid-late pregnancy in the second quintile, indicating an increased risk at 6 months. As for change in TC levels, subtracting mid-late pregnancy from delivery and early pregnancy from delivery showed significant risk reduction for PDS at 1 month. A significant risk reduction was also found for subtracting early pregnancy from mid-late pregnancy and early pregnancy from delivery at 6 months.

CONCLUSIONS

Increased cholesterol level during pregnancy is associated with reduced risk of PDS.

Causal model of the association of social support during pregnancy with a perinatal and postpartum depressive state: A nationwide birth cohort - the Japan Environment and Children's Study

BACKGROUND

Despite many epidemiological studies on the relationship between social support during pregnancy and perinatal/postpartum depression, its impact remains unclear. Therefore, this study examined this association using a causal model of risk based on various levels of social support.

METHODS

Participants were 88,711 mothers in an ongoing nationwide birth cohort study in Japan. Social support during pregnancy was set at four treatment levels. Depressive state was identified twice, with the Kessler Psychological Distress Scale (K6; score ≥ 5) and the Edinburgh Postnatal Depression Scale (EPDS; score ≥ 9). With the highest level of social support set as reference, marginal structural models were fitted to derive counterfactual risk ratios (cRRs).

RESULTS

cRRs (95% CIs) for EPDS cases increased as the level of social support decreased, with values of 1.06 (0.99-1.13) for upper-middle, 1.30 (1.23-1.39) for lower-middle, and 1.61 (1.52-1.71) for low. Also, cRRs (95% CIs) at the second measurement (interaction) tended to increase as social support decreased, with values of 1.05 (0.97-1.13) for upper-middle, 1.05 (0.98-1.13) for lower-middle, and 1.10 (1.03-1.18) for low. The same tendency was observed in K6 cases.

LIMITATION

Depressive state was identified by self-administered questionnaire.

CONCLUSIONS

Lower social support during pregnancy is associated with increased counterfactual risk of perinatal/postpartum depressive state and worsened counterfactual spontaneous recovery over time. These findings highlight the importance of sufficient social support for preventing perinatal/postpartum depression and promoting recovery.

TRIAL REGISTRATION

UMIN000030786.

Is GLP-1 insufficiency a coronary risk factor? A multicenter observational study, BOREAS-CAD2

Background and aim

Glucagon-like peptide-1 (GLP-1) regulates insulin secretion and also affords pleiotropic effects including protective effects on blood vessels. Multiple factors regulate GLP-1 secretion after meals, but a group of apparently healthy subjects showed blunted responses of GLP-1 secretion in our previous study. In this study, we examined the possibility that the reduced capacity of GLP-1 secretion is associated with increased extent of coronary artery stenosis in non-diabetic patients.

Methods and results

Non-diabetic patients who were admitted for coronary angiography without a history of coronary interventions were enrolled. Coronary artery stenosis was quantified by Gensini score (GS), and GS ≥10 was used as an outcome variable based on results of earlier studies indicating its predictive value for cardiovascular events. The patients (mean age, 66.5±8.8 years; 71% males, n=173) underwent oral 75 g-glucose tolerant tests for determination of glucose, insulin and active GLP-1 levels. The area under the curve of plasma active GLP-1 (AUC-GLP-1) was determined as an index of GLP-1 secretion capacity. AUC-GLP-1 was not correlated with fasting glucose, AUC-glucose, serum lipids, indices of insulin sensitivity or estimated glomerular filtration rate. In multivariate logistic regression analysis for GS ≥10, AUC-GLP-1 &lt; median, age and hypertension were selected as explanatory variables, though fasting GLP-1 level was not selected.

Conclusion

The findings indicate significant association of reduced GLP-1 secretion capacity with increased extent of coronary artery stenosis in non-diabetic patients. A causal relationship between change in GLP-1 secretion capacity and coronary stenosis remains to be examined by a longitudinal study

Funding Acknowledgement

Type of funding sources: Private company. Main funding source(s): This study was supported in part by a research grant from Investigator-Initiated Studies Program of Merck Sharp & Dohme Corp./MSD K.K.

Maternal exposure to smoking and infant's wheeze and asthma: Japan Environment and Children's Study

BACKGROUND

Evidence regarding independent effects of maternal smoking in different time frames of pregnancy and maternal exposure to secondhand smoke on the development of wheeze/asthma in her offspring is limited. We aimed to investigate the effect of maternal exposure to tobacco smoke on wheeze/asthma development at 1 year of age in her offspring using data from the nationwide birth cohort study in Japan.

METHODS

Pregnant women who lived in the 15 designated regional centers throughout Japan were recruited. We obtained information about maternal smoking or secondhand smoke status and wheeze/asthma development in the offspring from a self-administered questionnaire.

RESULTS

We analyzed 90,210 singleton births. Current maternal smoking during pregnancy increased the risks of wheeze/asthma in the offspring compared with no maternal smoking (wheeze: 1-10 cigarettes/day: adjusted odds ratio (aOR) 1.436, 95% CI 1.270-1.624; ≧11 cigarettes/day: aOR 1.669, 95% CI 1.341-2.078; asthma: 1-10 cigarettes/day: aOR 1.389, 95% CI 1.087-1.774; ≧11 cigarettes/day: aOR 1.565, 95% CI 1.045-2.344). Daily maternal exposure to secondhand smoke during pregnancy also increased the risks of wheeze/asthma in her offspring compared with no secondhand smoke exposure (wheeze: aOR 1.166, 95% CI 1.083-1.256; asthma: aOR 1.258, 95% CI 1.075-1.473). The combination of current maternal smoking during pregnancy and maternal history of allergy increased the risks of wheeze/asthma in her offspring (wheeze: aOR 2.007, 95% CI 1.739-2.317; asthma: aOR 1.995, 95% CI 1.528-2.605).

CONCLUSIONS

We found that current maternal smoking and maternal secondhand smoke exposure during pregnancy increased the risks of wheeze and asthma in her offspring.

Prospective association of air purifier use during pregnancy with the neurodevelopment of toddlers in the Japan Environment and Children's Study

We examined the association between maternal air purifier use during pregnancy and neurodevelopmental delay in toddlers by analysing data from 82,457 mother-toddler pairs. Air purifier use was measured using a simple yes/no question. Developmental delays at 1.5, 2.0, 2.5, and 3.0 years were assessed using the Ages and Stages Questionnaire, Third Edition. Generalized additive mixed model analysis with 21 covariates revealed that air purifier use was associated with lower prevalence of developmental delay in all five areas—communication, gross motor, fine motor, problem solving, and personal-social—at all four time points (adjusted risk ratios ranged from 0.827 to 0.927, and only one 95% confidence interval crossed the reference). These findings suggest a negative association between air purifier use during pregnancy and neurodevelopmental delay in toddlers.

Trial registration: UMIN000030786 (15/01/2018).

Association of cesarean birth with prevalence of functional constipation in toddlers at 3 years of age: results from the Japan Environment and Children's Study (JECS)

BACKGROUND

The association between delivery mode and subsequent development of diseases is a growing area of research. Cesarean delivery affects the diversity of the microbiota in the infant gut, which may be associated with gastrointestinal disorders, including functional constipation, in infants. In this study, we investigated the association between delivery mode and prevalence of functional constipation in 3-year-old Japanese toddlers.

METHODS

This study used data from the Japan Environment and Children's Study, an ongoing nationwide birth cohort study. We analyzed 71,878 toddler-mother pairs. The presence of functional constipation was determined according to the Rome III diagnostic criteria. Odds ratios and 95% confidence intervals were calculated using logistic regression analysis.

RESULTS

The prevalence of functional constipation in 3-year-old Japanese toddlers was estimated to be 12.3%. Logistic regression analysis revealed that the prevalence of functional constipation was higher in toddlers born by cesarean delivery (13.1%) compared with those born by vaginal delivery (12.1%), independent of 22 confounders (adjusted odds ratios = 1.064, 95% confidence interval = 1.004-1.128).

CONCLUSIONS

We determined the prevalence of functional constipation in 3-year-old Japanese toddlers and found that delivery mode was associated with the prevalence of functional constipation in Japanese toddlers.

Association between mothers' fish intake during pregnancy and infants' sleep duration: a nationwide longitudinal study-The Japan Environment and Children's Study (JECS)

Purpose

N-3 polyunsaturated fatty acids (n-3 PUFAs), which are an important nutrient for humans, are particularly essential to the growth and development of the central nervous system (CNS) in fetuses and infants. Consequently, sufficient n-3 PUFA intake by mothers during pregnancy is considered to contribute to CNS development in their infants. CNS development is known to be associated with sleep, but no large epidemiological studies have yet confirmed that n-3 PUFA intake during pregnancy is associated with infants’ sleep.

Methods

After exclusion and multiple imputation from a dataset comprising 104 065 records from the Japan Environment and Children’s Study (JECS), we examined 87 337 mother–child pairs for the association between mothers’ fish and n-3 PUFA intakes and risk of their infants sleeping less than 11 h at 1 year of age.

Results

Multiple logistic regression analysis with the lowest quintile used as a reference revealed odds ratios for the second through fifth quintiles of 0.81 (95% confidence interval [95% CI] 0.76–0.87), 0.81 (95% CI 0.76–0.87), 0.78 (95% CI 0.72–0.84), and 0.82 (95% CI 0.76–0.88) for fish intake (p for trend < 0.001) and 0.90 (95% CI 0.84–0.97), 0.88 (95% CI 0.81–0.94), 0.88 (95% CI 0.82–0.95), and 0.93 (95% CI 0.86–0.998) for n-3 PUFA intake (p for trend = 0.04).

Conclusions

Low fish intake during pregnancy may increase the risk of infants sleeping less than 11 h at 1 year of age. This relationship may have been mediated by maternal n-3 PUFA intake and infant neurodevelopment, but further evidence from interventional and other studies is needed to determine the appropriate level of fish intake during pregnancy.

Trial registration

The Japan Environment and Children’s Study, https://upload.umin.ac.jp/cgi-open-bin/ctr_e/ctr_view.cgi?recptno=R000035091 (Registration no. UMIN000030786).

Supplementary Information

The online version contains supplementary material available at 10.1007/s00394-021-02671-4.

Association between maternal smoking history and congenital anomalies in children: Results from the Japan Environment and Children's Study

We investigated the relationship between maternal smoking history and congenital anomalies in children. Drawing on data from the Japan Environment and Children's Study collected between January 2011 and March 2014, the smoking habits of pregnant women were categorized as "never smoked," "quit before pregnancy, "quit after pregnancy," and "full smoking." Of the 91 626 participants examined, a total of 2199 (2.4%) infants were born with any congenital anomalies. Logistic regression analysis was used to determine the odds ratio for congenital anomalies in each group based on maternal smoking history. No significant difference was seen between the full-smoking and never smoked groups in the odds ratios for congenital anomalies of the nervous system; the eyes, ears, face, and neck; the cardiovascular system; or the musculoskeletal system. However, in the full-smoking group, the odds ratios for trisomy (adjusted odds ratio, 2.14; 95% confidence interval, 1.15-3.97) and any congenital anomalies (adjusted odds ratio, 1.35; 95% confidence interval, 1.09-1.67) were significantly higher compared with the never smoked group. Our results indicate that continuing to smoke during pregnancy is associated with increased risk of trisomy and any congenital anomalies in the general Japanese population.

Effect estimate of time-varying social support and trust on the physical and mental health of mothers at 2.5 years postpartum: The Japan Environment and Children's Study (JECS)

BACKGROUND

Many epidemiological studies have reported the association between various social factors and health status in mothers during and after pregnancy. However, little is known about their joint and longitudinal impact. We therefore examined the association of lack of social support and trust during pregnancy and at 2.5 years postpartum with health status in mothers.

METHODS

To adequately address time-varying exposure, marginal structural models were fitted to a pseudopopulation constructed by inverse probability weighting. The model included records of 90,071 mothers participating in the Japan Environment and Children's Study. Social support and trust were measured using a 9-item questionnaire (Q1-9). Mental and physical health were measured using Mental and Physical Component Summary scores from the 8-item Short-Form Health Survey.

RESULTS

For the Mental Component Summary, the magnitude of the effect estimate was largest when participants lacked close friends/neighbors (Q4) at only 2.5 years postpartum (= -6.23), followed by a lack in emotional support (Q2) at the same time point (= -4.94). For the Physical Component Summary, effect estimates were negligible. The magnitude of the effect estimates of lack of social support and trust tended to be larger when there was a lack at only 2.5 years postpartum than at both time points.

CONCLUSIONS

These findings suggest that, after childbirth, a loss in social support, particularly in a concrete or instrumental aspect, carries high risk, especially for mental health. Our results highlight the importance of supporting mothers for more than a few years after pregnancy.

Association of the incidence of atopic dermatitis until 3 years old with birth month and with sunshine duration and humidity in the first 6 months of life: Japan Environment and Children's Study

OBJECTIVE

To compare the incidence of atopic dermatitis in children aged from 6 months to 3 years across birth seasons and climate conditions.

DESIGN

Cohort study.

SETTING

Fifteen regional centres across Japan.

PARTICIPANTS

A total of 100 304 children born from 2011 to 2014.

EXPOSURE

Birth month, and mean sunshine duration (short/long) and humidity (high/low) in the first 6 months of life.

PRIMARY OUTCOME MEASURE

Incidence of atopic dermatitis.

RESULTS

The highest incidence of atopic dermatitis was in children born in the months of October to December. The lowest incidence of atopic dermatitis was in the months of April to June and in periods with a long duration of sunshine and high humidity. Low humidity was significantly associated with a higher incidence of atopic dermatitis. However, this significant difference disappeared when the birth season and parental history of allergic disease were considered in multivariate analysis.

CONCLUSIONS

In Japan, being born in the late autumn to early winter months is associated with a risk of developing atopic dermatitis until the age of 3 years. Sunshine duration and humidity from birth to 6 months of age are not associated with the incidence of atopic dermatitis.

Paternal childcare at 6 months and risk of maternal psychological distress at 1 year after delivery: The Japan Environment and Children's Study (JECS)

Background

Paternal childcare is reported to benefit maternal mental health, but specific childcare behaviors have not been comprehensively determined. This study sought to identify paternal childcare behaviors associated with maternal mental health by adjusting for other covariates associated with maternal mental health and examining childcare behaviors.

Methods

This study investigated whether seven types of paternal childcare behaviors at 6 months after delivery were associated with maternal psychological distress at 1 year after delivery, which was assessed using the Kessler Psychological Distress Scale (K6). After exclusions from a dataset of 103,062 pregnancies obtained in the Japan Environment and Children’s Study, we evaluated data from 75,607 mothers.

Results

More than 70% of fathers were always or sometimes involved in “playing at home,” “playing outdoors,” “changing diapers,” and “bathing,” 60%–70% in “helping with feeding” and “dressing,” and 45.9% in “putting the child to bed.” All paternal childcare behaviors showed some beneficial association with less maternal psychological distress, both moderate (K6 score 5–12) and severe (K6 score ≥ 13) distress. Playing at home was the most beneficial association identified (adjusted odds ratio [aOR] 0.66, 95% confidence interval [CI] 0.56–0.76 for moderate psychological distress; aOR 0.36, 95% CI 0.28–0.48 for severe psychological distress).

Conclusions

These seven types of paternal childcare behaviors may help lessen maternal psychological distress. Emphasis should be given to building education systems and working environments that promote paternal childcare.

Influence of infants' feeding patterns and duration on mothers' postpartum depression: A nationwide birth cohort -The Japan Environment and Children's Study (JECS)

BACKGROUND

Breastfeeding is increasingly being promoted worldwide. Although several studies have examined breastfeeding and postpartum depression, contradictory results concerning their relationship have been found. This study investigated the influence of the feeding patterns of 1- to 6-month-old infants on maternal postpartum depression, as well as the influence of activities performed by mothers during feeding on postpartum depression.

METHODS

We used data from parents and children who participated in the Japan Environment and Children's Study (JECS). The data were from 71,448 mothers who did not show depressive symptoms at 1 month postpartum.

RESULTS

The group that continued exclusive breastfeeding for 6 months postpartum had a lower risk of postpartum depression compared with those who adopted other feeding patterns. Regardless of the pattern or duration of feeding, the group that maintained eye contact or talked to their baby during feeding had a lower risk of postpartum depression compared with the group that performed other activities. Furthermore, the group that continued both exclusive breastfeeding for 6 months and maintained eye contact or talked to their babies during feeding had an odds ratio of 0.69 for postpartum depression (95% confidence interval: 0.61-0.79), the lowest of any group.

LIMITATIONS

All variables were measured using a self-administered questionnaire.

CONCLUSIONS

It may be possible to control the onset of postpartum depression by recommending breastfeeding to new mothers, providing them with appropriate information on how to interact with their babies, and offering them support.

TRIAL REGISTRATION

UMIN000030786.

Factors influencing exclusive breastfeeding rates until 6 months postpartum: the Japan Environment and Children's Study

This research aimed to examine the efficacy of the early initiation of breastfeeding within 1 h of birth, early skin-to-skin contact, and rooming-in for the continuation of exclusive breastfeeding until 6 months postpartum. The research used data from the Japan Environment and Children's Study (JECS), a nationwide government-funded birth cohort study. A total of 80,491 mothers in Japan between January 2011 and March 2014 who succeeded or failed to exclusively breastfeed to 6 months were surveyed in JECS. Multiple logistic regression model was used to analyse the data. The percentage of mothers who succeeded in exclusively breastfeeding to 6 months is 37.4%. Adjusted odds ratios were analysed for all 35 variables. Early initiation of breastfeeding (adjusted odds ratio [AOR]: 1.455 [1.401-1.512]), early skin-to-skin contact (AOR: 1.233 [1.165-1.304]), and rooming-in (AOR: 1.567 [1.454-1.690]) affected continuation of exclusive breastfeeding. Regional social capital (AOR: 1.133 [1.061-1.210]) was also discovered to support the continuation of breastfeeding. In contrast, the most influential inhibiting factors were starting childcare (AOR: 0.126 [0.113-0.141]), smoking during pregnancy (AOR: 0.557 [0.496-0.627]), and obese body type during early pregnancy (AOR: 0.667 [0.627-0.710]).

Association of blood cadmium levels in pregnant women with infant birth size and small for gestational age infants: The Japan Environment and Children's study

BACKGROUND

There is growing evidence of an association between cadmium (Cd) and unfavorable birth outcomes. The effect of Cd exposure on anthropometric measures at birth or small for gestational age (SGA) infants in a large, nationwide Japanese cohort remains to be clarified.

OBJECTIVES

To analyze the association between maternal blood Cd levels at different sampling times and sex-dependent infant birth size, weight, body length, chest, and head circumferences, in addition to SGA.

METHODS

Data of 17,584 pregnant women in the Japan Environment and Children's Study were analyzed for anthropometric measurements. For SGA determination, 13,969 cases of vaginal delivery were analyzed after excluding infants born by cesarean section. Maternal blood Cd levels were categorized into quartiles (Q1-Q4), and the Q1 was used as a reference. Multiple linear regression analysis was performed for anthropometric measurements, and multiple logistic regression analysis was used to investigate the association of maternal blood Cd levels with the risk of SGA.

RESULTS

Birth weight tended to decrease according to the increase in quartiles of blood Cd levels (15.63 g decrease [95% confidence level (CI): -33.26, 2.01] for Q4). The overall analysis revealed no decreases in body length and head and chest circumference, but subgroup analysis revealed that chest circumference tended to decrease according to the increase in quartiles in the female sex/third-trimester stratification (0.16 cm decrease [95% CI: -0.32, 0.00] for Q4). SGA risk was also higher and paralleled the increase in blood Cd levels associated with the female sex/third-trimester group (Odds Ratio 1.90 [95% CI: 1.23, 2.94] for Q4).

CONCLUSION

Our results provide further evidence of sex-specific health risks associated with Cd exposure in early life in a large Japanese pregnancy cohort.

Dietary intake of fish and n-3 polyunsaturated fatty acids and risk of postpartum depression: a nationwide longitudinal study - the Japan Environment and Children's Study (JECS)

BACKGROUND

Pregnant women require increased levels of n-3 polyunsaturated fatty acids (PUFAs) due to the demands of the growing fetus. Although some evidence indicates that maternal intake of fish and n-3 PUFAs is associated with reduced risk of postpartum depression, the results are inconsistent.

METHODS

We investigated whether dietary consumption of fish and/or n-3 PUFAs during pregnancy is associated with a reduced risk of maternal postpartum depression at 6 months after delivery and of serious mental illness at 1 year in a Japanese population. After exclusion and multiple imputation from a dataset comprising 103 062 pregnancies obtained in the Japan Environment and Children's Study, we evaluated 84 181 and 81 924 women at 6 months and 1 year after delivery, respectively.

RESULTS

Multivariable logistic regression showed a reduced risk of postpartum depression at 6 months in the second to fifth quintiles v. the lowest quintile for fish and n-3 PUFA intake, with trend tests also revealing a significant linear association. At 1 year after delivery, fish intake was associated with a reduced risk of serious mental illness in the second to fifth quintiles v. the lowest quintile for fish and in the third to fifth quintiles v. the lowest quintile for n-3 PUFA intake, with trend tests also revealing a significant linear association.

CONCLUSIONS

Women with higher fish and/or n-3 PUFA intake showed reduced risk of postpartum depression at 6 months after delivery and of serious mental illness at 1 year after delivery.

Maternal dietary intake of fish and PUFAs and child neurodevelopment at 6 months and 1 year of age: a nationwide birth cohort-the Japan Environment and Children's Study (JECS)

BACKGROUND

Although emerging evidence indicates a relation between maternal intake of fish and improved child neurodevelopment, the results are inconsistent.

OBJECTIVES

This study investigated whether dietary consumption of fish during pregnancy is associated with offspring neurodevelopment at age 6 mo and 1 y. As exploratory research, we also examined the association between consumption of PUFAs and neurodevelopment at the same time points.

METHODS

After exclusion and multiple imputation from a dataset comprising 104,065 records from the Japan Environment and Children's Study, we evaluated 81,697 and 77,751 mother-child pairs at age 6 mo and 1 y, respectively.

RESULTS

Maternal fish intake during pregnancy was independently associated with reduced risk of delay in problem-solving at age 6 mo (lowest compared with highest quintile OR = 0.88; 95% CI: 0.79, 0.99; P-trend = 0.01) and in fine motor skills (highest quintile OR = 0.90; 95% CI: 0.81, 0.99; P-trend = 0.02) and problem-solving (fourth quintile OR = 0.89; 95% CI: 0.81, 0.98; and highest quintile OR = 0.90; 95% CI: 0.81, 0.99; P-trend = 0.005) at age 1 y. Dietary intake of total n-3 PUFAs was associated with reduced risk of delay in fine motor skills at 6 mo, and in fine motor skills and problem-solving at 1 y. Dietary intake of total n-6 PUFAs was associated with reduced risk of delay in communication and fine motor skills at 6 mo, and in gross motor skills, fine motor skills, and problem-solving at 1 y. In contrast, the dietary n-6/n-3 ratio was positively associated with increased risk of delay in problem-solving at 1 y.

CONCLUSIONS

The results of this study suggest there might be beneficial effects of fish intake during pregnancy on some domains of child psychomotor development and this effect might be partially explained by PUFA intake from fish. Trial registration: UMIN000030786.

Impact of individual and neighborhood social capital on the physical and mental health of pregnant women: the Japan Environment and Children's Study (JECS)

Background

Previous studies revealed positive, negative, and no influence of social capital on the health outcomes of pregnant women. It was considered that such differences were caused by the disparities of outcome measures and sample sizes between studies. Our chief aim was to verify the positive influence of social capital on the health condition of pregnant women using established health outcome measures and large-scale nationwide survey data.

Methods

We employed questionnaire survey data from 79,210 respondents to the Japan Environment and Children’s Study, and physical and mental component summary scores from the 8-Item Short-Form Health Survey as outcome measures. We estimated the effect of individual and neighborhood social capitals on physical and mental component summary scores. To consider the property that the richness of social capital would be generally determined by individual characteristics, and to estimate the causal influence of social capital on health without bias caused by said property, we adopted average treatment effect estimation with inverse probability weighting. Generally, average treatment effects are based on the difference of average outcomes between treated and untreated groups in an intervention. In this research, we reckoned individuals’ different levels of social capital as a kind of non-randomized treatment for respective individuals, and we applied average treatment effect estimation. The analysis regarded pregnant women with the lowest level of social capital as untreated samples and women with other levels of social capitals as treated samples.

Results

For mental component summary score, the maximum average treatment effects in the comparison between the lowest and highest levels of social capital were approximately 4.4 and 1.6 for individual and neighborhood social capital, respectively. The average treatment effects for the physical component summary score were negligible for both social capital types.

Conclusions

Social capital particularly contributes to improving mental component summary score in pregnant women. The likelihood of a mentally healthy pregnancy may be increased by enhancing social capital.

Dietary patterns during pregnancy and health-related quality of life: The Japan Environment and Children's Study

Background

Limited research exists on how dietary pattern (DP) influences pregnant women’s health-related quality of life (HRQOL). This study aimed to identify DPs in a cohort of 92,448 pregnant Japanese women using fixed data from the Japan Environment and Children’s Study (JECS) to investigate the associations of DP with HRQOL.

Methods

During the first trimester, DPs were assessed using the Food Frequency Questionnaire (FFQ), and HRQOL was assessed using the 8-Item Short-Form Health Survey (SF-8). DPs such as Western, Japanese and Unbalanced DP were identified through principal component analysis (PCA). Multivariable logistic model analysis was used to assess the associations between DP and HRQOL as good or poor.

Results

We found a significant association between poor mental HRQOL in the univariate analysis for the Western DP (p = 0.014). However, this association was not significant in the multivariate analysis adjusted for basic confounders (p = 0.078). Western DP was not highly associated with poor physical HRQOL (from low-medium to high levels of intake; adjusted odds ratio [OR] 0.87–0.88, all p≤0.001, when comparing highest to lowest intake levels). A high intake of the Japanese DP was significantly associated with poor mental HRQOL and physical HRQOL (adjusted OR 1.20, p<0.0001 and adjusted OR 1.12, p = 0.005, respectively). A medium-high intake of the Unbalanced DP was not highly associated with poor physical HRQOL (adjusted OR 0.93, p = 0.048) but with poor mental HRQOL (adjusted OR 1.29, p<0.0001).

Conclusion

This is the first known prospective study to establish an association between DP and HRQOL in pregnant women. We hope that our findings will help in the field of nutritional science.

Factor structure of the Edinburgh Postnatal Depression Scale in the Japan Environment and Children's Study

The Edinburgh Postnatal Depression Scale (EPDS) is frequently used to screen for postpartum depression. However, its factor structure exhibits noticeable inconsistencies between studies. We examined the EPDS at two postpartum time points using a large dataset from outside Western countries. Participants were 91,063 mothers in an ongoing birth cohort of the Japan Environment and Children's Study. One-, two-, and three-factor structures of the EPDS at 1- and 6-months postpartum were extracted using exploratory factor analysis (EFA) with oblique rotation. Goodness-of-fit indices of extracted factor structures were compared with prior ones by conducting a confirmatory factor analysis (CFA). CFA revealed that a three-factor model extracted from the current EFA-anxiety (items 3, 4, 5, and 6), depression (items 7, 9, and 10), and anhedonia (items 1 and 2)-showed acceptably high goodness-of-fit and invariability across time. These three factors explained about 65% of the total variance with good reliability (all Cronbach's αs ≥ 0.70). Most three-factor structures (vs. two-) showed higher goodness-of-fit indices. In conclusion, although we only examined the postpartum period, the EPDS likely comprises three dimensions: anxiety, depression, and anhedonia. Our findings raise questions about the one- or two-factor structure of the EPDS.Trial registration: UMIN000030786.

Prospective Association of Air-Purifier Usage during Pregnancy with Infant Neurodevelopment: A Nationwide Longitudinal Study-Japan Environment and Children's Study (JECS)

Fetal exposure to particulate matter (PM) is associated with infant developmental delay likely via neuroinflammation and prefrontal cortex lesions; however, whether air-purifier usage, which can reduce indoor PM levels, is related to infant developmental delay remains unknown. We therefore examined the prospective relationship between air-purifier usage during pregnancy and infant developmental delay by analyzing 82,441 mother-infant pairs using a simple yes/no questionnaire. Developmental delays at 6 and 12 months were assessed in five areas using the Ages and Stages Questionnaire, Third Edition. A generalized linear mixed model analysis was used to derive adjusted odds ratios (AORs) and 95% confidence intervals (95% CIs) while controlling for 20 covariates. The analysis revealed that air-purifier usage was associated with developmental delays in fine motor (AOR: 0.91, 95% CI: 0.83-0.99) and problem solving (AOR: 0.83, 95% CI: 0.77-0.90) at 6 months and in communication (AOR: 0.86, 95% CI: 0.79-0.93), fine motor (AOR: 0.87, 95% CI: 0.82-0.92), problem solving (AOR: 0.83, 95% CI: 0.77-0.88), and personal-social (AOR: 0.79, 95% CI: 0.72-0.86) at 12 months. In conclusion, a negative association exists between air-purifier usage during pregnancy and infant neurodevelopmental delay that strengthens with time. Our results outline the potential role of air purifiers in inhibiting infant neurodevelopmental delay.

The impact of exposure to desert dust on infants' symptoms and countermeasures to reduce the effects

BACKGROUND

The association between particulate matter (PM), including desert dust, and allergic symptoms has not been well studied. We examined whether PM exacerbated nose/eye/respiratory symptoms in infants, with a focus on the desert dust element, and assessed possible countermeasures.

METHODS

We conducted a panel study of 1492 infants from October 2014 to July 2016 in 3 regions in Japan as an adjunct study of the Japan Environment and Children's Study. Infants' daily symptom scores and behaviors were acquired by web-based questionnaires sent to mothers, who answered within a day using mobile phones. Odds ratios (OR) for symptom development per increased fine PM or desert dust exposure were estimated. Regular use of medications and behaviors on the day of exposure were investigated as possible effect modifiers.

RESULTS

Infants developed nose/eye/respiratory symptoms significantly more often in accordance with fine particulate levels (adjusted OR per 10 µg/m³ increase: 1.04, 95% confidence interval [CI]: 1.01-1.07). A model including both fine particulates and desert dust showed reduced OR for fine particulates and robust OR for desert dust (adjusted OR per 0.1/km increase: 1.16, 95% CI: 1.09-1.23). An increased OR was observed both in infants who had previously wheezed and in those who had never wheezed. Receiving information on the particulate forecast, reducing time outdoors, closing windows, and regular use of leukotriene receptor antagonists were significant effect modifiers.

CONCLUSIONS

Transborder desert dust arrival increased the risk of nose/eye/respiratory symptoms development in infants. Regular use of leukotriene receptor antagonists and other countermeasures reduced the risk.

Association of prenatal psychological distress and postpartum depression with varying physical activity intensity: Japan Environment and Children's Study (JECS)

Evidence is mixed on the associations between physical activity during pregnancy and perinatal depression, and it is limited for different physical activity intensities. Data for 92,743 pregnant women from the Japan Environment and Children’s Study were analyzed in this study. Psychological distress during pregnancy was assessed as moderate or severe using the Kessler Psychological Distress Scale (K6 5–12 and ≥13, respectively). Postpartum depression was assessed using the Edinburgh Postpartum Depression Scale (EPDS; cut-off score 9). Women with only light physical activity had significantly lower odds of psychological distress during pregnancy than those with no physical activity (K6 5–12: adjusted odds ratio [AOR] 0.86, 95% confidence interval [95%CI] 0.82, 0.90; K6 ≥ 13: AOR 0.64, 95%CI 0.58, 0.72). Women with a combination of light, moderate and vigorous physical activity had significantly higher odds of psychological distress during pregnancy (K6 5–12: AOR 1.32, 95%CI 1.18, 1.48; K6 ≥ 13: AOR 1.45, 95%CI 1.16, 1.81) and depression after childbirth (EPDS ≥ 9: AOR 1.42, 95%CI 1.24, 1.61). Physical activity intensity should be considered when assessing psychological distress risk during pregnancy and depression risk after delivery. Future research should evaluate specific physical activity programs with optimal intensity for pregnant women to prevent and treat their psychological distress and depression.

Author Correction: Roles of GalNAc-disialyl Lactotetraosyl Antigens in Renal Cancer Cells

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Long-term follow-up of the randomized trial of mesorectal excision with or without lateral lymph node dissection in rectal cancer (JCOG0212)

BACKGROUND

Japan Clinical Oncology Group (JCOG) 0212 (ClinicalTrials.gov NCT00190541) was a non-inferiority phase III trial of patients with clinical stage II-III rectal cancer without lateral pelvic lymph node enlargement. The trial compared mesorectal excision (ME) with ME and lateral lymph node dissection (LLND), with a primary endpoint of recurrence-free survival (RFS). The planned primary analysis at 5 years failed to confirm the non-inferiority of ME alone compared with ME and LLND. The present study aimed to compare ME alone and ME with LLND using long-term follow-up data from JCOG0212.

METHODS

Patients with clinical stage II-III rectal cancer below the peritoneal reflection and no lateral pelvic lymph node enlargement were included in this study. After surgeons confirmed R0 resection by ME, patients were randomized to receive ME alone or ME with LLND. The primary endpoint was RFS.

RESULTS

A total of 701 patients from 33 institutions were assigned to ME with LLND (351) or ME alone (350) between June 2003 and August 2010. The 7-year RFS rate was 71.1 per cent for ME with LLND and 70·7 per cent for ME alone (hazard ratio (HR) 1·09, 95 per cent c.i. 0·84 to 1·42; non-inferiority P = 0·064). Subgroup analysis showed improved RFS among patients with clinical stage III disease who underwent ME with LLND compared with ME alone (HR 1·49, 1·02 to 2·17).

CONCLUSION

Long-term follow-up data did not support the non-inferiority of ME alone compared with ME and LLND. ME with LLND is recommended for patients with clinical stage III disease, whereas LLND could be omitted in those with clinical stage II tumours.

Influence of parity and mode of delivery on mother-infant bonding: The Japan Environment and Children's Study

BACKGROUND

Although there has been an increase in reports regarding the association between perinatal risk factors and mother-infant bonding, the results have been inconsistent.

METHODS

This is an ongoing cohort designed study to measure the effect of environmental factors on children's health with the use of data from the Japan Environment and Children's Study. We investigated mother-infant bonding at 1 year old according to parity and mode of delivery.

RESULTS

A total of 82,540 participants, including 36,662 primipara mothers and 45,878 multipara mothers, were analyzed in the present study. Exclusive breastfeeding, marriage, and non-working factors were higher in multipara mothers than in primipara mothers. The total Mother-to-Infant Bonding Scale Japanese version (MIBS-J) score was higher (worse) in primipara than multipara (mean total: 1.129 vs. 0.897, p < 0.001). Primipara mothers also had higher anger and rejection scores than multipara mothers. When we analyzed only multipara mothers without any history of previous Cesarean section (CS), MIBS-J scores were higher in Cesarean delivery mothers than vaginal delivery mothers (p = 0.038).

LIMITATIONS

We used a self-reported bonding measure. Although a self-report measure is convenient and important, an observer rating may be less susceptible to bias in perception. We did not distinguish elective CS from emergency CS, which may have different influences on mother-infant bonding.

CONCLUSIONS

Primipara mothers showed worse mother-infant bonding than multipara mothers, regardless of mode of delivery. Caesarian delivery itself appears to have little effect on mother-infant bonding.

Understanding the relationship between postpartum depression one month and six months after delivery and mother-infant bonding failure one-year after birth: results from the Japan Environment and Children's study (JECS)

BACKGROUND

Postpartum depression is a major mental health issue. It not only adversely affects the mother's quality of life, but also mother-infant bonding. However, the relationship between postpartum depression (at multiple points after childbirth) and mother-infant bonding failure one year after birth is not well understood. This study investigates the relationship between postpartum depression at 1-month and 6-month after birth and mother-infant bonding failure at 1 year after birth with a large cohort.

METHODS

Data from 83 109 mothers from the Japan Environment and Children's Study were analyzed. Mother-infant bonding 1-year after delivery was assessed using the Mother-to-Infant Bonding Scale Japanese version (MIBS-J). Postpartum depression was measured using the Edinburgh Postnatal Depression Scale (EPDS) at 1-month and 6-month after delivery. Twenty covariates during pregnancy and one month after delivery were controlled for deriving the odds ratios (ORs) describing postpartum depression to mother-infant bonding.

RESULTS

EPDS Total Score crude ORs and adjusted ORs against the MIBS-J Total Score at 1-month and 6-month after delivery were calculated. Crude ORs were 1.111 (95% CI 1.110-1.112) and 1.122 (95% CI 1.121-1.124) respectively. In the fully adjusted model, ORs were 1.088 (95% CI 1.086-1.089) and 1.085 (95% CI 1.083-1.087), respectively.

CONCLUSIONS

This study demonstrated prospectively, in a large-scale cohort, that depression at multiple postpartum points, including associations with each EPDS and MIBS-J factors, may be a robust predictor of mother-infant bonding failure 1-year after birth.

Education level and risk of postpartum depression: results from the Japan Environment and Children's Study (JECS)

BACKGROUND

Lower socioeconomic status is often thought to be associated with an elevated risk of postpartum depression; however, this relationship exhibits noticeable heterogeneity between studies. The present study examined this relationship in Japan.

METHODS

Data were obtained from 90,194 mothers in an ongoing birth cohort of the Japan Environment and Children's Study. Socioeconomic status was assessed based on the mothers' highest education level during pregnancy. Postpartum depression was identified at 1 and 6 months postpartum based on an Edinburgh Postnatal Depression Scale score of ≥9, and analyses were also performed based on the sub-scores for anxiety, depression, and anhedonia symptoms. Logistic and generalized linear regression model analyses were used to calculate odds ratios for postpartum depression according to education level with the highest education group (≥16 years of education) defined as the reference group, while controlling for covariates in a stepwise fashion.

RESULTS

Univariate analysis revealed that a lower education level was associated with a higher prevalence of postpartum depression and related symptoms. Although these relationships weakened in the fully adjusted models, odds ratios for cases and related symptoms remained significant at 1 and 6 months postpartum. Among three symptom dimensions, the relationship was strongest and weakest in the depressive and anxiety symptoms, respectively.

CONCLUSIONS

A lower education level was an independent risk factor for postpartum depression. In view of the low mobility of the education level, this finding suggests the potential importance of collecting information regarding education levels at the earliest opportunity.

Factors of non-responsive or lost-to-follow-up Japanese mothers during the first year post partum following the Japan Environment and Children's Study: a longitudinal cohort study

OBJECTIVES

We examined the factors related to lost-to-follow-up of a birth cohort study during the first year after delivery.

DESIGN

Longitudinal cohort study.

SETTING

Questionnaires were provided by mail. Mothers answered the questionnaires about the children twice: at 6 months and 1 year.

PARTICIPANTS

Of 103 062 pregnancies who consented to participate in the Japan Environment and Children's Study (JECS), 93 417 mothers were included in the study after excluding those with multiple births, miscarriages or stillbirths and those who withdrew from the study within 1 year after providing informed consent.

PRIMARY AND SECONDARY OUTCOME MEASURES

Participants' socioeconomic status, medical history, health status, health-related behaviours, their children's health conditions and living situations were collected by self-administered questionnaires during pregnancy or 1 month after delivery as the baseline survey. In addition, two self-administered questionnaires were distributed 6 months and 1 year after delivery. Using the response status of the two questionnaires after delivery, participants' follow-up status was divided into four groups. The related factors were examined using logistic regression analysis.

RESULTS

Factors positively correlated with lost-to-follow-up to the questionnaires were postpartum physical conditions, psychological distress during pregnancy, the child's health status at birth, the child's primary caregiver and the number of siblings of the child. Partners' active participation in JECS was associated with a lower lost-to-follow-up rate to the two questionnaires, whereas inactive participation was positively associated with a higher lost-to-follow-up rate.

CONCLUSION

The response rate to the questionnaires seems to be related to the interest and understanding of participants' partners. In addition, the response rates are related to participants' physical conditions and living conditions. To decrease lost-to-follow-up rates in consecutive questionnaire surveys within a cohort study, it may be important for investigators to recognise that participants and their motivation in research can be influenced by perceptions they may have regarding the objectives of the research.