The preventive effect of breast-feeding for longer than 6 months on early pubertal development among children aged 7-9 years in Korea

Association between infant breastfeeding practices and timing of peak height velocity: A nationwide longitudinal survey in Japan

BACKGROUND

Several studies have discovered an association between infant feeding practices and puberty timing; however, most have involved female cohorts. We investigated the association between infant feeding practices and the timing of peak height velocity in boys and girls.

METHODS

Data on infant feeding methods and anthropometric measurements were collected from a nationwide Japanese birth cohort study. The age at peak height velocity (APV, years) was estimated and compared. Subsequently, the effects of breastfeeding duration were analyzed.

RESULTS

Of the 13,074 eligible participants, 650, 9455, and 2969 were formula-, mixed-, and exclusively breastfed, respectively. Among girls, the mean APV was significantly later in the mixed-fed (standardized regression coefficient (β): 0.094, 95% confidence interval (CI): 0.004-0.180) and exclusively breastfed (β: 0.150, 95% CI: 0.056-0.250) groups than in the formula-fed group. Among boys, the mean APV was not significantly different among the three groups; however, a sensitivity analysis that excluded preterm birth revealed more significantly delayed APV in the breastfed-only group compared to the formula-fed group. Furthermore, a multiple linear regression model revealed that a longer breastfeeding period was associated with later APV.

CONCLUSIONS

Infant breastfeeding practices can affect the timing of peak height velocity in both boys and girls.

IMPACT

Several studies have discovered an association between infant feeding practices and puberty timing; however, most have involved female cohorts. Age at peak height velocity, derived from longitudinal height measurements, is a useful marker of secondary sexual maturity milestones in boys and girls. A Japanese birth cohort study revealed that breastfed children had a later age at peak height velocity than their formula-fed counterparts; this was more prominent among girls than boys. Furthermore, a duration-effect relationship was observed, where longer breastfeeding duration was associated with a later age at peak height velocity.

Breast and Formula Milk and Early Puberty Onset

Nutrients have an enormous impact on many hormonal systems and aspects of health, and nutrition status is a crucial regulator of growth and pubertal development in children and adolescents. In this narrative review, we explore the connection between these feeding methods and the timing of puberty to provide a clearer understanding of how infant nutrition might contribute to the early development of puberty. Puberty is a key stage in the transition from childhood to adulthood and the timing of puberty represents a significant biological milestone of growth. Breast milk seems to have a pivotal role in puberty onset, mainly due to its dynamism, which shape indirectly the gut microbiota in early life, besides direct exposure of the baby to the milk microbiota through gut-breast axis. Concerning breast and formula milk and their effects on the onset of puberty, a protective role of the former occurs. As for the potential harmful effects of soy-based formulas and the isoflavones that they contain, the studies reported demonstrate conflicting opinions, underlining the need for further research on this topic. A healthy and well-nourished diet from the earliest stages of life has significant preventive potential for overall well-being, reducing the risk of many health problems later in life.

Pubertal progression in relation to peripubertal exposure to organochlorine chemicals in a cohort of Russian boys

Background

Peripubertal concentrations of serum dioxins and polychlorinated biphenyls (PCBs) have demonstrated associations with altered age of pubertal onset and sexual maturity in boys, but associations with pubertal progression have received less attention.

Methods

The Russian Children's Study is a prospective cohort of 516 boys enrolled in 2003-2005 at age 8 or 9 and followed annually up to 19 years of age. Serum concentrations of dioxin-like toxic equivalents (TEQs), polychlorinated dibenzodioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and non-dioxin-like PCBs (NDL-PCBs) and whole blood lead levels (BLLs) were quantified from blood samples collected at study entry (age 8-9). Testicular volume (TV) was assessed annually using a Prader orchidometer. Pubertal trajectories were identified by applying Group-Based Trajectory Models (GBTMs) to TV measured from ages 8-19. Associations of peripubertal serum TEQs, PCDDs, PCDFs, and NDL-PCBs with specific progression trajectories were modeled using multinomial logistic regression, adjusting for each boy's birthweight, and for BLL, body mass index and nutritional factors at study entry.

Results

Among 489 eligible boys with available exposure measures, we identified three pubertal trajectories using GBTMs: slower (34% of boys), moderate (48%) and faster (18%). Boys with higher peripubertal serum TEQs had higher adjusted odds of being in the moderate versus faster trajectory (adjusted odds ratio (aOR) 1.79, 95% CI 1.01, 3.13) and the slower versus faster trajectory (aOR 1.52, 95% CI 0.82, 2.78) per 1 log unit increase in serum TEQs. Boys with higher peripubertal serum PCDFs had higher adjusted odds of being in the moderate compared to the faster trajectory (aOR 1.92, 95% CI 1.20, 3.03) and of being in the slower versus the faster trajectory (aOR 1.42, 95% CI 0.91, 2.33) per 1 log unit increase. Boys with higher NDL-PCBs had higher adjusted odds of being in the faster trajectory versus the moderate (aOR 2.56, 95% CI 0.91-7.20) or slower (aOR 3.31, 95% CI 1.07, 10.25) trajectory. Boys with higher blood lead levels also had higher adjusted odds of being in the slower trajectory of pubertal progression, compared to either the faster (aOR 1.47, 95% CI 0.89, 2.44) or moderate (aOR 1.20, 95% CI 0.83, 1.75) trajectories, per 1 log unit increase in BLL, although these associations did not attain statistical significance.

Conclusion

Boys' peripubertal exposure to dioxins and certain PCBs may alter pubertal progression.

A systematic review on maternal and perinatal factors influencing breast development

BACKGROUND

A secular trend towards earlier age at menarche has been reported, but the trend in breast development is less clear. We reviewed the evidence on the relationship between in utero and early life events and breast onset/development.

METHODS

Eligible studies were identified in PubMed and Embase databases. We selected studies in which female human exposure during fetal or the first years of life was measured or estimated, and associations with breast onset or development were evaluated.

RESULTS

Of the 49 cohort studies and 5 cross-sectional studies identified, 43 provided sufficient data to assess associations. High maternal weight, primiparity, and early weight gain, were related to an increased risk of early breast onset/development in most of the studies that analysed these associations, whereas late breast onset/development was associated with preterm birth. Results were inconsistent for smoking in pregnancy, maternal hypertensive disorders, breastfeeding, diabetes, and small for gestational age. No association emerged for maternal age at delivery, alcohol drinking, and selected drug use during pregnancy, and low birth weight.

CONCLUSIONS

The results of this review show that high maternal weight, primiparity and early weight gain were associated with an increased risk of early breast onset/development. Late breast onset/development was associated with preterm birth. Breast development is a key physical marker of puberty onset, and early puberty development is linked to consequences that can reverberate throughout life. Answering the questions about the interconnections between pre/postnatal environmental exposures and their impact on puberty, represents an important area of multidisciplinary research.

Early-life exposures and age at thelarche in the Sister Study cohort

BACKGROUND

Early age at breast development (thelarche) has been associated with increased breast cancer risk. Average age at thelarche has declined over time, but there are few established risk factors for early thelarche. We examined associations between pre- and postnatal exposures and age at thelarche in a US cohort of women born between 1928 and 1974.

METHODS

Breast cancer-free women ages 35-74 years who had a sister diagnosed with breast cancer were enrolled in the Sister Study from 2003 to 2009 (N = 50,884). At enrollment, participants reported information on early-life exposures and age at thelarche, which we categorized as early (≤ 10 years), average (11-13 years), and late (≥ 14 years). For each exposure, we estimated odds ratios (ORs) and 95% confidence intervals (CIs) for early and late thelarche using polytomous logistic regression, adjusted for birth cohort, race/ethnicity and family income level in childhood.

RESULTS

Early thelarche was associated with multiple prenatal exposures: gestational hypertensive disorder (OR = 1.25, 95% CI 1.09-1.43), diethylstilbestrol use (OR = 1.23, 95% CI 1.04-1.45), smoking during pregnancy (OR = 1.20, 95% CI 1.13-1.27), young maternal age (OR 1.30, 95% CI 1.16-1.47 for < 20 vs. 25-29 years), and being firstborn (OR = 1.25, 95% CI 1.17-1.33). Birthweight < 2500 g and soy formula use in infancy were positively associated with both early and late thelarche.

CONCLUSIONS

Associations between pre- and postnatal exposures and age at thelarche suggest that the early-life environment influences breast development and therefore may also affect breast cancer risk by altering the timing of pubertal breast development.

The Role of Pediatric Nutrition as a Modifiable Risk Factor for Precocious Puberty

Puberty is a critical phase of growth and development characterized by a complex process regulated by the neuroendocrine system. Precocious puberty (PP) is defined as the appearance of physical and hormonal signs of pubertal development at an earlier age than is considered normal. The timing of puberty has important public health, clinical, and social implications. In fact, it is crucial in psychological and physical development and can impact future health. Nutritional status is considered as one of the most important factors modulating pubertal development. This narrative review presents an overview on the role of nutritional factors as determinants of the timing of sexual maturation, focusing on early-life and childhood nutrition. As reported, breast milk seems to have an important protective role against early puberty onset, mainly due to its positive influence on infant growth rate and childhood overweight prevention. The energy imbalance, macro/micronutrient food content, and dietary patterns may modulate the premature activation of the hypothalamic-pituitary-gonadal axis, inducing precocious activation of puberty. An increase in knowledge on the mechanism whereby nutrients may influence puberty will be useful in providing adequate nutritional recommendations to prevent PP and related complications.

Breast feeding and timing of puberty in boys and girls: A nationwide cohort study

BACKGROUND

Breast feeding has been associated with improved infant health, but its impact on pubertal timing remains uncertain, particularly in boys.

OBJECTIVE

The objective of this study was to investigate the association between duration of breast feeding and pubertal timing in boys and girls.

METHODS

This population-based cohort study included 13 511 boys and girls from the Puberty Cohort nested within the Danish National Birth Cohort. The children gave half-yearly, self-reported information on pubertal development through questionnaires (Tanner stages, age at menarche, first ejaculation, voice break, axillary hair growth, and acne). Information on breast feeding was provided by the mothers when the children were 6 months of age. We estimated mean differences (in months) in age at attaining each pubertal marker and for overall timing of puberty (combined estimate) for every additional month of exclusive breast feeding. Furthermore, we estimated differences in pubertal age when comparing children never exclusively breastfed and exclusively breastfed <4 months using children exclusively breastfed ≥4 months as reference. In sub-analyses, we further adjusted for infant weight gain and childhood BMI at 7 years to investigate whether these variables mediated the association.

RESULTS

Boys tended to reach pubertal markers later for every additional month of exclusive breast feeding (combined estimate: 0.2 (95% confidence interval [CI] 0.0, 0.4 months). Never exclusively breastfed boys reached pubertal markers earlier than the boys exclusively breastfed ≥4 months (combined estimate: -4.1 (95% CI -6.7, -1.6) months). Boys exclusively breastfed <4 months also reached pubertal markers earlier than those never exclusively breastfed but with smaller differences. In girls, duration of breast feeding was not associated with pubertal development. When including infant weight gain or childhood BMI, the results remained essentially unchanged.

CONCLUSIONS

Shorter duration of exclusive breast feeding was associated with earlier pubertal development in boys but not in girls.

Association of Soy and Exclusive Breastfeeding With Central Precocious Puberty: A Case-Control Study

Introduction

While soy is suggested as a possible risk factor, exclusive breastfeeding (EBF) has a likely protective effect in precocious puberty. Our aim was to evaluate the association between both of these variables with central precocious puberty (CPP).

Methods

We performed a retrospective, case-control study. A total of 161 girls were divided into two groups: 84 patients diagnosed with CPP composed the case group and 77 patients without the diagnosis of CPP (had gone through normal onset of puberty) were the control group.

Results

Our control group had a higher presence of EBF >6 months, which was an important protective factor for CPP (OR: 0.5; IC 95%: 0.3-0.9, p = 0.05) and also correlated negatively with the presence of it (r = -0.2; p < 0.05). Oppositely, the use of soy was significantly higher in the CPP group, (OR: 3.8; IC 95%: 1.5-6, p < 0.05) and positively correlating (r = 0.2; p < 0.01) with the presence of CPP. Duration of soy intake (years) correlated with bone age (r = 0.415; p < 0.05). A logistic regression was performed to evaluate the effects of EBF duration and soy on CPP. The model was significant (x² (2) = 20,715, p = <0.001) and explained 12.2% (Nagelkerke R2) of the variance, correctly classifying 62.5% of cases. EBF was associated with a reduction of likelihood of having CPP [OR = 0,187 (CI = 0.055-0,635); Wald = 7,222, p = 0.007], while soy intake increased the risk [OR = 3.505 (CI) = 1,688-7,279, Wald = 11,319, p = 0.001].

Conclusion

Our data found the use of soy was associated with CPP. Additionally, EBF was pointed as a protective factor. However, future prospective studies are needed to clarify this issue.

Cohort profile: the Ewha Birth and Growth Study

With the introduction of life-course epidemiology, researchers realized the importance of identifying risk factors in early life to prevent chronic diseases. This led to the establishment of the Ewha Birth and Growth Study in 2001; the study is a prospective birth cohort designed to provide evidence of early life risk factors for a child's growth and health. Participants were recruited from those who visited Ewha Womans University Mokdong Hospital (a tertiary hospital in southwest Seoul, Korea) for prenatal care at 24-28 weeks of gestation. In total, 891 mothers enrolled in this study between 2001 and 2006 and their offspring (n=940) were followed-up. Regular check-up examinations of offspring were conducted at 3 years, 5 years, and 7 years of age and every year thereafter. To consider age-related health issues, extensive data were collected using questionnaires and measurements. In 2021, the study subjects will reach 19 years of age, and we are planning a check-up examination for early adulthood. About 20 years have passed since the cohort data were collected, and we have published results on childhood health outcomes associated with prenatal and birth characteristics, genetic and epigenetic characteristics related to childhood metabolism, the effects of exposure to endocrine disruptors, and dietary patterns in childhood. Recently, we started reporting on topics related to adolescent health. The findings will facilitate identification of early life risk factors for chronic diseases and the development of interventions for diseases later in life.

The Role of Fetal, Infant, and Childhood Nutrition in the Timing of Sexual Maturation

Puberty is a crucial developmental stage in the life span, necessary to achieve reproductive and somatic maturity. Timing of puberty is modulated by and responds to central neurotransmitters, hormones, and environmental factors leading to hypothalamic-pituitary-gonadal axis maturation. The connection between hormones and nutrition during critical periods of growth, like fetal life or infancy, is fundamental for metabolic adaptation response and pubertal development control and prediction. Since birth weight is an important indicator of growth estimation during fetal life, restricted prenatal growth, such as intrauterine growth restriction (IUGR) and small for gestational age (SGA), may impact endocrine system, affecting pubertal development. Successively, lactation along with early life optimal nutrition during infancy and childhood may be important in order to set up timing of sexual maturation and provide successful reproduction at a later time. Sexual maturation and healthy growth are also influenced by nutrition requirements and diet composition. Early nutritional surveillance and monitoring of pubertal development is recommended in all children, particularly in those at risk, such as the ones born SGA and/or IUGR, as well as in the case of sudden weight gain during infancy. Adequate macro and micronutrient intake is essential for healthy growth and sexual maturity.

The association between metabolic components and markers of inflammatory and endothelial dysfunction in adolescents, based on the Ewha Birth and Growth Cohort Study

We assessed the association between metabolic health and markers of inflammation and of endothelial dysfunction using data from the Ewha Birth and Growth Cohort Study. The data of 195 subjects aged 13–15 years were analyzed. To assess metabolic syndrome, continuous metabolic syndrome (cMets) scores were calculated. We measured the levels of high-sensitivity C-reactive protein (hs-CRP), intercellular adhesion molecule 1 (ICAM-1), and vascular cell adhesion molecule 1 (VCAM-1) as markers of inflammation and endothelial dysfunction. An increase of one SD in the cMets score resulted in a 1.25-fold (95% CI 1.10–1.42) increase in the risk of acute inflammatory status and a 1.26-fold (95% CI 1.11–1.43) increase in the risk of endothelial dysfunction as defined by ICAM-1, while VCAM-1 showed a meaningless trend. Of the metabolic components, body mass index (BMI) was positively associated with elevated hs-CRP levels and high-density lipoprotein cholesterol (HDL-c) levels were negatively associated with elevated ICAM-1 levels. Additionally, a mediation analysis showed that a high BMI was directly related to elevated hs-CRP levels and indirectly related to elevated ICAM-1 levels via HDL-c. Our findings show that poor metabolic health was related to an unfavorable inflammatory status and endothelial dysfunction in adolescents.

Blood Pressure Curve for Children Less than 10 Years of Age: Findings from the Ewha Birth and Growth Cohort Study

BACKGROUND

Routine blood pressure (BP) measurement is recommended to begin at 3 years of age, but there are no national BP reference values for Korean children less than 7 years of age. Therefore, we developed sex-, age-, and height-specific BP reference values for non-overweight children aged 3-9 years.

METHODS

We analyzed the data of 416, 340, 321, 323, and 332 subjects aged 3, 5, 7, 8, and 9 years, respectively, who participated in the Ewha Birth and Growth Cohort Study. BP percentile curves were generated using generalized additive models for location, scale, and shape. Reference values for the 50th, 90th, and 95th percentiles of BP were determined according to sex, age, and height percentiles.

RESULTS

In both boys and girls, a gradual increase in systolic blood pressure (SBP) with age was more pronounced than that in diastolic blood pressure (DBP). In boys, the reference values for 90th percentile of SBP/DBP at median height for children aged 3 and 9 years were 105/69 and 118/70, respectively. In girls, the reference values corresponding to the above conditions were 105/69 and 116/70, respectively. Among children aged 7-9 years of median height, the 90th percentile of SBP in the current study was lower and that of DBP was similar to the national reference values of Korea. For children aged < 7 years of median height, the reference value for SBP, but not that for DBP, was similar to that developed in the European study.

CONCLUSION

Although further research is needed, our findings could be used to help identify high BP in children less than 10 years of age.

Breastfeeding and timing of pubertal onset in girls: a multiethnic population-based prospective cohort study

Background

Early puberty is associated with higher risk of adverse health and behavioral outcomes throughout adolescence and adulthood. US girls are experiencing earlier puberty with substantial racial/ethnic differences. We examined the association between breastfeeding and pubertal timing to identify modifiable risk factors of early puberty and potential sources of racial/ethnic differences in the timing of pubertal development.

Methods

A prospective cohort study of 3331 racially/ethnically diverse girls born at Kaiser Permanente Northern California (KPNC) between 2004 and 06. All data were obtained from KPNC electronic clinical and administrative datasets. Mother-reported duration of breastfeeding was obtained from questionnaires administered at each ‘well-baby’ check-up exam throughout the baby’s first year and categorized as ‘Not breastfed’, ‘Breastfed < 6 months’, and ‘Breastfed ≥ 6 months’. Pubertal development data used Tanner stages assessed by pediatricians during routine pediatric checkups starting at age 6. Pubertal onset was defined as transition from Tanner Stage 1 to Tanner Stage 2+ for breast (thelarche) and pubic hair (pubarche). Weibull regression models accommodating for left, right, and interval censoring were used in all analyses. Models were adjusted for maternal age, education, race/ethnicity, parity and prepubertal body mass index (BMI). We also examined race/ethnicity as a potential effect modifier of these associations.

Results

Not breastfeeding was associated with earlier onset of breast and pubic hair development compared to breastfeeding ≥6 months (adjusted hazard ratio [HR]: 1.25; 95% confidence interval [CI]: 1.07–1.46; HR: 1.24; 95% CI: 1.05–1.46, respectively). Breastfeeding for < 6 months was also associated with the risk of earlier pubic hair development (HR: 1.14; 95% CI: 1.00–1.30, compared to breastfeeding ≥6 months). Inclusion of girls’ prepubertal BMI slightly attenuated the association between breastfeeding and timing of breast onset but remained significant. The association between not breastfeeding and early breast development may be stronger among African American girls (HR: 1.92; 95% CI: 1.01–3.66, no breastfeeding vs. ≥6 months) than other racial/ethnic groups.

Conclusions

Breastfeeding is an independent predictor of pubertal onset in girls, and the strength of the association may vary by race/ethnicity. Providing breastfeeding support and lactation education for high risk mothers may help prevent earlier pubertal onset and promote positive health outcomes later in life.

MC4R and HNF4α promoter methylation at birth contribute to triglyceride levels in childhood: A prospective cohort study

Although the changes in DNA methylation are assumed to be due to the association between adverse intrauterine conditions and adult metabolic health, evidence from human studies is rare. Little is known about the changes in DNA methylation present at birth that affect metabolic profiles in childhood. Previous studies have shown that the melanocortin 4 receptor (MC4R) and hepatocyte nuclear factor 4 alpha (HNF4α) genes are associated with obesity and metabolic disorders. Thus, we investigated the associations of the DNA methylation statuses of MC4R and HNF4α in cord blood with metabolic profiles in childhood.We collected data from 90 children 7 to 9 years of age included in the Ewha Birth & Growth Cohort Study in Korea. DNA methylation was analyzed by pyrosequencing. The children were split into 2 groups according to the cutoff triglyceride (TG) levels (<110 and ≥110 mg/dL).The methylation statuses of MC4R and HNF4α at birth were significantly associated with the TG level in childhood (P < .05). It was interesting to note that the methylation statuses of MC4R and HNF4α in cord blood were significantly decreased, whereas childhood body mass index was significantly increased, in children with high TG levels compared with children with low TG levels (P < .05).Our findings show that the methylation statuses of MC4R and HNF4α at birth are associated with metabolic profiles in childhood. These epigenetic modifications occurring in early life may contribute to subsequent metabolic-related disorders. Thus, we suggest that DNA methylation status in cord blood may be predictive of the risk of developing metabolic syndrome.

Long-term effects of the SLC2A9 G844A and SLC22A12 C246T variants on serum uric acid concentrations in children

BACKGROUND

We evaluated the effects of two single-nucleotide polymorphisms on UA concentrations in the first decade of life using repeated-measures data.

METHODS

We included all subjects who were followed-up at least once and for whom we had both UA and genotypic data (i.e., 375, 204, 307, and 363 patients aged 3, 5, 7, and 9 years, respectively). All participated in the Ewha Birth and Growth Cohort study. We used a mixed model analysis to estimate the longitudinal association of serum UA concentration due to the rs3825017 (SLC22A12 c. 246C > T) and rs16890979 (SLC2A9 c. 844G > A) genotypes.

RESULTS

Overall, the tracking coefficient of UA concentrations in children 3 to 9 years of age was 0.31, and was higher in boys than in girls (0.34 vs. 0.29, respectively). Regarding individual variance, serum UA concentrations decreased as age increased (β = - 0.07, p < 0.05), but there were no significant differences by sex. The effects of rs3825017 on UA concentration were significant in boys, but not in girls. Boys with the T allele of rs3825017 had higher concentrations than their counterparts regardless of the time of follow-up. The rs16890979 genotypes were not significantly associated with serum UA concentration in either sex.

CONCLUSION

This study showed that rs3825017 in the SLC22A12 gene was associated with UA concentration in childhood.

Association between MKRN3 and LIN28B polymorphisms and precocious puberty

BACKGROUND

The present study aimed to investigate the association between MKRN3 and LIN28B gene polymorphisms and precocious puberty in Korean boys and girls.

RESULTS

Children 7 to 9 years of age in 2011 to 2012 who were part of the Ewha Birth & Growth Cohort Study were recruited for this study. A total of 103 girls and 70 boys were included in the analyses. Seven girls and 26 boys were identified to have precocious puberty. Among four single nucleotide polymorphisms (SNPs) of MKRN3 and two SNPs of LIN28B examined, three SNPs (rs2239669, rs6576457, and rs12441827) showed significant associations with precocious puberty in additive models in boys but no significance was found in any SNPs in girls. From the logistic regression analysis, boys with TT alleles in rs12441827 had about a four-times greater risk for precocious puberty when compared to C allele carriers (OR = 3.95, 95% CI = 1.27-12.32 in model 1). eQTL analysis revealed that SNPs of statistical significance from our study did not show the variation in expression profiles nor found in the database.

CONCLUSIONS

This study supports the impact of MKRN3 SNP rs12441827 on precocious puberty in Korean boys. The results add a further aspect to genetic association in precocious puberty along with complex interactions of environmental, nutritional and socioeconomic factors.

Comparison of methods to assess onset of breast development in the LEGACY Girls Study: methodological considerations for studies of breast cancer

Background

Younger age at onset of breast development, which has been declining in recent decades, is associated with increased breast cancer risk independent of age at menarche. Given the need to study the drivers of these trends, it is essential to validate methods to assess breast onset that can be used in large-scale studies when direct clinical assessment of breast onset is not feasible.

Methods

Breast development is usually measured by Tanner stages (TSs), assessed either by physical examination or by mother’s report using a picture-based Sexual Maturation Scale (SMS). As an alternative, a mother-reported Pubertal Development Scale (PDS) without pictures has been used in some studies. We compared agreement of SMS and PDS with each other (n = 1022) and the accuracy of PDS with clinical TS as a gold standard for the subset of girls with this measure (n = 282) using the LEGACY cohort. We further compared prediction of breast onset using ROC curves and tested whether adding urinary estrone 1-glucuronide (E1G) improved the AUC.

Results

The agreement of PDS with SMS was high (kappa = 0.80). The sensitivity of PDS vs clinical TS was 86.6%. The AUCs for PDS alone and SMS alone were 0.88 and 0.79, respectively. Including E1G concentrations improved the AUC for both methods (0.91 and 0.86 for PDS and SMS, respectively).

Conclusions

The PDS without pictures is a highly accurate, sensitive, and specific method for assessing breast onset, especially in settings where clinical TS is not feasible. In addition, it is comparable to SMS methods with pictures and thus easier to implement in large-scale studies, particularly phone-based interviews where pictures may not be available. Urinary E1G can improve accuracy over than PDS or SMS alone.

Electronic supplementary material

The online version of this article (10.1186/s13058-018-0943-9) contains supplementary material, which is available to authorized users.

A prospective cohort study of the association between bisphenol A exposure and the serum levels of liver enzymes in children

BACKGROUND

Bisphenol A (BPA) is an endocrine disrupter that acts in an estrogen-like manner. Few studies have investigated the association between urinary BPA concentrations and adverse liver function. Additionally, most studies were cross-sectional in nature and included only adults.

OBJECTIVES

We evaluated BPA exposure levels and prospectively explored the association between BPA exposure and liver function in children.

METHODS

Data were retrieved from the ongoing prospective Ewha Birth and Growth Cohort Study. Urinary BPA concentrations were measured in 164 children at 3-5 and 7-9 years of age. At each visit, fasting blood and urine samples were collected, and questionnaires were completed. The associations between the BPA concentrations at these ages and the serum levels of liver enzymes measured at 10-13 years of age were analyzed (n = 113). Multiple regression analysis was performed with adjustment for covariates. We also explored whether the BPA level exhibited dose-response relationships with liver enzyme levels.

RESULTS

The median urinary BPA concentrations were 0.76μg/g creatinine at 3-5 years and 0.61μg/g creatinine at 7-9 years of age. The urinary BPA concentrations at the two ages were correlated significantly (r = 0.23, p < 0.01). The urinary BPA concentrations at 7-9 years, but not that at 3-5 years, was associated significantly with the serum levels of liver enzymes at 10-13 years of age (p < 0.05). Those in the top tertile of urinary BPA concentration had higher levels of liver enzymes than did others. After adjustment for covariates, dose-response relationships of the BPA level with liver enzyme levels were evident at 7-9 years, but not at 3-5 years. Notably, the effect size was larger and the dose-response relationships were more evident in boys than in girls.

CONCLUSIONS

Exposure of children to even low doses of BPA may adversely affect later liver function.

The differential effects of changes in individual macronutrient intake on changes in lipid concentrations during childhood: From the Ewha Birth & Growth Cohort

BACKGROUND & AIMS

High carbohydrate or fat intake is responsible for abnormal lipid concentrations in adults, but few studies of children have been reported. Using data from a Korean children's cohort study, we assessed the association between macronutrient intake and lipid profile with a longitudinal association during a 4-year follow-up.

METHODS

Using 2 days of 24-h dietary data obtained at 3 (n = 323) and 7 (n = 292) years old from the Ewha Birth & Growth Cohort, we calculated changes (n = 103) in macronutrient intake in terms of energy-adjusted intake and percent total energy for nutrients. Changes in lipid profiles (TC: total cholesterol, TG: triglyceride, HDL-c: high-density lipoprotein cholesterol, LDL-c: low-density lipoprotein cholesterol) are the primary outcomes in this study. The effects of individual changes in macronutrient intake on changes in lipid profiles over time were assessed using multiple regression analyses.

RESULTS

The percentages of total energy from carbohydrates and fat were 59.1% and 27.4% at baseline, respectively. Those in the highest tertile of carbohydrate intake showed the highest mean TG and lowest mean TC and HDL-c levels, regardless of observation time. By contrast, those with the highest fat intake indicated the lowest mean TG and highest mean TC and HDL-c at 7 years old. In addition, increased intake of carbohydrates had an unfavorable effect on TG, while increased intake of fat, especially animal-based fat, increased LDL-c levels over time.

CONCLUSIONS

Our study showed that a relatively high intake of carbohydrate or fat among children had an unfavorable effect on lipid concentrations based on a longitudinal approach.

Which Diet-Related Behaviors in Childhood Influence a Healthier Dietary Pattern? From the Ewha Birth and Growth Cohort

This study was performed to examine how childhood dietary patterns change over the short term and which changes in diet-related behaviors influence later changes in individual dietary patterns. Using food frequency questionnaire data obtained from children at 7 and 9 years of age from the Ewha Birth and Growth Cohort, we examined dietary patterns by principal component analysis. We calculated the individual changes in dietary pattern scores. Changes in dietary habits such as eating a variety of food over two years were defined as “increased”, “stable”, or “decreased”. The dietary patterns, termed “healthy intake”, “animal food intake”, and “snack intake”, were similar at 7 and 9 years of age. These patterns explained 32.3% and 39.1% of total variation at the ages of 7 and 9 years, respectively. The tracking coefficient of snack intake had the highest coefficient (γ = 0.53) and that of animal food intake had the lowest (γ = 0.21). Intra-individual stability in dietary habits ranged from 0.23 to 0.47, based on the sex-adjusted weighted kappa values. Of the various behavioral factors, eating breakfast every day was most common in the “stable” group (83.1%), whereas consuming milk or dairy products every day was the least common (49.0%). Moreover, changes in behavior that improved the consumption of milk or dairy products or encouraged the consumption of vegetables with every meal had favorable effects on changes in healthy dietary pattern scores over two years. However, those with worsened habits, such as less food variety and more than two portions of fried or stir-fried food every week, had unfavorable effects on changes in healthy dietary pattern scores. Our results suggest that diet-related behaviors can change, even over a short period, and these changes can affect changes in dietary pattern.

The Effect of Exposure to Persistent Organic Pollutants on Metabolic Health among KOREAN Children during a 1-Year Follow-Up

Previous evidence suggests the potential for adverse effects of persistent organic pollutants (POPs) on metabolic health even at low-dose exposure levels common among the general population, but there is less evidence of these associations among children. Therefore, as part of a prospective cohort study, 214 children were measured for POPs exposure. After the 1-year follow-up, we assessed the effect of circulating POPs exposure among 158 children aged 7-9 years (at baseline) on the change of metabolic components of metabolic syndrome using multiple regression analysis. In addition, we calculated the continuous metabolic syndrome (cMetS) score and assessed the variation among individuals by POPs exposure. The concentrations of marker polychlorinated biphenyls (PCBs) were significantly associated with increased change in diastolic blood pressure (BP) and triglyceride levels during a 1-year follow-up, after controlling for sex, age, household income, and change in body mass index. Total PCBs also showed a marginal association with increasing cMetS score from the baseline. Of the metabolic components, change in diastolic BP over time showed a notable association with specific PCBs, but no association with organochlorine pesticides. Here, we found that low-dose exposures to PCBs among children in the general population could negatively influence metabolic health, particularly diastolic BP. Increased disease sensitivity during childhood can continue to adulthood, thus, these results support the need for continuous assessment of the health impact of POPs.