Characteristics of pubertal development in a multi-ethnic population of nine-year-old girls

Higher poultry consumption was associated with an earlier age at menarche

AIM

To examine the association between meat consumption and earlier age of menarche among schoolgirls in Shanghai.

METHODS

The study randomly selected 1981 schoolgirls aged 6-18 years in Shanghai using a two-stage random sampling design. Information on meat intake was collected using a semi-quantitative food frequency questionnaire. Menarche age, household income, physical activity and other covariates were obtained by standardised questionnaires. Logistic regression was used to analyse the association between intake of meat and earlier age of menarche. Earlier age of menarche was defined as first menstruation before 12 years of age.

RESULTS

Among the 986 girls who had experienced menarche, 518/986 (52.5%) had earlier age of menarche. After adjusting for body mass index, age, physical activity, sleep, household income and parental education, consumption of poultry was positively associated with risk of earlier age of menarche (P-trend = .03). Girls who never consumed poultry had a lower risk of earlier age of menarche (odds ratio [OR]: 0.61, 95% confidence interval [CI]: 0.39-0.96). Neither the consumption of pork, beef, lamb, processed meat nor total meat consumption was associated with menarche age.

CONCLUSION

Higher consumption of poultry was associated with an earlier age at menarche.

Exploring the relationship between adolescent biological maturation, physical activity, and sedentary behaviour: a systematic review and narrative synthesis

CONTEXT

Across adolescence, there is a notable decline in physical activity in boys and girls. Maturational timing may be a risk factor for disengagement from physical activity and increased sedentary behaviours during adolescence.

OBJECTIVE

This systematic review aimed to summarise literature that examined the relationship between maturational timing, physical activity and sedentary behaviour in adolescents.

METHODS

Six electronic databases were searched for articles that assessed biological maturation and physical activity (including sports participation and active transportation) or sedentary behaviours in adolescents. Two reviewers conducted title, abstract, and full-text screening, reference and forward citation searches. Included articles were evaluated for quality using a standardised tool. A narrative synthesis was used to analyse the findings due to the heterogeneity of the studies.

RESULTS

Searches yielded 78 articles (64 unique studies) that met the inclusion criteria, representing 242,316 participants (153,179 unique). Studies ranged from 30.0% (low) to 91.7% (high) in quality. An inverse relationship between maturational timing and physical activity (in 50 and 60% of studies in boys and girls, respectively) and a positive relationship between maturational timing and sedentary behaviour (in 100% and 53% of studies in boys and girls, respectively) was most commonly reported. Evidence supporting an association between maturational timing, sports participation, and active transportation was inconsistent.

CONCLUSIONS

While this review demonstrates some evidence for early maturational timing as a risk factor for disengagement from physical activity and increase in sedentary behaviours, the reviewed literature also demonstrates that this relationship is complex. Future research that tracks maturity-related variations in physical activity and sedentary behaviours over adolescence is warranted.

Ultrasound assessment of pubertal breast development in girls: intra- and interobserver agreement

BACKGROUND

Clinical assessment of pubertal breast development using Tanner staging is subjective. This has led to the introduction of ultrasound (US), aiming for a more objective analysis. However, information regarding its reliability is lacking.

OBJECTIVE

To examine intra- and interobserver agreement of breast maturity staging using US and to examine the precision of direct measurements of the gland.

MATERIALS AND METHODS

Fifty-seven healthy girls (mean age: 10.9 years, range: 6.1 to 15.9 years) were examined independently by two observers using US of the left breast to score the glandular maturity stage on a 0-5 scale, and to measure the depth and diameter. One observer repeated the examination after 20 to 35 min to assess intra-observer agreement. Cohen's kappa with linear weights was used to examine intra- and interobserver agreement of the US staging, while the measurement precision was analyzed using Bland-Altman plots and 95% limits of agreement.

RESULTS

The agreement of US staging on a 0-5 scale was very good (kappa 0.84; 95% confidence interval [CI] 0.78-0.91) for intra-observer observation and good (kappa 0.71; 95% CI 0.62-0.80) for interobserver observation. Measurements of glandular depth and diameter were unbiased for a single observer, but the variances were large both within and between observers.

CONCLUSION

US using a scale from 0 to 5 is a reliable method to stage the development of glandular breast tissue during puberty in healthy girls. Measurements of glandular depth and diameter were found to be imprecise.

Sources and Types of Social Support for Physical Activity Perceived by Fifth to Eighth Grade Girls

BACKGROUND

Information is lacking on forms and sources of social support for physical activity (PA) received by adolescent girls during various pubertal stages. Two study purposes were to (a) identify the sources and forms of social support for PA perceived by adolescent girls, and (b) examine associations of pubertal stage and social support with PA.

METHODS

A secondary analysis of data from a randomized trial was conducted. Fifth through eighth grade girls (N = 1,519) completed surveys on social support for PA and pubertal stage and wore an accelerometer.

RESULTS

Girls in early-middle and late-post puberty most frequently received social support from their mothers. A higher proportion of girls in late-post puberty, compared to early-middle puberty, received social support from nonfamily adults (4.2% vs. 3.0%, p = .019). Girls identifying three sources participated in more moderate-to-vigorous PA than those having fewer sources (t_1,512 = -3.57, p < .001). Various forms of social support, except for encouragement, were positively related to moderate-to-vigorous PA. Girls in early-middle puberty reported greater social support than those in late-post puberty (t_1,512 = 3.99, p < .001). Social support was positively associated with moderate-to-vigorous PA, while girls in late-post puberty had lower moderate-to-vigorous PA than those in early-middle puberty.

CONCLUSIONS

Mothers are important sources of social support for PA. Having more than two sources may result in greater PA. Encouraging girls to increase their PA may not be sufficient.

CLINICAL RELEVANCE

Efforts are needed from health professionals to prevent any decline in social support for PA as girls advance across adolescence.

Exposure to phytoestrogens in utero and age at menarche in a contemporary British cohort

Phytoestrogens are estrogenic compounds that occur naturally in plants. Phytoestrogens can cross the placenta, and animal studies have found associations between in utero exposure to phytoestrogens and markers of early puberty. We investigated the association between in utero exposure to phytoestrogens and early menarche (defined as <11.5 years of age at onset) using data from a nested case-control study within the Avon Longitudinal Study of Parents and Children, a longitudinal study involving families living in the South West of England. Concentrations of six phytoestrogens were measured in maternal urine samples collected during pregnancy. Logistic regression was used to explore associations between tertiles of phytoestrogen concentrations and menarche status, with adjustment for maternal age at menarche, maternal education, pre-pregnancy body mass index (BMI), child birth order, duration of breastfeeding, and gestational age at sample collection. Among 367 mother-daughter dyads, maternal median (interquartile range) creatinine-corrected concentrations (in µg/g creatinine) were: genistein 62.1 (27.1-160.9), daidzein 184.8 (88.8-383.7), equol 4.3 (2.8-9.0), O-desmethylangolensin (O-DMA) 13.0 (4.4-34.5), enterodiol 76.1 (39.1-135.8), and enterolactone 911.7 (448.1-1558.0). In analyses comparing those in the highest tertile relative to those in the lowest tertile of in utero phytoestrogen exposure, higher enterodiol levels were inversely associated with early menarche (odds ratio (OR)=0.47; 95% confidence interval (CI): 0.26-0.83), while higher O-DMA levels were associated with early menarche (OR=1.89; 95% CI: 1.04-3.42). These findings suggest that in utero exposure to phytoestrogens may be associated with earlier age at menarche, though the direction of association differs across phytoestrogens.

Comparison of Clinical, Maternal, and Self Pubertal Assessments: Implications for Health Studies

BACKGROUND

Most epidemiologic studies of puberty have only 1 source of pubertal development information (maternal, self or clinical). Interpretation of results across studies requires data on reliability and validity across sources.

METHODS

The LEGACY Girls Study, a 5-site prospective study of girls aged 6 to 13 years (n = 1040) collected information on breast and pubic hair development from mothers (for all daughters) and daughters (if ≥10 years) according to Tanner stage (T1-5) drawings. At 2 LEGACY sites, girls (n = 282) were also examined in the clinic by trained professionals. We assessed agreement (κ) and validity (sensitivity and specificity) with the clinical assessment (gold standard) for both the mothers' and daughters' assessment in the subcohort of 282. In the entire cohort, we examined the agreement between mothers and daughters.

RESULTS

Compared with clinical assessment, sensitivity of maternal assessment for breast development was 77.2 and specificity was 94.3. In girls aged ≥11 years, self-assessment had higher sensitivity and specificity than maternal report. Specificity for both mothers and self, but not sensitivity, was significantly lower for overweight girls. In the overall cohort, maternal and daughter agreement for breast development and pubic hair development (T2+ vs T1) were similar (0.66, [95% confidence interval 0.58-0.75] and 0.69 [95% confidence interval 0.61-0.77], respectively), but declined with age. Mothers were more likely to report a lower Tanner stage for both breast and pubic hair compared with self-assessments.

CONCLUSIONS

These differences in validity should be considered in studies measuring pubertal changes longitudinally when they do not have access to clinical assessments.

Nutritional Determinants of the Timing of Puberty

The timing of puberty has important public health, clinical, and social implications. The plasticity of sexual development onset could be a mechanism that adapts to prevailing environmental conditions. Early-life nutrition may provide cues for the environment's suitability for reproduction. This review focuses on recent developments in our understanding of the role of diet in the timing of sexual maturation. Population-based observational studies consistently indicate that childhood obesity is related to the earlier onset of puberty in girls. Similarly, intake of animal foods has been associated with earlier sexual development, whereas vegetable protein intake is related to delayed maturation. Evidence for prenatal nutrition, infant feeding practices, and childhood intake of fat, carbohydrate, and micronutrients is inconsistent. Secondary analyses of prenatal and early-life randomized nutritional interventions with extended follow-up through peripubertal years would help clarify the role of nutrition in the timing of sexual maturation.

Pubertal timing, bone acquisition, and risk of fracture throughout life

Pubertal maturation plays a fundamental role in bone acquisition. In retrospective epidemiological surveys in pre- and postmenopausal women, relatively later menarcheal age was associated with low bone mineral mass and increased risk of osteoporotic fracture. This association was usually ascribed to shorter time exposure to estrogen from the onset of pubertal maturation to peak bone mass attainment. Recent prospective studies in healthy children and adolescents do not corroborate the limited estrogen exposure hypothesis. In prepubertal girls who will experience later menarche, a reduced bone mineral density was observed before the onset of pubertal maturation, with no further accumulated deficit until peak bone mass attainment. In young adulthood, later menarche is associated with impaired microstructural bone components and reduced mechanical resistance. This intrinsic bone deficit can explain the fact that later menarche increases fracture risk during childhood and adolescence. In healthy individuals, both pubertal timing and bone development share several similar characteristics including wide physiological variability and strong effect of heritable factors but moderate influence of environmental determinants such as nutrition and physical activity. Several conditions modify pubertal timing and bone acquisition, a certain number of them acting in concert on both traits. Taken together, these facts should prompt the search for common genetic regulators of pubertal timing and bone acquisition. It should also open epigenetic investigation avenues to pinpoint which environmental exposure in fetal and infancy life, such as vitamin D, calcium, and/or protein supplies, influences both pubertal timing and bone acquisition.

Exposure to polyfluoroalkyl chemicals during pregnancy is not associated with offspring age at menarche in a contemporary British cohort

INTRODUCTION

Polyfluoroalkyl chemicals (PFCs) are commercially synthesized chemicals used in consumer products. Exposure to certain PFCs is widespread, and some PFCs may act as endocrine disruptors. We used data from the Avon Longitudinal Study of Parents and Children (ALSPAC) in the United Kingdom to conduct a nested case-control study examining the association between age at menarche, and exposure to PFCs during pregnancy.

METHODS

Cases were selected from female offspring in the ALSPAC who reported menarche before the age of 11.5 years (n = 218), and controls were a random sample of remaining girls (n = 230). Serum samples taken from the girls' mothers during pregnancy (1991-1992) were analyzed using on-line solid-phase extraction coupled to isotope dilution high-performance liquid chromatography-tandem mass spectrometry for 8 PFCs. Logistic regression was used to determine association between maternal serum PFC concentrations, and odds of earlier age at menarche.

RESULTS

PFOS and PFOA were the predominant PFCs (median serum concentrations of 19.8 ng/mL and 3.7 ng/mL). All but one PFC were detectable in most samples. Total PFC concentration varied by number of births (inverse association with birth order; p-value < 0.0001) and race of the child (higher among whites; p-value = 0.03). The serum concentrations of carboxylates were associated with increased odds of earlier age at menarche; concentrations of perfluorooctane sulfonamide, the sulfonamide esters and sulfonates were all associated with decreased odds of earlier age at menarche. However, all confidence intervals included the null value of 1.0.

CONCLUSIONS

ALSPAC study participants had nearly ubiquitous exposure to most PFCs examined, but PFC exposure did not appear to be associated with altered age at menarche of their offspring.

Prenatal and childhood environmental tobacco smoke exposure and age at menarche

Previous studies have reported mixed results regarding the association between age at menarche and environmental tobacco smoke exposure, both prenatally and during early childhood; however, few studies have had data available during both time periods. The present study examined whether exposure to prenatal tobacco smoke (PTS) via maternal smoking during pregnancy or childhood environmental tobacco smoke (ETS) was associated with age at menarche in a multi-ethnic birth cohort. With the uniquely available prospectively collected data on body size and growth at birth and in early life, we further examined whether the association between PTS and ETS exposure and age at menarche was mediated by these variables. From 2001 to 2006, we recruited 262 women born between 1959 and 1963 who were enrolled previously in a New York City site of the National Collaborative Perinatal Project. Mothers who smoked during pregnancy vs. those who did not were more likely to be White, younger, have more education and have lower birthweight babies. Daughters with heavy PTS exposure (≥ 20 cigarettes per day) had a later age at menarche (>12 years vs. ≤ 12 years), odds ratio (OR) =2.1 [95% confidence interval (CI) 0.9, 5.0] compared with daughters with no PTS. Daughters exposed to only childhood ETS had a later age at menarche, OR=2.1 [95% CI 1.0, 4.3], and those exposed to PTS and ETS combined had a statistically significant later age at menarche, OR=2.2 [95% CI 1.1, 4.6] compared with daughters with no PTS and no ETS. These results did not change after further adjustment for birthweight and postnatal growth suggesting that exposure to PTS and ETS is associated with later age at menarche even after considering possible relationships with growth.

Pubertal assessment method and baseline characteristics in a mixed longitudinal study of girls

OBJECTIVES

The objective of this study was to describe the assessment methods and maturation status for a multisite cohort of girls at baseline recruitment and at ages 7 and 8 years.

METHODS

The method for pubertal maturation staging was developed collaboratively across 3 sites. Girls at ages 6 to 8 years were recruited at 3 sites: East Harlem, New York; greater Cincinnati metropolitan area; and San Francisco Bay area, California. Baseline characteristics were obtained through interviews with caregivers and anthropometric measurements by trained examiners; breast stage 2 was defined as onset of pubertal maturation. The kappa statistic was used to evaluate agreement between master trainers and examiners. Logistic regression models were used to identify factors that are associated with pubertal maturation and linear regression models to examine factors that are associated with height velocity.

RESULTS

The baseline cohort included 1239 girls. The proportion of girls who had attained breast stage 2 varied by age, race/ethnicity, BMI percentile, and site. At 7 years, 10.4% of white, 23.4% of black non-Hispanic, and 14.9% of Hispanic girls had attained breast stage>or=2; at 8 years, 18.3%, 42.9%, and 30.9%, respectively, had attained breast stage>or=2. The prime determinant of height velocity was pubertal status.

CONCLUSIONS

In this multisite study, there was substantial agreement regarding pubertal staging between examiners across sites. The proportion of girls who had breast development at ages 7 and 8 years, particularly among white girls, is greater than that reported from studies of girls who were born 10 to 30 years earlier.

Role of prenatal characteristics and early growth on pubertal attainment of British girls

OBJECTIVES

The objective of this study was to explore the influence of maternal prenatal characteristics and behaviors and of weight and BMI gain during early childhood on the timing of various puberty outcomes in girls who were enrolled in the Avon Longitudinal Study of Parents and Children.

METHODS

Repeated self-assessments of pubertal development were obtained from approximately 4000 girls between the ages of 8 and 14. Data on prenatal characteristics and weight at birth and 2, 9, and 20 months of age were obtained from questionnaires, birth records, and clinic visits. Infants' weights were converted to weight-for-age and BMI SD scores (SDSs; z scores), and change values were obtained for the 0- to 20-month and other intervals within that age range. We used parametric survival models to estimate associations with age of entry into Tanner stages of breast and pubic hair and menarche.

RESULTS

Maternal initiation of menarche at age<12, smoking during pregnancy, and primiparity were associated with earlier puberty. A 1-unit increase in the weight SDS change values for the 0- to 20-month age interval was associated with earlier ages of entry into pubertal outcomes (0.19-0.31 years). Increases in the BMI SDS change values were also associated with earlier entry into pubertal outcomes (0.07-0.11 years).

CONCLUSIONS

Many of the maternal prenatal characteristics and weight and BMI gain during infancy seemed to have similar influences across different puberty outcomes. Either such early factors have comparable influences on each of the hormonal processes involved in puberty, or processes are linked and awakening of 1 aspect triggers the others.

Dietary protein intake throughout childhood is associated with the timing of puberty

Early puberty onset is associated with hormone-related cancers, but whether diet in childhood influences pubertal timing is controversial. We examined the association of protein intake in early and mid-childhood with the ages at take-off of the pubertal growth spurt (ATO), peak height velocity (APHV), and menarche in girls and voice break in boys using data from the longitudinal Dortmund Nutritional and Anthropometric Longitudinally Designed Study. Among participants who provided 3-d weighed dietary records at 12 mo, 18-24 mo, 3-4 y, and 5-6 y, 112 had sufficient anthropometric measurements between 6 and 13 y to allow estimation of ATO. Life-course plots were used to identify critical periods of total, animal, and vegetable protein intake (percentage of total energy intake) for pubertal timing. At these ages, the association between tertiles of protein intake (T1-T3) and the outcomes was investigated using multiple linear regression analysis. A higher total and animal protein intake at 5-6 y was related to an earlier ATO. In the highest tertile of animal protein intake at 5-6 y, ATO occurred 0.6 y earlier than in the lowest [(mean, 95% CI) T1: 9.6, 9.4-9.9 vs. T2: 9.4, 9.1-9.7 vs. T3: 9.0, 8.7-9.3 y; P-trend = 0.003, adjusted for sex, total energy, breast-feeding, birth year, and paternal university degree]. Similar findings were seen for APHV (P-trend = 0.001) and the timing of menarche/voice break (P-trend = 0.02). Conversely, a higher vegetable protein intake at 3-4 and 5-6 y was related to later ATO, APHV, and menarche/voice break (P-trend = 0.02-0.04). These results suggest that animal and vegetable protein intake in mid-childhood might be differentially related to pubertal timing.

Timing of maturation and predictors of menarche in girls enrolled in a contemporary British cohort

This study describes the timing of puberty in 8- to 13-year-old girls enrolled in the Avon Longitudinal Study of Parents and Children (ALSPAC) and identifies factors associated with earlier achievement of menarche. Women were enrolled during pregnancy and their offspring were followed prospectively. We analysed self-reported Tanner staging and menstrual status information collected annually from daughters up to age 13. We used survival models to estimate median age of attainment of stage >1 and stage >2 of breast and pubic hair development and of menarche. We also constructed multivariable logistic regression models to identify factors associated with earlier achievement of menarche. About 12% of girls reported Tanner breast stage >1 at age 8; 98% of girls were above stage 1 by age 13. For pubic hair, 5% and 95% of girls had attained a stage >1 by 8 and 13 years, respectively. The estimated median age of entry into stage >1 of breast development was 10.14 years (95% confidence interval [CI], 10.08, 10.19), and for pubic hair development the median age was 10.92 years [95% CI, 10.87, 10.97]. One girl (out of 2953) had attained menarche by age 8; 60% had attained menarche by age 13. The estimated median age at menarche was 12.93 years [95% CI, 12.89, 12.98]. Prenatal predictors of menarche by age 11 (12% of girls) included earlier maternal age at menarche, high maternal pre-pregnancy body mass index, smoking during the third trimester, and non-white race; the single postnatal predictor was the girl's body size at 8 years. Age at attainment of breast and pubic hair Tanner stage and age at menarche in the ALSPAC cohort are similar to ages reported in other European studies that were conducted during overlapping time periods. The results also give added support to the strong influence of maternal maturation, pre-adolescent body size and race on the timing of a girl's menarche. This cohort will continue to be followed for maturational information until age 17.

Dietary fat alters body composition, mammary development, and cytochrome p450 induction after maternal TCDD exposure in DBA/2J mice with low-responsive aryl hydrocarbon receptors

BACKGROUND

Increased fat intake is associated with obesity and may make obese individuals uniquely susceptible to the effects of lipophilic aryl hydrocarbon receptor (AHR) ligands.

OBJECTIVES

We investigated the consequences of high-fat diet (HFD) and AHR ligands on body composition, mammary development, and hepatic P450 expression.

METHODS

Pregnant C57BL/6J (B6) and DBA/2J (D2) dams, respectively expressing high- or low-responsive AHR, were dosed at mid-gestation with TCDD. At parturition, mice were placed on an HFD or a low-fat diet (LFD). Body fat of progeny was measured before dosing with 7,12-dimethylbenz[a]anthracene (DMBA). Fasting blood glucose was measured, and liver and mammary glands were analyzed.

RESULTS

Maternal TCDD exposure resulted in reduced litter size in D2 mice and, on HFD, reduced postpartum survival in B6 mice. In D2 mice, HFD increased body mass and fat in off-spring, induced precocious mammary gland development, and increased AHR expression compared with mice given an LFD. Maternal TCDD exposure increased hepatic Cyp1a1 and Cyp1b1 expression in offspring on both diets, but DMBA depressed Cyp1b1 expression only in mice fed an HFD. In D2 progeny, TCDD exposure decreased mammary terminal end bud size, and DMBA exposure decreased the number of terminal end buds. Only in D2 progeny fed HFD did perinatal TCDD increase blood glucose and the size of mammary fat pads, while decreasing both branch elongation and the number of terminal end buds.

CONCLUSIONS

We conclude that despite having a low-responsive AHR, D2 progeny fed a diet similar to that consumed by most people are susceptible to TCDD and DMBA exposure effects blood glucose levels, mammary differentiation, and hepatic Cyp1 expression.

Birth weight, postnatal growth, and age at menarche

Larger body size in childhood is correlated with earlier age at menarche; whether birth and infant body size changes are also associated with age at menarche is less clear. The authors contacted female participants enrolled in the New York site of the US National Collaborative Perinatal Project born between 1959 and 1963 (n = 262). This racially and ethnically diverse cohort (38% white, 40% African American, and 22% Puerto Rican) was used to investigate whether maternal (body size, pregnancy weight gain, age at menarche, smoking) and birth (birth weight, birth length, placental weight) variables and early infant body size changes were associated with age at menarche even after considering later childhood body size. Higher percentile change in weight from ages 4 months to 1 year was associated with earlier age at menarche even after adjustment for later childhood growth (beta = -0.15, 95% confidence interval: -0.27, -0.02 years per 10-percentile change in weight from ages 4 months to 1 year). The association was in the same direction for all 3 racial/ethnic groups but was largest for the white group. These New York Women's Birth Cohort Adult Follow-up data (2001-2006) suggest that infant weight gain, in addition to childhood weight gain, may be associated with earlier age at menarche.

The difficult issue of age assessment on pedo-pornographic material

The issue of juvenile pornography has seen an increase in the past few years of the number of expert opinions requested to forensic pathologists, paediatricians and other various experts within the forensic and medical fields concerning the age of represented individuals. Regardless of the entity of the problem, no actual method exists which can allow us to give an objective and scientific answer, particularly in the postpubertal stage. Using parameters related to sexual maturation can be very dangerous. Nonetheless some experts still insist with similar types of "expertises". This study aims at verifying the ability of different experts in assessing age of postpubertal individuals represented in pornographic material. Results underline the difficulties and major uncertainties of age evaluation by visual observation of photographic material particularly when the subjects have reached the sexual maturation stage - and therefore in verifying whether the individual is above or below 18 years of age (an important age limit for most European countries as far as this type of crime is concerned). Furthermore the study stresses the need both to search for an alternate approach and to apply extreme caution in judicial evaluation.

Environmental exposures and puberty in inner-city girls

BACKGROUND

Hormonally active environmental exposures are suspected to alter onset of puberty in girls, but research on this question has been very limited.

OBJECTIVE

We investigated pubertal status in relation to hormonally active environmental exposures among a multiethnic group of 192 healthy 9-year-old girls residing in New York City.

METHODS

Information was collected on breast and pubic hair stages, weight and height. Phytoestrogen intake was estimated from a food-frequency questionnaire. Three phytoestrogens and bis-phenolA (BPA) were measured in urine. In a subset, 1,1'-dichloro-2,2'-bis(4-chlorophenyl)ethylene (DDE), polychlorinated biphenyls (PCBs) were measured in blood plasma and lead (Pb) in blood. Associations of exposures with pubertal stages (present=stage 2+ vs absent=stage 1) were examined using t-tests and Poisson multivariate regression to derive prevalence ratios (PR, 95%-confidence limits [CI]).

RESULTS

Breast development was present in 53% of girls. DDE, Pb, and dietary intakes of phytoestrogens were not significantly associated with breast stage. Urinary phytoestrogen biomarker concentrations were lower among girls with breast development compared with no development. In multivariate models, main effects were strongest for two urinary isoflavones, daidzein (PR 0.89 [0.83-0.96] per ln microg/g creatinine) and genistein (0.94 [0.88-1.01]). Body mass index (BMI) is a hormonally relevant, strong risk factor for breast development. Therefore, BMI-modification of exposure effects was examined, and associations became stronger. Delayed breast development was observed among girls with below-median BMI and third tertile (high exposure) of urinary daidzein (PR 0.46 [0.26-0.78]); a similar effect was seen with genistein, comparing to girls >or= median BMI and lowest two tertiles (combined) of these isoflavones. With urinary enterolactone a phytoestrogen effect was seen only among girls with high BMI, where breast development was delayed among those with high urinary enterolactone (PR 0.55 [0.32-0.96] for the upper tertile vs lower two combined). There was no main effect of PCBs on breast stage, but girls with below-median BMI and >or= median PCB levels had reduced risk for breast development (any vs none) compared with other BMI-PCB groups. No biomarkers were associated with hair development, which was present in 31% of girls.

CONCLUSIONS

Phytoestrogens and PCBs are environmental exposures that may delay breast development, especially in conjunction with BMI, which governs the endogenous hormonal milieu. Further research to confirm these findings may improve our understanding of the role of early life development in breast cancer risk and other chronic diseases related to obesity.

Comparisons between African American girls' and parents' perceptions of girls' weight concerns and weight control behaviors

Weight concerns and weight control behaviors were evaluated among sixty 8-10 year-old African American girls and their parents/caregivers. Girls completed the McKnight Risk Factor Survey and parents completed a modified version regarding perceptions of their daughters' concerns and behaviors. Significant correlations between girls' and parents' were seen for Overconcern with Weight and Shape (r = .56) and Weight Control Behaviors (r = .33). Parents' correctly identified 72% of girls' responses for Overconcern with Weight and Shape, 60% for Binge, 85% for Purging and 58% for Weight Control Behaviors scales using clinical cutoffs. However, more stringent agreement coefficients indicated generally poor concordance between girls and parents. The modified McKnight may be useful for assessing awareness of these issues.

Dietary patterns are associated with sexual maturation in Korean children

The purpose of this study was to investigate the association between dietary patterns and sexual maturation among Korean children. A cross-sectional study was conducted in 422 boys and 365 girls aged 9–12 years living in Seoul, Korea. Three-day food records were obtained, and pubertal stages were determined with a questionnaire using Tanner stages. Body fat was measured by bioelectrical impedance analysis, and bone mass content at the right calcaneus was measured by portable dual-emission X-ray absorptiometry. Exploratory factor analysis with a Varimax rotation was applied to identify dietary patterns using twenty-four food groups. Four distinct dietary patterns – ‘rice and Kimchi’, ‘shellfish and processed meat’, ‘pizza and drinks’ and ‘milk and cereal’ – were obtained. Twenty-six per cent (24% stage 2, 2% stage 3) of boys had genital development, and 79% (63% stage 2, 16% stage 3) of girls showed breast development. In boys, genital development was weakly positively associated with ‘shellfish and processed meat’ dietary factor scores (odds ratio 1·65, CI 0·95, 2·89,pfor trend 0·07) after adjusting for confounders. In girls, breast development was significantly positively associated with the factor score of ‘shellfish and processed meat’ (odds ratio 1·88, CI 1·08, 3·26,pfor trend 0·05). These results suggest that dietary patterns were related to body composition and sexual maturation among the Korean children. Further investigations are needed to identify components of the foods consumed in high amounts in these patterns and how they are related to sexual maturation.

Correlates of persistent thinness in black and white young women

OBJECTIVE

To examine health and psychosocial correlates of persistent thinness in black and white young adult women.

RESEARCH METHODS AND PROCEDURES

1,830 females (n = 988 black, n = 842 white) who participated in the National Heart, Lung, and Blood Institute Growth and Health Study were asked to indicate their current body size from a series of nine pictograms (1, emaciated to 9, obese). Persistent thinness was defined as having at least seven non-missing measurement points between ages 9 to 18 with a body size rating of <4 at all points. Generalized linear models were used to examine whether persistently thin women differed from comparison women on cardiovascular disease risk factors measured at age 18.5 and psychosocial variables measured at age 21.5. Prospective associations between psychological measures in childhood and persistent thinness through the course of adolescence were also examined.

RESULTS

In the sample, 145 women (7.9%) met criteria for persistent thinness and 1,685 women (92.1%) were classified as not persistently thin. Persistently thin women had a later age of menarche, fewer weight concerns, and healthier eating attitudes, were less likely to have had a child, came from higher socioeconomic backgrounds, and had significantly lower blood pressure and higher high-density lipoprotein-cholesterol than comparison women. Differences were not found on measures of depression or health services use. Girls with higher self-esteem in childhood were more likely to remain persistently thin throughout adolescence.

DISCUSSION

Persistently thin women seem to be healthier on several indicators relative to comparison women, and race did not moderate these differences.

Early Age at Menarche and Allostatic Load: Data from the Third National Health and Nutrition Examination Survey

PURPOSE

To examine whether there is an association between early age at menarche and allostatic load-a measure of cumulative biologic risk-using data from the Third National Health and Nutrition Examination Survey (NHANES III).

METHODS

A total of 2470 (weighted N=25,544,838) women aged between 17 and 30 years with interview and examination data who did not report oral contraceptive use before menarche and were not missing data on the exposure or outcome were included. Early menarche was defined as menarche at age 10 or younger. The allostatic load score was the sum of the number of 11 components for which an individual had a value within the high-risk range.

RESULTS

The prevalence of early menarche was 7%. Although the overall allostatic load scores were low when compared with older adults, the mean allostatic load score was higher among those with menarche at ages 10 or younger compared with those with later ages at menarche (1.99 vs. 1.33). After adjusting for age, race/ethnicity, level of education, household poverty income ratio, smoking, and depression history, women with high allostatic load scores had more than 2 times the odds as those with low scores of experiencing menarche at age 10 or earlier (OR=2.18; 95% CI, 1.29-3.68).

CONCLUSIONS

This study is the first to report and examine the relationship between age at menarche and allostatic load. Future studies involving prospective measurement of allostatic load biomarkers may prove essential for disentangling the association between allostatic load and early age at menarche.

One-Mile Run/Walk and Body Mass Index of an Ethnically Diverse Sample of Youth

PURPOSE

The purpose of this study was to explore the relationship between cardiovascular fitness levels and body mass index (BMI) status among an ethnically diverse sample of youth.

METHODS

The cross-sectional sample consisted of California fifth, seventh, and ninth graders (10-15 yr). Data presented included a total of 767,809 youth (M = 389,925, F = 377,884) from the following ethnic groups: African American 58,491; American Indian-Alaskan Natives 8,971; Asian 63,292; Filipino 22,598; Hispanic 330,758; Pacific Islanders 7,977; and white non-Hispanics 275,722. Performance on the 1-mile run/walk (seconds, MRW), height (cm), and weight (kg) measures were taken by physical education staff in public schools across California. Comparisons of MRW were analyzed with hierarchical multiple linear regression, controlling for height and weight for each age strata for males and females, separately. Youth were classified as overweight (> or = 95th percentile) or at risk for overweight (> or = 85th percentile, < 95th percentile) based on age-sex specific BMI growth charts. White non-Hispanics served as the comparison group for each analysis.

RESULTS

Overall, significant (P < 0.01) differences were observed between white non-Hispanics and their ethnic peers for each age-sex strata for MRW. For males, MRW differences among ethnic groups minimized with increasing age, while differences in MRW increased for females with increasing age. Odds ratios calculated by logistic regression indicated that for both sexes, being Hispanic was associated with the greatest likelihood of being at risk or overweight, whereas being Asian and female was associated with a preventive effect.

CONCLUSIONS

These data suggest 1) disparities in MRW exist among ethnic groups, after controlling for confounders; and 2) the variation observed in MRW is similar to those observed for physical activity.