Genetics of age at menarche: a systematic review

Indications of younger age at menarche in Greek adolescents but with no relation to body mass index

PURPOSE

This study aimed to present recent trends in the pubertal timing of a Greek female sample.

METHODS

Data were collected retrospectively from medical records of healthy females aged 6-18 years who attended a tertiary Adolescent Friendly Health Center over a 5-year period (2016-2020) and included gestational age, birth anthropometrics, and age of thelarche and/or pubarche and/or menarche, along with corresponding anthropometric, hormonal, and biochemical measurements.

RESULTS

Data from 298 girls' medical records were included in the analysis. Median age at menarche, thelarche, and pubarche was 12, 9, and 9 years, respectively. The mean interval between pubertal onset and menarche was 1.99 years. The mean body mass index (BMI) at menarche and thelarche was 20.99 kg/m2 and 18.90 kg/m2, respectively. The mean weight at menarche was 49.6 kg, whereas the mean height difference between thelarche and menarche was 19.17 cm. Among participants, 6.3% had premature menarche, while 24.0% had premature thelarche. Birth weight was moderately correlated with BMI at thelarche/pubarche (rs=0.334, p = 0.005). Birth weight and BMI at thelarche/pubarche were not predictive of premature menarche or premature thelarche. Median (interquartile range, IQR) levels at menarche vs. thelarche were significantly higher for insulin-like growth factor-1 [358.00 (140.50) vs. 176.00 (55.00) ng/ml], follicle stimulation hormone [5.65 (3.14) vs. 3.10 (4.23) mIU/ml], testosterone [25.50 (31.00) vs. 13.00 (21.00) ng/dl], dehydroepiandrosterone sulfate [117.00 (112.50) vs. 46.40 (51.90) µg/dl], and insulin [17.40 (15.05) vs. 8.47 (4.97) µIU/ml].

CONCLUSION

The timing of pubertal stages in the Greek female sample studied followed the recent international downward trends. Younger age at menarche was not related to BMI.

Altered pubertal timing in 7q11.23 copy number variations and associated genetic mechanisms

Pubertal timing, including age at menarche (AAM), is a heritable trait linked to lifetime health outcomes. Here, we investigate genetic mechanisms underlying AAM by combining genome-wide association study (GWAS) data with investigations of two rare genetic conditions clinically associated with altered AAM: Williams syndrome (WS), a 7q11.23 hemideletion characterized by early puberty; and duplication of the same genes (7q11.23 Duplication syndrome [Dup7]) characterized by delayed puberty. First, we confirm that AAM-derived polygenic scores in typically developing children (TD) explain a modest amount of variance in AAM (R2 = 0.09; p = 0.04). Next, we demonstrate that 7q11.23 copy number impacts AAM (WS < TD < Dup7; p = 1.2x10-8, η2 = 0.45) and pituitary volume (WS < TD < Dup7; p = 3x10-5, ηp2 = 0.2) with greater effect sizes. Finally, we relate an AAM-GWAS signal in 7q11.23 to altered expression in postmortem brains of STAG3L2 (p = 1.7x10-17), a gene we also find differentially expressed with 7q11.23 copy number (p = 0.03). Collectively, these data explicate the role of 7q11.23 in pubertal onset, with STAG3L2 and pituitary development as potential mediators.

Estimated effect of age of marriage on utilisation of India's Integrated Child Development Service programme

BACKGROUND

Age of marriage among women is considered an important indicator of their readiness for familial integration and parenting. This study estimated the effect of age of marriage of young mothers (aged 15-24 years) on utilisation of various services for their children, provided under the Integrated Child Development Service (ICDS) programme in India.

METHODS

Data from the nationally representative 2019-2021 National Family Health Survey of India were analysed. Mothers' age of menarche was used as an instrumental variable to isolate the effect of age of marriage on whether their children received (1) food, (2) health check-up, (3) immunisation, (4) early childhood care or preschooling or (5) weight measurement services from ICDS.

RESULTS

Nationally, 67.9% (95% CI 67.6%, 68.3%) of children received food (sample: 60 578), 61.8% (95% CI 61.4%, 62.1%) received a health check-up (sample: 60 316), 60.0% (95% CI 59.6%, 60.4%) received immunisation services (sample: 60 537), 52.0% (95% CI 51.6%, 52.4%) received early childhood care or preschooling (sample: 60 458) and 62.9% (95% CI 62.5%, 63.3%) received weight measurement services (sample: 60 278). Findings from instrumental variable analysis suggest that a 1-year increase in age of marriage could yield a 9 percentage point increase (95% CI 4%-13%; p<0.001) in utilisation of immunisation services. Although postponement of marriage positively affected utilisation of each of the other four ICDS components, these effects were not statistically significant.

CONCLUSION

Postponing age of marriage among young women is an effective intervention for promoting uptake of child immunisation services. Our findings support the Government of India's 2021 Bill to raise legal age of marriage of women.

Chromosomal polymorphisms and susceptibility to menstrual disorders: a retrospective analysis of 24,578 women

PURPOSE

To evaluate the association between the polymorphic variants of chromosomes and menstrual disorders.

METHODS

The data from our previous retrospective, single-center cohort study were re-analyzed. Women with regular menstruation were included as controls. Women with menstrual cycle abnormalities were subgrouped according to reproductive causes. The frequency of chromosomal polymorphisms was compared between groups. Regression analysis was used to adjust for potential confounding variables.

RESULT

A total of 24,578 women composed of 8062 women with regular cycles as the control group and 16,516 women as the menstrual cycle irregularity group were included. When compared with the control group, the incidence of chromosomal polymorphisms in the total menstrual cycle irregularity group, Polycystic ovary syndrome group, and Primary ovarian insufficiency group were significantly higher (4.49% versus 5.34%, P = 0.004, 4.49% versus 5.35%, P = 0.018 and 4.49% versus 5.94%, P = 0.002, respectively). The incidences of inv(9) in the Primary ovarian insufficiency group were significantly higher than that in the control individuals (1.0% versus 1.6%, P = 0.024). Logistic regression analysis showed an effect of chromosomal polymorphisms on menstrual cycle irregularity (OR: 1.62, 95% CI: 1.234-2.187, P = 0.007; adjusted OR: 1.46, 95% CI: 1.153-1.819, P < 0.001). The result demonstrated an effect of chromosomal polymorphisms on the Primary ovarian insufficiency group (OR: 2.52, 95% CI: 1.307-5.177, P < 0.001; adjusted OR: 2.61, 95% CI: 1.371-4.605, P < 0.001).

CONCLUSION

The study suggests chromosomal polymorphisms adversely affect female menstrual cycle irregularity.

Evaluating significance of European-associated index SNPs in the East Asian population for 31 complex phenotypes

BACKGROUND

Genome-wide association studies (GWASs) have identified many single-nucleotide polymorphisms (SNPs) associated with complex phenotypes in the European (EUR) population; however, the extent to which EUR-associated SNPs can be generalized to other populations such as East Asian (EAS) is not clear.

RESULTS

By leveraging summary statistics of 31 phenotypes in the EUR and EAS populations, we first evaluated the difference in heritability between the two populations and calculated the trans-ethnic genetic correlation. We observed the heritability estimates of some phenotypes varied substantially across populations and 53.3% of trans-ethnic genetic correlations were significantly smaller than one. Next, we examined whether EUR-associated SNPs of these phenotypes could be identified in EAS using the trans-ethnic false discovery rate method while accounting for winner's curse for SNP effect in EUR and difference of sample sizes in EAS. We found on average 54.5% of EUR-associated SNPs were also significant in EAS. Furthermore, we discovered non-significant SNPs had higher effect heterogeneity, and significant SNPs showed more consistent linkage disequilibrium and allele frequency patterns between the two populations. We also demonstrated non-significant SNPs were more likely to undergo natural selection.

CONCLUSIONS

Our study revealed the extent to which EUR-associated SNPs could be significant in the EAS population and offered deep insights into the similarity and diversity of genetic architectures underlying phenotypes in distinct ancestral groups.

Similarity and diversity of genetic architecture for complex traits between East Asian and European populations

BACKGROUND

Genome-wide association studies have detected a large number of single-nucleotide polymorphisms (SNPs) associated with complex traits in diverse ancestral groups. However, the trans-ethnic similarity and diversity of genetic architecture is not well understood currently.

RESULTS

By leveraging summary statistics of 37 traits from East Asian (N_max=254,373) or European (N_max=693,529) populations, we first evaluated the trans-ethnic genetic correlation (ρ_g) and found substantial evidence of shared genetic overlap underlying these traits between the two populations, with [Formula: see text] ranging from 0.53 (se = 0.11) for adult-onset asthma to 0.98 (se = 0.17) for hemoglobin A1c. However, 88.9% of the genetic correlation estimates were significantly less than one, indicating potential heterogeneity in genetic effect across populations. We next identified common associated SNPs using the conjunction conditional false discovery rate method and observed 21.7% of trait-associated SNPs can be identified simultaneously in both populations. Among these shared associated SNPs, 20.8% showed heterogeneous influence on traits between the two ancestral populations. Moreover, we demonstrated that population-common associated SNPs often exhibited more consistent linkage disequilibrium and allele frequency pattern across ancestral groups compared to population-specific or null ones. We also revealed population-specific associated SNPs were much likely to undergo natural selection compared to population-common associated SNPs.

CONCLUSIONS

Our study provides an in-depth understanding of similarity and diversity regarding genetic architecture for complex traits across diverse populations, and can assist in trans-ethnic association analysis, genetic risk prediction, and causal variant fine mapping.

Relationship between age at menarche and metabolic diseases in Korean postmenopausal women: The Korea National Health and Nutrition Examination Survey 2016-2018

BACKGROUND

Cardiovascular disease is the leading cause of morbidity and mortality in postmenopausal women. Early menarche may be associated with an increased risk of metabolic diseases such as diabetes and cardiovascular disease. This study aimed to investigate the effect of menarche age and the risk of diabetes and metabolic syndrome in Korean postmenopausal women.

METHODS

We analyzed 4,933 postmenopausal women (mean age: 64.7 years) using the Korean National Health and Nutritional Examination Survey 2016-2018. Subjects were divided into three groups according to menarche age (early menarche: ≤ 12 years (n = 451), reference: 13-16 years (n = 3,421), and late menarche: ≥ 17 years (n = 1,061)). Logistic regression analysis was used to estimate the odds ratio (OR) for diabetes and metabolic syndrome.

RESULTS

Women with an early menarche age were younger, more educated, and had higher income than the other groups (p-value < 0.001). There were no differences in body mass index, blood pressure, fasting glucose, HbA1c, and cholesterol levels among the three groups. After adjusting for potential confounding factors, early menarche age was significantly associated with the risk of diabetes (OR 1.435, 95% confidence interval (CI): 1.069-1.928). The prevalence of metabolic syndrome in all subjects was 41.1%. After adjusting for potential confounding factors, the OR of metabolic syndrome in the early menarche group was 1.213 (95% CI: 0.971-1.515).

CONCLUSION

The risk of diabetes was 1.43 times higher in postmenopausal Korean women with early menarche. Although the risk of metabolic syndrome was not statistically significant, it showed a tendency to increase in the early menarche group. Our results suggest that age at menarche may be helpful in diabetes risk stratification and early interventions for postmenopausal women.

Metabolically favorable adiposity and bone mineral density: a Mendelian randomization analysis

OBJECTIVE

This analysis assessed the putative causal association between genetically predicted percent body fat and areal bone mineral density (aBMD) and, more specifically, the association between genetically predicted metabolically "favorable adiposity" (MFA) and aBMD at clinically relevant bone sites.

METHODS

Mendelian randomization was used to assess the relationship of MFA and percent body fat with whole-body, lumbar spine, femoral neck, and forearm aBMD. Sex-stratified and age-stratified exploratory analyses were conducted.

RESULTS

In all MR analyses, genetically predicted MFA was inversely associated with aBMD for the whole body (β = -0.053, p = 0.0002), lumbar spine (β = -0.075; p = 0.0001), femoral neck (β = -0.045; p = 0.008), and forearm (β = -0.115; p = 0.001). This negative relationship was strongest in older individuals and did not differ by sex. The relationship between genetically predicted percent body fat and aBMD was nonsignificant across all Mendelian randomization analyses. Several loci that were associated at a genome-wide significance level (p < 5 × 10^-8 ) in opposite directions with body fat and aBMD measures were also identified.

CONCLUSIONS

This study did not support the hypothesis that MFA protects against low aBMD. Instead, it showed that MFA may result in lower aBMD. Further research is needed to understand how MFA affects aBMD and other components of bone health such as bone turnover, bone architecture, and osteoporotic fractures.

Chinese familial central precocious puberty with hyperuricemia due to recurrent DLK1 mutation: Case report and review of the literature

BACKGROUND

Central precocious puberty (CPP) is a precocious puberty due to premature activation of the hypothalamic-pituitary-gonadal axis (HPG). MKRN3 defects are well-known causes of CPP, while DLK1 mutations were recently identified in a few patients with CPP.

METHODS

The study was approved by the Institutional Review and the scientific committee of the hospital. The clinical data were collected. Whole-exome sequencing (WES) was performed to detect causative variants. Key words 'DLK1', 'MKRN3', and "central precocious puberty" were used for literature search in PubMed, Google Scholar, HGMD, and OMIM databases.

RESULTS

The patient, a male, whose puberty began before age nine, had significant metabolic abnormalities including overweight, hyperlipidemia, and hyperuricemia. WES detected a recurrent frame-shift mutation, NM_003836.5:c.479delC(p.P160fs*50) in DLK1 in the patient and his father.

CONCLUSION

The familial DLK1-CPP was identified in China for the first time, which supported that short stature is predicted in patients with CPP without GnRHa treatment. Therefore, we recommend that children with DLK1-CPP should be treated as early as possible to improve adult height. The patient in this study had persistent hyperuricemia, further suggests that this antiadipogenic factor represents a link between reproduction and metabolism.

Age at menarche and ischemic heart disease: An update mendelian randomization study

Background: Although earlier menarche age has been associated with ischemic heart disease in previous observational studies, the relationship's causation has not been shown. Through two-sample Mendelian randomization (MR), we were able to define the causal connection. Methods: We performed Mendelian Randomization (MR) analysis to explore the associations between genetically predicted AAM and IHD. Summary-level databases for exposure and outcome were selected from the MR-Base database (https://gwas.mrcieu.ac.uk/). Single-nucleotide polymorphisms (SNPs) connected to AAM at genome-wide significance level (p < 5 × 10-8) were considered as instrumental variables (IVs). We used four methods to pool MR estimates, including fixed-effects inverse variance weighting (fe-IVW), multiplicative random-effects inverse variance weighting (mre-IVW), weighted median (WM), and MR-Egger regression methods. Sensitivity analyses were performed to evaluate the robustness of the results. PhenoScanner searches and Multivariable Mendelian randomization (MVMR) analysis was used for assessing confounders. Results: 117 SNPs significantly correlated with AAM were screened as instruments, the results of three main methods showed that genetically earlier AAM may have a causal effect on the higher risk of IHD (fe-IVW: OR = 0.80, 95% CI: 0.72-0.88, p < 0.001; mre-IVW: OR = 0.80, 95% CI: 0.70-0.90, p < 0.001; WE: OR = 0.79, 95% CI: 0.66-0.93, p = 0.006). These results were consistent across sensitivity analyses. MR analysis revealed that there was still a relationship between AAM and IHD even when pleiotropic SNPs of confounders were removed employing PhenoScanner searches. In MVMR, the significant association remained after adjusting for biological sex, but it was attenuated with adjustment of body mass index including childhood and adult. Conclusion: Our MR analysis revealed a substantial genetically determined confounder-mediated relationship between an increase in genetically predicted AAM and a lower risk of IHD. By addressing the intervention of body mass index, the risk of IHD may be lowered.

Aberrant Notch Signaling Pathway as a Potential Mechanism of Central Precocious Puberty

The Notch signaling pathway is highly conserved during evolution. It has been well documented that Notch signaling regulates cell proliferation, migration, and death in the nervous, cardiac, and endocrine systems. The Notch pathway is relatively simple, but its activity is regulated by numerous complex mechanisms. Ligands bind to Notch receptors, inducing their activation and cleavage. Various post-translational processes regulate Notch signaling by affecting the synthesis, secretion, activation, and degradation of Notch pathway-related proteins. Through such post-translational regulatory processes, Notch signaling has versatile effects in many tissues, including the hypothalamus. Recently, several studies have reported that mutations in genes related to the Notch signaling pathway were found in patients with central precocious puberty (CPP). CPP is characterized by the early activation of the hypothalamus–pituitary–gonadal (HPG) axis. Although genetic factors play an important role in CPP development, few associated genetic variants have been identified. Aberrant Notch signaling may be associated with abnormal pubertal development. In this review, we discuss the current knowledge about the role of the Notch signaling pathway in puberty and consider the potential mechanisms underlying CPP.

Identifying Environmental Endocrine Disruptors Associated With the Age at Menarche by Integrating a Transcriptome-Wide Association Study With Chemical-Gene-Interaction Analysis

Menarche is the first occurrence of menstrual bleeding and one of the most important events of female puberty. Alarmingly, over the last several decades, the mean age at menarche (AAM) has decreased. Environmental endocrine disruptors (EEDs) are chemicals that may interfere with the endocrine system, resulting in adverse developmental, immunological, neurological, and reproductive effects in humans. Thus, the effects of EEDs on fertility and reproduction are growing concerns in modern societies. In this study, we aimed to determine the influence of genetic and environmental factors on AAM. We used data from an AAM genome-wide association study of 329,345 women to conduct a transcriptome-wide association study (TWAS) with FUSION software. As references, we determined the gene-expression levels in the hypothalamus, pituitary gland, ovaries, uterus, and whole blood. We performed Gene Ontology and Kyoto Encyclopedia of Genes and Genomes enrichment analyses using the significantly dysregulated genes identified by the TWAS. Using the STRING database, we also generated a protein-protein-interaction network to analyze common AAM-specific genes identified by the TWAS with different tissues. We performed chemical-related gene set enrichment analysis (CGSEA) and identified significant TWAS genes to uncover relationships between different chemicals and AAM. The TWAS identified 9,848 genes; among these, 1580 genes were significant (P < 0.05), and 11 genes were significant among the hypothalamus, pituitary, ovary, uterus, and whole blood. CGSEA identified 1,634 chemicals, including 120 chemicals significantly correlated with AAM. In summary, we performed a TWAS (for genetic factors) and CGSEA (for environmental factors) focusing on AAM and identified several AAM-associated genes and EEDs. The results of this study expand our understanding of genetic and environmental factors related to the onset of female puberty.

Genetic etiologies of central precocious puberty

Pubertal onset is a complex process, which is influenced by genetic and environmental factors, such as obesity and endocrine-disrupting chemicals. In addition, the timing of normal puberty varies between individuals and is a highly polygenic trait with both rare and common variants. Central precocious puberty (CPP) is defined as the early activation of the hypothalamic-pituitary-gonadal axis. Genetic factors are suggested to account for 50% to 80% of the variation in puberty initiation, as indicated by the greater concordance of pubertal timing observed in monozygotic twins than in dizygotic twins. Although genetic factors play a crucial role in CPP development, only few associated genes have been identified. To date, four monogenic genes have been identified: KISS1, KISS1R, MKRN3, and DLK1. Moreover, mutation prevalence in these genes varies considerably depending on the ethnicity of patients with CPP. This article reviews the current knowledge on the normal pubertal timing and physiology and discusses the CPP-causing genes.

Can time to menopause be predicted?

Menopause represents the definite end of a woman's reproductive life and the onset of a persistent hypoestrogenic state. This postmenopausal period will for most women last several decades. Although mean menopausal age seems to have increased somewhat during the last century, there is a significant individual variation in age at natural menopause. With efficient contraception, women of reproductive age can now, to some extent, choose when they want to have children. As a consequence of this and other sociodemographic changes, age at first birth has increased significantly over the last 50 years. It is well documented that long before a woman enters the menopausal transition and subsequent menopause, fertility declines and finally ceases. Being able to predict when a woman will enter menopause would therefore, from a reproductive perspective, be of major interest. Several sociodemographic, morphometric, and endocrine factors are associated with age at menopause or time to menopause. Unfortunately the sensitivity and specificity of these in predicting time to or age at menopause are low. Therefore, with the exception of anti-Müllerian hormone measurements, either alone or in combination with chronological age close to menopause, there are as of now no reliable ways of predicting when a woman will enter menopause.

Joint Associations of Actual Age and Genetically Determined Age at Menarche With Risk of Mortality

IMPORTANCE

Previous studies have shown an association between actual age at menarche and risk of all-cause mortality; however, the results are inconsistent, and no study has analyzed the joint associations between genetic susceptibility and actual age at menarche with the risk of mortality in prospective cohorts.

OBJECTIVES

To investigate joint associations of actual age and genetically determined age at menarche with risk of all-cause mortality.

DESIGN, SETTING, AND PARTICIPANTS

This prospective cohort study was conducted using data from the UK Biobank population across the United Kingdom from March 13, 2006, to October 1, 2010. A total of 264 546 women aged between 39 and 71 years with actual menarcheal age were included in this study; 246 676 of these women had genetic data available. Actual age at menarche was obtained from the touchscreen questionnaire at recruitment from 2006 to 2010. Genetically determined age at menarche was assessed by a genetic risk score. Statistical analysis was performed from August 22 to December 12, 2019.

EXPOSURE

Age at menarche.

MAIN OUTCOMES AND MEASURES

A multivariable Cox proportional hazards regression model was used to assess associations of actual or genetically determined age at menarche with risk of all-cause mortality.

RESULTS

The mean (SD) age of the study population at baseline was 56.4 (8.0) years, and the mean (SD) age at menarche included in the analyses was 13.0 (1.6) years. During a median of 9.0 years (range, 8.3-9.7 years) of follow-up, 7761 deaths were documented among the women with actual age at menarche, and 7054 deaths were documented among the women with genetically determined age at menarche. Both the actual age at menarche and the genetically determined age at menarche showed a U-shaped association with the risk of all-cause mortality (lowest actual age [<12 years] vs reference age [15 years]: hazard ratio [HR], 1.16 [95% CI, 1.07-1.26]; highest actual age [≥16 years] vs reference age [15 years]: HR, 1.17 [95% CI, 1.05-1.31]; P < .001 for quadratic trend; genetic risk score [GRS] of 1 vs reference score [GRS of 4]: HR, 1.10 [95% CI, 1.01-1.19; GRS of 6 vs reference score [GRS of 4]: HR, 1.09 [95% CI, 1.00-1.18]; P = .03 for quadratic trend). Significant interactions were also found between actual age at menarche and genetically determined age at menarche with all-cause mortality (HR of mortality associated with age of menarche <12 year was 1.24 [95% CI, 1.10-1.40] in the GRS of 1 group and 1.44 [95% CI, 1.21-1.72] in the GRS of 6 group; P = .001 for interaction). Women with mismatch of actual age and genetically determined age at menarche had the highest mortality risks; participants with the lowest genetic risk score and the highest age at menarche had an HR of 2.12 (95% CI, 1.58-2.83), and participants with the highest GRS and the lowest age at menarche had an HR of 1.44 (95% CI, 1.21-1.72).

CONCLUSIONS AND RELEVANCE

The results suggest that both actual age and genetically determined age at menarche exhibit U-shaped associations with all-cause mortality. Women with mismatch of actual age and genetically determined age at menarche may have the highest risk of all-cause mortality.

Early menarche and its consequence in Korean female: reducing fructose intake could be one solution

The mean age at menarche (AAM) of Korean females has been rapidly decreasing over the last 50 years; currently, the prevalence of early menarche (<12 years) is 22.3%. Female adolescents who experience early menarche are known to be at greater risk of psychosocial and behavioral problems along with several physical health problems such as menstrual problems. They also tend to achieve a shorter final height and develop obesity. Population-based Korean studies have shown a strong association between early menarche and the risk of obesity, insulin resistance, metabolic syndrome, nonalcoholic fatty liver disease, diabetes, breast cancer, and cardiovascular disease in adulthood. Although the exact mechanism of how early menarche causes cardiometabolic derangement in later adulthood is unknown, childhood obesity and insulin resistance might be major contributors. Recent studies demonstrated that an excessive consumption of fructose might underlie the development of obesity and insulin resistance along with an earlier AAM. A positive association was observed between sugar-sweetened beverages (a major source of fructose) intake and obesity, metabolic syndrome, insulin resistance, and cardiometabolic risk in Korean females. In pediatrics, establishing risk factors is important in preventing disease in later life. In this regard, early menarche is a simple and good marker for the management of cardiometabolic diseases in adulthood. Decreasing one's fructose intake might prevent early menarche as well as the development of obesity, insulin resistance, and cardiometabolic diseases.

Recovery of menses after functional hypothalamic amenorrhoea: if, when and why

BACKGROUND

Prolonged amenorrhoea occurs as a consequence of functional hypothalamic amenorrhoea (FHA) which is most often induced by weight loss, vigorous exercise or emotional stress. Unfortunately, removal of these triggers does not always result in the return of menses. The prevalence and conditions underlying the timing of return of menses vary strongly and some women report amenorrhoea several years after having achieved and maintained normal weight and/or energy balance. A better understanding of these factors would also allow improved counselling in the context of infertility. Although BMI, percentage body fat and hormonal parameters are known to be involved in the initiation of the menstrual cycle, their role in the physiology of return of menses is currently poorly understood. We summarise here the current knowledge on the epidemiology and physiology of return of menses.

OBJECTIVE AND RATIONALE

The aim of this review was to provide an overview of (i) factors determining the recovery of menses and its timing, (ii) how such factors may exert their physiological effects and (iii) whether there are useful therapeutic options to induce recovery.

SEARCH METHODS

We searched articles published in English, French or German language containing keywords related to return of menses after FHA published in PubMed between 1966 and February 2020. Manuscripts reporting data on either the epidemiology or the physiology of recovery of menses were included and bibliographies were reviewed for further relevant literature. The Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) criteria served to assess quality of observational studies.

OUTCOMES

Few studies investigate return of menses and most of them have serious qualitative and methodological limitations. These include (i) the lack of precise definitions for FHA or resumption of menses, (ii) the use of short observation periods with unsatisfactory descriptions and (iii) the inclusion of poorly characterised small study groups. The comparison of studies is further hampered by very inhomogeneous study designs. Consequently, the exact prevalence of resumption of menses after FHA is unknown. Also, the timepoint of return of menses varies strongly and reliable prediction models are lacking. While weight, body fat and energy availability are associated with the return of menses, psychological factors also have a strong impact on the menstrual cycle and on behaviour known to increase the risk of FHA. Drug therapies with metreleptin or naltrexone might represent further opportunities to increase the chances of return of menses, but these require further evaluation.

WIDER IMPLICATIONS

Although knowledge on the physiology of return of menses is presently rudimentary, the available data indicate the importance of BMI/weight (gain), energy balance and mental health. The physiological processes and genetics underlying the impact of these factors on the return of menses require further research. Larger prospective studies are necessary to identify clinical parameters for accurate prediction of return of menses as well as reliable therapeutic options.

Secular trend and social gradients in the menarcheal age of girls from eastern Poland between 1986 and 2016

The age at menarche is changing together with the development of society. The intensities of secular trends vary in different countries, regions or even towns and villages. Therefore, the objective of the paper was to assess the changes of the menarcheal age of girls in groups defined by different levels of parental education and the number of children in a family as well as the general index of socioeconomic status. The paper utilises the results of research conducted in the years 1985–1986, 2005–2006 and 2015–2016, covering 11 671 girls aged 10–16 from eastern provinces of Poland. Information about the date of birth, the date of the first period, place of residence, fathers’ and mothers’ education and the number of children in a family was collected. Research material was divided into groups stratified by mother’s education, father’s education, number of children in a family, size of place of residence and the general index of socioeconomic status (SES) was calculated. The results were processed statistically using one-way analysis of variance (ANOVA) and the Newman-Keuls method.

In all the assessed groups of girls the acceleration of maturation has been observed. Greater socio-economic differences of the menarcheal age of the respondents were observed in the years 1986–2006, whereas in the years 2006–2016 the differences were smaller. During the assessed period of 30 years, the most intensive acceleration in menarche was observed in the lowest social strata, i.e. in the daughters of parents with primary or vocational education, in those from the largest families and in those who were included in the group with the lowest SES point values. The lowest acceleration in the described indicator of development was found in girls from families with one or two children, whose parents had higher education degrees and the highest SES values.

The assessed schoolgirls still demonstrate the existence of social gradients in the menarcheal age but the gradients are smaller than 30 years ago.

The association between menarche and myopia and its interaction with related risk behaviors among Chinese school-aged girls: a nationwide cross-sectional study

Nearly 80% of new cases of myopia arise between 9 and 13 years old when puberty development also progresses rapidly. However, little is known about the association between myopia and puberty. We aim to evaluate the association between myopia and menarche, the most important puberty indicator for girls, and to test whether menarche could modify the effects of myopia-related behaviors. The participants came from two consecutive national surveys conducted in 30 provinces in mainland China in 2010 and 2014. We included 102,883 girls (61% had experienced menarche) aged 10-15 years. Risk behaviors for myopia which included sleep duration, homework time, and outdoor activity were measured by self-administrated questionnaire. Myopia was defined according to a validated method, and its relationships with menarche status and behaviors were evaluated by robust Poisson regression models based on generalized estimated equation adjusting for cluster effect of school. We found that postmenarche girls were at 13% (95% confidence interval: 11%-16%) higher risk of myopia than premenarche girls, after adjusting for exact age, urban-rural location, survey year, and four behavioral covariates. Short sleep duration (<7 h/d), long homework time (>1 h/d) and low frequency of weekend outdoor activity tended to be stronger (with higher prevalence ratios associated with myopia) risk factors for myopia in postmenarche girls than in premenarche girls, and their interaction with menarche status was all statistically significant (P < 0.05). Overall, our study suggests that menarche onset may be associated with increased risk of myopia among school-aged girls and could also enhance girls' sensitivity to myopia-related risk behaviors.

Association study of DLK1 in girls with idiopathic central precocious puberty

Objective Mutations in the delta-like 1 homolog (DLK1) gene have recently been reported in patients with idiopathic central precocious puberty (CPP). We aimed to investigate DLK1 mutations or polymorphisms in girls with CPP. Methods A total of 100 girls diagnosed with idiopathic CPP were enrolled. DLK1 coding regions were sequenced in girls with idiopathic CPP and healthy girls (controls). The relationship between identified sequence variations and CPP was evaluated via comparison of allele frequencies between patients with CPP and normal healthy controls. Results We identified five polymorphisms in DLK1. There was no significant difference with regard to allele frequency between patients with CPP and controls. Polymorphism c.549C>T (p.G183G) in DLK1 gene was identified in only one patient with CPP. In silico analysis with human splicing finder suggested that the variant (c.549C>T) leads to splicing defect. Conclusions The sequencing of DLK1 gene has uncovered only one potentially meaningful variant. However, our results demonstrate that DLK1 mutations are a relatively rare cause of idiopathic CPP.

DDT exposure during pregnancy and DNA methylation alterations in female offspring in the Child Health and Development Study

Studies measuring dichlorodiphenyltrichloroethane (DDT) exposure during key windows of susceptibility including the intrauterine period suggest that DDT exposure is associated with breast cancer risk. We hypothesized that prenatal DDT exposure is associated with DNA methylation. Using prospective data from 316 daughters in the Child Health and Development Study, we examined the association between prenatal exposure to DDTs and DNA methylation in blood collected in midlife (mean age: 49 years). To identify differentially methylated regions (DMRs) associated with markers of DDTs (p,p'-DDT and the primary metabolite of p,p'-DDT, p,p'-DDE, and o,p'-DDT, the primary constituents of technical DDT), we measured methylation in 30 genes important to breast cancer. We observed DDT DMRs in three genes, CCDC85A, CYP1A1 and ZFPM2, each of which has been previously implicated in pubertal development and breast cancer susceptibility. These findings suggest prenatal DDT exposure may have life-long consequence through alteration in genes relevant to breast cancer.

Secular trends in age at menarche in 20th century Mexico: Differences by ethnicity, area of residency, and socioeconomic status

OBJECTIVES

This study aims to assess the secular trend in age at menarche (AAM) in Mexico over the 20th century, and compare the patterns according to area of residence (rural/urban), socioeconomic status (SES), and ethnicity (indigenous/nonindigenous).

METHODS

Data on AAM from 24 380 women aged ≥20 years born between 1906 and 1986 were obtained from the Mexican National Health and Nutrition Survey 2006. Birth cohorts were compared to test for a secular trend and differences in mean AAM by area of residence, SES, and ethnicity were evaluated using the Welch test for heterogeneous variances followed by Tamhane T² for post hoc comparisons.

RESULTS

Mean AAM declined from 13.3 years among Mexican women born before the 1940s to 12.56 years among those born in the 1980s. Across birth cohorts, urban women had significantly earlier AAM than their rural counterparts. Nonindigenous urban women reached menarche the earliest and rural indigenous women the latest of all groups. Nonindigenous urban residents experienced a comparatively earlier decline, while that for the indigenous rural women occurred last. High SES women reached menarche the earliest and low SES women the latest. The historical decline in AAM for high and medium SES groups occurred relatively early, whereas that for the low SES occurred last.

CONCLUSIONS

Mean AAM was associated with area of residence, ethnicity, and SES. Our findings indirectly suggest that advances in living conditions experienced in Mexico during the 20th century appear to have been insufficient to overcome the social and biological inequalities accumulated over centuries in some groups.

Genome-wide scans identify known and novel regions associated with prolificacy and reproduction traits in a sub-Saharan African indigenous sheep (Ovis aries)

Maximizing the number of offspring born per female is a key functionality trait in commercial- and/or subsistence-oriented livestock enterprises. Although the number of offspring born is closely associated with female fertility and reproductive success, the genetic control of these traits remains poorly understood in sub-Saharan Africa livestock. Using selection signature analysis performed on Ovine HD BeadChip data from the prolific Bonga sheep in Ethiopia, 41 candidate regions under selection were identified. The analysis revealed one strong selection signature on a candidate region on chromosome X spanning BMP15, suggesting this to be the primary candidate prolificacy gene in the breed. The analysis also identified several candidate regions spanning genes not reported before in prolific sheep but underlying fertility and reproduction in other species. The genes associated with female reproduction traits included SPOCK1 (age at first oestrus), GPR173 (mediator of ovarian cyclicity), HB-EGF (signalling early pregnancy success) and SMARCAL1 and HMGN3a (regulate gene expression during embryogenesis). The genes involved in male reproduction were FOXJ1 (sperm function and successful fertilization) and NME5 (spermatogenesis). We also observed genes such as PKD2L2, MAGED1 and KDM3B, which have been associated with diverse fertility traits in both sexes of other species. The results confirm the complexity of the genetic mechanisms underlying reproduction while suggesting that prolificacy in the Bonga sheep, and possibly African indigenous sheep is partly under the control of BMP15 while other genes that enhance male and female fertility are essential for reproductive fitness.

Early Menarche is a Risk Factor for Short Stature in Young Korean Females: An Epidemiologic Study

OBJECTIVE

To assess the association between age at menarche and adult height [and body mass index (BMI)] in young Korean females and also to investigate whether early menarche (<12 years) is a risk factor for short stature and obesity in young Korean females.

METHODS

Data on 1148 females aged 18-30 years and 612 mother (612 pairs of mothers and daughters) from the 6^th Korea National Health and Nutrition Examination Survey (2013-2015) were analyzed.

RESULTS

Among 1148 females, 256 (22.3%) had early menarche. Their stature was approximately 0.445 cm shorter when menarche had occurred one year earlier. The prevalence of short stature (≤153 cm) and obesity (BMI ≥25) was higher in females with early menarche compared to those with later menarche (short stature: 10.5% vs 6.4%, obesity; 20.7% vs 13.1%, all p<0.001). In multivariate regression, the odds ratio (OR) for short stature was 2.62 [95% confidence interval (CI): 1.26-5.44] after adjusting for current age and mother’s height. OR for obesity was 1.74 (95% CI: 0.98-3.07) after adjusting for age and maternal BMI.

CONCLUSION

Final height in girls is influenced by age of menarche. Early menarche increased the risk for adult short stature in young Korean females.

Sibling relatedness rather than father absence predicts earlier age at menarche in ELSPAC cohort

Many studies during the past 50 years have found an association between father absence and earlier menarche. In connection with these findings, several evolutionary theories assume that father absence is a causal factor accelerating reproductive development. However, a recent study analysing data from the Avon Longitudinal Study of Parents and Children (ALSPAC) found that father absence does not predict age at menarche when adjusted for sibling relatedness. In this study, we have replicated these results in the Czech section of the European Longitudinal Study of Pregnancy and Childhood (ELSPAC), which used the same questionnaires as ALSPAC to study a geographically distinct population. Our results support the conclusion that sibling relatedness rather than father absence predicts age at menarche. Furthermore, our results show that age at menarche in 1990s UK and Czech cohorts is very similar despite socioeconomic differences between the two countries.

Older menarche age and short reproductive period linked to chronic kidney disease risk

This study aimed to investigate the association between reproductive period and menarche age and chronic kidney disease (CKD) in South Korean postmenopausal women.This was a cross-sectional study of the data for 8510 postmenopausal women using the results of Korean National Health and Nutrition Examination Surveys over the past 6 years.Of the total 8510 postmenopausal women, 790 (10.23%) were CKD patients. The menarche age in the CKD group was 16.2 ± 1.9 years old, which was higher than that in the non-CKD group (P < .001). The reproductive period of the CKD group was 32.4 ± 5.7 years, which was shorter than 33.3 ± 5.4 years in the non-CKD group (P < .001). The prevalence of CKD was 4.7% at a menarche age of 11 years or younger, which increased with increasing of menarche age, reaching 9.9% at menarche age of 16 years or older. According to the length of the reproductive period, the prevalence of CKD was 13.9% for the group less than 20 years of period and decreased significantly with increasing length of reproductive period. The prevalence of proteinuria was 7.2% in women with reproductive period of less than 20 years and significantly less in women with a reproductive period longer than 45 years (2.3%). The prevalence of CKD and proteinuria increased with increasing of menarche age, and the prevalence of CKD and proteinuria decreased with increasing of reproductive period.The results suggest that CKD was associated with older menarche age and a short reproductive period. Management of life patterns and medical problems in women with old age at menarche and a short reproductive period should be considered.

Age at menarche and prevention of hypertension through lifestyle in young Chinese adult women: result from project ELEFANT

Background

Early and late age at menarche are associated with risk of hypertension, but little is known whether modifiable lifestyle can reduce this risk.

Methods

Our study leverages 60,135 healthy young Chinese women from the Environmental and LifEstyle FActors iN metabolic health throughout life-course Trajectories (ELEFANT) study. Menarche age and lifestyle factors were assessed by self-reported questionnaires and hypertension was diagnosed by physicians. We estimated the odds ratios (ORs) of hypertension associated with menarche age using multivariable logistic regression. We further investigated whether modifiable lifestyles (body mass index, BMI; psychological stress; passive smoking; and imbalanced diet) increased risk in joint analyses.

Results

The association between age at menarche and hypertension was U-shaped, with age ≤ 12 at menarche giving the highest OR (1.46, 95% confidence interval [CI], 1.27–1.69) and ≥ 16 the second highest (OR = 1.36, 95% CI = 1.15–1.62). Simultaneous analysis of lifestyle risk factors and age of menarche showed that having one or more modifiable risk factors increased the menarche age-hypertension association. The risk of hypertension among participants with menarche age ≤ 12 decreased from OR 13.21 (95% CI = 5.17–29.36) with four high-risk lifestyle factors to 12.36 (95% CI = 9.51–16.05) with three high-risk factors, 5.24 (95% CI = 4.11–6.69) with two, and 2.76 (95% CI = 2.09–3.60) with one, in comparison to individuals with no high-risk lifestyle factors and menarche age 14.

Conclusions

Our results suggest that modification of lifestyle, including maintenance of normal weight and a balanced diet, are associated with substantially reduce the risk of hypertension in high-risk individuals.

Plain English summary

Early and late age at menarche are risk factors for the development of hypertension in Western populations, and there is limited evidence that this is also true of Chinese populations. Targeted prevention of hypertension in vulnerable populations would be highly beneficial in efforts to reduce the incidence of cardiovascular disease, but it is not currently known whether lifestyle intervention could reduce hypertension risk.

In this study, we analysed the risk of hypertension by age at menarche and four modifiable lifestyle factors (BMI, diet, psychological stress, and smoking tobacco) in a cohort of 60,135 young adult Chinese women (mean age 29).

We identified that early and late age at menarche are associated with increased risk of hypertension in young Chinese women. There was joint effects between age at menarche and lifestyles on hypertension only participants with age at menarche ≤12 and being overweight or obese. Modification of lifestyle, including maintenance of normal weight and a balanced diet, can substantially reduce the risk of hypertension in high-risk individuals.

In conclusion, our study has revealed that early and late menarche age are associated with the development of hypertension in young Chinese women, and that this risk is modified by healthy lifestyle traits.

Electronic supplementary material

The online version of this article (10.1186/s12905-018-0677-y) contains supplementary material, which is available to authorized users.

Early Menarche and Risk of Metabolic Syndrome: A Systematic Review and Meta-Analysis

BACKGROUND

The association between age at menarche and metabolic syndrome was inconsistent across studies and remains unclear. We conducted a systematic review and meta-analysis of observational studies to assess the association between age at menarche and risk of metabolic syndrome, comprehensively.

MATERIALS AND METHODS

The PubMed and ISI Web of Science databases were searched for all articles published through May 2017, and the reference lists of the retrieved articles were reviewed. Pooled relative risks (RRs) with 95% confidence intervals (CIs) were calculated using a random-effects model through combining the study-specific estimates adjusting for potential confounders.

RESULTS

Sixteen observational studies were eligible for the meta-analysis of age at menarche and metabolic syndrome, which included 13,657 cases among 51,453 subjects. The pooled RR of metabolic syndrome for the youngest versus the oldest categories of age at menarche was 1.62 (95% CI: 1.40-1.88) (p for heterogeneity = 0.01, I² = 57.3%). The analysis of 1-year decrease in age at menarche conferred a pooled RR of 1.08 (95% CI: 1.01-1.15), suggesting an 8% increase in risk of metabolic syndrome. The association between age at menarche and the risk of metabolic syndrome did not vary by study design, geographical region, number of subjects, and adjustment for confounders.

CONCLUSIONS

Our findings from the current meta-analysis suggest that earlier menarcheal age is associated with higher risk of metabolic syndrome. Age at menarche may help identify women with higher risk of metabolic syndrome. Further well-designed cohort studies are warranted to provide definitive evidence.

Relationship between Age at Menarche and Metabolic Syndrome in Premenopausal Women: Korea National Health and Nutrition Examination Survey 2013-2014

BACKGROUND

Early menarche may be associated with increased risk of cardiovascular disease. The aim of this study was to evaluate the relationship between age at menarche and metabolic syndrome (MetS) in Korean premenopausal women.

METHODS

We used nationally representative data from the Korea National Health and Nutrition Examination Survey from 2013 to 2014, and 3,023 premenopausal women aged 20-55 years were our subjects. We defined early menarche as age at first menstrual period less than 12 years. Multivariable logistic regression analysis was used to evaluate the relationship between age at menarche and MetS after adjusting for current age, and socioeconomic, lifestyle, and reproductive variables.

RESULTS

MetS was much more common in women aged 40-55 years than in women aged 20-39 years (4.1% vs. 15.1%). Compared with women who experienced menarche at age 12-15 years, the risk of MetS in the early menarche group was not higher in either age group, after adjusting for current age, and socioeconomic, lifestyle, and reproductive variables (odds ratio [OR], 1.767; 95% confidence interval [CI], 0.718-4.351 in those aged 20-39 years; OR, 1.780; 95% CI, 0.775-4.085 in those aged 40-55 years). The risk of MetS in women with menarche at age ≥16 years was not higher than in women with menarche at age 12-15 years.

CONCLUSION

Early or late menarche was not associated with an increased risk of MetS in premenopausal Korean women. Even before menopause, current age has a major influence on the development of MetS.

Body height and age at menarche of girls from eastern Poland in the period of political transformation

Biological state of a group of people or particular individuals in various phases of ontogenesis should be treated as a positive health measure. The aim of the study was to assess the directions of changes in body height and age at menarche of girls from eastern Poland in the years 1986-2016. The data regarding 30784 students aged 10-16 living in towns and villages of the eastern parts of such regions as Podkarpackie, Lubelskie, Podlaskie, Warminsko-mazurskie and, to a slight extent, Mazowieckie were used in the study. Body height was measured and information concerning the place of living and age at menarche (yes-no) was gathered during interviews. Acceleration of body height and age at menarche was observed in girls from the east of Poland in the period of political transformation and after European Union (EU) accession, while the level of secular trends was connected with the pace of changes in the environment. Biological effects of the EU preservation of Polish agriculture and particular care of the eastern provinces of Poland reduced developmental differences between these provinces and other regions of Poland. Moreover, in the analysed period of three decades (1986-2016), the disappearance of differences in body height and age at menarche between the inhabitants of rural and urban areas was noted, which indicates larger positive socio-economic changes in the countryside. In turn, greater body height was noted in non-menstruating girls compared to their menstruating counterparts. However, in subsequent observations, smaller differences between these groups were observed.

Breast cancer family history and allele-specific DNA methylation in the legacy girls study

Family history, a well-established risk factor for breast cancer, can have both genetic and environmental contributions. Shared environment in families as well as epigenetic changes that also may be influenced by shared genetics and environment may also explain familial clustering of cancers. Epigenetic regulation, such as DNA methylation, can change the activity of a DNA segment without a change in the sequence; environmental exposures experienced across the life course can induce such changes. However, genetic-epigenetic interactions, detected as methylation quantitative trait loci (mQTLs; a.k.a. meQTLs) and haplotype-dependent allele-specific methylation (hap-ASM), can also contribute to inter-individual differences in DNA methylation patterns. To identify differentially methylated regions (DMRs) associated with breast cancer susceptibility, we examined differences in white blood cell DNA methylation in 29 candidate genes in 426 girls (ages 6-13 years) from the LEGACY Girls Study, 239 with and 187 without a breast cancer family history (BCFH). We measured methylation by targeted massively parallel bisulfite sequencing (bis-seq) and observed BCFH DMRs in two genes: ESR1 (Δ4.9%, P = 0.003) and SEC16B (Δ3.6%, P = 0.026), each of which has been previously implicated in breast cancer susceptibility and pubertal development. These DMRs showed high inter-individual variability in methylation, suggesting the presence of mQTLs/hap-ASM. Using single nucleotide polymorphisms data in the bis-seq amplicon, we found strong hap-ASM in SEC16B (with allele specific-differences ranging from 42% to 74%). These findings suggest that differential methylation in genes relevant to breast cancer susceptibility may be present early in life, and that inherited genetic factors underlie some of these epigenetic differences.

Age at menarche and depressive symptoms in older Southern Chinese women: A Mendelian randomization study in the Guangzhou Biobank Cohort Study

To clarify the causal role of age at menarche in depressive symptoms we conducted a Mendelian randomization study using a large Southern Chinese cohort (n = 12,233). A genetic allele score was derived using stepwise regression with cross validation. Older age at menarche was not associated with geriatric depression scale score. Our findings suggest that higher rates of depression in women are likely attributable to other factors which require investigation.

Early menarche is associated with non-alcoholic fatty liver disease in adulthood

BACKGROUND

The aim of this study was to examine the association between early menarche (<12 years) and non-alcoholic fatty liver disease (NAFLD) in premenopausal women and to explore whether it is mediated by adult obesity and insulin resistance.

METHODS

We analyzed data of premenopausal women, aged ≥15 years, from the Korea National Health and Nutrition Examination Survey (2007-2009). We divided the women into three groups: early menarche, reference (12.00-15.99 years), and late menarche. The presence of NAFLD was determined using hepatic steatosis index >36.0.

RESULTS

Of the 4,387 women evaluated, 673 (15.4%) met the criteria for NAFLD. The prevalence of NAFLD was higher in both women with early and late menarche compared with the reference (early, 23.4%; reference, 14.0%; late, 19.9%, P < 0.001). After adjustment of confounders including age, the OR for NAFLD in early menarche compared with the reference was 3.04 (95%CI: 1.99-4.65). Further adjustment of mediators, such as central obesity or insulin resistance, attenuated the association to 1.91-2.17. There was no association, however, between late menarche and NAFLD after adjustment of confounders.

CONCLUSIONS

Early menarche was associated with an increased risk of NAFLD in young and middle-aged premenopausal Korean women.

Genetic Polymorphism of NUCKS1 Is Associated With the Susceptibility of Adolescent Idiopathic Scoliosis

STUDY DESIGN

A genetic association study.

OBJECTIVE

The aim of this study was to investigate whether NUCKS1 is a susceptible gene of adolescent idiopathic scoliosis (AIS) in Chinese population and to further narrate its association with the clinical phenotypes.

SUMMARY OF BACKGROUND DATA

AIS is characterized by late onset of menarche and disturbed growth rhythm. Previous studies showed that NUCKS1 is associated with age at menarche and pubertal height growth.

METHODS

Single-nucleotide polymorphism rs951366 of NUCKS1 was genotyped in 972 patients and 1454 healthy controls. The differences of genotype and allele distributions between AIS patients and healthy controls were evaluated using the χ test. One-way analysis of variance test was used to compare the relationship between different genotypes and clinical features including tissue expression of NUCKS1, age at menarche, and curve magnitude.

RESULTS

Patients were found to have a significantly lower frequency of CC than the controls (5.9% vs. 10.6%, P < 0.001). Besides, the frequency of allele C was found to be remarkably lower in the patients than the controls (26.4% vs. 30.9%, P < 0.001), with an odds ratio of 0.80 (95% confidential interval = 0.71-0.91). Patients with genotype CC had a remarkably lower age at menarche than patients with genotype TT (12.1 ± 1.7 vs. 12.8 ± 2.4 years, P = 0.02). Patients with genotype TT had a remarkably lower expression level of NUCKS1 than patients with genotype CC (2.8 ± 1.9 vs. 4.3 ± 2.2, P = 0.03). As for curve magnitude, no significant difference was found among patients with different genotypes.

CONCLUSION

Patients with allele T of rs951366 can be more vulnerable to the incidence of AIS as well as a late onset of menarche. Further functional analysis is warranted for a comprehensive knowledge on the contribution of this variant to the development of AIS.

LEVEL OF EVIDENCE

4.

Age at Menarche and Time Spent in Education: A Mendelian Randomization Study

Menarche signifies the primary event in female puberty and is associated with changes in self-identity. It is not clear whether earlier puberty causes girls to spend less time in education. Observational studies on this topic are likely to be affected by confounding environmental factors. The Mendelian randomization (MR) approach addresses these issues by using genetic variants (such as single nucleotide polymorphisms, SNPs) as proxies for the risk factor of interest. We use this technique to explore whether there is a causal effect of age at menarche on time spent in education. Instruments and SNP-age at menarche estimates are identified from a Genome Wide Association Study (GWAS) meta-analysis of 182,416 women of European descent. The effects of instruments on time spent in education are estimated using a GWAS meta-analysis of 118,443 women performed by the Social Science Genetic Association Consortium (SSGAC). In our main analysis, we demonstrate a small but statistically significant causal effect of age at menarche on time spent in education: a 1 year increase in age at menarche is associated with 0.14 years (53 days) increase in time spent in education (95% CI 0.10–0.21 years, p = 3.5 × 10⁻⁸). The causal effect is confirmed in sensitivity analyses. In identifying this positive causal effect of age at menarche on time spent in education, we offer further insight into the social effects of puberty in girls.

Age at menarche and cardiovascular risk factors using Mendelian randomization in the Guangzhou Biobank Cohort Study

Observational studies show earlier age at menarche associated with higher risk of cardiovascular disease although these studies could be confounded by childhood obesity or childhood socioeconomic position. We tested the hypothesis that earlier age at menarche is associated with poorer cardiovascular risk factors using a Mendelian randomization design. We conducted a Mendelian randomization study in a large Southern Chinese cohort, the Guangzhou Biobank Cohort Study (n=12,279), to clarify the causal role of menarche in cardiovascular disease risk factors including blood pressure, lipids, fasting glucose, adiposity and type 2 diabetes. A genetic allele score was obtained from single nucleotide polymorphisms associated with age at menarche using stepwise regression and with cross validation. Estimates of the association of age at menarche with cardiovascular disease risk factors were obtained using two stage least squares regression. Height was included as a positive control outcome. The F-statistic for the allele score (rs17268785, rs1859345, rs2090409, rs4452860 and rs4946651) was 19.9. Older age at menarche was associated with lower glucose (-0.39mmol/L per year older menarche, 95% confidence interval (CI) -0.78 to -0.001) but not clearly with any other cardiovascular risk factors. Older age at menarche was also associated with taller height. Age at menarche did not appear to affect cardiovascular disease risk factors except for glucose in an inverse manner. However, these results need to be confirmed in larger Mendelian randomization studies.

Predictability of BRCA1/2 mutation status in patients with ovarian cancer: How to select women for genetic testing in middle-income countries

OBJECTIVES

To evaluate the accuracy of algorithms for predicting BRCA1/2 germ-line mutation carrier probability, and to identify factors that could improve their performance among Brazilian women with ovarian cancer (OC).

STUDY DESIGN

In this cross-sectional study, we enrolled patients (unselected for family history of cancer) undergoing treatment or follow-up for OC in a single centre in Brazil. Clinical and demographic data, including family history of cancer, were obtained. Blood samples were collected for genetic testing.

MAIN OUTCOME MEASURES

The entire coding sequence of BRCA1 and BRCA2 was evaluated for mutations. Mutation carrier probability was calculated using BOADICEA, BRCAPRO, Myriad and the Manchester score. Sensitivity, specificity, positive and negative predictive values, and area under the receiver operating characteristic curves (AUC) were calculated for each algorithm. Logistic regression was used to detect additional factors associated with BRCA1/2 status, and these were added to the algorithms before recalculating the AUCs.

RESULTS

BRCA1/2 mutations were identified in 19 of the 100 included patients. BOADICEA outperformed other algorithms (sensitivity, 73.7%; specificity, 87.7%; AUC, 0.87, with a threshold of a 10% risk of mutation). Later menarche was associated with the presence of a BRCA1/2 mutation. Although adding age at menarche resulted in a larger AUC for all models, this increase was significant only for the Myriad algorithm.

CONCLUSION

A BOADICEA risk evaluation of 10% or more most accurately predicted BRCA1/2 status, and the inclusion of age at menarche tended to improve the performance of all algorithms. Using these tools could reduce the number of tests, but at the expense of missing a significant proportion of mutation carriers.

Body structure and maturation – the association with environmental factors

The main objective of the study was to determine the relationship between physique, maturation and some environmental factors. The study was conducted in Warsaw, between 2012 and 2013 in randomly selected schools. The material included 171 girls, aged 12–20 years. Body height and weight, upper and lower extremity length, subcutaneous fat folds on arm, subscapular and abdominal, circumferences of arm, chest, waist and hip were measured. Body proportion indices were calculated. The questionnaire form provided information on parental education and profession, and the number of children in family. Girls were asked about age at menarche, number of daily meals, level of physical activity, participation is sport, and level of stress at home and at school. The principal component analysis was applied and 4 factors were extracted from the set of living condition characteristics (F1 – Parental education & father’s occupation, F2 – Mother’s occupation and the number of children, F3 – Stress, F4 – Physical activity and number of daily meals). Regression analysis allowed to evaluate the association of body build characteristics and age at menarche with the four factors. Factor 1 and 4 were the only ones which showed a statistically significant association with body build. The results showed that girls who were taller, with smaller arm and waist circumferences and less adiposity came from families with higher parental education and better father’s profession. Taller stature, longer legs and less adiposity characterized girls who were more physically active and consumed more than three meals a day.

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.

Infection and pubertal timing: a systematic review

The decline in age of pubertal timing has serious public health implications ranging from psychosocial adjustment problems to a possible increase in reproductive cancers. One biologically plausible explanation for the decline is a decrease in exposures to infections. To systematically review studies that assess the role of infection in pubertal timing, Medline, Web of Science and EMBASE were systematically searched and retrieved studies were reviewed for eligibility. Eligible studies examined the association between infections, including microbial exposures, and physical pubertal characteristics (breast, genitalia and pubic hair development) or age at menarche. We excluded studies that were published in a language other than English, focused on precocious puberty, were case studies, and/or included youth with autoimmune diseases. We report on study design, population characteristics, measurement of infection and puberty and the main effects of infection on pubertal development. Based on our search terms we identified 1372 unique articles, of which only 15 human and five animal studies met our eligibility criteria. Not all studies examined all outcomes. Infection was associated with later breast development (4/4 human studies), with less consistent evidence for genitalia and pubic hair development. Seven studies assessed age at menarche with inconsistent findings (three supporting later, four no association). We conclude that a small but consistent literature supports that infection is associated with later breast development; the evidence for other pubertal events and age at menarche is less clear. Where fewer childhood infections coincide with the rise in incidence of hormone-related cancers.

Early menarche is associated with metabolic syndrome and insulin resistance in premenopausal Korean women

In pediatrics, identifying risk factors is important in planning the prevention of cardiovascular disease. The aim of this study was to determine whether there is an independent association between early menarche (<12 years) and metabolic syndrome (MetS) in Korean women. We analyzed data from 4463 premenopausal women from the Fourth Korea National Health and Nutrition Examination Survey-IV (2007-2009). MetS was defined by the International Diabetes Federation for Asians and insulin resistance (IR) was defined as HOMA-IR more than 3.05. The prevalence of MetS and IR was 7.9 and 15.0%. Women (55.6%) with MetS also showed IR. The prevalence of MetS was higher in both women with early menarche and late menarche (≥16 years) compared with the reference group (early, 12.8%; reference, 7.0%; late, 11.0%, both P = 0.002). However, the odds ratio for MetS was 3.54 (95% confidence interval (CI), 2.14-5.87) and for IR was 2.98 (95% CI, 1.99-4.47) after adjusting for age and other confounders such as lifestyle variables, reproductive variables and sociodemographic variables only in women with early menarche

CONCLUSION

Early menarche was associated with an increased risk of MetS and IR in premenopausal Korean women.

WHAT IS KNOWN

Early menarche is associated with higher risk of CVD-related death and all-cause mortality in Western studies. Early menarche is associated with higher risk of diabetes in Korean premenopausal women.

WHAT IS NEW

Early menarche (<12 years) is associated with metabolic syndrome and insulin resistance in nationally representative Korean premenopausal women. However, late menarche (>16 years) is not associated with metabolic syndrome after controlling for age and other confounders.

Earlier menarcheal age in Spanish girls is related with an increase in body mass index between pre-pubertal school age and adolescence

BACKGROUND

Higher body mass index (BMI) has been associated with earlier pubertal development.

OBJECTIVE

The aim of this longitudinal study was to determine menarcheal age in a Spanish cohort and to assess its association with anthropometric variables at birth, childhood and adolescence. We also analyse whether the tracking of weight between different ages could affect the timing of menarche.

METHODS

The sample population included 195 randomly selected 6-8-year-old girls who participated in the baseline of the Four Provinces Study and in the follow-up of this study at 13-16 years old. Anthropometrical variables were measured and BMI and BMI z-score were calculated. Information regarding birth weight and menarche was obtained by means of self-report questionnaire.

RESULTS

Correlation analysis showed a significant negative association of age at menarche with weight, BMI and BMI z-score in the baseline and follow-up groups but not with weight at birth. Fat mass at adolescence is related to a significantly earlier menarcheal age. When comparing weight categories, earliest menarcheal age is associated with an increase of BMI between 6-8-year-old and 13-16-year-old girls.

CONCLUSION

In our study, high weight in girls is associated with the earliest age at menarche. This becomes a major influence when weight gain occurs between pre-pubertal school age and adolescence.

A meta-analysis provides evidence that prenatal smoking exposure decreases age at menarche

Since studies of association between prenatal tobacco exposure and age at menarche have reported inconsistent results so far, we conducted a meta-analysis to examine this association. In total 36 relevant articles (1995-2014) were identified, 17 of which satisfied the inclusion criteria and were used in the analysis. Nearly one month decrease (-0.092 [95%CI:-0.160, -0.024] year) in age at menarche was found in women who were exposed to tobacco in utero. The meta-regression analysis showed that average year of birth in the cohorts might significantly influence association between maternal smoking and daughter's age at menarche. Based on results obtained from 5 studies where age at menarche was treated as a categorical variable, maternal smoking status during pregnancy increased a risk for daughters to have menarche earlier than at 11 years old by 15%.

Bivariate Genome-Wide Association Study Implicates ATP6V1G1 as a Novel Pleiotropic Locus Underlying Osteoporosis and Age at Menarche

OBJECTIVE

Age at menarche (AAM) is determined by the overall duration of endocrine-tissue sex hormone exposure levels. Osteoporosis, the most common metabolic bone disease, is characterized primarily by reduced bone mineral density (BMD) and an increased risk of low trauma fractures. Bone was an endocrine organ regulating the synthesis and secretion of sex steroid hormones. The mutual dependence between bone and gonads underscore the importance of genetic approaches to identify novel pleiotropic genetic factors coregulating BMD and AAM. In this study, we performed a bivariate genome-wide association study (GWAS) to explore novel ethnic common loci and/or genes that may influence both AAM and BMD.

METHODS

We analyzed genotyping data available for 826 unrelated Chinese subjects using genome-wide human genotyping arrays. After quality control, a total of 702 413 single-nucleotide polymorphisms (SNPs) were tested for association using a bivariate linear regression model. The interesting SNPs were replicated in three independent cohorts including 1728 unrelated Caucasians, 709 African-Americans, and 408 Hispanic-Americans.

RESULTS

We found four SNPs (rs10817638, rs7851259, rs10982287, and rs4979427), located upstream of the ATP6V1G1 gene, were bivariately associated with hip BMD-AAM (P = 4.90 × 10(-7), P = 1.07 × 10(-6), P = 1.28 × 10(-5), and P = 5.42 × 10(-5), respectively). These four SNPs were replicated in African-Americans, with corresponding values of P = 1.95 × 10(-2), P = 3.18 × 10(-2), P = 2.57 × 10(-2), and P = 3.64 × 10(-2), respectively. rs10817638 and rs10982287 were further replicated in Caucasians (P = 1.76 × 10(-2) and P = 9.42 × 10(-3), respectively) and Hispanic-Americans (P = 8.37 × 10(-3) and P = 1.52 × 10(-3), respectively). Meta-analyses yielded stronger association signals for rs10817638 and rs10982287 with combined values of P = 3.02 × 10(-9) and P = 3.49 × 10(-9), respectively.

CONCLUSIONS

Our study implicated ATP6V1G1 as a novel pleiotropic gene underlying variation of both BMD and AAM. The findings enhance our knowledge of genetic associations between BMD and AAM and provide a rationale for subsequent functional studies of these implicated genes in the pathophysiology of diseases/traits, such as osteoporosis and AAM.

Correlation between cervical vertebral maturation and chronological age in a group of Iranian females

BACKGROUND

Correlation between chronological age at different stages of cervical vertebral maturation (CVM) is important in clinical orthodontic practice. The objective of this study was to evaluate the correlation between CVM stage and chronological age in a group of Iranian female patients.

MATERIALS AND METHODS

This study was conducted on 196 digital lateral cephalometry of female patients with the age ranged 9-14 years. The CVM stage was determined with two calibrated examiners, using the method developed by Baccetti and its correlation with mean chronological age was assessed by the Spearman rank-order. The intra and inter-agreements were evaluated by weighted Kappa statistics in overall diagnosis of stages, in addition to determination of presence or absent of concavities at the lower border of second, third and fourth cervical vertebrae and the shapes of the third and fourth vertebrae. P < 0.05 was considered as significant.

RESULTS

The correlation coefficient between CVM stages and chronological age was relatively low (r = 0.62). The least amount of inter-observer agreement was determined to be at the clinical decision of the shape of the fourth vertebra.

CONCLUSION

Regarding the low reported correlation, the concomitant usage of other skeletal indicators seems necessary for precise determination of physiological age of the patients.

Biosocial correlates of age at menarche in a British cohort

BACKGROUND

A large number of biosocial variables have been shown to associate with age at menarche, but the results are inconsistent and differentiate not only between countries but within countries as well.

AIM

This study examined age at menarche in a British national cohort in relation to 21 biosocial and anthropometric variables.

SUBJECTS AND METHODS

The analyses were based on 4483 girls from the British National Child Development Study (NCDS).

RESULTS

The majority of girls reached menarche between 12-14 years of age. Girls from smaller families, those living in the East and South East, South West, West Midlands and Wales regions, in tied housing and uncrowded conditions, not sharing a bedroom, not having free school meals, whose families lived in households without financial problems had started menstruating earlier than their peers from families with lower socioeconomic status. However, when all the significant variables were analysed together significant associations remained only for mother's age at menarche, height and weight at 7 years, family size and tenure.

CONCLUSIONS

The results of this study support the hypotheses that intra-uterine growth and conditions in early life as well as socio-economic background are associated with the timing of menarche and that greater childhood growth and better SES are related to earlier menarche.

Gene polymorphisms in RANKL/RANK/OPG pathway are associated with ages at menarche and natural menopause in Chinese women

Background

Age at menarche (AAM) and age at natural menopause (AANM) have been shown intimately associated with woman’s health later in life. Previous studies have indicated that AAM and AANM are highly heritable. RANKL/RANK/OPG signaling pathway is essential for mammary gland development, which is also found associated with post-menopausal and hormone-related diseases. The aim of this study was to evaluate associations between the polymorphisms in the TNFSF11, TNFRSF11A and TNFRSF11B genes in the RANKL/RANK/OPG pathway with AAM and AANM in Chinese women.

Methods

Post-menopausal Chinese women (n = 845) aged from 42 to 89 years were recruited in the study. Information about AAM and AANM were obtained through questionnaires and the genomic DNA was isolated from peripheral blood from the participants. Total 21 tagging single nucleotide polymorphisms (SNPs) of TNFSF11, TNFRSF11A and TNFRSF11B were genotyped.

Results

Three SNPs of TNFRSF11A (rs4500848, rs6567270 and rs1805034) showed significant association with AAM (P < 0.01, P = 0.02 and P = 0.01, respectively), and one SNP (rs9962159) was significantly associated with AANM (P = 0.03). Haplotypes TC and AT (rs6567270-rs1805034) of TNFRSF11A were found to be significantly associated with AAM (P = 0.01 and P = 0.02, respectively), and haplotypes GC and AC (rs9962159-rs4603673) of TNFRSF11A showed significant association with AANM (P = 0.03 and P < 0.01, respectively). No significant association between TNFSF11 or TNFRSF11B gene with AAM or AANM was found.

Conclusions

The present study suggests that TNFRSF11A but not TNFSF11 and TNFRSF11B genetic polymorphisms are associated with AAM and AANM in Chinese women. The findings provide evidence that genetic variations in RANKL/RANK/OPG pathway may be associated with the onset and cessation of the menstruation cycle.

Sugar-sweetened beverage consumption and age at menarche in a prospective study of US girls

STUDY QUESTION

Is sugar-sweetened beverage (SSB) consumption associated with age at menarche?

SUMMARY ANSWER

More frequent SSB consumption was associated with earlier menarche in a population of US girls.

WHAT IS KNOWN ALREADY

SSB consumption is associated with metabolic changes that could potentially impact menarcheal timing, but direct associations with age at menarche have yet to be investigated.

STUDY DESIGN, SIZE, DURATION

The Growing up Today Study, a prospective cohort study of 16 875 children of Nurses' Health Study II participants residing in all 50 US states. This analysis followed 5583 girls, aged 9-14 years and premenarcheal at baseline, between 1996 and 2001. During 10 555 person-years of follow-up, 94% (n = 5227) of girls reported their age at menarche, and 3% (n = 159) remained premenarcheal in 2001; 4% (n = 197) of eligible girls were censored, primarily for missing age at menarche.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Cumulative updated SSB consumption (composed of non-carbonated fruit drinks, sugar-sweetened soda and iced tea) was calculated using annual Youth/Adolescent Food Frequency Questionnaires from 1996 to 1998. Age at menarche was self-reported annually. The association between SSB consumption and age at menarche was assessed using Cox proportional hazards regression.

MAIN RESULTS AND THE ROLE OF CHANCE

More frequent SSB consumption predicted earlier menarche. At any given age between 9 and 18.5 years, premenarcheal girls who reported consuming >1.5 servings of SSBs per day were, on average, 24% more likely [95% confidence interval (CI): 13, 36%; P-trend: <0.001] to attain menarche in the next month relative to girls consuming ≤2 servings of SSBs weekly, adjusting for potential confounders including height, but not BMI (considered an intermediate). Correspondingly, girls consuming >1.5 SSBs daily had an estimated 2.7-month earlier menarche (95% CI: -4.1, -1.3 months) relative to those consuming ≤2 SSBs weekly. The frequency of non-carbonated fruit drink (P-trend: 0.03) and sugar-sweetened soda (P-trend: 0.001), but not iced tea (P-trend: 0.49), consumption also predicted earlier menarche. The effect of SSB consumption on age at menarche was observed in every tertile of baseline BMI. Diet soda and fruit juice consumption were not associated with age at menarche.

LIMITATIONS, REASONS FOR CAUTION

Although we adjusted for a variety of suspected confounders, residual confounding is possible. We did not measure SSB consumption during early childhood, which may be an important window of exposure.

WIDER IMPLICATIONS OF THE FINDINGS

More frequent SSB consumption may predict earlier menarche through mechanisms other than increased BMI. Our findings provide further support for public health efforts to reduce SSB consumption.

STUDY FUNDING/COMPETING INTERESTS

The Growing up Today Study is supported by grant R03 CA 106238. J.L.C. was supported by the Breast Cancer Research Foundation; Training Grant T32ES007069 in Environmental Epidemiology from the National Institute of Environmental Health Sciences, National Institutes of Health; and Training Grant T32HD060454 in Reproductive, Perinatal and Pediatric Epidemiology from the National Institute of Child Health and Human Development, National Institutes of Health. A.L.F. is supported by the American Cancer Society, Research Scholar Grant in Cancer Control. K.B.M. was supported in part by the National Cancer Institute at the National Institutes of Health (Public Health Service grants R01CA158313 and R03CA170952). There are no conflicts of interest to declare.

Estrogen receptors genes polymorphisms and age at menarche in idiopathic scoliosis

Background

The age at menarche (AAM) is commonly in use in patients with IS as one of the maturity indicator suggesting deceleration of the growth velocity. The AAM was suggested to be related to predisposition and curve progression potential of IS. The late age at menarche was reported to be associated with higher prevalence of adolescent idiopathic scoliosis. The age at menarche is determined by both genetic and environmental factors as well as their interactions. Estrogen receptors 1 and 2 polymorphism were reported to be associated with AAM: in ESR1 XbaI and PvuII site polymorphism and in ESR2 AluI site polymorphism.

The purpose of the study was to investigate associations of the ESR1 and ESR2 polymorphisms with AAM in IS patients and to evaluate association of AAM with IS severity.

Methods

208 females with IS Caucasian females from Central Europe underwent clinical, radiological and genetic examinations. Four SNPs were selected XbaI (A/Grs9340799) and PvuII (C/T rs2234693) in ESR1 and AluI (A/G rs4986938) and RasI (A/G rs1256049) in ESR2. Samples were analyzed with polymerase chain reaction followed by restriction fragments length polymorphism analysis (PCR-RFLP). The age of a menarche was established during personal interview with the patients and in case of children with their parents. The Cobb angle was measured.

Results

All genotypes followed HWE. Mean AAM for patients was 154.8 ± 14.7 months (12.9 ± 1.2 years). The earliest AAM was 121 and latest 192 months. There was no statistically significant difference between AAM mean values in each genotype, for the XbaI, PvuII, AluI and RsaI site polymorphisms the p values were p = 0.7141, p = 0.9774, p = 0.7973 and p = 0.2282, respectively. Patients divided according to Cobb into mild (<30°), moderate (30°-49°) or severe (≥50°) IS revealed tendency to delay AAM: 151.9 ± 14.7; 155.2 ± 14.8 and 157.9 ± 14.0 months, respectively. There was statistical significant difference between patients with mild <30° and severe ≥50° IS, p = 0.0267.

Conclusions

In IS patients estrogen receptors polymorphisms did not show association with the AAM. Patients with severe IS form revealed delayed AAM than patients with mild IS form.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2474-15-383) contains supplementary material, which is available to authorized users.