The mean age of menarche among Chinese schoolgirls declined by 6 months from 2005 to 2014

Sex Differences in Grip Strength From Birth to Age 16: A Meta-Analysis

In 1985, Thomas and French published results of a meta-analysis that examined sex differences in grip strength in children 5 years of age and older. Their analysis included results from only four studies, and no update has been published. The purpose of the current study was to use meta-analysis to examine sex differences in grip strength from birth to age 16. The analysis included 808 effects from 169 studies conducted in 45 countries between 1961 and 2023. The total sample was 353,676 (178,588 boys, 175,088 girls). From birth to 16 years of age, grip strength was consistently greater in boys than girls. Between 3 and 10 years old, the effect size was small-to-moderate, with female grip strength equaling 90% of male grip strength (Hedges g = 0.33-0.46). At age 11, the effect size decreased slightly, likely due to girls reaching puberty before boys (g = 0.29, 95% confidence intervals (CI) [0.22, 0.35]). At age 13, the effect size increased markedly likely due to male puberty (g = 0.63, 95% CIs [0.55, 0.70]). By age 16, the sex difference in grip strength was substantial, with female grip strength equaling 65% of male grip strength (g = 2.07, 95% CIs [1.86, 2.27]). Secondary analyses revealed that the sex difference in grip strength is broadly similar between countries and has been mostly stable since the 1960s, except for a narrowing of the difference among 5-10-year-olds after 2010. Various biological factors explain why, on average, boys are stronger than girls from birth onward.

Secular Trends in the Median Age at Menarche and Spermarche Among Chinese Children From 2000 to 2019 and Analysis of Physical Examination Indicators Factor

OBJECTIVES

This research aimed to understand the long-term trends in the age of menarche among girls and spermarche among boys, and to analyze the factors that may influence the onset of menarche and first spermarche.

METHODS

The study was based on data from 49 566 students in Henan Province collected from the Chinese National Surveys on Students' Constitution and Health (CNSSCH) conducted between 2000 and 2019. Median age at menarche and spermarche was estimated by probit analysis. t-Tests were used to analyze the influence of menarche and first spermarche on physical examination indexes of adolescent children, and the chi-squared test was used to compare whether the differences in physical activity were statistically significant.

RESULTS

The age at menarche has decreased from 12.33 years in 2000 to 12.00 years in 2019, and the age at first spermarche has decreased from 14.01 years in 2000 to 13.99 years in 2019. The age at first spermarche in urban boys (13.61 years in 2000; 12.94 years in 2014) was consistently younger than that in rural boys (14.43 years in 2000; aged 13.08 in 2014), except in 2019. The age of menarche in urban girls (12.23 years in 2000; 11.89 years in 2019) was always earlier than that in rural girls (12.44 years in 2000; 12.05 years in 2019).

CONCLUSIONS

The age at menarche and spermarche for children in Henan Province generally showed a decreasing trend from 2000 to 2019. The status of BMI is significantly associated with the early onset of puberty in children.

Assessment of the differences in Mean Age at Menarche (MAM) among adolescent girls in rural and urban Nigeria: a systematic review

INTRODUCTION

Globally, there has been a decline in the age of menarche; the decline is higher in poorer countries than in richer ones. The measurement of the decline was based on the reported mean age at menarche (MAM) across the countries. There is a significant knowledge gap in investigating the generational decline in MAM in low- and median-income countries (LMC). In Nigeria, different studies have reported MAM, but none have attempted to investigate the generational shift in the reported MAM in girls residing in rural and urban areas. This review sought to understand if there is a rural-urban disparity in the MAM.

METHODS

Documents were searched in the relevant bibliometric database and Population intervention, comparison(s) and outcome (PICO) framework were used as eligibility criteria for extracting data from the documents based on some inclusion and exclusion criteria. The population are adolescent schoolgirls in rural and urban settlements in Nigeria. The comparator is the age of menarche of urban versus rural adolescent schoolgirls in Nigeria, while the mean age at menarche (MAM) is the outcome. Data quality assessment was done to critically appraise the included studies and enhance. Data were synthesized using narrative review, descriptive and inferential statistics.

RESULTS

Ten articles were included in the study, following the PRISMA framework. The overall mean evaluation of the risk of bias in the individual studies included in the review was computed to be 88%. Generally, there seems to be a decline in the age at menarche from 1976 to 2023. The rural MAM is higher than the urban MAM, and the gap between the two appears to be narrowing. The t-test showed no statistically significant mean differences between the rural and urban mean age at menarche (T = 2.1009, p value = 0.4679). The mean menarcheal age for girls in rural and urban areas is 13.44 and 13.04, respectively. There is a strong positive correlation between the rural and urban MAMs (Pearson = 0.93, p < 0.001). The Gaussian kernel estimated a bimodal distribution for rural girls, where they are most likely to experience menarche at 11 and 13 years, respectively, while urban girls are most likely to experience menarche at 13 years. In both locations, the incidence of menarche decreases just after the peak at 13 years.

CONCLUSION

Although rural girls have delayed menarche, there is no statistically significant mean difference between the age at menarche reported for rural and urban areas in Nigeria. Interventions in the form of counseling and reproductive education are recommended. The review provides a strong foundation for further research and policy development aimed at improving the health and well-being of adolescent girls in Nigeria and other similar settings.

PROSPERO REGISTRATION

CRD42024529497.

Longitudinal associations of menstrual characteristics with mental health problems among Chinese girls

Cross-sectional studies indicate that menstrual problems are related to poorer mental health; however, longitudinal studies are limited. This longitudinal study aimed to determine whether baseline menstrual characteristics were risk factors for incident and persistent mental health problems. The study was conducted among Chinese adolescent girls. Menstrual characteristics including menarche, menstrual cycle and menstrual pain were assessed at baseline, whereas mental health problems including PTSD, depression, anxiety, ADHD, insomnia, psychotic-like experiences, non-suicidal self-injury, suicide ideation, suicide plan, and suicide attempt were assessed at baseline (n = 1039) and at the 1-year follow-up (n = 946) by self-administered, structured questionnaires. Multiple logistic regressions were performed to examine whether menstrual characteristics were associated with incident (e.g., PTSD at follow-up but not baseline) and persistent (e.g., PTSD at both time points) mental health problems. The results demonstrated that early menarche was related to persistence of psychotic-like experiences; irregular menstruation was associated with higher rates of incident anxiety and insomnia, and persistent depression, anxiety, ADHD, insomnia, non-suicidal self-injury, suicide ideation, and suicide plan; menstrual pain was associated with elevated rates of incident PTSD and depression, and persistent depression, insomnia, psychotic-like experiences, non-suicidal self-injury, suicidal ideation, suicide plan, and suicide attempt. In conclusion, irregular menstruation and menstrual pain specifically contributed to the development of emotional problems and insomnia, and were associated with maintenance of the most mental health problems in early adolescence. The long-term effects of menstrual problems on mental health need further study.

Matching actions to needs: shifting policy responses to the changing health needs of Chinese children and adolescents

China is home to the second largest population of children and adolescents in the world. Yet demographic shifts mean that the government must manage the challenge of fewer children with the needs of an ageing population, while considering the delicate tension between economic growth and environmental sustainability. We mapped the health problems and risks of contemporary school-aged children and adolescents in China against current national health policies. We involved multidisciplinary experts, including young people, with the aim of identifying actionable strategies and specific recommendations to promote child and adolescent health and wellbeing. Notwithstanding major improvements in their health over the past few decades, contemporary Chinese children and adolescents face distinct social challenges, including high academic pressures and youth unemployment, and new health concerns including obesity, mental health issues, and sexually transmitted infections. Inequality by gender, geography, and ethnicity remains a feature of health risks and outcomes. We identified a mismatch between current health determinants, risks and outcomes, and government policies. To promote the health of children and adolescents in China, we recommend a set of strategies that target government-led initiatives across the health, education, and community sectors, which aim to build supportive and responsive families, safe communities, and engaging and respectful learning environments. TRANSLATION: For the Chinese translation of the abstract see Supplementary Materials section.

Prediction of body mass index and skeletal maturity for early menarche risk at menarche onset: a cross-sectional study of Chinese girls

BACKGROUND

This study aimed to assess the predictive value of body mass index (BMI) and skeletal maturity for the occurrence of early menarche in Chinese girls.

METHODS

A cross-sectional analysis was conducted on 785 girls aged 8.1-14.6 years who visited our hospital within 3 months of menarche onset. Early menarche was defined as menarche age (MA) <10 years. Skeletal maturity was classified based on the difference between bone age (BA) and chronological age (CA), termed BA-CA; advanced BA was defined as BA-CA>2 years.

RESULTS

The average MA was 10.7 (SD: 1.1) years, with a prevalence of early menarche of 23.3%. BA exhibited relative stability compared with MA, with an average of 12.8 (SD: 0.5) years at menarche onset. At menarche onset, the average height, weight and BMI were 149.1 (SD: 5.1) cm, 43.3 (SD: 7.2) kg and 19.4 (SD: 2.8) kg/m², respectively. Logistic regression analyses indicated that every 1-year increment in BA-CA was independently associated with a 18.90-fold higher risk of early menarche (95% CI 11.77 to 30.32), respectively, and remained statistically significant even after adjusting for height or mid-parental height. Furthermore, the prediction of BA-CA for early menarche demonstrated a dose-dependent pattern across BMI categories, with the greatest risk observed in normal-weight girls, the lowest risk in obese girls and an intermediate risk in overweight girls at the same degree of BA advancement.

CONCLUSIONS

Our findings provide evidence supporting the significant contributions of BMI and skeletal maturity in predicting early menarche among Chinese girls at menarche onset. Additionally, the results suggest a dose-dependent relationship between skeletal maturity and BMI categories, with normal-weight girls displaying a higher risk of early menarche compared to overweight and obese girls with the same degree of BA advancement.

Impact of Chemicals on the Age of Menarche: A Literature Review

A growing body of evidence suggests that chemicals interfere with the age of onset of menarche. We conducted a review in order to demonstrate the relationship between several categories of chemicals and menarche. We searched for English language papers using the Medline/PubMed database until April 2023. The chemical factors found to affect menarche were prenatal and antenatal smoke, phthalates, phenols, organochlorines, perfluoroalkyls and polyfluoroalkyls, metals, air pollutants and polybrominated diphenyl ethers. Low or high exposure to each chemical compound could affect the age of menarche, leading to early or delayed menarche. Furthermore, the results show that intrauterine exposure may have a different impact from antenatal exposure. There is evidence that endocrine-disrupting chemicals affect the age of menarche, but more research needs to be conducted.

Prospective association of dietary soy and fibre intake with puberty timing: a cohort study among Chinese children

BACKGROUND

Dietary phytoestrogens have been suggested to influence puberty timing, a critical stage for well-being in adulthood. We hypothesized that childhood soy intake might prospectively influence puberty timing and that dietary fibre and the key isoflavone metabolite equol might play roles.

METHODS

Cox proportional hazard regression models were performed in 4781 children (2152 girls and 2629 boys) aged 6-8 years old from the Chinese Adolescent Cohort Study for whom a food frequency questionnaire at baseline and information about potential confounders were available. Anthropometry and pubertal status including age at Tanner stage 2 for breast development (B2) or age at the initiation of gonadal growth (G2), and age at menarche (M) or voice break (VB) were assessed annually. Equol excretion was determined by urine samples from 1311 participants.

RESULTS

Among girls and boys, higher soy intake was associated with later puberty timing (hazard ratio (HR)-B2: 0.88 (95% CI, 0.80-0.96), p=0.02; HR-M, 0.87 (0.77-0.94), p=0.01; HR-G2, 0.91 (0.82-0.98), p=0.013; HR-VB, 0.90 (0.82-0.9), p=0.02), independent of prepubertal body fatness and fibre intake. These associations were more pronounced among children with a high urinary equol level (p_{for-interaction} ≤ 0.04) or with a high cereal fibre intake (p_{for-interaction} ≤ 0.06). Intake of dietary fibre or its subtype was not prospectively associated with puberty onset after adjusting for dietary soy intake (p≥0.06).

CONCLUSION

Higher childhood soy intake is prospectively associated with later puberty timing in both Chinese girls and boys, independent of prepubertal body fatness, and the association is particularly pronounced among individuals with a higher urinary equol level.