Predictive factors for age at menopause in Caucasian females

Association of lifetime lactation and characteristics of menopause: a longitudinal cohort study

BACKGROUND

Lactation has many established benefits for women's long-term health; however, its influence on menopause is less clear. This study investigated the association between lifetime duration of lactation and the timing and type of menopause in midlife women.

METHODS

We analyzed survey data on 19,783 parous women aged 40 to 65 years at enrollment in the Alberta's Tomorrow Project (2000-2022), a prospective community-based cohort study in Alberta, Canada. Duration of lifetime lactation across all births was categorized as: <1 month (reference group; 19.8% of women), 1-3 months (12.1%), 4-6 months (11.7%), 7-12 months (18.8%), and ≥ 13 months (37.7%). Women were classified as premenopause, natural menopause (age at 1 year after the final menstrual period), surgical menopause (age at bilateral oophorectomy), or indeterminate menopause (age at premenopausal hysterectomy with ovarian preservation). Flexible parametric survival analysis and multinomial logistic regression were used to analyze menopause timing and type, respectively, according to lactation status and controlling for birth year, education, parity, hormonal contraceptive use, and smoking.

RESULTS

In a dose-response manner, longer lactation was associated with reduced risk of natural menopause before age 50 (for ≥ 13 months of lactation, adjusted hazard ratio at age 45: 0.68, 95% CI 0.59-0.78), surgical menopause before age 55 (age 45: 0.56, 0.50-0.63), and indeterminate menopause before age 50 (age 45: 0.75, 0.69-0.82). Longer lactation was associated with lower odds of surgical (adjusted odds ratio 0.54, 95% CI 0.45-0.66) and indeterminate menopause (0.63, 0.55-0.73), compared to natural menopause.

CONCLUSIONS

Optimizing the timing of natural menopause and reducing risks of early surgical and indeterminate menopause may be novel maternal benefits of breastfeeding.

Strong evidence supports the use of estradiol therapy for the treatment of vaginal inflammation: a two-way Mendelian randomization study

OBJECTIVE

Nowadays, there has been limited Mendelian randomization (MR) research focusing on the causal relationship between estradiol and vaginitis. Therefore, this study conducted a two-way MR study to clarify the causal effect and related influencing factors between them.

METHODS

All genetic datasets were obtained using publicly available summary statistics based on individuals of European ancestry from the IEU GWAS database. MR analysis was performed using MR-Egger, weighted median (WM) and inverse variance weighted (IVW) methods to assess the causal relationship between exposure and outcome and to validate the findings by comprehensively evaluating the effects of pleiotropic effects and outliers.

RESULTS

MR analysis revealed no significant causal relationship between estradiol and vaginitis risk. There was a negative correlation between estradiol and age at menarche (IVW, OR: 0.9996, 95% CI: 0.9992-1.0000, P = 0.0295; WM, OR: 0.9995, 95% CI: 0.9993-0.9998, P = 0.0003), and there was a positive correlation between age at menarche and vaginitis (IVW, OR: 1.5108, 95% CI: 1.1474-2.0930, P = 0.0043; MR-Egger, OR: 2.5575, 95% CI: 1.7664-9.6580, P = 0.0013). Estradiol was negatively correlated with age at menopause (IVW, OR: 0.9872, 95% CI: 0.9786-0.9959, P = 0.0041). However, there was no causal relationship between age at menopause and vaginitis (P > 0.05). In addition, HPV E7 Type 16, HPV E7 Type 18, and Lactobacillus had no direct causal effects on estradiol and vaginitis (P > 0.05). Sensitivity analyses revealed no heterogeneity and horizontal pleiotropy.

CONCLUSION

When estrogen levels drop, it will lead to a later age of menarche, and a later age of menarche may increase the risk of vaginitis, highlighting that the longer the female reproductive tract receives estrogen stimulation, the stronger the defense ability is formed, and the prevalence of vaginitis is reduced. In conclusion, this study indirectly supports an association between reduced level of estrogen or short time of estrogen stimulation and increased risk of vaginitis.

The dose-response relationship of pre-menopausal alcohol consumption with age at menopause: a population study of 280 497 women in Norway

BACKGROUND

Previous research suggests that alcohol consumption is associated with high age at menopause. Yet, knowledge about the dose-response relationship is inconsistent. Thus, we studied the pattern of the association of pre-menopausal alcohol consumption with age at natural menopause.

METHODS

We performed a retrospective population-based study using self-reported data from 280 497 women aged 50-69 years attending the Norwegian breast cancer screening programme (BreastScreen Norway) during 2006-15. Associations of weekly alcohol consumption between the age of 20 and 49 years with age at menopause were estimated as hazard ratios (HRs) using Cox proportional hazard models with restricted cubic splines to allow for non-linear associations. We adjusted for year and place of birth, number of childbirths, educational level, body mass index and smoking habits.

RESULTS

Mean age at natural menopause was 51.20 years (interquartile range: 49-54 years). The adjusted HR of reaching menopause was highest for women with no alcohol consumption (reference) and the HR decreased by alcohol consumption up to 50 grams per week (adjusted HR 0.87; 95% CI: 0.86-0.88). Above 50 grams, there was no further decrease in the HR of reaching menopause (P for non-linearity of <0.001).

CONCLUSIONS

Women who did not consume alcohol were youngest at menopause. The lack of a dose-response association among alcohol consumers implies virtually no relation of alcohol consumption with age at menopause. Our findings may suggest that characteristics of the women who did not consume alcohol, not accounted for in the data analyses, explain their younger age at menopause.

Association of lifetime lactation and age at natural menopause: a prospective cohort study

OBJECTIVE

The aim of this study was to examine the association between duration of lifetime lactation and age at natural menopause.

METHODS

In this prospective cohort study, we analyzed parous premenopausal women in the multiethnic Study of Women's Health Across the Nation who were followed approximately annually for 10 years (1995-2008). Lifetime lactation was defined as the duration of breastfeeding across all births in months. Age at natural menopause was defined as age in years after 12 consecutive months of amenorrhea after the final menstrual period for no other reported cause. We used Cox proportional hazard models to analyze time to natural menopause with age as the underlying time scale. Multivariable models controlled for education, race/ethnicity, parity, smoking, body mass index, and oral contraceptive use.

RESULTS

Among 2,377 women, 52.6% experienced natural menopause during follow-up and reported a valid final menstrual period date. The small, crude association between lifetime lactation up to 24 months and later age at natural menopause attenuated to nonsignificance in adjusted models (6 months: adjusted hazard ratio [AHR], 0.96; 95% confidence interval (CI), 0.87-1.06; 12 months: AHR, 0.95; 95% CI, 0.82-1.11; 18 months: AHR, 0.96; 95% CI, 0.82-1.13; 24 months: AHR, 0.99; 95% CI, 0.84-1.16).

CONCLUSIONS

Duration of lifetime lactation was not associated with age at natural menopause after controlling for sociodemographic characteristics.

Association of Estrogen Receptor Genes Polymorphisms With Polycystic Ovary Syndrome: A Systematic Review and Meta-Analysis Based on Observational Studies

PURPOSE

Controversial results existed in amounts of studies investigating the authentic association of estrogen receptor genes (ESR1 and ESR2) polymorphisms with the occurrence and progression of polycystic ovary syndrome (PCOS). The inconsistency might result from different loci, sample sizes, and ethnicities. To find the potential correlations between ESR1/ESR2 polymorphisms and PCOS risk, we conducted the first systematic review and meta-analysis to comprehensively summarize current studies in a large combined population.

METHODS

Eligible studies were retrieved from PubMed, MEDLINE, EMBASE, Cochrane Library, CBM, CNKI, WANFANG, and VIP up to February 28, 2021. The quality of studies was assessed using the Newcastle-Ottawa Scale (NOS) scoring system. Odds ratios (ORs) and 95% confidence intervals (95%CIs) were calculated to synthesize data in five genetic models. Subgroup analyses were conducted by ethnicity. Heterogeneity and publication bias were also assessed. The protocol was registered in PROSPERO under the number CRD42021239200.

RESULTS

A total of 8 studies involving 1,522 PCOS patients and 4,198 controls were included. No evidence demonstrated the association of ESR1 rs2234693 (OR=1.07 95%CI 0.98-1.18), ESR1 rs9340799 (OR=0.99 95%CI 0.69-1.43), or ESR2 rs4986938 (OR=1.06 95%CI 0.81-1.38) polymorphisms and PCOS risk in five genetic models. According to stratified subgroup analyses, ethnicity was considered the major source of heterogeneity. No publication bias was found in eligible studies.

CONCLUSION

The present meta-analysis found no significant associations between the variants of ESR1 rs2234693, ESR1 rs9340799, ESR2 rs4936938, and individual PCOS susceptibility, even if ethnicity was taken into account.

SYSTEMATIC REVIEW REGISTRATION

The protocol was registered in PROSPERO (available from https://www.crd.york.ac.uk/PROSPERO) with the ID number CRD42021239200.

Association of Parity and Breastfeeding With Risk of Early Natural Menopause

IMPORTANCE

Pregnancy and breastfeeding prevent ovulation and may slow the depletion of the ovarian follicle pool. These factors may lower the risk of early menopause, a condition associated with increased risk of cardiovascular disease and other adverse health outcomes.

OBJECTIVE

To examine the association of parity and breastfeeding with the risk of early menopause.

DESIGN, SETTING, AND PARTICIPANTS

This population-based cohort study within the Nurses' Health Study II cohort (1989-2015) included premenopausal participants who were aged 25 to 42 years at baseline. Response rates were 85% to 90% for each cycle, and follow-up continued until menopause, age 45 years, hysterectomy, oophorectomy, death, cancer diagnosis, loss to follow-up, or end of follow-up in May 2015. Hypotheses were formulated after data collection. Data analysis took place from February to July 2019.

EXPOSURES

Parity (ie, number of pregnancies lasting ≥6 months) was measured at baseline and every 2 years. History and duration of total and exclusive breastfeeding were assessed 3 times during follow-up. Menopause status and age were assessed every 2 years.

MAIN OUTCOMES AND MEASURES

Risk of natural menopause before age 45 years.

RESULTS

At baseline, 108 887 premenopausal women aged 25 to 42 years (mean [SD] age, 34.1 [4.6] years; 102 246 [93.9%] non-Hispanic white) were included in the study. In multivariable models, higher parity was associated with lower risk of early menopause. Hazard ratios were attenuated with adjustment for breastfeeding but remained significant. Compared with nulliparous women, those reporting 1, 2, 3, and 4 or more pregnancies lasting at least 6 months had hazard ratios for early menopause of 0.92 (95% CI, 0.79-1.06), 0.84 (95% CI, 0.73-0.96), 0.78 (95% CI, 0.67-0.92), and 0.81 (95% CI, 0.66-1.01), respectively (P for trend = .006). In multivariable models also adjusted for parity, hazard ratios for duration of exclusive breastfeeding of 1 to 6, 7 to 12, 13 to 18, and 19 or more months were 0.95 (95% CI, 0.85-1.07), 0.72 (95% CI, 0.62-0.83), 0.80 (95% CI, 0.66-0.97), and 0.89 (95% CI, 0.69-1.16), respectively, compared with less than 1 month of exclusive breastfeeding (P for trend = .001). Despite the significant test for trend, estimates were not observed to be lower as duration of exclusive breastfeeding increased. In a stratified analysis of parous women, risk of early menopause was lowest among those reporting exclusive breastfeeding for 7 to 12 months in each level of parity (women with 2 pregnancies and 7-12 months of breastfeeding: HR, 0.79; 95% CI, 0.66-0.96; ≥3 pregnancies and 7-12 months of breastfeeding: HR, 0.68; 95% CI, 0.52-0.88; 2 pregnancies and ≥13 months of breastfeeding: HR, 0.87; 95% CI, 0.66-1.15; ≥3 pregnancies and 13-18 months of breastfeeding: HR, 0.86; 95% CI, 0.66-1.13; and ≥3 pregnancies and ≥19 months of breastfeeding: HR, 0.98; 95% CI, 0.72-1.32).

CONCLUSIONS AND RELEVANCE

In this study, an inverse association of parity with risk of early menopause was observed. Breastfeeding was associated with significantly lower risk, even after accounting for parity. Breastfeeding at levels consistent with current recommendations may confer an additional benefit of lower risk of early menopause.

Epidemiology and Risk Factors of Menopause Syndrome Among Uyghur, Han, and Kazak Women in Xinjiang, China

BACKGROUND This study analyzed the epidemiology and the risk factors of menopause syndrome (MPS) among Uyghur, Han, and Kazak women in Xinjiang. MATERIAL AND METHODS This was a cross-sectional study. The stratified-cluster random-sampling method was used. A total of 3382 women aged 40 to 60 years of age were included from Urumqi City, Kashgar City, Altay City, Ili Kazakh Autonomous Prefecture, Künes County, Mongolkure County, Tekes County,Talede town, Alemale Township, and Ulugchat County (Kashgar Prefecture) in Xinjiang Province. A questionnaire was used to survey the clinical characteristics of MPS. Logistic regression analysis was used to analyze the MPS risk factors among Uyghur, Han, and Kazak women. RESULTS Oral contraceptives, negative life events, and menopause stages can influence MPS in Han women. In addition, occupation, body weight, mental illness, drug or alcohol abuse, and income level also affect the MPS of Uyghur women. In contrast to Han and Uyghur participants, education, menopausal pattern (natural or artificial), reproductive factors, and smoking are risk factors of MPS in Kazakh women. CONCLUSIONS The menopausal stages and the risk factors for MPS are different among Uyghur, Han, and Kazak women.

Detrimental Effects of Higher Body Mass Index and Smoking Habits on Menstrual Cycles in Korean Women

BACKGROUND

Alteration of menstrual cycle by individual lifestyles and unfavorable habits may cause menstrual irregularity. We aimed to investigate the relationship between lifestyle factors and menstrual irregularity in Korean women using data from the Fifth Korea National Health and Nutrition Examination Survey (KNHANES) 2010-2012.

MATERIALS AND METHODS

This cross-sectional study included 3779 nondiabetic Korean women aged 19-49 years who did not take any oral contraceptives or sex hormonal compounds. We examined the association of menstrual irregularity with age, body mass index (BMI), drinking experience, and smoking habits.

RESULTS

Age, Asian BMI, marriage status, age at menarche, and smoking habits were significantly associated with menstrual cycle irregularity (p < 0.01). The prevalence of menstrual irregularity was significantly increased at younger ages: 18.4%, 10.3%, and 10.5% at 19-29, 30-39, and 40-49 years, respectively. Moreover, obesity groups, defined as per Asian BMI using modified WHO criteria, were strongly associated with menstrual irregularity. BMI 25.0-29.9 [obesity class I] (adjusted odds ratios [OR], 1.94; 95% confidence intervals [CI], 1.37-2.74) and ≥30.0 [obesity class II] (adjusted OR, 2.18; 95% CI, 1.22-3.91) presented significantly higher risk of menstrual irregularity compared with BMI 18.5-22.9 [normal weight]. Multivariable analysis revealed that high BMI in younger women aged 19-29 years (p < 0.001) and smoking habits in middle-aged women aged 30-39 years (p < 0.005) significantly predicted menstrual irregularity.

CONCLUSION

This study substantiated that menstrual irregularity was closely associated with higher BMI and smoking habits in nondiabetic Korean women. Weight loss and smoking cessation should be recommended to promote women's reproductive health.

Age at Natural Menopause and Related Factors in Isfahan, Iran

Objective

This study was aimed to evaluate the age at natural menopause and related factors among women in a population based study in 2015 in Isfahan, Islamic Republic of Iran.

Methods

In this cross-sectional study 960 menopausal women were selected by cluster sampling. Demographic, socioeconomic, lifestyle behavior and reproductive history aspects were collected using a structured questionnaire. Woman and her husband's educational level and occupation with family income were the variables to construct socioeconomic status using principal component analysis.

Results

Mean and median of natural menopause age were 48.66 and 48 years, respectively. Women body mass index (BMI) more than 30 kg/m² had significantly higher menopausal age than women with lower BMI (P value = 0.022). The mean of menopausal age was not statistically significant in regard to marital status, physical activity, smoking status, menarche age, age at first pregnancy and history of abortion. Menopause age with pregnancy numbers and age at last pregnancy had a significant positive association. Women with better socioeconomic status had significantly higher natural menopause age. Multiple linear regression shows significant relationship between lower age at menopause with higher age at marriage, higher number of pregnancy and lower socioeconomic status.

Conclusion

Age at menopause in our studied sample is similar to previous estimates reported for other Iranian populations. Age at marriage, higher number of pregnancy and lower socioeconomic status were the significant factors in relations to age at menopause.

Perfluorooctanoic acid exposure and natural menopause: A longitudinal study in a community cohort

INTRODUCTION

Perfluorooctanoic acid (PFOA), a suspected endocrine disruptor, is a bio-persistent chemical found at low levels in the serum of nearly all U.S. residents. Early menopause has been positively associated with serum PFOA in prior cross-sectional studies.

METHODS

We conducted a longitudinal analysis of age at menopause among women, aged ≥40 years, (N=8759) in a Mid-Ohio Valley community cohort, exposed to high PFOA levels via contaminated drinking water. Using estimated retrospective year-specific serum PFOA concentrations (1951-2011), we examined the associations between PFOA, as cumulative exposure or year-specific serum estimates, and natural menopause using a Cox proportional hazards models. As participants were initially recruited in 2005-2006, we also analyzed the cohort prospectively (i.e., from the time of enrollment), using both modeled cumulative PFOA, and PFOA serum levels measured in 2005-2006. Women with hysterectomy (a competing risk) were either censored or excluded from the analysis.

RESULTS

Neither in the retrospective nor the prospective cohort did we find a significant (at α=0.05) trend between PFOA exposure and natural menopause. The non-significant, hazard ratios by quintile of increasing cumulative serum PFOA were 1.00 (referent), 1.00, 1.09, 1.05 and 1.06 (trend test for log cumulative exposure: p=0.37) with hysterectomies censored, and 1.00 (referent), 1.06, 1.13, 1.09 and 1.11 (trend test for log cumulative exposure: p=0.85) with hysterectomies excluded. Year-specific serum estimates were also not associated with early menopause.

CONCLUSION

Our data suggest that earlier age at menopause is not associated with PFOA exposure.

Relationship between some indicators of reproductive history, body fatness and the menopausal transition in Hungarian women

BACKGROUND

This paper analyzed the relationship between some indicators of reproductive history and body fatness in relation to the timing of the menopause transition in Hungarian women using survival analysis after controlling for birth cohort.

METHODS

Data on menstruation and reproductive history were collected during the personal interviews in a sample of 1932 women (aged 35+ years). Menarcheal age, the length of menstrual cycles and menstrual bleedings, regularity of menstrual cycles, number of gestations, lactation, the ever use of contraceptives, menopausal status and age at menopause were used as indicators of reproductive history. The body fat fraction was estimated by bioelectrical impedance analysis. Body fatness was also estimated by dividing women into obese and non-obese categories (considering body mass index and waist-to-hip ratio). Survival analyses were used to analyze the relationship between the indicators of reproductive history and body fatness during the menopausal transition.

RESULTS

Only the menarcheal age among the investigated reproductive life characteristics showed secular changes in the studied decades in Hungary; the mean age at menarche decreased by approximately 2.5 months per decade from the 1920s until the 1970s. Ever use of hormonal contraceptives, a relatively long cycle length in the perimenopausal transition and higher parity were all related with lower risk of early menopause. Later menarcheal age, normal length of menstrual cycle or bleeding in the climacterium, irregular bleeding pattern and postmenopausal status were associated with a higher amount of body fatness, while never use of contraceptives, regular menstruation, postmenopausal status and relatively early menopause were associated with a higher risk of abdominal obesity.

CONCLUSION

This report confirms that age of menarche is not significantly predictive of age at menopause but prior use of oral contraceptives, longer mean cycle length and smaller number of gestations all are. In addition, age of menarche, irregular bleeding pattern before the climacterium, length of menstrual cycles and bleedings during the climacterium and postmenopausal status were associated with obesity during the climacterium.

Sulfur dioxide exposure and other factors affecting age at natural menopause in the Jinchuan cohort

OBJECTIVE

To describe the associations between occupational exposures and age at natural menopause in the Jinchuan cohort.

METHODS

The Jinchuan cohort consists of all current or retired workers of the Jinchuan Nonferrous Metals Corporation (JNMC) in Jinchang, Gansu, China. Our final study population consisted of 3167 postmenopausal women. The data used for this study were derived from the epidemiological survey and were self-reported. Age at natural menopause (ANM) was defined as the age at the last period prior to 12 months of amenorrhea in women who experienced natural menopause. ANM was related to five commonly reported occupational exposures using bivariate and multivariate Cox proportional hazards regressions.

RESULTS

Blue-collar workers have significantly earlier mean ANM (49.0 years) than white-collar workers (49.5 years). Sulfur dioxide exposure was found to be associated with earlier mean ANM in blue-collar workers. After stratifying both blue-collar workers and white-collar workers further by exposure time for each of the exposures, blue-collar workers exposed to sulfur dioxide for 21-25 years had the earliest mean ANM (47.8 years) of any level of any exposure in this study.

CONCLUSION

This paper is significant because it is the first report of an association between sulfur dioxide and menopause, and one of few papers to look at the determinants of ANM in an occupational cohort. Blue-collar workers had earlier mean ANM than white-collar workers. Blue-collar workers are more exposed to sulfur dioxide and other occupational exposures than white-collar workers, and blue-collar workers who are more exposed to sulfur dioxide have earlier menopause. Sulfur dioxide may be part of the reason that blue-collar workers experience earlier menopause than white-collar workers.

Socioeconomic position, lifestyle factors and age at natural menopause: a systematic review and meta-analyses of studies across six continents

Background: Age at natural menopause (ANM) is considered a marker of biological ageing and is increasingly recognized as a sentinel for chronic disease risk in later life. Socioeconomic position (SEP) and lifestyle factors are thought to be associated with ANM.

Methods: We performed a systematic review and meta-analyses to determine the overall mean ANM, and the effect of SEP and lifestyle factors on ANM by calculating the weighted mean difference (WMD) and pooling adjusted hazard ratios. We explored heterogeneity using meta-regression and also included unpublished findings from the Australian Longitudinal Study on Women’s Health.

Results: We identified 46 studies across 24 countries. Mean ANM was 48.8 years [95% confidence interval (CI): 48.3, 49.2], with between-study heterogeneity partly explained by geographical region. ANM was lowest among African, Latin American, Asian and Middle Eastern countries and highest in Europe and Australia, followed by the USA. Education was associated with later ANM (WMD middle vs low education 0.30, 95% CI: 0.10, 0.51; high vs low education 0.64, 95% CI 0.26, 1.02). A similar dose-response relationship was also observed for occupation. Smoking was associated with a 1-year reduction of ANM (WMD: -0.91, 95% CI: –1.34, –0.48). Being overweight and moderate/high physical activity were modestly associated with later ANM, but findings were less conclusive.

Conclusions: ANM varies across populations, partly due to differences across geographical regions. SEP and some lifestyle factors are associated with ANM, but further research is needed to examine the impact of the associations between risk factors and ANM on future health outcomes.

Genome-wide association studies of age at menarche and age at natural menopause

Genome-wide association studies (GWAS) have been successful in uncovering genetic determinants of age at menarche and age at natural menopause. To date, more than 30 novel genetic loci have been identified in GWAS for age at menarche and 17 for age at natural menopause. These findings have stimulated a plethora of follow-up studies particularly with respect to the functional characterization of these novel loci and how these results can be translated into risk prediction. However, the genetic loci identified so far account for only a small fraction of the overall heritability. This review provides an overview of the current state of our knowledge of the genetic basis of menarche and menopause timing. It emphasizes recent GWAS results and outlines strategies for discovering the missing heritability and strategies to further our understanding of the underlying molecular mechanisms of the observed genetic associations.

ApoE genotypes are associated with age at natural menopause in Chinese females

Ages at natural menarche and menopause are influenced by several genetic factors. This study aimed to investigate the possible relationship between the apolipoprotein E (ApoE) genotype and the age at menarche and natural menopause in Chinese females. In the current study, 398 (elderly group, aged 47-80 years) and 825 (young group, aged 15-25 years) Chinese females were enrolled under informed content. Ages at natural menarche and menopause were obtained by questionnaires. ApoE genotypes were identified by restriction fragment length polymorphism analysis. In the elderly group, the number of pregnancies and live births and breastfeeding were associated with the age at menopause (P = 0.008, P = 0.002, and P = 0.023, respectively). One-way ANOVA analysis revealed that the ApoE genotype was significantly associated with age at natural menopause (ANM; P = 0.010). Compared with ApoE ε3/3 carriers, ApoE ε3/4 females showed a 1.8-year delay in ANM (P = 0.002). Single ApoE allele-positive/allele-negative analysis also showed that the age at menopause of ApoE ε4 carriers was delayed compared with those who were not carriers (P = 0.023). In the young group, no statistical difference was found in the age of menarche between the carriers of ApoE ε3/3 and ε3/4. Single ApoE allele-positive/allele-negative analysis showed that the age at menarche in ApoE ε4 carriers was slightly earlier than in those who were not carriers (P = 0.048). Meanwhile, univariate association analysis revealed that the ApoE genotypes were not significantly associated with the age at menarche using age as a covariate in the pooled group (young + elderly) (P = 0.143). We demonstrated that the ApoE genotype is significantly linked to the age at natural menopause.

Polymorphisms in adiposity-related genes are associated with age at menarche and menopause in breast cancer patients and healthy women

STUDY QUESTION

Is there any effect of genetic polymorphisms in adiposity-related genes on the timing of menarche and menopause and the total duration of menstruation among Korean women?

SUMMARY ANSWER

Our results suggest that the adiposity-related genes LEP, LEPR and PPARγ may play a role in the onset and cessation of menstruation, and the total duration of menstruation.

WHAT IS KNOWN AND WHAT THIS PAPER ADDS

Previous candidate-gene approaches have mainly presented the results for genes related to the estrogen metabolism pathway. Most genes of interest that participate in steroid-hormone metabolism, such as estrogen receptor α and estrogen receptor β, have been associated with age at menarche and menopause. This study shows the possibility that adiposity-related genes also influence the duration of menstruation.

PARTICIPANTS AND SETTING

We recruited 400 breast cancer patients and 452 healthy participants from a case-control study at the Center for Breast Cancer, National Cancer Center in Korea. Ten single nucleotide polymorphisms (SNPs) in the leptin (LEP), leptin receptor (LEPR) and peroxisome proliferator-activated receptor gamma (PPARγ) genes were investigated to evaluate their possible effects on menstruation. Associations between SNPs and age at menarche, age at menopause and duration of menstruation were evaluated.

MAIN RESULTS

Four SNPs (rs2167270 of LEP, rs7602 of LEPR and rs4684846 and rs3856806 of PPARγ) were associated with late menarche (≥ 17-year-old). Four SNPs (rs2167270 of LEP and rs1801282, rs2120825, and rs3856806 of PPARγ) were associated with early menopause (<40-year-old) among post-menopausal women. In logistic regression models with covariate adjustment, women with the GG genotype of rs7602 (LEPR) had a higher risk for late menarche [odds ratio (OR) = 1.83, 95% confidence interval (CI) = 1.01-3.31] compared with their counterparts carrying the GA or AA genotypes. In addition, the GG genotype of rs2167270 (LEP) was inversely associated with a duration of menstruation of <30 years (OR = 0.59, 95% CI = 0.31-1.00) compared with the GA or AA genotypes. BIAS, LIMITATIONS AND GENERALIZABILITY TO OTHER POPULATIONS: We obtained information on the age at menarche and menopause from self-administered questionnaires, and some participants might have had difficulty in remembering their age at menarche and menopause. However, this is a non-differential misclassification and should not appreciably affect the interpretation of the results of this study.

Estrogen receptor-1 genetic polymorphisms for the risk of premature ovarian failure and early menopause

BACKGROUND

The aim of this study was to investigate the role of the estrogen receptor 1 (ESR1) genetic polymorphisms for early menopause that was classified as premature ovarian failure (POF) and early menopause (EM) and to examine whether the associations of ESR1 genetic variants are different for POF and EM.

METHODS

We selected 100 POF cases and matched 100 EM cases and 200 normal menopause (NM) controls from the Korean Multi-Center Cohort. Among them, we restricted idiopathic POF and EM cases vs NM controls by excluding POF/EM cases with medical/surgical causes. The XbaI (rs9340799) and PvuII (rs2234693) in the ESR1 gene were genotyped. The single-nucleotide polymorphism (SNP) and haplotype effects were analyzed by multivariate logistic regression and haplotype analysis. Also nominal polytomous logistic regression was used to find whether ESR1 genetic variants are differently associated with POF and EM.

RESULTS

The global p values for idiopathic POF and EM were 0.08 and 0.39 (SNP-based), and <0.001 and 0.12 (haplotype-based), respectively. The XbaI genetic variant containing the X allele was marginally significantly associated with a reduced risk of idiopathic POF (OR = 0.6, 95% CI 0.3-1.0). The P-x haplotype and diplotypes significantly decreased the risk of idiopathic POF (OR = 0.5, 95% CI 0.2-0.9; OR = 0.4, 95% CI 0.2-0.9, respectively). In contrast from POF, the P-x haplotypes and diplotypes insignificantly increased the risk for both idiopathic EM (p(polytomous) = 0.009 for P-x haplotype; p(polytomous) = 0.02 for P-x diplotypes).

CONCLUSION

Our results suggest that the ESR1 gene including PvuII and XbaI polymorphisms may modify the risk of idiopathic premature ovarian failure (POF) but not idiopathic early menopause (EM) risk.

Genetics of age at menarche: a systematic review

BACKGROUND

Menarche is the first menstrual period of a girl at puberty. The timing of menarche is important for health in later life. Age at menarche is a complex trait and has a strong genetic component. This review summarizes the results of the genetic studies of age at menarche conducted to date, highlights existing problems in this area and outlines prospects of future studies on genetic factors for the trait.

METHODS

PubMed and Google Scholar were searched until May 2011 using the keywords: 'menarche', 'puberty' and 'age at menarche' in combination with the keywords 'polymorphism', 'candidate gene', 'genome-wide association study' and 'linkage'.

RESULTS

Our search yielded 170 papers, 35 of which were selected for further analysis. Several large-scale genome-wide association studies along with a powerful meta-analysis of their aggregated data identified about 50 candidate genes for the trait. Some genes were replicated in different studies of Caucasians (e.g. LIN28B, TMEM38B) or in different ethnicities (e.g. SPOCK, RANK and RANKL). However, despite the large volume of results obtained, there is a huge gap in relevant data on ethnic groups other than Caucasians.

CONCLUSIONS

The reviewed studies laid a solid basis for future research on genetics of age at menarche. However, as yet specific genes for this trait have not been identified consistently in all ethnicities and types of studies. We suggest expanding the research to different ethnicities and propose several methodologies to increase the efficiency of studies in this area, including a systems approach, which combines existing high-throughput methods in a single pipeline.

Association of endometriosis-related infertility with age at menopause

OBJECTIVE

The influence of past history of infertility, which is closely associated with reproductive factors, on menopause has not been clarified. The purpose of this study was to clarify the association of reproductive factors, including past history of infertility, with menopause in Japanese women.

STUDY DESIGN

This study was a cross-sectional analysis of the Japan Nurses' Health Study (JNHS) baseline survey. The JNHS is a nationwide prospective cohort study on the health of Japanese women, and the baseline survey was conducted between 2001 and 2007.

MAIN OUTCOME MEASURE

We analyzed data for 24,153 pre- and postmenopausal women who were enrolled in the JNHS at the ages 40-59 years. The main outcome measure was menopause.

RESULTS

Reproductive factors influencing the onset of natural menopause were past history of infertility [relative risk (RR) (age-adjusted odds ratio and 95% confidence interval): 1.28 (1.10-1.48)], past history of endometriosis: 1.32 (1.07-1.64), age at menarche: 0.919 (0.886-0.953) and number of pregnancies: 0.943 (0.911-0.976). Endometriosis as the cause of infertility was significantly associated with earlier onset of menopause (3.43 [2.17-5.44]) after adjustment for age. The strong association of past history of infertility related to endometriosis was still significant after multivariate adjustment.

CONCLUSION

Menopause in women who have a past history of infertility, especially in those who have suffered from endometriosis, is significantly earlier than that in women without such a history.

Early menopause association with employment, smoking, divorced marital status and low leptin levels

AIMS

The aims of this study were (1) to investigate the determining risk factors related to early menopause and (2) to compare the relationships between demographic characteristics and hormonal status and leptin levels in subjects with early (no surgical) and natural menopause.

STUDY DESIGN

The prospective study was conducted on 500 women with early and 2700 women with natural menopause. Detailed information was collected about their employment status, past and present smoking habits, coffee and alcohol use, educational level and other factors relevant to health. Thirty participants with early menopause and 30 participants with natural menopause were evaluated for hormone and leptin levels.

RESULTS

Employment status (OR: 1.94), current smoking (OR: 1.80) and divorced marital status (OR: 1.79) were found to be significant risk factors for early menopause. Mean levels of leptin in natural and early menopause were measured 11.40 ± 4.1 ng/ml and 8.01 ± 3.9 ng/ml, respectively (p = 0001). Leptin levels in the early (r = 0.765, p = 0.001) and natural (r = 0.750, p = 0.001) menopause subjects correlated positively with oestradiol (E2) levels.

CONCLUSION

This study shows that early onset of menopause is correlated with smoking, employment status, divorced marital status and lower leptin levels.

A large-scale candidate gene association study of age at menarche and age at natural menopause

Recent genome-wide association (GWA) studies have identified several novel genetic loci associated with age at menarche and age at natural menopause. However, the stringent significance threshold used in GWA studies potentially led to false negatives and true associations may have been overlooked. Incorporating biologically relevant information, we examined whether common genetic polymorphisms in candidate genes of nine groups of biologically plausible pathways and related phenotypes are associated with age at menarche and age at natural menopause. A total of 18,862 genotyped and imputed single nucleotide polymorphisms (SNPs) in 278 genes were assessed for their associations with these two traits among a total of 24,341 women from the Nurses' Health Study (NHS, N = 2,287) and the Women's Genome Health Study (WGHS, N = 22,054). Linear regression was used to assess the marginal association of each SNP with each phenotype. We adjusted for multiple testing within each gene to identify statistically significant SNP associations at the gene level. To evaluate the overall evidence for an excess of statistically significant gene associations over the proportion expected by chance, we applied a one-sample test of proportion to each group of candidate genes. The steroid-hormone metabolism and biosynthesis pathway was found significantly associated with both age at menarche and age at natural menopause (P = 0.040 and 0.011, respectively). In addition, the group of genes associated with precocious or delayed puberty was found significantly associated with age at menarche (P = 0.013), and the group of genes involved in premature ovarian failure with age at menopause (P = 0.025).

Age at menopause and factors associated with attainment of menopause in an urban community in Ibadan, Nigeria

OBJECTIVES

To determine the age at natural menopause and identify sociodemographic, reproductive and other factors associated with the attainment of natural menopause among women in Ibadan, Nigeria.

METHODS

This was a cross-sectional, descriptive, community-based study, using a cluster sample of eligible women 40-60 years of age residing in selected areas. Questionnaires were administered to women at home or in their work place. Data were analyzed using SPSS 16.0.

RESULTS

A total of 1189 Nigerian women responded. Their mean age (+/- SD) was 48.0 +/- 5.9 years and their median age 48 years. The majority, 1000 (84.1%), were currently married. Of the women, 581 (48.9%) were premenopausal, 119 (10.0%) perimenopausal and 489 (41.1%) postmenopausal. The median age at menopause using probit analysis was 50.2 years. Following logistic regression analysis, women who were not married and those who had no formal education were more likely to have attained menopause. Similarly, women who were younger, had managerial or professional jobs, and had used oral contraceptive pills were less likely to have attained natural menopause.

CONCLUSIONS

Efforts should be made to provide education about the menopause to all women in their respective communities, especially to those who are approaching their fifth decade and who have no formal education, to better prepare them for this change of life.

Association analyses suggest multiple interaction effects of the methylenetetrahydrofolate reductase polymorphisms on timing of menarche and natural menopause in white women

OBJECTIVE

This study aimed to investigate whether polymorphisms of the methylenetetrahydrofolate reductase (MTHFR) gene are associated with age at menarche and age at natural menopause in white women.

METHODS

In a cross-sectional study, a total of 305 randomly selected unrelated white women were genotyped for six single nucleotide polymorphisms (SNPs) of the MTHFR gene (including one common replacement, rs1801133). This sample was comprehensively analyzed for the association of the SNPs with age at menarche. Then a subsample of 210 women who experienced natural menopause was analyzed for the association of the MTHFR gene with age at natural menopause.

RESULTS

Duration of breast-feeding was a significant predictor of earlier natural menopause (P < 0.05). No individual SNPs were associated with either age at menarche or age at natural menopause. However, three significant (P < 0.05) SNP-SNP interaction effects (rs2066470/rs1476413, rs2066470/rs4846049, and rs17037390/rs4846049) on the onset of menarche were determined. Three haplotypes were significantly associated with age at menopause (P < 0.05). Four SNPs (rs2066470, rs17037390, rs1801133, and rs4846048) indicated significant interaction effects with various lifestyle factors on age at natural menopause.

CONCLUSIONS

The results of our study suggest that the MTHFR gene may influence the onset of menarche and natural menopause. This effect is probably due to the multiple SNP-SNP and SNP-environment interactions. More independent studies are needed to further clarify the possible contribution of this gene to the timing of menarche and menopause.

Effect of menopause on gene expression profiles of circulating monocytes: a pilot in vivo microarray study

Menopause is one of the key physiological events in the female life and can increase the risk for a number of complex autoimmune, neurodegenerative, metabolic, and cardiovascular disorders. Circulating monocytes can differentiate into various cell types and play an important role in tissue morphogenesis and immune response. We studied gene expression profiles of peripheral blood monocytes in healthy pre- and postmenopausal women using Affymetrix Human U133A GeneChip array that contains probes for approximately 14,500 genes. Comparative analyses between the samples showed that 20 genes were up- and 20 were down-regulated. Of these genes, 28 were classified into six major GO categories relevant to such biological processes as the cell proliferation, immune response, cellular metabolism, and the others. The remaining 12 genes have yet unidentified biological functions. Our results support the hypothesis that functional state of circulating monocytes is indeed affected by menopause, and resulting changes may be determined through the genomewide gene expression profiling. Several differentially expressed genes identified in this study may be candidates for further studies of menopause-associated systemic autoimmune, neurodegenerative, and cardiovascular disorders. Our study is only the first attempt in this direction, but it lays a basis for further research.

A polymorphism of apolipoprotein E (APOE) gene is associated with age at natural menopause in Caucasian females

OBJECTIVE

The present study aimed to investigate possible association of the apolipoprotein E (APOE) gene polymorphisms with age at natural menopause (ANM) in Caucasian females.

DESIGN

Four SNPs (including two replacements, SNP3 Cys112Arg and SNP4 Arg158Cys) were genotyped in 253 randomly selected unrelated Caucasian women having experienced natural menopause. The comprehensive statistical analyses focusing on the association of the APOE gene and some environmental factors with ANM were conducted.

RESULTS

Alcohol consumption was a significantly predictor of earlier natural menopause (P<0.05). One SNP (rs769450) was significantly associated with ANM according to both population based and the transmission disequilibrium test (TDT) analyses (P=0.007 and 0.046, respectively). However, no association was observed between APOE varepsilon2, varepsilon3, varepsilon4 and ANM.

CONCLUSIONS

Genetic variation in the APOE gene may influence the variation in ANM in Caucasian women.

The relationship between smoking and age at the menopause: A systematic review

CONTEXT AND OBJECTIVE

Increasing life expectancy has made it ever more important to study the factors that influence the age at the menopause, given that when it is reached outside of the normal range, it is associated with increased risk of osteoporosis and cardiovascular diseases, among other conditions. Among the factors studied in relation to early menopause, smoking is prominent. Destruction of the ovarian follicles is one of the mechanisms postulated for this effect. The aim of this study was to review and describe the associations between age at the menopause and the habit of smoking, its duration and its intensity.

METHOD

A systematic review of the literature indexed in the MEDLINE and LILACS databases was conducted, without restriction on publication date. After initially identifying 1325 articles and preselecting 161 articles for consideration of their complete texts, 96 articles reporting on the results from 109 studies were selected for analysis.

RESULTS

A great majority of the studies reported an association between the habit of smoking and early menopause, but there was no clear evidence that the duration of smoking and quantity of cigarettes smoked had any association with age at the natural menopause.

CONCLUSION

Additional studies are needed, preferably of prospective nature and with a large number of women, in order to deepen the knowledge of the effects of various aspects of smoking on age at the menopause. Experimental studies on animals may also contribute towards clarifying the physiopathological mechanisms through which smoking influences age at the menopause.

Environmental contexts of menopause in Spain

OBJECTIVE

This study had two main objectives: (1) to detect the differences in basic aspects of the reproductive aging process (age at menopause, menopausal symptoms, the medicalization of aging) among women from the region of Madrid, who at the time of the study were living in three different environmental contexts (rural, semiurban, and urban), and (2) to identify the main factors responsible for these differences.

DESIGN

Data from two different research projects have been pooled for the DAMES project (Decisions At MEnopause Study), and the Ecology of Reproductive Aging Project. The sample size was 1,142, women 45 to 55 years of age (103 rural, 744 semiurban, 295 urban).

RESULTS

Probit analysis was used to estimate median age at natural menopause in the three contexts. Rural women have a later onset of menopause (rural, 52.07 y; semiurban, 51.9 y; urban, 51.23 y) and significantly higher levels of the symptoms related to declines in estrogen, eg, hot flashes (rural, 56%; semiurban, 43%; urban, 46%; chi2=6.717, P=0.035) or loss of sexual desire (rural, 51%; semiurban, 44%; urban, 41%; chi2=24.934, P=0.001). Conversely, urban women suffer more from symptoms related to stress, eg, impatience (rural, 34%; semiurban, 25%; urban, 45%; chi2=41.328, P<0.001). The medicalization of menopause, measured in terms of both surgical menopause and the use of hormone therapy, is significantly higher in the urban population (surgical menopause: rural, 5.8%; semiurban, 8.7; urban, 10%; chi2=16.009, P<0.001). Despite these differences, levels of postmenopausal hormone therapy use are still somewhat lower than in other West European and North American populations. Two different logistic regression analyses were carried out to identify (1) factors associated with differences in ovarian aging, measured through menopausal status, and (2) factors associated with prevalence of hot flashes with respect to ovarian aging. Parity, body mass index, age, environmental context, and, slightly less so, smoking, alcohol consumption, age, education, age at menarche, and marital status all contribute significantly or nearly significantly and independently to the explanation of differences found. For the likelihood of having hot flashes, environmental context, age, education, age at menarche, menopausal status, and postmenopausal hormone therapy use all hae a significant or borderline significant effect.

CONCLUSIONS

Significant differences have been shown to exist in rural, semiurban and urban settings in the median age at menopause, in basic symptom frequency and type, and in the levels of medicalization of the process of reproductive aging. Within multivariate regression models, it has been shown that body mass index, age, and environmental context all contribute to differences in reproductive aging. The factors associated with ovarian aging and hot flashes are comparable to those in other industrialized populations, although standard interpretations should be expanded to include context-based realities, including (1) the higher levels of modernization of urban women that influence differential behavior with respekt to risk factors at menopausal age; (2) the different ecological realities surrounding nutrition, physical activity, and social support that characterize women's period of development; and (3) the differential construction of their identity as women in terms of assertiveness, aesthetic perceptions, and the use of health services. Context does, indeed, matter.

An evolutionary perspective on the origin and ontogeny of menopause

The "grandmother hypothesis" proposes that menopause evolved because ancestral middle-aged women gained greater reproductive success from investing in extant genetic relatives than from continuing to reproduce [Williams GC. Pleiotropy, natural selection, and the evolution of senescence. Evolution 1957;11:398-411]. Because middle-aged women faced greater risks of maternal death during pregnancy and their offspring's infancy than did younger women, offspring of middle-aged women may not have received the needed level of prolonged maternal investment to survive to reproductive age. I put forward the "absent father hypothesis" proposing that reduced paternal investment linked with increasing maternal age was an additional impetus for the evolution of menopause. Reduced paternal investment was linked with increasing maternal age because men died at a younger age than their mates and because some men were increasingly likely to defect from their mateships as their mates aged. The absent father hypothesis is not an alternative to the grandmother hypothesis but rather a complement. It outlines an additional cost--reduced paternal investment--associated with continued reproduction by ancestral middle-aged women that could have been an additional impetus for the evolution of menopause. After reviewing additional explanations for the origin of menopause ("patriarch hypothesis," "lifespan-artifact" hypotheses), I close by proposing a novel hypothesis for the ontogeny of menopause. According to the "adaptive onset hypothesis," the developmental timing of menopause is a conditional reproductive strategy in which a woman's age at onset is influenced by the likelihood that any children she could produce would survive to reproductive age. Twelve variables predicted to be associated with age at onset and evidence that bears upon the predictions is discussed.

Premenopausal factors influencing premature ovarian failure and early menopause

OBJECTIVES

We conducted this study to examine premenopausal risk factors associated with premature ovarian failure (POF) and early menopause (EM) among Korean women.

METHODS

A 73% of total women aged 30-69 at four districts in the KMCC (Korean Multi-center Cancer Cohort) was participated in this study during 2002-2003. We selected 137 POF and 281 EM cases who had menopause before age 40 and at age 40-44, respectively, and 1318 normal menopause (NM) controls that experienced menopause at age 45-60, and among them, selected idiopathic POF (n=84) and EM (n=261) after excluding surgical/medical menopause. We collected the information of premenopausal lifestyle and reproductive risk factors. Multivariate and polytomous logistic regression were used to estimate POF and EM risk and to differentiate POF and EM risk using ordinal and nominal scale.

RESULTS

Cigarette smoking was associated with an increased risk of idiopathic POF (OR=1.82 [1.03-3.23]), whereas oral contraceptive use was associated with a reduced risk of natural EM (OR=0.62 [0.43-0.90]). Idiopathic POF risk by both factors differed from idiopathic EM risk (p-nominal<0.05). Factors related to ovulation, such as later menarche, irregular menstruation and longer breast feeding cumulatively reduced the risk of natural EM and POF (p-ordinal<0.05). In analysis including medical and surgical menopause, lung tuberculosis, hysterectomy, past cancers, and lower number of deliveries before menopause were associated with POF.

CONCLUSIONS

Our findings indicate that etiology in POF development may partly differ from that in EM.

The timing of natural menopause in Poland and associated factors

OBJECTIVES

The outcome of interest was the assessment of age at natural menopause and the variables hypothesized as covariates of age at menopause were indicators of demographic and social status, characteristics of the reproductive history and lifestyle behaviour.

METHODOLOGY

Seven thousand one hundred and eighty-three women from all social strata of non-clinical population, and aged between 35 and 65 years were investigated in cross-sectional survey across Poland in 2000-2004. The demographic, social, lifestyle behaviour and reproductive history aspects of the menopause-specific questionnaire were examined. The non-parametric Kaplan-Meier cumulative survivorship estimates were used to assess the timing of natural menopause. Univariate and multivariate Cox proportional hazards regression models were used to assess the association of age at natural menopause with factors of interest and to estimate relevant relative risk (the hazard ratio) for earlier age at menopause.

RESULTS

The overall median age at natural menopause was 51.25 years; 25th percentile 49; 75th percentile 54 years. Temporal changes in age at menopause were not demonstrated in the sample (p=0.9 for differences among age cohorts). Univariate Cox models were first fitted to the age at natural menopause for all covariates singly. The findings revealed that marital status, living environment, employment, BMI, age at first live birth delivered by a woman, breastfeeding, physical activity, smoking amount, and consumption of alcohol were not associated with age at menopause (p>0.05). The multiple Cox model revealed that early menarche, short menstrual cycle length, smoking cigarettes, a low level of education, and a negative health perception were associated with younger age at menopause (p<0.01). Use of oral contraceptives and parity were associated with later menopause (p<0.01).

CONCLUSION

The present study provides an estimate of median age at natural menopause in Poland that may be used as a measure of health for the growing number of Polish women whose survival is calculated at 30 years after menopause. This study has revealed that the pattern of relationship between age at menopause and the study factors reflects its population-specific character for its social and cultural backgrounds, socio-economic status, and social behaviours.

HDC gene polymorphisms are associated with age at natural menopause in Caucasian women

Histidine decarboxylase gene (HDC) encodes histidine decarboxylase which is the crucial enzyme for the biosynthesis of histidine. Studies have shown that histamine is likely to be involved in the regulation of reproduction system. To find the possible correlation between HDC gene and AANM (age at natural menopause), we selected 265 postmenopausal women from 131 nuclear families and performed a transmission disequilibrium test. Significant within-family associations with AANM for SNP rs854163 and SNP rs854158 of HDC gene were observed (P values=0.0018 and 0.0197, respectively). After 1000 permutations, SNP rs854163 still remained significant within-family association with AANM. Consistently, we also detected a significant within-family association between haplotype block 2 (defined by SNP rs854163 and rs860526) and AANM in the haplotype analyses (P value=0.0397). Our results suggest that the HDC gene polymorphisms are significantly associated with AANM in Caucasian women.