Temporal trends of main reproductive characteristics in ten urban and rural regions of China: the China Kadoorie biobank study of 300 000 women

Reproductive factors and risk of lung cancer among 300,000 Chinese female never-smokers: evidence from the China Kadoorie Biobank study

BACKGROUND

Lung cancer is the leading cause of cancer mortality among Chinese females despite the low smoking prevalence among this population. This study assessed the roles of reproductive factors in lung cancer development among Chinese female never-smokers.

METHODS

The prospective China Kadoorie Biobank (CKB) recruited over 0.5 million Chinese adults (0.3 million females) from 10 geographical areas in China in 2004-2008 when information on socio-demographic/lifestyle/environmental factors, physical measurements, medical history, and reproductive history collected through interviewer-administered questionnaires. Cox proportional hazard regression was used to estimate adjusted hazard ratios (HRs) of lung cancer by reproductive factors. Subgroup analyses by menopausal status, birth year, and geographical region were performed.

RESULTS

During a median follow-up of 11 years, 2,284 incident lung cancers occurred among 282,558 female never-smokers. Ever oral contraceptive use was associated with a higher risk of lung cancer (HR = 1.16, 95% CI: 1.02-1.33) with a significant increasing trend associated with longer duration of use (p-trend = 0.03). Longer average breastfeeding duration per child was associated with a decreased risk (0.86, 0.78-0.95) for > 12 months compared with those who breastfed for 7-12 months. No statistically significant association was detected between other reproductive factors and lung cancer risk.

CONCLUSION

Oral contraceptive use was associated with an increased risk of lung cancer in Chinese female never-smokers. Further studies are needed to assess lung cancer risk related to different types of oral contraceptives in similar populations.

Optimising health after early menopause

The typical age at menopause is 50-51 years in high-income countries. However, early menopause is common, with around 8% of women in high-income countries and 12% of women globally experiencing menopause between the ages of 40 years and 44 years. Menopause before age 40 years (premature ovarian insufficiency) affects an additional 2-4% of women. Both early menopause and premature ovarian insufficiency can herald an increased risk of chronic disease, including osteoporosis and cardiovascular disease. People who enter menopause at younger ages might also experience distress and feel less supported than those who reach menopause at the average age. Clinical practice guidelines are available for the diagnosis and management of premature ovarian insufficiency, but there is a gap in clinical guidance for early menopause. We argue that instead of distinct age thresholds being applied, early menopause should be seen on a spectrum between premature ovarian insufficiency and menopause at the average age. This Series paper presents evidence for the short-term and long-term consequences of early menopause. We offer a practical framework for clinicians to guide diagnosis and management of early menopause, which considers the nature and severity of symptoms, age and medical history, and the individual's wishes and priorities to optimise their quality of life and short-term and long-term health. We conclude with recommendations for future research to address key gaps in the current evidence.

Differential patterns of reproductive and lifestyle risk factors for breast cancer according to birth cohorts among women in China, Japan and Korea

BACKGROUND

The birth cohort effect has been suggested to influence the rate of breast cancer incidence and the trends of associated reproductive and lifestyle factors. We conducted a cohort study to determine whether a differential pattern of associations exists between certain factors and breast cancer risk based on birth cohorts.

METHODS

This was a cohort study using pooled data from 12 cohort studies. We analysed associations between reproductive (menarche age, menopause age, parity and age at first delivery) and lifestyle (smoking and alcohol consumption) factors and breast cancer risk. We obtained hazard ratios (HRs) with 95% confidence intervals (CIs) using the Cox proportional hazard regression analysis on the 1920s, 1930s, 1940s and 1950s birth cohorts.

RESULTS

Parity was found to lower the risk of breast cancer in the older but not in the younger birth cohort, whereas lifestyle factors showed associations with breast cancer risk only among the participants born in the 1950s. In the younger birth cohort group, the effect size was lower for parous women compared to the other cohort groups (HR [95% CI] 0.86 [0.66-1.13] compared to 0.60 [0.49-0.73], 0.46 [0.38-0.56] and 0.62 [0.51-0.77]). Meanwhile, a higher effect size was found for smoking (1.45 [1.14-1.84] compared to 1.25 [0.99-1.58], 1.06 [0.85-1.32] and 0.86 [0.69-1.08]) and alcohol consumption (1.22 [1.01-1.48] compared to 1.10 [0.90-1.33], 1.15 [0.96-1.38], and 1.07 [0.91-1.26]).

CONCLUSION

We observed different associations of parity, smoking and alcohol consumption with breast cancer risk across various birth cohorts.

Sleep patterns and risks of incident cardiovascular disease and mortality among people with type 2 diabetes: a prospective study of the UK Biobank

BACKGROUND

To explore the relationship between sleep patterns and cardiovascular disease (CVD) incidence and mortality risk in a population with type 2 diabetes through a UK Biobank sample.

METHODS

A total of 6860 patients with type 2 diabetes were included in this study. Five sleep factors (including Chronotype, sleep duration, insomnia, daytime sleepiness, and snoring) were collected as a questionnaire. The calculation generates a sleep score of 0-5, and then three sleep patterns were defined based on the sleep scores: poor sleep pattern (0-2), Intermediate sleep pattern (3-4), and healthy sleep pattern (5). HRs and 95% confidence intervals were calculated by multivariate COX proportional risk model adjustment. Restricted cubic splines were used to validate linear associations between sleep scores CVD events.

RESULTS

Our results found a reduced risk of CVD events in individuals with healthy sleep patterns compared to participants with poor sleep patterns. CVD Mortality (HR, 0.690; 95% CI 0.519-0.916), ASCVD (Atherosclerosis CVD) (HR, 0.784; 95% CI 0.671-0.915), CAD (Coronary Artery Disease) (HR, 0.737; 95% CI 0.618-0.879), PAD (Peripheral Arterial Disease) (HR, 0.612; 95% CI 0.418-0.896), Heart Failure (HR, 0.653; 95% CI 0.488-0.875). Restricted cubic spline responded to a negative linear correlation between sleep scores and CVD Mortality, ASCVD, CAD, PAD, and Heart Failure.

CONCLUSIONS

Healthy sleep patterns are significantly associated with a reduced risk of CVD Mortality, ASCVD, CAD, PAD, and Heart Failure in the diabetes population.

Comparisons of clinical characteristics, prognosis, epidemiological factors, and genetic susceptibility between HER2-low and HER2-zero breast cancer among Chinese females

BACKGROUND

Traditional human epidermal growth factor receptor 2 (HER2)-negative breast cancer (BC) is recommended to be divided into HER2-low and HER2-zero subtypes due to different prognosis. However, few studies investigated their differences in clinical characteristics and prognosis among Chinese HER2-negative BC and their stratified differences by hormone receptor (HR), while fewer studies investigated their differences in epidemiological factors and genetic susceptibility.

METHODS

A total of 11,911 HER2-negative BC were included to compare the clinical characteristics and prognosis between HER2-zero and HER2-low BC, and 4227 of the 11,911 HER2-negative BC were further compared to 5653 controls to investigate subtype-specific epidemiological factors and single nucleotide polymorphisms(SNPs).

RESULTS

Overall, 64.2% of HER2-negative BC were HER2-low BC, and the stratified proportions of HER2-low BC were 61.9% and 75.2% for HR-positive and HR-negative BC, respectively. Compared to HER2-zero BC, HER2-low BC among HR-positive BC showed younger age at diagnosis, later stage, poorer differentiation, and higher Ki-67, while elder age at diagnosis and lower mortality were observed for HER2-low BC among HR-negative BC (all p values <0.05). Compared to healthy controls, both HER2-low and HER2-zero BC are associated with similar epidemiological factors and SNPs. However, stronger interaction between epidemiological factors and polygenic risk scores were observed for HER2-zero BC than HER2-low BC among either HR-positive [odds ratios: 10.71 (7.55-15.17) and 8.84 (6.19-12.62) for the highest risk group compared to the lowest risk group] or HR-negative BC [7.00 (3.14-15.63) and 5.70 (3.26-9.98)].

CONCLUSIONS

HER2-low BC should deserve more attention than HER2-zero BC, especially in HR-negative BC, due to larger proportion, less clinical heterogeneity, better prognosis, and less susceptibility to risk factors.

Female reproductive and hormonal factors and lung cancer mortality among never-smokers: A prospective cohort study of 287 408 Chinese women

There is growing, but inconsistent evidence suggesting oestrogen may play a key role in lung cancer development, especially among never-smoking women for whom lung cancer risk factors remain largely elusive. Using the China Kadoorie Biobank, a large-scale prospective cohort with 302 510 women aged 30 to 79 years recruited from 10 regions in China during 2004 to 2008, we assessed the risk of lung cancer death among self-reported never-smoking women who were cancer-free at baseline, in relation to age at menarche, age at menopause, time since menopause, prior use of oral contraceptives (OCP), number of livebirths, breastfeeding and age at first livebirth. Women were followed up to December 31, 2016 with linkage to mortality data. Hazard ratios (HR) and 95% confidence intervals (CI) were estimated using Cox regression, adjusting for key confounders including several socio-demographic, environmental and lifestyle factors. Among 287 408 never-smoking women, 814 died from lung cancer with a median follow-up of 10.3 years. Women who had used OCP within 15 years prior to baseline had a significantly higher hazard of lung cancer death compared with never-users: HR = 1.85 (95% CI: 1.14-3.00) and risk increased by 6% with each additional year of use: HR = 1.06 (1.01-1.10). Among parous women, the hazard of lung cancer death increased by 13% with each single livebirth: HR = 1.13 (1.05-1.23); and among post-menopausal women, the risk increased by 2% with each year since menopause: HR = 1.02 (1.01-1.04). These results suggest that reproductive factors which were proxies for lower endogenous oestrogen level, for example, longer duration of OCP use, could play a role in lung cancer development.

The Introduction of Low-Dose CT Imaging and Lung Cancer Overdiagnosis in Chinese Women

BACKGROUND

Overdiagnosis of lung cancer by low-dose CT (LDCT) screening has raised concerns globally. LDCT screening has been used widely in employee health examinations in China since 2011.

RESEARCH QUESTION

Has the increasing use of LDCT in low-risk populations in China led to lung cancer overdiagnosis?

STUDY DESIGN AND METHODS

A total of 34,152 incident cases of and 27,208 deaths resulting from lung cancer in a population of approximately 3 million were derived from the Cancer Surveillance of Shanghai between 2002 and 2017. Changes in stage-specific and histologic type-specific incidence and mortality and incidence rate ratio (IRR) relative to the base year 2002 or to the period 2002 through 2005 were calculated by sex and were used to evaluate potential overdiagnosisve of lung cancer.

RESULTS

In men, both age-adjusted incidence of and mortality as a result of lung cancer decreased significantly up to 2008 and thereafter remained stable; in women, the incidence increased rapidly from 2011 (annual percentage change, 11.98%; 95% CI, 9.57%-14.45%), whereas the mortality declined persistently. The upward trend of incidence mainly was observed in lung adenocarcinoma in both sexes, with a sharper increase from 2012 through 2017. In men, the incidence of early-stage cancer increased 6.9 per 100,000 (95% CI, 5.1-8.7 per 100,000) and was accompanied by 5.5 per 100,000 (95% CI, -9.2 to -1.7 per 100,000) decline in late-stagecancer from 2002 through 2017. In women, early-stage incidence rose 16.1 per 100,000 (95% CI, 14.0-18.3 per 100,000), but no significant decline in late-stage cancer was found (absolute difference, -0.6 per 100,000; 95% CI, -2.8 to 1.7 per 100,000). The IRR was highest in most recent period and increased most in young women, mainly for early-stage cancer or lung adenocarcinoma.

INTERPRETATION

The results provide evidence at a population level for lung cancer overdiagnosis in Chinese women resulting from increasing LDCT screening in the low-risk populations. Criteria for LDCT screening and management of screening-detected nodules need to be addressed fully for expanded application of LDCT screening in China.

Global Burden of Female Breast Cancer: Age-Period-Cohort Analysis of Incidence Trends From 1990 to 2019 and Forecasts for 2035

Introduction

This study aimed to describe the latest epidemiology of female breast cancer globally, analyze the change pattern of the incidence rates and the disease’s association with age, period, and birth cohort, and subsequently present a forecast of breast cancer incidence.

Methods

Data for analysis were obtained from Global Burden of Disease (GBD) Study 2019 and World Population Prospects 2019 revision by the United Nations (UN). We described the age-standardized incidence rates (ASIRs) from 1990 to 2019 and then calculated the relative risks of period and cohort using an age-period-cohort model, and predicted the trends of ASIRs to 2035.

Results

In 2019, the global incidence of breast cancer in women increased to 1,977,212 (95% uncertainty interval = 1 807 615 to 2 145 215), with an ASIR of 45.86 (41.91 to 49.76) per 100 000 person-year. Among the six selected countries facing burdensome ASIRs, only the USA showed a downward trend from 1990 to 2019, whereas the others showed an increasing or stable trend. The overall net drift was similar in Japan (1.78%), India (1.66%), and Russia (1.27%), reflecting increasing morbidity from 1990 to 2019. The increase in morbidity was particularly striking in China (2.60%) and not significant in Germany (0.42%). The ASIRs were predicted to continue to increase globally, from 45.26 in 2010 to 47.36 in 2035. In most countries and regions, the age specific incidence rate is the highest in those aged over 70 years and will increase in all age groups until 2035. In high-income regions, the age specific incidence rates are expected to decline in women aged over 50 years.

Conclusions

The global burden of female breast cancer is becoming more serious, especially in developing countries. Raising awareness of the risk factors and prevention strategies for female breast cancer is necessary to reduce future burden.

Secular trends of age at menarche and the effect of famine exposure on age at menarche in rural Chinese women

BACKGROUND

Over the past few decades, more studies have suggested that the age at menarche (AAM) has continued to decline. However, the AAM for women in resource-constrained areas is not clear. Moreover, the association between the China famine and AAM is still unclear in rural regions.

AIM

The study aimed to investigate the secular trends of AAM for women born between 1935 and 2000 and to further explore the effect of famine on AAM in rural China.

SUBJECTS AND METHODS

The study included 23444 women participants from the baseline study of Henan Rural Cohort study. Changing AAM over time was analysed using linear regressions. Multinomial logistic regression was conducted to analyse the association between famine exposure and AAM subgroups.

RESULTS

The age-standardized mean AAM was 14.74 years. The average AAM declined from 16.98 years for those born in 1935 to 13.87 years for those born in 2000, a decline of 0.077 years per 1 year and 0.729 years per decade. Compared to the reference group, women exposed to famine during fetal, early childhood, middle childhood, and late childhood were 1.376 (95% CI, 1.071 - 1.769), 1.848(95% CI, 1.512 - 2.259), 2.084(95% CI, 1.725 - 2.518), and 2.146 (95% CI, 1.788 - 2.576) times more likely to be ≥18 years of AAM than unexposed famine women, respectively.

CONCLUSION

AAM showed a decreasing trend in rural China. Furthermore, both fetal and childhood famine exposure, especially in late childhood, were positively associated with increased AAM compared to unexposed famine.

OUP accepted manuscript

STUDY QUESTION

What is the scope of literature regarding women’s reproductive span in terms of definitions, trends and determinants?

SUMMARY ANSWER

The scoping review found a wide variation in definitions, trends and determinants of biological, social and effective women’s reproductive span.

WHAT IS KNOWN ALREADY

A woman’s reproductive span refers to her childbearing years. Its span influences a woman’s reproductive decisions.

STUDY DESIGN, SIZE, DURATION

A systematic scoping review was conducted. We searched MEDLINE, PubMed, JSTOR, CINAHL, Web of Science and Scopus electronic databases from inception to January 2021 without imposing language or date restrictions. We searched unpublished sources including the Global Burden of Disease, Demographic and Health Surveys, and National Health and Nutrition Examination Surveys. The list of relevant references was searched by hand. Sixty-seven reports on women’s reproductive span were included in this review.

PARTICIPANTS/MATERIALS, SETTING, METHODS

This scoping systematic review followed an established framework. The reporting of this scoping review followed the reporting requirements provided in the Preferred Reporting Items for Systematic Reviews and Meta-Analyses, Extension for Scoping Reviews. Identified records were independently screened and data were extracted. We performed conceptual synthesis by grouping the studies by available concepts of reproductive span and then summarized definitions, measures used, temporal trends, determinants, and broad findings of implications on population demographics and assisted reproduction. Structured tabulation and graphical synthesis were used to show patterns in the data and convey detailed information efficiently, along with a narrative commentary.

MAIN RESULTS AND THE ROLE OF CHANCE

A total of 67 relevant reports on women’s reproductive span were published between 1980 and 2020 from 74 countries. Most reports (42/67) were cross-sectional in design. Literature on reproductive span was conceptually grouped as biological (the interval between age at menarche and age at menopause), effective (when a woman is both fertile and engaging in sexual activity) and social (period of exposure to sexual activity). We summarized the working definitions, trends and determinants of each concept. Few articles addressed implications on demographics and assisted reproduction.

LIMITATIONS, REASONS FOR CAUTION

A formal assessment of methodological quality of the included studies was not performed because the aim of this review was to provide an overview of the existing evidence base regardless of quality.

WIDER IMPLICATIONS OF THE FINDINGS

The review produced a comprehensive set of possible definitions of women’s reproductive span, trends, and potential determinants. Further advancement of these findings will involve collaboration with relevant stakeholders to rate the importance of each definition in relation to demography and fertility care, outline a set of core definitions, identify implications for policy, practice or research and define future research opportunities to explore linkages between reproductive spans, their determinants, and the need for assisted reproduction.

STUDY FUNDING/COMPETING INTEREST(S)

This work received funding from the UNDP-UNFPA-UNICEF-WHO-World Bank Special Programme of Research, Development and Research Training in Human Reproduction (HRP), a cosponsored programme executed by the World Health Organization (WHO). The authors had no competing interests.

STUDY REGISTRATION NUMBER

N/A.

Age at menarche, age at menopause, reproductive years and risk of fatal stroke occurrence among Chinese women: the Guangzhou Biobank Cohort Study

Background

The relationship between women’s reproductive characteristics and stroke events is unclear. We aimed to investigate age at menarche, age at menopause and number of reproductive years in relation to fatal stroke occurrence in the Guangzhou Biobank Cohort Study.

Methods

In total, 16,504 postmenopausal women without stroke, heart disease or a cancer history at baseline were included and followed up for a median of 12.0 years. After review of available records, 222 stroke deaths were recorded. Cox proportional hazards regression was used to assess the associations between the risk of fatal stroke occurrence and age at menarche, age at menopause and number of reproductive years.

Results

In the whole cohort, compared with those aged 15 years at menarche, an increased risk of fatal stroke among women at menarche showed respectively in those aged 12 years (aHR (adjusted hazard ratio) = 1.86, 95% confidence interval (CI) 0.96–3.60), aged 13 years (aHR = 1.69, 95% CI 0.98–2.92), aged 17 years (aHR = 1.83, 95% CI 1.10–3.05) and aged ≥ 18 years (aHR = 1.66, 95% CI 1.03–2.70), wherein the associations revealed an atypically U-shaped; similar U-shaped association to the cohort of postmenopausal women born before 1940 released a range of incremental risks of fatal stroke in women at menarche aged ≤ 12 years (aHR = 3.68, 95% CI 1.68–8.05), aged 13 years (aHR = 2.11, 95% CI 1.02–4.34), aged 14 years (aHR = 2.07, 95% CI 1.04), aged 17 years (aHR = 2.30, 95% CI 1.20–4.39) and aged 18 years (aHR = 2.50, 95% CI 1.37–4.57), respectively. Compared with menopausal women aged 51–52 years, those aged < 43 years at menopause had an increased risk for fatal stroke among postmenopausal women born in and after 1940 (aHR = 1.64, 95% CI 0.97–2.78) and postmenopausal women born before 1940 (aHR = 1.97, 95% CI 1.05–3.69). Additionally, compared with those with 32–34 reproductive years, women with ≤ 28 reproductive years had an increased risk for fatal stroke in the whole cohort (aHR = 1.91, 95% CI 1.28–2.86) and the cohort of postmenopausal women born before 1940 (aHR = 1.79, 95% CI 1.15–2.80).

Conclusions

Younger and older age at menarche, younger age at menopause and fewer reproductive ages were related to an increased risk of fatal stroke in postmenopausal women.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12905-021-01579-9.

Reproductive and environmental exposures and the breast cancer risk in Taiwanese women

Breast cancer (BC) incidence is increasing around the globe, including in Taiwan, though the cause of the increasing incidence is less clear. We followed up 11,296 Taiwanese females who did not have BC at baseline, and ascertained new invasive BC (N = 351) through data linkage to the National Cancer Registry from 1991 to 2018 to examine whether reproductive, lifestyle and environmental risk factors including polycyclic aromatic hydrocarbons (PAH) were associated with BC risk. We conducted a nested case–control study using baseline blood available from a total of 305 women with BC and 598 women without BC matched on time in cohort. We examined the association of PAH-albumin adducts and BC risk using conditional logistic regression models. Age at menarche (HR 0.6 (95% CI 0.5–0.9) for ≥ 15 vs. < 13 years) and multiparity were associated with BC risk (HR 2.0 (95% CI 1.4–2.8), 2.8 (1.9–4.2), and 2.4 (1.0–5.0) for 3–4, 1–2 and 0 live birth, compared with women ≥ 5 births). PAH-albumin adducts were not associated with BC risk. Given the increasing BC incidence in Taiwan, there is a need to identify environmental factors that are important to this population.

Factors related to age at natural menopause in China: results from the China Kadoorie Biobank

OBJECTIVES

The aim of this study was to investigate the potentially modifiable factors affecting age at natural menopause (ANM) in Chinese women.

METHODS

We used cross-sectional data from the China Kadoorie Biobank study which that recruited 0.5 million (0.3 million women) Chinese adults aged 30 to 79 from 2004 to 2008. Multinomial logistic regression models were used to examine the relationships between ANM and various factors recorded at baseline.

RESULTS

Among 87,349 postmenopausal women, the mean ANM (SD) was 48.7 (4.3) years. Older age, being a housewife, earlier menarche, and passive smoking were associated with both premature menopause (PM, ie, ANM <40 years) and early menopause (EM, ie, ANM between 40 and 44 years). A higher odds for EM was observed in women who were widowed (odds ratio: 1.10, 95% confidence interval: 1.04-1.16), had spontaneous abortions (1.33 [1.05-1.69]), current regular smoking (1.19 [1.07-1.37]), and frequent spicy food intake (1.11 [1.05-1.08]). Higher socioeconomic status; later first birth; more live births and induced abortions; longer breastfeeding; tea drinking, as well as intakes of meat, fruits, dairy, and soybean products; and increased body mass index gain were inversely associated with PM and/or EM. In contrast, women who had more pregnancies, occasional alcohol drinking, higher levels of physical activity or body mass index, vitamin intake, and hypertension were more likely to have a later age at menopause (LM, ie, ANM ≥53 years).

CONCLUSIONS

This large epidemiological study found a wide range of sociodemographic, lifestyle, dietary, and reproductive factors related to PM, EM, and LM in Chinese women.

Age at menarche, ideal cardiovascular health metrics, and risk of diabetes in adulthood: Findings from the REACTION study

BACKGROUND

Age at menarche was reported to be associated with the risk of diabetes. However, the impact of ideal cardiovascular health metrics (ICVHMs) on the association between age at menarche and adulthood diabetes risk was unclear.

METHODS

We included 121 431 women from the nationwide, population-based cohort of the REACTION study (Risk Evaluation of Cancers in Chinese Diabetic Individuals: a Longitudinal Study). The diagnosis of diabetes was based on the oral glucose tolerance test (OGTT) and glycosylated hemoglobin (HbA1c) measurement. Logistic regression and multiplicative interaction analysis were conducted to investigate the potential interaction effect between age at menarche and ICVHMs on the development of diabetes.

RESULTS

The multivariable-adjusted odds ratios of diabetes across categories of age at menarche (<14, 14-17, and > 17 years) were 1.22 (95% confidence interval [CI]: 1.17, 1.28), 1.00 (reference), and 0.89 (95% CI: 0.85, 0.93), respectively. In subgroup analysis, significant interactions were detected between total cholesterol/blood pressure levels and age at menarche regarding the risk of diabetes (P for interaction = .0091 and .0019, respectively). The increased risk associated with age at menarche <14 years was observed in participants with three or fewer ICVHMs, but not in women with four or more ICVHMs (P for interaction = .0001).

CONCLUSIONS

Age at menarche was inversely associated with the risk of diabetes in adulthood in Chinese women, and it appeared to be modified by the presence of ICVHMs. Further studies are needed to clarify the precise interrelationship and the generalizability of our results.

Breast cancer incidence and mortality in women in China: temporal trends and projections to 2030

OBJECTIVE

Breast cancer was the most common cancer and the fifth cause of cancer deaths among women in China in 2015. The evaluation of the long-term incidence and mortality trends and the prediction of the future burden of breast cancer could provide valuable information for developing prevention and control strategies.

METHODS

The burden of breast cancer in China in 2015 was estimated by using qualified data from 368 cancer registries from the National Central Cancer Registry. Incident cases and deaths in 22 cancer registries were used to assess the time trends from 2000 to 2015. A Bayesian age-period-cohort model was used to project the burden of breast cancer to 2030.

RESULTS

Approximately 303,600 new cases of breast cancer (205,100 from urban areas and 98,500 from rural areas) and 70,400 breast cancer deaths (45,100 from urban areas and 24,500 from rural areas) occurred in China in 2015. Urban regions of China had the highest incidence and mortality rates. The most common histological subtype of breast cancer was invasive ductal carcinoma, followed by invasive lobular carcinoma. The age-standardized incidence and mortality rates increased by 3.3% and 1.0% per year during 2000-2015, and were projected to increase by more than 11% until 2030. Changes in risk and demographic factors between 2015 and 2030 in cases are predicted to increase by approximately 13.3% and 22.9%, whereas deaths are predicted to increase by 13.1% and 40.9%, respectively.

CONCLUSIONS

The incidence and mortality of breast cancer continue to increase in China. There are no signs that this trend will stop by 2030, particularly in rural areas. Effective breast cancer prevention strategies are therefore urgently needed in China.

Temporal trends in age at menarche and age at menopause: a population study of 312 656 women in Norway

STUDY QUESTION

Have mean age at menarche or mean age at natural menopause changed from the 1939 birth cohort to the 1964 birth cohort?

SUMMARY ANSWER

We estimated a minor decrease in mean age at menarche and an increase by nearly 3 years in mean age at natural menopause.

WHAT IS KNOWN ALREADY

In the Western world, age at menarche decreased across birth cohorts from the early 1800s until the 1950s. Whether mean age at menarche has continued to decrease in birth cohorts after the 1950s remains uncertain. It is also uncertain whether mean age at natural menopause has changed across birth cohorts.

STUDY DESIGN, SIZE, DURATION

We performed a retrospective population study of 312 656 women who were born in Norway during the years 1936–1964.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The data were obtained by two self-administered questionnaires from women who participated in the Norwegian breast cancer screening program (BreastScreen Norway) during the years 2006–2014. We used flexible parametric survival models with restricted cubic splines to estimate mean age at menarche, mean age at menopause and mean number of years between menarche and menopause according to the women’s year of birth. The women who were still having menstrual periods contributed with follow-up time until the time of data collection, and the women who had reported surgical removal of the uterus and/or both ovaries prior to natural menopause contributed with follow-up time until the time of surgery.

MAIN RESULTS AND THE ROLE OF CHANCE

The mean age at menarche was 13.42 years (95% CI: 13.40–13.44 years) among women born during 1936–1939, and it was 13.24 years (95% CI: 13.22–13.25 years) among women born during 1960–1964. The mean age at natural menopause increased from 50.31 years (95% CI: 50.25–50.37 years) among women born during 1936–1939 to 52.73 years (95% CI: 52.64–52.82 years) among women born during 1960–1964. The mean number of years between menarche and menopause increased from 36.83 years (95% CI: 36.77–36.89 years) to 40.22 years (95% CI: 40.11–40.34 years).

LIMITATIONS, REASONS FOR CAUTION

Information about age at menarche and age at menopause was based on self-reports.

WIDER IMPLICATIONS OF THE FINDINGS

Late menopause is associated with increased risk of breast cancer but also with increased life expectancy. Thus, higher mean age at menopause may partly explain the increase in breast cancer incidence after menopause and the increase in life expectancy in recent time. Also, a longer interval between menarche and menopause could suggest that the number of years of female fecundity has increased.

STUDY FUNDING/COMPETING INTEREST(S)

This work was funded by the South-Eastern Norway Regional Health Authority [grant number 2016112 to M.S.G.] and by the Norwegian Cancer Society [grant number 6863294-2015 to E.K.B.]. The authors declare no conflicts of interest.

International trends in ovarian cancer incidence from 1973 to 2012

PURPOSE

Ovarian cancer is the 7th leading cancer diagnosis and the 8th leading cause of cancer death in women worldwide. We conducted this study to investigate the incidence of ovarian cancer internationally.

METHODS

The trends in ovarian cancer incidence were analyzed through the latest data of CI5 over the 40-year period from 21 populations in 4 continents using Joinpoint analysis, ASRs and proportions of different histological subtypes in those populations were also analyzed using volume XI of CI5.

RESULTS

ASRs of ovarian cancer were from 7.0 to 11.6 per 100,000 in non-Asia populations during 2008-2012. In Asia, the ASR in Israel (Jews) were the highest, up to 8.1 per 100,000 in the same period. The international trends from 1973 to 2012 showed that ASRs of ovarian cancer were decreasing in 8 of 21 selected populations, whereas ASRs in Slovakia, Spain (Navarra) and China (Shanghai) were increasing. Meanwhile, there are certain differences in the main pathological classification patterns within different regions. In Asia, China (Hong Kong) and Japan both have a higher ASRs and proportions for clear cell and endometrioid carcinomas, while Japan has the highest ASRs and proportions for mucinous carcinomas.

CONCLUSION

Although the reasons for those trends were not entirely clear, environmental, reproductive and genetic factors were likely to have led to these patterns. Meanwhile, more attention and further study should be given to the etiological factors of histology-specific ovarian cancer.

Trends in prevalence of gestational diabetes mellitus in Zhejiang Province, China, 2016-2018

Background

Limited population-based studies have investigated the secular trend of prevalence of gestational diabetes mellitus (GDM) in mainland China. Therefore, this study aimed to estimate the prevalence of GDM and time trends in Chinese female population.

Methods

Based on Diabetes Surveillance System of Zhejiang Province, 97,063 diagnosed GDM cases aged 20–50 years were identified from January 1, 2016 to December 31, 2018. Annual prevalence, prevalence rate ratios (PRRs) and average annual percentage change with their 95% confidence intervals (CIs) were reported.

Results

The age-standardized overall prevalence of GDM was reported to be 7.30% (95% CI 7.27–7.33%); 9.13% (95% CI 9.07–9.19%) in urban areas and 6.24% (95% CI 6.21–6.27%) in rural areas. Compared with 20–24 years age group, women in advanced age groups (25–50 years) were at higher risk for GDM (PRRs ranged from 1.37 to 8.95 and the 95% CIs did not include the null). Compared with rural areas, the risk for GDM was higher in urban areas (PRR: 1.69, 95% CI 1.67–1.72). The standardized annual prevalence increased from 6.02% in 2016 to 7.94% in 2018, with an average annual increase of 5.48%, and grew more rapidly in rural than urban areas (11.28% vs. 0.00%).

Conclusions

This study suggested a significant increase in the prevalence of GDM among Chinese female population in Zhejiang province during 2016–2018, especially in women characterized by advanced age and rural areas.

Sleep patterns, genetic susceptibility, and incident cardiovascular disease: a prospective study of 385 292 UK biobank participants

AIMS

To quantify the association of combined sleep behaviours and genetic susceptibility with the incidence of cardiovascular disease (CVD).

METHODS AND RESULTS

This study included 385 292 participants initially free of CVD from UK Biobank. We newly created a healthy sleep score according to five sleep factors and defined the low-risk groups as follows: early chronotype, sleep 7-8 h per day, never/rarely insomnia, no snoring, and no frequent excessive daytime sleepiness. Weighted genetic risk scores of coronary heart disease (CHD) or stroke were calculated. During a median of 8.5 years of follow-up, we documented 7280 incident CVD cases including 4667 CHD and 2650 stroke cases. Compared to those with a sleep score of 0-1, participants with a score of 5 had a 35% (19-48%), 34% (22-44%), and 34% (25-42%) reduced risk of CVD, CHD, and stroke, respectively. Nearly 10% of cardiovascular events in this cohort could be attributed to poor sleep pattern. Participants with poor sleep pattern and high genetic risk showed the highest risk of CHD and stroke.

CONCLUSION

In this large prospective study, a healthy sleep pattern was associated with reduced risks of CVD, CHD, and stroke among participants with low, intermediate, or high genetic risk.

Pregnancy, pregnancy loss and the risk of diabetes in Chinese women: findings from the China Kadoorie Biobank

Pregnancy and pregnancy loss may be associated with increased risk of diabetes in later life. However, the evidence is inconsistent and sparse, especially among East Asians where reproductive patterns differ importantly from those in the West. We examined the associations of pregnancy and pregnancy loss (miscarriage, induced abortion, and still birth) with the risk of incident diabetes in later life among Chinese women. In 2004-2008, the nationwide China Kadoorie Biobank recruited 302 669 women aged 30-79 years from 10 (5 urban, 5 rural) diverse localities. During 9.2 years of follow-up, 7780 incident cases of diabetes were recorded among 273,383 women without prior diabetes and cardiovascular disease at baseline. Cox regression yielded multiple-adjusted hazard ratios (HRs) for the risk of diabetes associated with pregnancy and pregnancy loss. Overall, 99% of women had been pregnant, of whom 10%, 53%, and 6% reported having a history of miscarriage, induced abortion, and stillbirth, respectively. Among ever pregnant women, each additional pregnancy was associated with an adjusted HR of 1.04 (95% CI 1.03; 1.06) for diabetes. Compared with those without pregnancy loss, women with a history of pregnancy loss had an adjusted HR of 1.07 (1.02; 1.13) and the HRs increased with increasing number of pregnancy losses, irrespective of the number of livebirths; the adjusted HR was 1.03 (1.00; 1.05) for each additional pregnancy loss. The strength of the relationships differed marginally by type of pregnancy loss. Among Chinese women, a higher number of pregnancies and pregnancy losses were associated with a greater risk of diabetes.

Socio-Demographic Determinants of Mortality from Chronic Noncommunicable Diseases in Women of Reproductive Age in the Republic of Georgia: Evidence from the National Reproductive Age Mortality Study (2014)

Purpose

Worldwide, noncommunicable diseases (NCDs) are the leading cause of premature death of women, taking the highest toll in developing countries. This study aimed to identify key socio-demographic determinants of NCD mortality in reproductive-aged women (15-49 years) in Georgia.

Materials and Methods

The study employed the verbal autopsy data from the second National Reproductive Age Mortality Survey 2014. Univariate and multivariate logistic regression models were fitted to explore the association between each risk factor and NCD mortality, measured by crude and adjusted odds ratio (AOR) with respective 95% confidence intervals (95% CI).

Results

In the final sample of 843 women, 586 (69.5%) deaths were attributed to NCDs, the majority of which occurred outside a hospital (72.7%) and among women aged 45-49 years (46.8%), ethnic Georgians (85.2%), urban residents (60.1%), those being married (60.6%), unemployed (75.1%) or having secondary and higher education (69.5%), but with nearly equal distribution across the wealth quintiles. After multivariate adjustment, the odds of dying from NCDs were significantly higher in women aged 45-49 years (AOR=17.69, 95% CI= 9.35 to 33.50), those being least educated (AOR=1.55, 95% CI= 1.01 to 2.37) and unemployed (AOR=1.47, 95% CI= 1.01 to 2.14) compared, respectively, to their youngest (15-24 years), more educated and employed counterparts. Strikingly, the adjusted odds were significantly lower in "other" ethnic minorities (AOR=0.29, 95% CI= 0.14 to 0.61) relative to ethnic Georgians. Contrariwise, there were no significant associations between NCD mortality and women's marital or wealth status, place of residence (rural/urban) or place of death.

Conclusion

Age, ethnicity, education, and employment were found to be strong independent predictors of young women's NCD mortality in Georgia. Further research on root causes of inequalities in mortality across the socioeconomic spectrum is warranted to inform equity- and life course-based multisectoral, integrated policy responses that would be conducive to enhancing women's survival during and beyond reproduction.

Effect of Pregnancy in Arrhythmogenic Right Ventricular Cardiomyopathy

Less is known about pregnancy in women with arrhythmogenic right ventricular cardiomyopathy (ARVC). From April 1995 to May 2018, 157 women with ARVC were retrospectively enrolled. Data on pregnancy and cardiac outcomes were analyzed. There were 224 pregnancies in 120 patients including 30 (13.4%) spontaneous and 2 (0.9%) medical abortions, 12 cardiac adverse events were recorded including new onset frequent premature ventricular contractions (PVC) in 3 (2.5%) patients, previous PVC numbers increased more than 100% in 5 (4.2%), syncope in 2 (1.7%), sustained ventricular tachycardia and heart failure required hospitalization each in one patient (0.8%). Women with cardiac events showed lower left ventricular ejection fraction (LVEF) (50.3 ± 2.7 vs 60.0 ± 7.3; p = 0.004). No significant change in cardiac structure and function was found at 1 year follow-up postpartum. At a median follow-up of 8 (1 to 32) years, 36 (22.9%) women died. Earlier symptom onset age (hazard ratio 1.046; 95% confidence interval 1.017 to 1.075; p = 0.002) and decreased LVEF (hazard ratio 1.127; 95% confidence interval 1.001 to 1.154; p = 0.041) increased the risk of all-cause mortality, pregnancy had no negative influence on survival. In all the 192 offsprings (mean age 26.3 ± 13.5 years), 2 died of sudden death, no definite ARVC was found. Pregnancy seemed to be acceptable in ARVC, decreased LVEF increased the risk of pregnancy and was associated with poorer long-term survival.

Trends of gallbladder cancer incidence, mortality, and diagnostic approach in urban Shanghai between 1973 and 2009

PURPOSE

To describe and interpret secular time trends in gallbladder cancer (GBC) incidence, mortality, and diagnostic approach using 37 years of cancer registry data in urban Shanghai.

METHODS

Data on registration of GBC in urban Shanghai during 1973 and 2009 were collected by the Shanghai Cancer Registry. To describe time trends and to identify specific time points when significant changes occurred, we used joinpoint regression analysis.

RESULTS

The age-standardized rates (ASRs) of incidence increased from 1.1/100,000 (1973-1975) to 2.9/100,000 (2006-2009) in men and from 1.7/100,000 (1973-1975) to 3.9/100,000 (2006-2009) in women. ASRs of incidence increased significantly with estimated annual percent changes (EAPCs) of 2.8% in men and 2.5% in women. The mortality trends increased significantly, with EAPCs of 2.8% in men and 2.5% in women. The increasing incidence and mortality rates were primarily observed in men ⩾60 years of age and in women ⩾70 years of age. Notable downward trends in incidence and mortality were identified among women age 60-69 years over the last decade. The percentage of GBC diagnosed by pathology increased steadily over the years while the percentage of GBC diagnosed by imaging, surgery, and biochemistry sharply increased from 1987 onwards.

CONCLUSIONS

Thirty-seven years of cancer registry data document a tremendous increase in incidence/mortality and a slight decline in incidence/mortality over the last decades for GBC, especially among women, in Shanghai. The development of diagnostic approaches and aging population may play important roles.

Association between age at first childbirth and type 2 diabetes in Chinese women

AIMS/INTRODUCTION

The present study aims to explore the relationship between age at first childbirth and developing type 2 diabetes, and analyze potential modifiers of its relationship.

MATERIALS AND METHODS

The data were obtained from the baseline survey of a large-scale cohort study in 10 diverse areas of China. Multivariate logistic regressions were used to analyze the association between developing type 2 diabetes and the age at first childbirth. Adjustments were made in each model on sociodemographic, socioeconomic and reproductive covariates. Subgroup analyses were further carried out to investigate the effects of reproductive factors, body mass index at 25 years of age and hypertension on the above-mentioned association.

RESULTS

Women who have their first child at age <20 years (odds ratio [OR] 1.33, 95% confidence interval [CI] 1.22-1.44) and between the ages of 20 and 24 years (OR 1.16, 95% CI 1.10-1.23) were more likely to be diagnosed with type 2 diabetes compared with those who have their first child between the ages of 25 and 29 years; equal to or more than three parities (OR 1.44, 95% CI 1.30-1.60), premenopausal status (OR 1.58, 95% CI 0.99-2.54), overweight at age 25 years (OR 1.62, 95% CI 1.37-1.93) and hypertension (OR 1.37, 95% CI 1.22-1.53) are all conditions found to increase the odds of developing type 2 diabetes in those who have their their first child at an early age (<20 years).

CONCLUSIONS

The study concluded that having the first child at an early age is associated with an increased likelihood of developing type 2 diabetes later in life; reproductive factors, overweight at age 25 years and status of hypotension could modify such an association.

Early menarche is associated with an increased risk of type 2 diabetes in rural Chinese women and is partially mediated by BMI: the Henan Rural Cohort Study

OBJECTIVE

The aim of the study was to determine if early menarche is associated with an increased risk of type 2 diabetes mellitus (T2DM) in rural Chinese women and to estimate the proportion that can be attributed to adiposity.

METHODS

A total of 15,346 postmenopausal women were enrolled in this study. Logistic regression and restricted cubic spline analysis were performed to estimate the relationship between age at menarche and T2DM. Mediation analysis was used to investigate whether the association was mediated by body mass index (BMI).

RESULTS

After adjusting for multiple confounders, the early menarche group (≤14 y) had a higher risk of T2DM (odds ratio [OR] = 1.21; 95% CI = 1.06-1.38; P = 0.004) compared with the reference group (16-17 y), whereas the late onset group (≥19 y) had a lower risk of T2DM (OR = 0.78; 95% CI = 0.66-0.92; P = 0.003). BMI partially mediated the association between age at menarche and T2DM, and the proportion of the effect was 28%.

CONCLUSIONS

Early menarche increases the risk of T2DM, whereas later menarche decreases the risk. The association seems to be partially mediated by BMI.

Global patterns and trends in ovarian cancer incidence: age, period and birth cohort analysis

BACKGROUND

Ovarian cancer (OC) is the seventh most common malignancy worldwide and the most lethal gynaecological malignancy. We aimed to explore global geographical patterns and temporal trends from 1973 to 2015 for 41 countries in OC incidence and especially to analyse the birth cohort effect to gain further insight into the underlying causal factors of OC and identify countries with increasing risk of OC.

METHODS

OC data were drawn from the Cancer Incidence in Five Continents databases and online databases published by governments. The joinpoint regression model was applied to detect changes in OC trends. The age-period-cohort model was applied to explore age and birth cohort effects.

RESULTS

The age-standardized rate of OC incidence ranged from 3.0 to 11.4 per 100,000 women worldwide in 2012. The highest age-standardized rate was observed in Central and Eastern Europe, with 11.4 per 100,000 women in 2012. For the most recent 10-year period, the increasing trends were mainly observed in Central and South America, Asia and Central and Eastern Europe. The largest significant increase was observed in Brazil, with an average annual percentage change of 4.4%. For recent birth cohorts, cohort-specific increases in risk were pronounced in Estonia, Finland, Iceland, Lithuania, the United Kingdom, Germany, the Netherlands, Italy, Malta, Slovenia, Bulgaria, Russia, Australia, New Zealand, Brazil, Costa Rica, Ecuador, India, Japan, the Philippines and Thailand.

CONCLUSIONS

Disparities in the incidence and risk of OC persist worldwide. The increased risk of birth cohort in OC incidence was observed for most countries in Asia, Central and Eastern Europe, and Central and South America. The reason for the increasing OC risk for recent birth cohorts in these countries should be investigated with further epidemiology studies.

Tobacco Smoking Modifies the Association between Hormonal Factors and Lung Cancer Occurrence among Post-Menopausal Chinese Women

Inconsistent evidence has been reported on the role of female hormonal factors in the development of lung cancer. This population-based case–control study evaluated the main effect of menstrual/reproductive factors on the risk of lung cancer, and the effect modification by smoking status. Multivariable unconditional logistic regression models were applied adjusted for age, income, education, county of residence, body mass index, smoking status, pack-years of smoking, and family history of lung cancer. Among 680 lung cancer cases and 1,808 controls, later menopause (at >54 vs. <46 years old) was associated with increased risk of lung cancer (SBOR, semi-Bayes adjusted odds ratio = 1.61, 95% PI, posterior interval = 1.10–2.36). More pregnancies (2 or 3 vs. 0 or 1) was associated with decreased risk (SBOR = 0.71, 95% PI = 0.53, 0.95). Ever being a smoker and having two or fewer pregnancies in one's lifetime could jointly increase the odds of lung cancer (RERI, relative excess risk due to interaction = 1.71, 95% CI = 0.03, 3.38). An increased number of ovulatory cycles was associated with increased risk of lung cancer (SBOR for 13 ovulatory cycles = 1.02, 95% CI = 1.00+, 1.04).

Urban-Rural Disparity in Cancer Incidence, Mortality, and Survivals in Shanghai, China, During 2002 and 2015

Introduction: Disparities in the incidence, mortality, and survival of cancer types between urban and rural areas in China reflect the effects of different risk factor exposure, education, and different medical availability. We aimed to characterize the disparities in the incidence, mortality, and survivals of cancer types between urban and rural areas in Shanghai, China, 2002-2015.

Materials and Methods: The incidence and mortality were standardized by Segi's world standard population. Trends in the incidence and mortality of cancers were compared using annual percent change. The 5-year observed and relative survivals were calculated with life table and Ederer II methods.

Results: Age-standardized incidences and mortalities were 212.55/10⁵ and 109.45/10⁵ in urban areas and 210.14/10⁵ and 103.99/10⁵ in rural areas, respectively. Female breast cancer and colorectal cancer occurred more frequently in urban than in rural areas, quite in contrast to liver cancer and cervical cancer. Cancers of lung and bronchus, liver, stomach, and colon and rectum were the leading causes of cancer death in both areas. Age-standardized incidence of female breast cancer and colorectal cancer in urban areas increased while gastric cancer and liver cancer decreased in both areas. Age-standardized mortalities of cancers of breast, esophagus, stomach, colon and rectum, liver, and lung and bronchus decreased in both areas. For all cancers combined, the 5-year observed and relative survivals of cancer patients were higher in urban than in rural areas. The 5-year observed and relative survivals of cancers of liver, pancreas, stomach, brain and central nervous system (CNS), and prostate were higher in urban than in rural areas. The 5-year observed and relative survivals of cervical cancer were higher in rural than in urban areas.

Conclusions: Factors promoting female breast cancer and colorectal cancer in urban areas and liver cancer and cervical cancer in rural areas should be specifically intervened in cancer prophylaxis. Improved medical services can greatly prolong the survival of major cancers in rural areas.

Menopause Characteristics, Total Reproductive Years, and Risk of Cardiovascular Disease Among Chinese Women

Supplemental Digital Content is available in the text.

Background—

Previous studies, mostly of Western women, have reported inconsistent findings on the association of menopause characteristics (status, age, and time since menopause) and total reproductive years with risk of cardiovascular disease (CVD).

Methods and Results—

The China Kadoorie Biobank recruited 302 632 women in 2004 to 2008 from 10 regions across China. During 9-year follow-up, 19 393 incident cases of stroke, 18 611 of ischemic heart disease, and 4978 CVD deaths occurred. Cox regression yielded adjusted hazard ratios relating each menopause characteristic and total reproductive years to CVD risk. Among 274 233 women with no prior CVD at baseline, 134 010 were naturally postmenopausal women (mean [SD] age at menopause of 48.6 [4.0] years and total reproductive years 32.7 [4.4]). Compared with premenopausal women, naturally peri- or postmenopausal women were at a higher risk of either fatal or nonfatal CVD. Among women who had had menopause, inverse associations were observed between age at menopause and risks of CVD mortality, incident ischemic heart disease, stroke, and subtypes of stroke, with 1.5% higher risk of CVD death (P<0.001), 0.7% for incident ischemic heart disease (P=0.002), and 0.5% for incident stroke (P=0.02) for every 1 year lower age at menopause. Compared with women who had menopause at age 48 to 50 years, lower age at menopause (ie, <43 years) was associated with 14% higher risk of CVD death and 6% higher risks of both incident ischemic heart disease and stroke. Higher risks of both fatal and nonfatal CVD were also found in women with 5 to 10, 10 to 15, 15 to 20, or >20 years since menopause compared with <5 years since menopause. Total reproductive years were inversely associated with risks of both fatal and nonfatal CVD, with 1.4% lower risk of CVD death per additional reproductive year (P<0.001).

Conclusions—

Women with younger age at menopause, longer time since menopause, or fewer total reproductive years had a higher risk of CVD.

Age at natural menopause and associated factors in adult women: Findings from the China Kadoorie Biobank study in Zhejiang rural area

Objectives

To investigate the factors associated with age at natural menopause in a large population of Chinese adult women.

Methods

This cross-sectional study was part of the baseline survey of China Kadoorie Biobank in Zhejiang Province. A total of 17,076 postmenopausal women were included in the present study. Relevant data of socio-demographic, lifestyle, dietary and reproductive characteristics were collected. Multinomial logistic regression models were used to examine the associated factors of age at natural menopause with adjusted odds ratios (ORs) and their 95% confidence intervals (CIs) were reported.

Results

The mean age at natural menopause was 48.94 years, with 3.40% of the women experienced premature menopause and 6.75% early menopause. Younger age, higher education, consumption of meat (1–3 days per week) and increased parity were associated with late menopause. Current smoking, underweight, higher physical activity, consumption of sea food (1–3 days per week), fresh eggs (≥4 days per week), fresh fruits (≥1 day per week), taking vitamins, experiencing severe food shortage, earlier age at menarche and older age at first birth were associated with earlier age at natural menopause.

Conclusions

These results suggest that certain factors involved with socio-demographic, lifestyle, dietary and reproductive characteristics are related to the age at natural menopause in Chinese women.

Age at Menarche and Incidence of Diabetes: A Prospective Study of 300,000 Women in China

Previous studies of predominantly Western populations have reported inconsistent associations between age at menarche and risk of diabetes. We examined this relationship among Chinese women, who generally experience menarche at a later age than Western women. In 2004–2008, China Kadoorie Biobank recruited 302,632 women aged 30–79 years from 10 areas across China, and recorded 5,391 incident cases of diabetes during 7 years of follow-up among 270,345 women without baseline diabetes, cardiovascular disease or cancer. Cox regression models yielded adjusted hazard ratios for incident diabetes associated with age at menarche. Overall, the mean age at menarche was 15.4 years, and decreased across successive generations. Age at menarche was linearly and inversely associated with incident diabetes, with adjusted hazard ratio of 0.96 (95% confidence interval (CI): 0.94, 0.97) per year delay. Hazard ratios were greater in younger generations (for women born in the 1960s–1970s, hazard ratio (HR) = 0.93, 95% CI: 0.90, 0.97; for women born in the 1950s, HR = 0.95, 95% CI: 0.93, 0.98; and for women born in the 1920s–1940s, HR = 0.97, 95% CI: 0.95, 0.99). Further adjustment for adulthood body mass index significantly attenuated the association (HR = 0.99, 95% CI: 0.97, 1.00), especially among those born before 1950 (HR = 1.00, 95% CI: 0.97, 1.02). Much of the inverse association between age at menarche and incident diabetes was mediated through increased adiposity associated with early menarche, especially in older generations.

Pregnancy, pregnancy loss, and the risk of cardiovascular disease in Chinese women: findings from the China Kadoorie Biobank

BACKGROUND

Pregnancy and pregnancy loss may be linked to cardiovascular disease (CVD). However, the evidence is still inconsistent, especially in East Asians, whose reproductive patterns differ importantly from those in the West. We examined the associations of pregnancy, miscarriage, induced abortion, and stillbirth with CVD incidence among Chinese women.

METHODS

In 2004-2008, the nationwide China Kadoorie Biobank recruited 302,669 women aged 30-79 years from ten diverse localities. During 7 years of follow-up, 43,968 incident cases of circulatory disease, 14,440 of coronary heart disease, and 19,925 of stroke (including 11,430 ischaemic and 2170 haemorrhagic strokes), were recorded among 289,573 women without prior CVD at baseline. Cox regression yielded multiple adjusted hazard ratios (HRs) for CVD risks associated with pregnancy outcomes.

RESULTS

Overall, 99% of women had been pregnant, and among them 10%, 53%, and 7% reported having a history of miscarriage, induced abortion, and stillbirth, respectively. Each additional pregnancy was associated with an adjusted HR of 1.03 (95% confidence interval, CI: 1.02; 1.04) for circulatory disease. A history of miscarriage, induced abortion, and stillbirth, respectively, were associated with adjusted HRs of 1.04 (1.01; 1.07), 1.04 (1.02; 1.07), and 1.07 (1.03; 1.11) for circulatory disease. The relationship was stronger with recurrent pregnancy loss; adjusted HRs for each additional loss being 1.04 (1.00; 1.09) for miscarriage, 1.02 (1.01; 1.04) for induced abortion, and 1.04 (1.00; 1.08) for stillbirth.

CONCLUSIONS

Among Chinese women, increases in pregnancy, and a history and recurrence of miscarriage, induced abortion, and stillbirth are each associated with a higher risk of CVD.

Urinary concentrations of phthalate metabolites in early pregnancy associated with clinical pregnancy loss in Chinese women

Limited evidence revealed conflicting results on relationship between phthalate exposure and clinical pregnancy loss (gestational weeks >6). A prospective cohort study in Chinese pregnant women (n = 3220) was conducted to investigate the association between urinary phthalate metabolites and clinical pregnancy loss (gestational weeks 6 to 27; n = 109). Morning urine samples during gestational weeks 5 to 14 (mean 10.42) were collected to measure monomethyl phthalate (MMP), monoethyl phthalate (MEP), monobutyl phthalate (MBP), monobenzyl phthalate (MBzP), mono (2-ethylhexyl) phthalate (MEHP), mono (2-ethyl-5-oxohexyl) phthalate (MEOHP) and mono (2-ethyl-5-hydroxyhexyl) phthalate (MEHHP). The concentrations of low- and high-molecular weight phthalate metabolites (ΣLMWP <250 Da and ΣHMWP >250 Da) were calculated. Adjusted logistic regression models showed increased risks of clinical pregnancy loss in women with higher creatinine- normalized concentrations of MEP, MBP, MEOHP, MEHHP, ΣLMWP and ΣHMWP. Stratified analysis by gestational weeks (10 weeks) of miscarriage indicated positive associations of MEP, MEOHP, MEHHP and ΣHMWP with embryonic loss (during gestational weeks 6 to 10). The only association of foetal loss (during gestational weeks 11 to 27) was observed with MEHHP. Our findings suggested that Chinese women who were exposed to phthalates during early pregnancy had an increased risk of clinical pregnancy loss, especially embryonic loss.

Breastfeeding and the Risk of Maternal Cardiovascular Disease: A Prospective Study of 300 000 Chinese Women

BACKGROUND

Breastfeeding confers substantial benefits to child health and has also been associated with lower risk of maternal cardiovascular diseases (CVDs) in later life. However, the evidence on the effects of CVD is still inconsistent, especially in East Asians, in whom the frequency and duration of breastfeeding significantly differ from those in the West.

METHODS AND RESULTS

In 2004-2008, the nationwide China Kadoorie Biobank recruited 0.5 million individuals aged 30 to 79 years from 10 diverse regions across China. During 8 years of follow-up, 16 671 incident cases of coronary heart disease and 23 983 cases of stroke were recorded among 289 573 women without prior CVD at baseline. Cox regression yielded adjusted hazard ratios (HRs) and 95% CIs for incident CVD by breastfeeding. Overall, ≈99% of women had given birth, among whom 97% reported a history of breastfeeding, with a median duration of 12 months per child. Compared with parous women who had never breastfed, ever breastfeeding was associated with a significantly lower risk of CVD, with adjusted HRs of 0.91 (95% CI, 0.84-0.99) for coronary heart disease and 0.92 (95% CI, 0.85-0.99) for stroke. Women who had breastfed for ≥24 months had an 18% (HR, 0.82; 0.77-0.87) lower risk of coronary heart disease and a 17% (HR, 0.83; 0.79-0.87) lower risk of stroke compared with women who had never breastfed. Among women who ever breastfed, each additional 6 months of breastfeeding per child was associated with an adjusted HR of 0.96 (95% CI, 0.94-0.98) for coronary heart disease and 0.97 (95% CI, 0.96-0.98) for stroke.

CONCLUSIONS

Among Chinese women, a history of breastfeeding was associated with an ≈10% lower risk of CVD in later life and the magnitude of the inverse association was stronger among those with a longer duration of breastfeeding.

Adiposity in relation to age at menarche and other reproductive factors among 300 000 Chinese women: findings from China Kadoorie Biobank study

Background

Adiposity is increasing rapidly in China but little is known about the relevance to it of women's reproductive factors, which differ inter-generationally and from that in the West. We assess associations of adiposity with life-course reproductive factors in Chinese women.

Methods

In 2004-08, the nationwide China Kadoorie Biobank recruited 303 000 women aged 30-79 (mean 50) years from 10 diverse regions. Multivariable linear regression was used to examine associations of reproductive factors (e.g. age at menarche/first birth/menopause, parity, breastfeeding and reproductive years) with measures of general [e.g. body mass index (BMI)] and central [e.g. waist circumference (WC)] adiposity in adulthood.

Results

Overall, the mean BMI was 23.7 (standard deviation 3.3) kg/m 2 , mean age at menarche was 15 (2) years and nearly all had given birth (99%) and breastfed children (98%). Adiposity was associated inversely with age at menarche and at first birth, with 0.19 and 0.05 kg/m 2 lower BMI and 0.38 and 0.12 cm lower WC per 1-year delay respectively ( P  < 0.001). Among 128 259 post-menopausal women, adiposity was associated positively with age at menopause and reproductive years, with 0.05 and 0.07 kg/m 2 higher BMI and 0.12 and 0.17 cm higher WC per 1-year increase, respectively ( P  < 0.001). The proportion with overweight/obesity had similar associations with these reproductive factors. Adiposity had a non-linear positive association with parity, but no association with breastfeeding duration.

Conclusion

Among Chinese women, earlier age at menarche and at first birth, later age at menopause and longer reproductive years were independently associated with increased adiposity late in life.

Changing trends in reproductive/lifestyle factors in UK women: descriptive study within the UK Collaborative Trial of Ovarian Cancer Screening (UKCTOCS)

OBJECTIVE

There has been considerable interest in the impact of reproductive factors on health but there are little data on how these have varied over time. We explore trends in reproductive/lifestyle factors of postmenopausal British women by analysing self-reported data from participants of the UK Collaborative Trial of Ovarian Cancer Screening (UKCTOCS).

DESIGN

Prospective birth cohort analysis.

SETTING

Population cohort invited between 2001 and 2005 from age-sex registers of 27 Primary Care Trusts in England, Wales and Northern Ireland and recruited through 13 National Health Service Trusts.

PARTICIPANTS

202 638 postmenopausal women aged 50-74 years at randomisation to UKCTOCS between April 2001 and October 2005.

INTERVENTIONS

Women were stratified into the following six birth cohorts (1925-1929, 1930-1934, 1935-1939, 1940-1944, 1945-1949, 1950-1955) based on year of birth. Self-reported data on reproductive factors provided at recruitment were explored using tabular and graphical summaries to examine for differences between the birth cohorts.

OUTCOME MEASURES

Trends in mean age at menarche and menopause, use of oral contraceptives, change in family size, infertility treatments, tubal ligation and hysterectomy rates.

RESULTS

Women born between 1935 and 1955 made up 86% of the cohort. Median age at menarche decreased from 13.4 for women born between 1925 and 1929 to 12.8 for women born between 1950 and 1955. Increased use of the oral contraceptives, infertility treatments and smaller family size was observed in the younger birth cohorts. Tubal ligation rates increased for those born between 1925 and 1945, but this increase did not persist in subsequent cohorts. Hysterectomy rates (17-20%) did not change over time.

CONCLUSIONS

The trends seen in this large cohort are likely to reflect the reproductive history of the UK female postmenopausal population of similar age. Since these are risk factors for hormone-related cancers, these trends are important in understanding the changing incidence of these cancers.

TRIAL REGISTRATION NUMBER

International Standard Randomised Controlled Trial Number: 22488978.

Factors associated with spontaneous abortion: a cross-sectional study of Chinese populations

Background

Spontaneous abortion (SA) is one of the prevalent negative reproductive outcomes among women around the world, which is a great challenge faced by maternal health promotion. The present study is aimed to explore the association between SA and socioeconomic status (SES) and provides reference for policy makers to improve strategies on maternal health promotion.

Methods

A cross-sectional analysis was conducted with baseline data from a large-scale population-based cohort study of 0.5 million people from 10 geographically diverse areas of China recruited from 2004 to 2008. The study collected data from 84,531 women aged 35–45 years old in the baseline survey of China Kadoorie Biobank. Participants were interviewed using a standardized questionnaire, and information on demographic-socioeconomic as well as reproductive health status was collected. Odds ratios (OR) with 95% CI, estimated by a multistep logistic regression, were used to approximate the associations between SA occurrence and characteristics of SES. A stratification analysis was also applied to find out how SES influenced women’s reproductive health outcomes differently between rural and urban areas. The model was adjusted for age at study date, tea consumption, alcohol consumption, cigarette smoking, and number of induced abortion.

Results

The risk of SA in rural was 1.68 times greater than in urban (AOR = 1.68, 95%CI: 1.54–1.84). Women with high income had a decreased risk of SA when compared with that of women with low income (AOR = 0.90, 95%CI: 0.84–0.97). Compared with women in low educational attainment, women in higher educational attainment had a lower prevalence of SA (AOR = 0.90, 95%CI: 0.82–0.98). The risk of SA only reduced in factory worker (AOR = 0.59, 95%CI: 0.53–0.66) and professional worker (AOR = 0.75, 95%CI: 0.66–0.84) compared with agriculture and related workers. After stratifying by rural/urban, the association between income and SA in urban (AOR = 0.88, 95%CI: 0.78–0.99) was stronger than that in rural (AOR = 0.92, 95%CI: 0.84–1.00). Association between education and SA was found in urban (AOR = 0.66, 95%CI: 0.55–0.78) but not in rural (AOR = 1.05, 95%CI: 0.34–1.17), and there was no difference on how occupation impacted SA among women between the two subgroups.

Conclusions

Generally women with lower SES status had a higher risk of SA. Lower income and educational attainment were inversely associated with the risk of SA. Women with agricultural and related work had a significantly higher prevalence of SA. Interventions could be targeted more on women with low SES to increase both health profits as well as economic gains for health programs.

Electronic supplementary material

The online version of this article (doi:10.1186/s12978-017-0297-2) contains supplementary material, which is available to authorized users.

Parenthood and the risk of cardiovascular diseases among 0.5 million men and women: findings from the China Kadoorie Biobank

Background

Women's parity has been associated with risk of cardiovascular disease (CVD). It is unclear, however, whether it reflects biological effects of childbearing or uncontrolled socio-economic and lifestyle factors associated with childrearing. We assessed the association between number of children and incident CVD outcomes separately in women and men.

Methods

In 2004-08, the nationwide China Kadoorie Biobank recruited 0.5 million individuals aged 30-79 years from 10 diverse regions. During 7 years of follow-up, 24 432 incident cases of coronary heart disease (CHD) and 35 736 of stroke were recorded among 489 762 individuals without prior CVD. Multivariable Cox regression models were used to estimate sex-specific hazard ratios (HRs) and 95% confidence intervals (CIs) for CHD and stroke associated with number of children.

Results

Overall, 98% of all participants had children and the mean number of children declined progressively from four in older participants to one or two in younger participants. Compared with childless women, women with children had an increased risk of CHD, but not of stroke [HR (95% CI): 1.14 (1.00; 1.30) and 1.03 (0.92; 1.16)]. Corresponding results for men were 1.20 (1.06; 1.35) and 1.13 (1.03; 1.24), respectively. In individuals with children, there was a log-linear association between number of children and CVD outcomes; in women, each additional child was associated with adjusted HRs of 1.02 (1.01; 1.04) for CHD and 1.02 (1.01; 1.03) for stroke, similar in magnitude to that in men [1.03 (1.01; 1.04) for CHD and 1.02 (1.01; 1.03) for stroke].

Conclusion

In Chinese adults, the association between the number of children and risk of CHD and stroke was similar between men and women, suggesting that factors associated with parenthood and childrearing are more likely to affect the risk of CVD outcomes than factors associated with childbearing.

Age at menarche and risk of major cardiovascular diseases: Evidence of birth cohort effects from a prospective study of 300,000 Chinese women

Background

Previous studies of mostly Western women have reported inconsistent findings on the association between age at menarche and risk of cardiovascular disease (CVD). Little is known about the association in China where there has been a large intergenerational decrease in women's mean age at menarche.

Methods

The China Kadoorie Biobank recruited 302,632 women aged 30–79 (mean 50.5) years in 2004–8 from 10 diverse regional sites across China. During 7 years follow-up, 14,111 incident cases of stroke, 14,093 of coronary heart disease (CHD), and 3200 CVD deaths were reported among 281,491 women who had no prior history of CVD at baseline. Cox regression yielded adjusted hazard ratios (HRs) relating age at menarche to CVD risks.

Results

The mean (SD) age of menarche was 15.4 (1.9) years, decreasing from 16.2 (2.0) among women born before 1940 to 14.7 (1.6) for those born during the 1960s–1970s. The patterns of association between age at menarche and CVD risk appeared to differ between different birth cohorts, with null associations in older generations but U-shaped or weak positive associations in younger women, especially those born after the 1960s. After minimizing the potential confounding effects from major CVD risk factors, both early and late menarche, compared with menarche at age 13 years, were associated with increased risk of CVD morbidity and mortality, which was more pronounced in younger generations.

Conclusion

Among Chinese women the associations between age at menarche and risk of CVD differed by birth cohort, suggesting other factors may underpin the association.

Parenthood and the risk of diabetes in men and women: a 7 year prospective study of 0.5 million individuals

AIMS/HYPOTHESIS

In women, higher parity has been associated with increased risk of diabetes later in life. It is unclear, however, whether this association is mainly due to biological effects of childbearing, or to socioeconomic and lifestyle factors associated with childrearing. We assessed the association between number of children and diabetes risk separately in women and men.

METHODS

Between 2004 and 2008, the nationwide China Kadoorie Biobank recruited 0.5 million individuals aged 30-79 (mean 51 years) from ten diverse regions across China. During 7 years of follow-up, 8,840 incident cases of diabetes were recorded among 463,347 participants without prior cardiovascular diseases or diabetes. Multivariable Cox regression yielded sex-specific HRs and 95% CIs for incident diabetes by number of children.

RESULTS

Overall, ∼98% of all participants had children. In women, there was a J-shaped association between number of children and risk of diabetes. Compared with women with one child, the adjusted HRs for diabetes were 1.39 (95% CI 1.11, 1.73) for childless women, 1.12 (95% CI 1.07, 1.18) for those with two children, 1.23 (95% CI 1.16, 1.31) for those with three children, and 1.32 (95% CI 1.21, 1.44) for those with four or more children. In men, there was a similar association with risk of diabetes; the corresponding HRs were 1.28 (95% CI 1.02, 1.60), 1.19 (95% CI 1.12, 1.26), 1.32 (95% CI 1.21, 1.44) and 1.41 (95% CI 1.24, 1.60), respectively. In both sexes, the findings were broadly similar in different population subgroups.

CONCLUSIONS/INTERPRETATION

The similarity between women and men in the association between number of children and risk of diabetes suggests that parenthood is most likely to affect diabetes risk through factors associated with childrearing rather than via biological effects of childbearing.

Incidence and mortality of gynaecological cancers: Secular trends in urban Shanghai, China over 40 years

AIM

Appraisal of cancer trends is essential for future cancer control, but relevant studies in China are scarce due to a lack of long-term data. With 40-years of cancer registry data, we sought to evaluate secular time trends in incidence and mortality of gynaecological cancers in an urban Chinese population.

MATERIALS AND METHODS

Data on incidence and mortality of invasive cervical, uterine and ovarian cancer were collected by the Shanghai Cancer Registry. Age-standardised incidence and mortality rates were calculated for women aged 20-84 in urban Shanghai between 1973 and 2012. Age-period-cohort Poisson regression models were used to evaluate age, period and cohort effects. Overall linear trends, interpreted as the estimated annual percentage change (EAPC), were derived from the net drift in age-drift models.

RESULTS

Overall, cervical cancer incidence and mortality substantially decreased (EAPC = -4.5% and -5.5%, respectively); however, an upward trend was apparent among younger women (age <60). Uterine cancer incidence increased slightly (EAPC = 1.8%), while mortality decreased over time (EAPC = -2.4%). Ovarian cancer incidence and mortality both increased, although the increase in incidence (EAPC = 1.8%) was larger than mortality (EAPC = 0.6%). While cohort effects were most evident for cervical cancer incidence and mortality, significant age, period, and cohort effects were found for all three gynaecological cancers evaluated.

CONCLUSIONS

These secular trends in incidence and mortality of gynaecological cancers in Shanghai likely reflect changing risk factor profiles and improved cancer prognosis over time, and suggest new priorities and call for additional efforts for gynaecological cancer prevention and control for women in China.

Breast cancer incidence and mortality: trends over 40 years among women in Shanghai, China

BACKGROUND

Breast cancer incidence rates are increasing among Asian women, likely due to the changes in risk factors caused by globalization. Trends in breast cancer rates among Chinese women may differ from other Asian regions due to the implementation of a nationwide family planning program and resulting changes in women's reproductive practices. Appraisal of cancer trends can direct cancer control and public health planning, but relevant studies in China are scarce due to a lack of long-term data. We sought to evaluate secular time trends in breast cancer incidence and mortality using 40 years of cancer registry data for women in urban Shanghai.

MATERIALS AND METHODS

Data on invasive breast cancer incidence and mortality were collected by the Shanghai Cancer Registry. Age-standardized rates (ASRs) for incidence and mortality were calculated using the Segi/Doll 1960 world standard population. Age, period, and birth cohort effects were evaluated using age-period-cohort (APC) Poisson regression models. Overall linear trends, interpreted as the estimated annual percentage change (EAPC), were derived from the net drift in age-drift models.

RESULTS

A total of 53 885 breast cancer cases and 17 235 breast cancer-specific deaths were documented among women in urban Shanghai between 1 January 1973 and 31 December 2012. Breast cancer incidence and mortality ASRs increased by 141.2% and 26.6%, respectively. Significant age, cohort, and period effects were identified in both incidence and mortality APC models; cohort effects were pronounced. Overall, a substantial increase in breast cancer incidence (EAPC = 2.96%/year) and a moderate increase in breast cancer mortality (EAPC = 0.87%/year) was observed. A notable downward trend in mortality was identified among younger women born after 1960.

CONCLUSIONS

Forty years of cancer registry data document a tremendous increase in incidence and a slight increase in mortality for breast cancer among women in Shanghai. Effective, appropriate, and affordable breast cancer prevention and control strategies are urgently needed in China.

Women's reproductive health factors and body adiposity: findings from the UK Biobank

OBJECTIVE

To conduct a comprehensive examination of the association between women's reproductive health factors and measures of body adiposity in a contemporary Western population.

METHODS

A cross-sectional analysis of 502 664 individuals from the UK Biobank was conducted. Multivariable linear regression models were used to examine the association of age at menarche, age at first birth, parity and age at menopause with measures of general and central body adiposity, adjusted for age, smoking and socioeconomic status. The association between number of children and body adiposity in men was also assessed.

RESULTS

Age at menarche was inversely associated with body mass index (BMI); adjusted mean BMI was 29.0 kg m(-2) in women with menarche before the age of 12 years, compared with 26.5 kg m(-2) in those who had menarche after 14 years of age. Age at first birth was linearly and inversely associated with BMI: 0.16 kg m(-2) lower BMI per year increase in age of first birth. Each additional live birth or child fathered was associated with a 0.22 kg m(-2) higher BMI in women and a 0.14 kg m(-2) higher BMI in men. There was no evidence for an association between age at menopause and BMI. Corresponding associations for other markers of general or abdominal adiposity were similar to those for BMI. Findings were broadly similar in analyses stratified by age, smoking status, socioeconomic status, ethnic background, and history of diabetes or cardiovascular disease.

CONCLUSIONS

In women from a contemporary Western population, earlier age at menarche and age at first birth, and higher number of total live births were associated with higher levels of body adiposity. Prospective evaluations of the association between reproductive health factors, adiposity and the onset of cardiometabolic diseases are needed to assess causality, and to explore the mechanisms involved.

Variation in the association between socioeconomic status and breastfeeding practices by immigration status in Taiwan: a population based birth cohort study

BACKGROUND

The relationship between socioeconomic status (SES) and breastfeeding has been extensively discussed in the literature. However, there is some evidence that this relationship can differ with immigration status. To date the majority of research investigating the relationships among SES, breastfeeding and immigration status has been conducted in Europe and the United States with a lack of similar research from Asia. Therefore, the aim of this study was to describe differences in breastfeeding practices between native-born Taiwanese mothers and immigrant mothers in Taiwan and to investigate any differences in the relationship between SES and breastfeeding practices by immigration status.

METHODS

Data analyzed came from the Taiwan Birth Cohort Study, the first longitudinal study of babies in Taiwan with a nationally representative sample born in 2005. In the present study, we included 21,217 mothers or primary caregivers who completed interview surveys when their child was 6 months old. Socioeconomic status was measured by the education level of mothers and fathers, and the couple's monthly income. Data analysis involved multiple logistic regression. Control variables included residential area, mother's employment status, age of the father and mother, and sex of the infant.

RESULTS

The proportion of immigrant mothers predominantly breastfeeding for 4 and for 6 months (Mainland Chinese mothers: 18.25 %, 36.29 %; Southeast Asian mothers: 10.71 %, 24.85 %) was significantly higher than that observed in their Taiwan-born counterparts (7.03 %, 16.22 %). Analysis stratified by immigration status showed that a higher level of parental education was associated with a greater likelihood of predominantly breastfeeding in Taiwanese mothers. However, no statistically significant relationship was observed between education and predominantly breastfeeding in immigrant mothers. Higher monthly income was also significantly associated with a greater likelihood of predominantly breastfeeding in Taiwanese mothers. However, there was no significant linear relationship between monthly income and predominantly breastfeeding in immigrant women.

CONCLUSION

The relationship between SES and breastfeeding is different in immigrant mothers and native-born Taiwanese mothers. Taiwanese policy should continue to encourage breastfeeding in immigrant mothers. However, greater attention should be placed on Taiwanese mothers from a low SES background.

Childhood Passive Smoking Exposure and Age at Menarche in Chinese Women Who Had Never Smoked: The Guangzhou Biobank Cohort Study

OBJECTIVE

We examined the associations between childhood passive smoking exposure and age at menarche in women who had never smoked in southern China.

METHODS

Among 30,518 participants in Guangzhou Biobank Cohort Study (GBCS) from 2003-2008, 20,061 women who had never smoked and had complete outcome data were included. Childhood passive smoking exposure was defined as living with 1 or more smokers in the same household during childhood. Data on the number of smokers in the household and frequency of exposure (density and frequency) were also obtained. Age at menarche was measured as a continuous variable.

RESULTS

11,379 (56.7%) participants were exposed to passive smoking during childhood. Compared to those with no passive smoking exposure during childhood, those with exposure ≥ 5 days/week had menarche 0.19 year (95% confidence interval (CI): 0.13-0.25) earlier on average. Those exposed to more than two smokers had menarche 0.38 year earlier (95% CI: 0.29-0.47). Childhood exposure was associated with early age at menarche (≤ 13 vs. >13 years), with an adjusted odds ratio of 1.34 (95% CI: 1.21-1.48) for high density, and 1.17 (95% CI: 1.09-1.26) for high frequency of exposure.

CONCLUSION

Childhood passive smoking exposure was associated with earlier age at menarche, with a dose-response relationship in Chinese women who had never smoked. If causal, the results support the promotion of smoking cessation in families with children, particularly young girls.

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.

Secular trends in age at menarche among women born between 1955 and 1985 in Southeastern China

Background

Improvements in socioeconomic conditions and population health have been linked to declining age at menarche. In China, secular trends in age at menarche following extensive economic reform during recent decades have not been thoroughly investigated. This study examined the overall trend in age at menarche and assessed differences in the rate of change of age at menarche over time, and between urban and rural populations and education levels in southeastern China.

Methods

Age at menarche was retrospectively collected from 1,167,119 Han Chinese women born 1955–1985, who registered in the Perinatal Health Care Surveillance System in 19 cities and counties in two southeast provinces during 1993–2005. Multivariable linear regression was used to estimate trends in age at menarche overall and stratified by urban/rural residence and education level.

Results

Age at menarche declined by 0.33 [95% CI 0.33, 0.32] years/decade overall, with the fastest decline in women born in 1966–1975. For the earliest birth cohorts (1955–1965), age at menarche declined faster in urban versus rural regions, and for women with high school education or above versus primary school or less. In contrast, age at menarche declined slower among urban women born 1976–1985, and among those with higher education born 1966–1985.

Conclusions

Mean age at menarche declined for women born in 1955–1985 in southeast China. Further study is warranted to identify specific factors contributing to earlier age at menarche and associated health outcomes.

Electronic supplementary material

The online version of this article (doi:10.1186/s12905-014-0155-0) contains supplementary material, which is available to authorized users.