Is the age of menopause determined in-utero?

Risk factors for natural menopause before the age of 45: evidence from two British population-based birth cohort studies

Background

Menopause that occurs before the age of 45 and is not medically induced (referred to here as ‘early natural menopause’) affects around one in 10 women and has serious health consequences. These consequences include increased risk of all-cause mortality, cardiovascular disease, osteoporosis, and type 2 diabetes.

Methods

We investigate risk factors for the onset of natural menopause before the age of 45 in two population-based prospective cohort studies in Britain: the 1958 cohort following 8959 women and the 1970 cohort following 8655 women. These studies follow women from birth to adulthood, and we use harmonized data on birth and early life characteristics, reproductive health, health behaviour, and socioeconomic characteristics for 6805 women who were pre-menopausal, peri-menopausal or had undergone natural menopause. Of these 6805 women, 3614 participated in the 1958 cohort (of which 368 had early menopause) and 3191 participated in the 1970 cohort (of which 206 had early menopause). Taking a life course approach, we focus on three distinct life stages - birth/early life, childhood, and early adulthood - to understand when risk factors are most harmful. Respecting the temporal sequence of exposures, we use a series of multivariable logistic regression models to estimate associations between early menopause and each potential risk factor adjusted for confounders.

Results

We find that early menopause is influenced by circumstances at birth. Women born in lower social class families, whose mother smoked during the pregnancy or who were breastfed 1 month or less were more likely to undergo early menopause. Early menopause is also associated with poorer cognitive ability and smoking in childhood. Adult health behaviour also matters. Smoking is positively correlated with early menopause, while regular exercise and moderate frequency of alcohol drinking in women’s early thirties are associated with reduced risk of early menopause. The occurrence of gynaecological problems by women’s early thirties is also linked to early menopause.

Conclusions

We demonstrate that characteristics at different periods of life are associated with early menopause. Some of these associations relate to modifiable behaviours and thus the risks of early menopause and the adverse health outcomes associated with it may be preventable.

Maternal nutritional status and offspring childlessness: Evidence from the late-nineteenth to early-twentieth centuries in a group of Italian populations

The role of maternal nutrition in affecting offspring fertility, through alteration of foetal programming, has been demonstrated in animal-based experiments. However, results from human populations appear inconsistent and sometimes contradictory, likely because they have been based on single famine events. In this paper, we adopt a different approach. We combine official annual time series of daily nutrient availability with a sample of women's reproductive histories from the 1961 Italian Census to investigate the role of maternal nutritional status in pregnancy on offspring childlessness. The analysis therefore covers cohorts of females born between 1861 and 1939. Our results show a negative association between calorie availability in pregnancy and the odds of offspring childlessness, whereas no association is found between protein availability and offspring childlessness. The consequences of poor calorie intake were aggravated during the summer, likely due to the participation of pregnant women in physically demanding work.

Association of In Utero Exposures With Risk of Early Natural Menopause

Suboptimal pregnancy conditions may affect ovarian development in the fetus and be associated with early natural menopause (ENM) for offspring. A total of 106,633 premenopausal participants in Nurses' Health Study II who provided data on their own prenatal characteristics, including diethylstilbestrol (DES) exposure, maternal cigarette smoking exposure, multiplicity, prematurity, and birth weight, were followed from 1989 to 2017. Cox regression models were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for the associations of in utero exposures with ENM. During 1.6 million person-years of follow-up, 2,579 participants experienced ENM. In multivariable models, women with prenatal DES exposure had higher risk of ENM compared with those without it (HR = 1.33, 95% CI: 1.06, 1.67). Increased risk of ENM was observed for those with low (<5.5 pounds (<2.5 kg)) versus normal (7.0-8.4 pounds (3.2-3.8 kg)) birth weight (HR = 1.21, 95% CI: 1.01, 1.45). Decreasing risk was observed per 1-pound (0.45-kg) increase in birth weight (HR = 0.93, 95% CI: 0.90, 0.97). Prenatal smoking exposure, being part of a multiple birth, and prematurity were not associated with ENM. In this large cohort study, lower birth weight and prenatal DES exposure were associated with higher risk of ENM. Our results support a need for future research to examine in utero exposures that may affect offspring reproductive health.

The association between chronic diseases and the age at natural menopause: a systematic review

Despite several existing studies on the age at natural menopause (ANM) and its related factors, epidemiologic data on the associations between chronic diseases and ANM are scarce with conflicting and inconclusive results. The aim of this systematic review was to summarize the results of the studies investigating the association between chronic disease and ANM. PubMed, Scopus, and Web of Science were searched for retrieving and summarizing studies published up to October 2020 investigating the association between chronic medical conditions and ANM. All types of observational studies published in the English language were eligible to be included in the systematic review. Studies needed to report the effect of at least one chronic disease on ANM. Studies with other designs, studies with unreliable and incomplete results, and those that assessed none of the chronic diseases as outcomes of interest were excluded. Of the 6294 records retrieved by searching the databases, a total of 28 observational studies were included for this review. According to the Newcastle-Ottawa scale, nine studies were classified as high-quality, fifteen studies as moderate, and four as low-quality. Among the five studies investigating the association between polycystic ovary syndrome (PCOS) and ANM, three studies reported that PCOS was associated with a later ANM, whereas others found no such association. Eight studies showed that diabetes was associated with an earlier ANM, whereas eight other studies found no such association. While only one study showed a younger age at the onset of menopause in patients with a history of hypertension, five studies did not report such an effect. Only one study assessed the effect of dyslipidemia on ANM and showed no association between these variables. While three studies documented the effects of cardiovascular diseases (CVD) and heart disease on earlier ANM, one study found no association between these diseases and ANM. Most included studies showed the association of mood disorders with earlier ANM. There were no sufficient data for assessing the effects of thyroid, skin, and autoimmune diseases on ANM. Chronic diseases particularly cardio-metabolic disturbances, cardiovascular events, and psycho-emotional disorders are associated with earlier menopause, whereas other diseases such as PCOS may lead to later menopause. Accordingly, early diagnosis and managing chronic medical conditions in women can potentially prevent early or late menopause.

The association of birthweight with age at natural menopause: a population study of women in Norway

Background

Previous studies suggest that birthweight may influence age at natural menopause, but the evidence remains inconclusive. Thus, we aimed to estimate the association of birthweight with age at natural menopause.

Methods

A retrospective population study of 164 608 women in Norway, aged 48–71 years. Data were obtained by two self-administered questionnaires among participants in BreastScreen Norway during 2006–2014. We used Cox proportional hazard models to estimate hazard ratios and logistic regression models to estimate odds ratios of menopause according to birthweight. Restricted cubic splines were applied to allow for possible non-linear associations, and adjustments were made for year and country of birth.

Results

Women with birthweight <2500 g were median 51 years at menopause (interquartile range 49–54 years), whereas women with birthweight 3500–3999 g were median 52 years at menopause (interquartile range 49–54 years). The hazard ratio of menopause decreased with increasing birthweight up until 3500 g. At birthweights >3500 g, we estimated no further decrease (P for non-linearity = 0.007). Birthweight at 2500 g increased the odds ratios of menopause before the age of 45 [1.20; 95% confidence interval (CI): 1.14–1.25] and the age of 40 (1.26; 95% CI: 1.15–1.38) compared with birthweight at 3500 g. At birthweights 4000 g and 4500 g, the odds ratio estimates were very similar to the reference group and the CIs overlapped 1.00.

Conclusions

We found a non-linear dose-relationship of birthweight with age at natural menopause, and low birthweight was associated with early natural menopause. Our findings suggest that growth restriction during fetal life may influence the timing of natural menopause.

Idiopathic primary ovarian insufficiency is associated with anogenital distance, a marker for prenatal environment

OBJECTIVE

In a significant number of women diagnosed with primary ovarian insufficiency (POI), the underlying cause cannot be found. On the other hand, the ovarian reserve set prenatally has been shown to be affected by intrauterine nutrition, environmental and hormonal factors. We aimed to evaluate the relationship between anogenital distance (AGD), which is considered as a biomarker for prenatal hormonal environment, and idiopathic POI in adolescents and young women.

STUDY DESIGN

This case control study was conducted between September 2018 and December 2019. The study group consisted of patients between the ages of 15-30, who developed POI following menarche without any identified genetic or iatrogenic cause. Controls were patients of the same age range who were having regular menstrual periods and were not diagnosed with polycystic ovary syndrome or endometriosis. Patients were excluded from the study if they were pregnant, had vaginal delivery or genital surgery. Distance between the anterior clitoral surface and the upper verge of the anus (AGD_AC), and between the posterior fourchette and the upper verge of the anus (AGD_AF) were measured in all subjects.

RESULTS

In total, 37 POI patients and 44 controls were included in the study. Two groups were similar for demographic parameters such as age and body mass index (BMI). Shorter AGD_AC and AGD_AF measurements were found to be associated with idiopathic POI.

CONCLUSION

Our results provide the first evidence of a strong association between shorter AGD measurements and the presence of idiopathic POI suggesting that prenatal environment may have role in the development of POI.

Foetal and childhood exposure to famine and the risks of cardiometabolic conditions in adulthood: A systematic review and meta-analysis of observational studies

A systematic review and meta-analysis of observational studies was performed to provide a deeper understanding of the associations between foetal and childhood exposure to famine and the risks of type 2 diabetes mellitus (T2DM), metabolic syndrome, hypertension, hyperglycaemia, dyslipidaemia, obesity, overweight, coronary heart disease, stroke, and nonalcoholic fatty liver disease (NAFLD) in adulthood. Both foetal and childhood exposure to famine were positively associated with the risks of T2DM (foetal exposure: RR 1.37, 95% CI, 1.23-1.52; childhood exposure: RR 1.33, 95% CI, 1.08-1.64), metabolic syndrome (RR 1.26, 95% CI, 1.07-1.50; RR 1.24, 95% CI, 1.13-1.35), hypertension (RR 1.30, 95% CI, 1.07-1.57; RR 1.33, 95% CI, 1.02-1.74), hyperglycaemia (RR 1.27, 95% CI, 1.11-1.45; RR 1.25, 95% CI, 1.10-1.42), dyslipidaemia (RR 1.48, 95% CI, 1.33-1.66; RR 1.27, 95% CI, 1.12-1.45), obesity (RR 1.19, 95% CI, 1.02-1.39; RR 1.13, 95% CI, 1.00-1.28), overweight (RR 1.17, 95% CI, 1.07-1.29; RR 1.07, 95% CI, 1.00-1.14), coronary heart disease (RR 1.22, 95% CI, 1.00-1.51; RR 1.21, 95% CI, 1.09-1.35), and moderate-to-severe NAFLD (RR 1.66, 95% CI, 1.07-2.57; RR 1.68, 95% CI, 1.41-1.99) in adulthood. No association was observed for the risks of stroke or mild NAFLD. Adjustments for age, alcohol, smoking, body mass index, and physical activity nullified some associations. The associations were generally stronger in women than in men. In summary, foetal and childhood exposure to famine may confer greater risks of developing certain cardiometabolic conditions in adulthood, particularly in women. The extent to which risks for cardiometabolic conditions are associated with early-life famine appears to be determined by certain factors in adulthood.

Demographic and evolutionary trends in ovarian function and aging

BACKGROUND

The human female reproductive lifespan is regulated by the dynamics of ovarian function, which in turn is influenced by several factors: from the basic molecular biological mechanisms governing folliculogenesis, to environmental and lifestyle factors affecting the ovarian reserve between conception and menopause. From a broader point of view, global and regional demographic trends play an additional important role in shaping the female reproductive lifespan, and finally, influences on an evolutionary scale have led to the reproductive senescence that precedes somatic senescence in humans.

OBJECTIVE AND RATIONALE

The narrative review covers reproductive medicine, by integrating the molecular mechanisms of ovarian function and aging with short-term demographic and long-term evolutionary trends.

SEARCH METHODS

PubMed and Google Scholar searches were performed with relevant keywords (menopause, folliculogenesis, reproductive aging, reproductive lifespan and life history theory). The reviewed articles and their references were restricted to those written in English.

OUTCOMES

We discuss and summarize the rapidly accumulating information from large-scale population-based and single-reproductive-cell genomic studies, their constraints and advantages in the context of female reproductive aging as well as their possible evolutionary significance on the life history trajectory from foetal-stage folliculogenesis until cessation of ovarian function in menopause. The relevant environmental and lifestyle factors and demographic trends are also discussed in the framework of predominant evolutionary hypotheses explaining the origin and maintenance of menopause.

WIDER IMPLICATIONS

The high speed at which new data are generated has so far raised more questions than it has provided solid answers and has been paralleled by a lack of satisfactory interpretations of the findings in the context of human life history theory. Therefore, the recent flood of data could offer an unprecedented tool for future research to possibly confirm or rewrite human evolutionary reproductive history, at the same time providing novel grounds for patient counselling and family planning strategies.

Caloric restriction reduces age at menopause: the effect of the 1944-1945 Dutch famine

OBJECTIVE

To assess the effect of caloric restriction, as endured during the 1944-1945 Dutch famine, on the age at which natural menopause occurs and to identify specific vulnerable age periods in which caloric restriction has the largest effect.

DESIGN

This was a population-based cohort study conducted in Utrecht, the Netherlands. Between 1983 and 1986, 9,471 women aged 40 to 73 years at the time of interview were classified regarding their exposure to the famine. Age at natural menopause was obtained from all available data, retrospectively as well as prospectively. We estimated differences in mean age at natural menopause between famine exposure categories (not, moderately, and severely exposed), with adjustment for smoking, parity, socioeconomic status, body mass index, age at menarche, and year of birth.

RESULTS

Women experienced natural menopause on average 0.36 years earlier (95% CI: -0.60, -0.11) when severely exposed to the famine and 0.06 years earlier (95% CI: -0.22, 0.09) when moderately exposed compared with the unexposed women. This effect was particularly pronounced in those severely exposed from 2 to 6 years of age: -1.83 years (95% CI: -3.03, -0.63).

CONCLUSIONS

Our findings suggest that caloric restriction decreases age at natural menopause. Early childhood seems to be a particularly sensitive age period for this effect.

Female ponderal index at birth and idiopathic infertility

Epidemiological studies have demonstrated an increased risk of developing non-transmittable diseases in adults subjected to adverse early developmental conditions. Metabolic and cardiovascular diseases have been the focus of most studies. Nevertheless, data from animal models also suggest early programming of fertility. In humans, it is difficult to assess the impact of the in utero environment retrospectively. Birthweight is commonly used as an indirect indicator of intrauterine development. This research is part of the ALIFERT study. We investigated a potential link between ponderal index at birth and female fertility in adulthood. Data from 51 infertile and 74 fertile women were analysed. BW was on average higher in infertile women, whereas birth length did not differ between the two groups; thus, resulting in a significantly higher ponderal index at birth in infertile women. Ponderal index at birth has been identified as a risk factor for infertility. These results suggest the importance of the intra-uterine environment, not only for long-term metabolic health but also for fertility.

Ovarian response is associated with anogenital distance in patients undergoing controlled ovarian stimulation for IVF

STUDY QUESTION

Is the length of the anogenital distance (AGD) a biomarker of ovarian reserve and response to controlled ovarian stimulation (COS)?

SUMMARY ANSWER

Shorter AGD is associated with presence of poor ovarian response.

WHAT IS KNOWN ALREADY

Organ development during prenatal life is influenced by the prevailing intrauterine environment, and it has been suggested that nutritional, environmental and toxic factors could affect ovarian reserve set prenatally. AGD is a biomarker of prenatal-hormonal environment and observational studies have shown an association between its length and reproductive parameters in both sexes.

STUDY DESIGN, SIZE, DURATION

This was a prospective cohort study of 437 women treated with IVF/ICSI conducted in a tertiary-care university hospital between January and December 2016.

PARTICIPANTS/MATERIALS, SETTING, METHODS

All women underwent their first COS for IVF/ICSI and reached criteria for oocyte retrieval. Based on the number of oocytes obtained, patients were divided into three groups: poor responders (≤3 oocytes) (n = 50), normoresponders (4-15 oocytes) (n = 332) and high responders (>15 oocytes) (n = 55). Before retrieval, the following patient data were recorded: age, body mass index (BMI), ovarian reserve markers (anti-Müllerian hormone [AMH], antral follicle count [AFC] and follicular stimulation hormone [FSH]), cause of infertility, total doses of gonadotropins used and ovarian sensitivity index (OSI). Patients with previous pregnancies, polycystic ovary syndrome (PCOS), endometriosis and previous ovarian or genital surgery were excluded. Anthropometric biomarkers of AGDAC (anus-clitoris) and AGDAF (anus-fourchette) were measured in all patients under sedation on the day of retrieval and before proceeding to oocyte pick-up. Multiple linear regression analyses were used to examine the association between both AGD and ovarian reserve markers, the total units of gonadotropins used, the number of oocytes obtained and the OSI. Logistic regression was used to predict poor response in COS for IVF/ICSI, while accounting for confounders such as age and BMI.

MAIN RESULTS AND THE ROLE OF CHANCE

Baseline FSH, AMH, AFC and age were significantly different among the three groups of ovarian response, as were the units of gonadotropin used, and the ovarian sensitivity index (OSI) (P < 0.001). Both AGDAC and AGDAF measurements were positively correlated with AMH levels (r = 0.38 and r = 0.21; P < 0.05), AFC (r = 0.41 and r = 0.20; P < 0.05), the OSI (r = 0.24 and r = 0.19; P < 0.05) and the number of oocytes retrieved (r = 0.29 and r = 0.28, respectively; P < 0.05). Conversely, there was a negative correlation between both AGD measurements and the doses of gonadotropins used (r= -0.19 and r= -0.15; P < 0.05). The area under the curve (AUC) for prediction of poor response of AGDAC was 0.70 (95% CI 0.66, 0.75), which was comparable to the classic ovarian reserve markers, such as AFC and AMH. AGDAF showed a significantly worse predictive capacity for poor ovarian response (AUC 0.60 [95% CI 0.55, 0.60]) than AMH and AFC.

LIMITATIONS, REASONS FOR CAUTION

The population used for the study was a highly selected group of infertile women who underwent COS for IVF, so the findings of this research may not be applicable for general population. Besides, measurement or selection biases might have been possible and must be considered.

WIDER IMPLICATIONS OF THE FINDINGS

The findings of this study suggest that in utero exposure to certain hormonal environments could affect the ovarian reserve set prenatally.

STUDY FUNDING/COMPETING INTEREST(S)

None. The authors have no competing interests to declare.

Starvation during pregnancy impairs fetal oogenesis and folliculogenesis in offspring in the mouse

Although it is becoming increasingly evident that maternal starvation during pregnancy can have permanent effects on a range of physiological processes in the offspring, scant information is available about the consequence of such condition for oogenesis and hence for lifetime reproductive success of progeny in mammals. In the present study, we address this topic by starving pregnant mice at the time of ovarian differentiation (12.5 days post coitum (dpc)) for three consecutive days and analyzed the consequence first on the survival of the fetal oocytes and their capability to progress throughout the stages of meiotic prophase I (MPI) and then on the postnatal folliculogenesis of the offspring. The results showed that maternal starvation increased apoptosis in the fetal ovaries, resulting in reduction of the oocyte number. Moreover, MPI progression was slowed down in the surviving oocytes and the expression of DNA repair players in the starved ovaries increased. Transcriptome analysis identified 61 differentially expressed genes between control and starved ovaries, the most part of these being involved in metabolic processes. A significant decrease in the percentage of oocytes enclosed in primordial follicles and the expression of oocyte genes critically involved in folliculogenesis such as Nobox, Lhx8 and Sohlh2 in the 3 days post partum (dpp) starved ovaries were found. Finally, at the time of juvenile period (21 dpp), the number of oocytes and antral follicles resulted significantly lower in the ovaries of the offspring from starved mothers in comparison to controls. Our findings support the notion that maternal starvation can affect ovary development in the offspring that could adversely affect their reproductive success in the adult life.

The effect of adverse intrauterine conditions, early childhood growth and famine exposure on age at menopause: a systematic review

When the follicle reserve, which is developed solely during the fetal period, is depleted, women enter menopause. Intrauterine and childhood adverse conditions might affect the ovarian capacity by influencing follicle production in the first trimester, limiting the initial follicle pool or mediate an accelerated follicular loss thereafter. To investigate if adverse early life influences result in younger age at menopause, the following online databases were systematically searched: PubMed, EMBASE, CINHAL (EBSCO) and Cochrane library (Wiley) up to 1 January 2017. Eligibility, data extraction and quality assessment was independently performed by two researchers. A total of 5278 studies were identified, 11 studies were deemed eligible and included. Nine were cohort studies, 1 case–control study and 1 twin study. Due to the diversity of reported data and risk estimates we were unable to pool data or perform meta-analysis on pooled data. Prenatal and childhood exposure to famine was significantly associated to an earlier age at menopause in three studies. Mean differences in age at menopause varied from 4 months up to 1.7 years between famine exposed and unexposed women. Three studies described a significant association between a low weight at ages 1 or 2 and a younger age at menopause. A younger age at menopause was associated with a higher weight at birth in only one study and with a high ponderal index, a measure for fatness at birth in another study. None of the nine studies reporting on low birth weight and age at natural menopause find a significant association.

Childhood disadvantages and the timing of the onset of natural menopause in Latin America and the Caribbean

The aim of this study is to investigate the association of early life factors with the timing of the onset of natural menopause in Costa Rica and Puerto Rico. We use Cox proportional hazard models to estimate the risk of the onset of menopause. Our results suggest that socioeconomic disadvantages, as expressed by difficulties attending school due to economic hardships or parents never living together, increase the risk of the onset of natural menopause among Puerto Rican women. Among Costa Rican women, early life nutrition, estimated using anthropometric measures, is related to the timing of the onset of natural menopause.

Factors which Determine the Age of the Menopause

Menopause is the final cessation of menstruation. Humans are the only primates to experience a menopause, and its origins and purpose remain unclear. The age of menopause has remained constant since Aristotle, although the age of menarche has fallen in the past 100 years. The incidence of natural premature ovarian failure before age 40 is 1%. The factors controlling the timing of the menopause are not well understood. The possession of two X chromosomes is essential for normal ovarian function. Genetic, reproductive and lifestyle factors, chemotherapy and radiation, pelvic surgery, infection, and autoimmunity have all been implicated. There is an association between age of menopause of mothers and daughters and greater concordance with identical than non-identical twins. However, with the exception of smoking which advances menopause by two years, these factors have failed to show a consistent influence on age at menopause.

Events in Early Life are Associated with Female Reproductive Ageing: A UK Biobank Study

The available oocyte pool is determined before birth, with the majority of oocytes lost before puberty. We hypothesised that events occurring before birth, in childhood or in adolescence (‘early-life risk factors’) could influence the size of the oocyte pool and thus the timing of menopause. We included cross-sectional data from 273,474 women from the UK Biobank, recruited in 2006–2010 from across the UK. We analysed the association of early menopause with events occurring before adulthood in 11,781 cases (menopause aged under 45) and 173,641 controls (menopause/pre-menopausal at ≥45 years), in models controlling for potential confounding variables. Being part of a multiple birth was strongly associated with early menopause (odds ratio = 1.42, confidence interval: 1.11, 1.82, P = 8.0 × 10⁻⁹, fully-adjusted model). Earlier age at menarche (odds ratio = 1.03, confidence interval: 1.01, 1.06, P = 2.5 × 10⁻⁶) and earlier year of birth were also associated with EM (odds ratio = 1.02, confidence interval: 1.00, 1.04, P = 8.0 × 10⁻⁶). We also confirmed previously reported associations with smoking, drinking alcohol, educational level and number of births. We identified an association between multiple births and early menopause, which connects events pre-birth, when the oocyte pool is formed, with reproductive ageing in later life.

Oral oestrogen reverses ovariectomy-induced morning surge hypertension in growth-restricted mice

Perinatal growth restriction (GR) is associated with heightened sympathetic tone and hypertension. We have previously shown that naturally occurring neonatal GR programmes hypertension in male but not female mice. We therefore hypothesized that intact ovarian function or post-ovariectomy (OVX) oestrogen administration protects GR female mice from hypertension. Utilizing a non-interventional model that categorizes mice with weanling weights below the tenth percentile as GR, control and GR adult mice were studied at three distinct time points: baseline, post-OVX and post-OVX with oral oestrogen replacement. OVX elicited hypertension in GR mice that was significantly exacerbated by psychomotor arousal (systolic blood pressure at light to dark transition: control 122 ± 2; GR 119 ± 2; control-OVX 116 ± 3; GR-OVX 126 ± 3 mmHg). Oestrogen partially normalized the rising blood pressure surge seen in GR-OVX mice (23 ± 7% reduction). GR mice had left ventricular hypertrophy, and GR-OVX mice in particular had exaggerated bradycardic responses to sympathetic blockade. For GR mice, a baseline increase in baroreceptor reflex sensitivity and high frequency spectral power support a vagal compensatory mechanism, and that compensation was lost following OVX. For GR mice, the OVX-induced parasympathetic withdrawal was partially restored by oestrogen (40 ± 25% increase in high frequency spectral power, P<0.05). In conclusion, GR alters cardiac morphology and cardiovascular regulation. The haemodynamic consequences of GR are attenuated in ovarian-sufficient or oestrogen-replete females. Further investigations are needed to define the role of hormone replacement therapy targeted towards young women with oestrogen deficiency and additional cardiovascular risk factors, including perinatal GR, cardiac hypertrophy and morning surge hypertension.

Natural fertility and longevity

Much empirical work suggests an association between fertility patterns and longevity. I review this association, focusing on natural fertility populations and emphasizing the role of both the timing and the intensity of fertility. Overall, it appears that although age at last reproduction routinely correlates with post-reproductive longevity, suggesting a slower rate of senescence among late fertile women, the same is not true for age at first reproduction and parity. I discuss some of the conceptual and methodologic issues, as well as the sources of the biases, that have been a persistent feature of this body of research. I conclude by suggesting avenues of research that could be initiated or pursued in the area.

Are semen parameters related to birth weight?

Several experimental models suggest a link between maternal nutrition during gestation and reproductive function in offspring, but the impact of birth weight on male fertility in adulthood in humans is poorly documented. To study whether birth weight is associated with unexplained male subfertility later in life, we evaluated the relationship between birth weight and sperm parameters in adulthood in white subfertile men, partners of couples with primary idiopathic subfertility, and fertile men recruited within the ALIFERT (Diet and Its Relationship with Couple Infertility) study. Total sperm count, progressive motility, and sperm DNA fragmentation were analyzed in sperm, and metabolic assays were performed on blood. Birth weight was associated with sperm DNA fragmentation and inversely correlated with total sperm count, underlining the importance of the in utero environment for male reproductive function.

CLINICAL TRIAL REGISTRATION NUMBER

NCT01093378.

Effect of low birth weight on women's health

PURPOSE

The theory of the developmental origins of health and disease hypothesizes that low birth weight (≤5.5 lb) indicative of poor fetal growth is associated with an increased risk of chronic, noncommunicable disease in later life, including hypertension, type 2 diabetes mellitus, and osteoporosis. Whether women are at greater risk than men is not clear. Experimental studies that mimic the cause of slow fetal growth are being used to examine the underlying mechanisms that link a poor fetal environment with later chronic disease and investigate how sex and age affect programmed risk. Thus, the aims of this review are to summarize the current literature related to the effect of low birth weight on women's health and provide insight into potential mechanisms that program increased risk of chronic disease across the lifespan.

METHODS

A search of PubMed was performed with the keywords low birth weight, women's health, female, and sex differences; additional terms included blood pressure, hypertension, renal, cardiovascular, obesity, glucose intolerance, type 2 diabetes, osteoporosis, bone health, reproductive senescence, menopause, and aging.

FINDINGS

The major chronic diseases associated with low birth weight include high blood pressure and cardiovascular disease, impaired glucose homeostasis and type 2 diabetes, impaired bone mass and osteoporosis, and early reproductive aging.

IMPLICATIONS

Low birth weight increases the risk of chronic disease in men and women. Low birth weight is also associated with increased risk of early menopause. Further studies are needed to fully address the effect of sex and age on the developmental programming of adult health and disease in women across their lifespan.

Age at menopause and determinants of hysterectomy and menopause in a multi-ethnic community: the Hilo Women's Health Study

OBJECTIVES

A lifespan approach was used to evaluate age at menopause, and determinants of surgical and natural menopause, in the multi-ethnic community of Hilo, Hawaii.

STUDY DESIGN

Participants aged 40-60 years (n=898) were drawn from a larger, randomly generated sample recruited by postal questionnaires. Median age at natural menopause was computed by probit analysis. Logistic regression analysis was applied to examine determinants of hysterectomy, and Cox regression analysis was used to examine risk factors for an earlier age at menopause.

MAIN OUTCOME MEASURES

History of hysterectomy, age at menopause.

RESULTS

Frequency of hysterectomy was 19.2% at a mean age of 40.5 years. The likelihood of hysterectomy increased with older ages, lower education, mixed ancestry, having been overweight at age 30, and married 20 years prior to survey. Median age at natural menopause was 53.0 years. Smoking and not being married 10 years before survey were associated with an earlier age at menopause.

CONCLUSIONS

Median age at menopause was later than the national average. Ethnicity and education were determinants of hysterectomy, but not associated with age at natural menopause. Events later in the lifespan (e.g., smoking and not being married 10 years prior to the survey) were more important than earlier events (e.g., childhood residence) in relation to age at menopause. The timing of weight gain and marital status appear to be important in relation to surgical menopause, and the timing of marital status appears to be important in relation to the timing of natural menopause.

Prenatal famine, birthweight, reproductive performance and age at menopause: the Dutch hunger winter families study

STUDY QUESTION

Is there an association between acute prenatal famine exposure or birthweight and subsequent reproductive performance and age at menopause?

SUMMARY ANSWER

No association was found between intrauterine famine exposure and reproductive performance, but survival analysis showed that women exposed in utero were 24% more likely to experience menopause at any age.

WHAT IS KNOWN ALREADY

Associations between prenatal famine and subsequent reproductive performance have been examined previously with inconsistent results. Evidence for the effects of famine exposure on age at natural menopause is limited to one study of post-natal exposure.

STUDY DESIGN, SIZE, DURATION

This cohort study included men and women born around the time of the Dutch famine of 1944-1945. The study participants (n = 1070) underwent standardized interviews on reproductive parameters at a mean age of 59 years.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The participants were grouped as men and women with prenatal famine exposure (n = 407), their same-sex siblings (family controls, n = 319) or other men and women born before or after the famine period (time controls, n = 344). Associations of famine exposure with reproductive performance and menopause were analysed using logistic regression and survival analysis with competing risk, after controlling for family clustering.

MAIN RESULTS AND THE ROLE OF CHANCE

Gestational famine exposure was not associated with nulliparity, age at birth of first child, difficulties conceiving or pregnancy outcome (all P> 0.05) in men or women. At any given age, women were more likely to experience menopause after gestational exposure to famine (hazard ratio 1.24; 95% CI 1.03, 1.51). The association was not attenuated with an additional control for a woman's birthweight. In this study, there was no association between birthweight and age at menopause after adjustment for gestational famine exposure.

LIMITATIONS, REASON FOR CAUTION

Age at menopause was self-reported and assessed retrospectively. The study power to examine associations with specific gestational periods of famine exposure and reproductive function was limited.

WIDER IMPLICATIONS OF THE FINDINGS

Our findings support previous results that prenatal famine exposure is not related to reproductive performance in adult life. However, natural menopause occurs earlier after prenatal famine exposure, suggesting that early life events can affect organ function even at the ovarian level.

STUDY FUNDING/COMPETING INTEREST(S)

This study was funded by the NHLBI/NIH (R01 HL-067914).

TRIAL REGISTRATION NUMBER

Not applicable.

Life-course origins of the ages at menarche and menopause

A woman's age at menarche (first menstrual period) and her age at menopause are the alpha and omega of her reproductive years. The timing of these milestones is critical for a woman's health trajectory over her lifespan, as they are indicators of ovarian function and aging. Both early and late timing of either event are associated with risk for adverse health and psychosocial outcomes. Thus, the search for a relationship between age at menarche and menopause has consequences for chronic disease prevention and implications for public health. This article is a review of evidence from the fields of developmental biology, epidemiology, nutrition, demography, sociology, and psychology that examine the menarche-menopause connection. Trends in ages at menarche and menopause worldwide and in subpopulations are presented; however, challenges exist in constructing trends. Among 36 studies that examine the association between the two sentinel events, ten reported a significant direct association, two an inverse association, and the remainder had null findings. Multiple factors, including hormonal and environmental exposures, socioeconomic status, and stress throughout the life course are hypothesized to influence the tempo of growth, including body size and height, development, menarche, menopause, and the aging process in women. The complexity of these factors and the pathways related to their effects on each sentinel event complicate evaluation of the relationship between menarche and menopause. Limitations of past investigations are discussed, including lack of comparability of socioeconomic status indicators and biomarker use across studies, while minority group differences have received scant attention. Suggestions for future directions are proposed. As research across endocrinology, epidemiology, and the social sciences becomes more integrated, the confluence of perspectives will yield a richer understanding of the influences on the tempo of a woman's reproductive life cycle as well as accelerate progress toward more sophisticated preventive strategies for chronic disease.

Birth weight, breast cancer and the potential mediating hormonal environment

Background

Previous studies have shown that woman’s risk of breast cancer in later life is associated with her infants birth weights. The objective of this study was to determine if this association is independent of breast cancer risk factors, mother’s own birth weight and to evaluate association between infants birth weight and hormonal environment during pregnancy. Independent association would have implications for understanding the mechanism, but also for prediction and prevention of breast cancer.

Methods and Findings

Risk of breast cancer in relation to a first infant’s birth weight, mother’s own birth weight and breast cancer risk factors were evaluated in a prospective cohort of 410 women in the Framingham Study. Serum concentrations of estriol (E3), anti-estrogen alpha-fetoprotein (AFP), and pregnancy-associated plasma protein-A (PAPP-A) were measured in 23,824 pregnant women from a separate prospective cohort, the FASTER trial. During follow-up (median, 14 years) 31 women (7.6 %) were diagnosed with breast cancer. Women with large birth weight infants (in the top quintile) had a higher breast cancer risk compared to other women (hazard ratio (HR), 2.5; 95% confidence interval (CI), 1.2–5.2; P = 0.012). The finding was not affected by adjustment for birth weight of the mother and traditional breast cancer risk factors (adjusted HR, 2.5; 95% CI, 1.2–5.6; P = 0.021). An infant’s birth weight had a strong positive relationship with the mother’s serum E3/AFP ratio and PAPP-A concentration during pregnancy. Adjustment for breast cancer risk factors did not have a material effect on these relationships.

Conclusions

Giving birth to an infant with high birth weight was associated with increased breast cancer risk in later life, independently of mother’s own birth weight and breast cancer risk factors and was also associated with a hormonal environment during pregnancy favoring future breast cancer development and progression.

Fetal programming of adult disease: implications for prenatal care

The obesity epidemic, including a marked increase in the prevalence of obesity among pregnant women, represents a critical public health problem in the United States and throughout the world. Over the past two decades, it has been increasingly recognized that the risk of adult health disorders, particularly metabolic syndrome, can be markedly influenced by prenatal and infant environmental exposures (ie, developmental programming). Low birth weight, together with infant catch-up growth, is associated with a significant risk of adult obesity and cardiovascular disease, as well as adverse effects on pulmonary, renal, and cerebral function. Conversely, exposure to maternal obesity or high birth weight also represents an increased risk for childhood and adult obesity. In addition, fetal exposure to select chemicals (eg, phytoestrogens) or environmental pollutants (eg, tobacco smoke) may affect the predisposition to adult disease. Animal models have confirmed human epidemiologic findings and provided insight into putative programming mechanisms, including altered organ development, cellular signaling responses, and epigenetic modifications (ie, control of gene expression without modification of DNA sequence). Prenatal care is transitioning to incorporate goals of optimizing maternal, fetal, and neonatal health to prevent or reduce adult-onset diseases. Guidelines regarding optimal pregnancy nutrition and weight gain, management of low- and high-fetal-weight pregnancies, use of maternal glucocorticoids, and newborn feeding strategies, among others, have yet to fully integrate long-term consequences on adult health.

Ovarian reserve in young women with low birth weight and normal puberty: a pilot case-control study

AIM

Studies indicate that women born small for gestational age (SGA) have impaired ovarian function. The origin of this ovarian dysfunction is still debatable. The aim of this study was to compare ovarian ageing between girls born appropriate for gestational age (AGA) and SGA. Therefore, we measured Luteinizing hormone (LH), Follicle-stimulating hormone (FSH), E2, Anti-Müllerian hormone (AMH) levels and the pituitary response to endogenous Gonadotropin-releasing hormone (GnRH) in adolescent girls born SGA and AGA.

METHODS

A case-controlled pilot study consisting of seven SGA women (birth weight < 10th percentile AGA) and 13 AGA women with regular menstrual cycles, age 19.9 ± 0.42). Early follicular FSH, LH, Oestradiol (E2) and AMH levels were measured. After baseline samples, 100 μg GnRH was administered intravenously and at 30, 60 and 90 min blood samples were taken to measure gonadotropin levels and to compute the response to endogenous GnRH.

RESULTS

Mean follicular phase LH, FSH, E2 and AMH levels did not significantly differ between young women born SGA and AGA. Furthermore, the response to endogenous GnRH showed no significant differences either.

CONCLUSIONS

We concluded against extension of this pilot study. Based on our observations it seems unlikely that limited ovarian reserve is a predominated problem in adolescent SGA.

The timing of the age at which natural menopause occurs

The timing of natural menopause is a clinically important indicator of longevity and risk of morbidity and mortality. Demographic, menstrual, reproductive, familial, genetic, and lifestyle factors seem to be important in this timing. Smoking, lower parity and poor socioeconomic status are associated with earlier menopause. However, a number of relationships have been inconsistent; others remain largely unexplored. Much remains to be learned about factors that affect follicular atresia and the onset and duration of perimenopause and the timing of the natural menopause. Knowledge about these relationships offers women and their health care providers enhanced understanding and choices to deal with menopause.

Association of intrauterine and early-life exposures with age at menopause in the Sister Study

Oocytes are formed in utero; menopause occurs when the oocyte pool is depleted. The authors hypothesized that early-life events could affect the number of a woman's oocytes and determine age at menopause. To test their hypothesis, the authors conducted a secondary analysis of baseline data from 22,165 participants in the Sister Study (2003-2007) who were aged 35-59 years at enrollment. To estimate the association between early-life events and age at natural menopause, the authors used Cox proportional hazards models to estimate hazard ratios with 95% confidence intervals, adjusting for current age, race/ethnicity, education, childhood family income, and smoking history. Earlier menopause was associated with in-utero diethylstilbestrol exposure (hazard ratio (HR) = 1.45, 95% confidence interval (CI): 1.27, 1.65). Suggestive associations included maternal prepregnancy diabetes (HR = 1.33, 95% CI: 0.89, 1.98) and low birth weight (HR = 1.09, 95% CI: 0.99, 1.20). Having a mother aged 35 years or older at birth appeared to be associated with a later age at menopause (HR = 0.95, 95% CI: 0.89, 1.01). Birth order, in-utero smoke exposure, and having been breastfed were not related to age at menopause. In-utero and perinatal events may subsequently influence age at menopause.

Effect of the early-life nutritional environment on fecundity and fertility of mammals

The early-life developmental environment is instrumental in shaping our overall adult health and well-being. Early-life diet and endocrine exposure may independently, or in concert with our genetic constitution, induce a pathophysiological process that amplifies with age and leads to premature morbidity and mortality. Recently, this has become known as ‘programming’ but is akin to ‘maternal effects’ described for many years in the biological sciences and is defined as any influence that acts during critical developmental windows to induce long-term changes in the organisms' phenotype. To date, such delayed maternal effects have largely been characterized in terms of susceptibility to cardiovascular or metabolic disease. Here, we review evidence from experimental animal species, non-human primates and man for an effect of the early-life nutritional environment on adult fecundity and fertility. In addition, using a database of pedigree sheep, we also specifically test the hypothesis that being born small for gestational age with or without post-natal growth acceleration directly programmes fertility. We conclude that there is a lack of compelling evidence to suggest pre-natal undernutrition may directly reduce adult fecundity and fertility, but may exert some effects secondarily via an increased incidence of ‘metabolic syndrome’. Possible effects of being born relatively large on subsequent fecundity and fertility warrant further investigation.

Fetal environment and early age at natural menopause in a British birth cohort study

BACKGROUND

Early life development may influence the timing of natural menopause through association with size of the initial follicle pool or early follicular loss. This study examines the relationships of birthweight, gestational age and birthweight standardized by gestational age with early menopause in the 1958 British birth cohort study.

METHODS

Study participants were over 2900 women with data on birthweight, gestational age (obtained at birth), menopausal status at age 44-45 years and potential confounding factors. Logistic regression was used to study relationships of birthweight, gestational age and birthweight standardized by gestational age with post-menopausal status by 44-45 years, with and without adjustments for confounding factors.

RESULTS

There was a U-shaped association between birthweight and menopausal status at 44-45 years: women at either extremes of birthweight (<2.5 and >or=4.0 kg) had increased odds of post-menopausal status compared with those weighing 3.0-3.49 kg [odds ratio (OR) = 1.91, 95% confidence interval (CI) 1.08, 3.38; 1.81, 95% CI 1.11, 2.97, respectively]. Women with higher birthweight standardized by gestational age (which indicates faster fetal growth rate) also had increased odds of being post-menopausal by 44-45 years (OR for fastest quarter versus second fastest quarter = 1.80; 95% CI 1.16, 2.81). These associations persisted after adjustment for socioeconomic position at birth, adult smoking status and use of oral contraceptives.

CONCLUSIONS

These findings suggest that variations in fetal environment may be associated with the timing of menopause. Given that extremes of birthweight and higher birthweight standardized by gestational age were associated with earlier age at menopause, mechanisms related to these characteristics that also regulate ovarian function should be investigated further.

Early life circumstances and their impact on menarche and menopause

Ages at menarche and menopause have been shown to be associated with adverse health outcomes in later life. For example, earlier menarche and later menopause have been independently linked to higher risk of breast cancer. Earlier menarche may also be associated with an increased risk of endometrial cancer, menstrual problems and adult obesity. Given the associations of ages at menarche and menopause with future health outcomes, it is important to establish what factors across life, and generations, may influence these. This article examines the associations of early life factors, namely birthweight, bodyweight and growth during childhood, childhood socioeconomic circumstances and psychosocial factors with ages at menarche and menopause. It examines possible explanations of the associations found, including life history theory, and discusses areas for future research.

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.

Are the effects of risk factors for timing of menopause modified by age? Results from a British birth cohort study

OBJECTIVES

This study investigated the influence of mother's age at menopause, early life and adult behavioral factors on the timing of menopause until age 57 years, and whether these effects vary according to the women's age at menopause.

DESIGN

A nationally representative cohort of 1,583 British women born in March 1946 with prospective data across the life course. For factors that vary with age at menopause, analyses were stratified by age at menopause younger than 50 years or 50 years or older.

RESULTS

Cox regression models indicated that for women with earlier menopause, those who were heaviest at 2 years had a 59% lower hazard ratio for menopause than those who were the lightest (hazard ratio [HR]=0.41, 95% CI: 0.16-1.01), whereas this figure was 35% lower (HR=0.65; 95% CI: 0.42-1.00) for the later menopause group. For women in the earlier group with parental divorce during childhood, the HR was 6.5 (95% CI: 2.021.3) times higher than that of other women. This rate decreased to 2.5 (95% CI: 1.5-4.2) for those with later menopause. In both groups, increasing mother's age at menopause was associated with decreasing HR (P<0.0001). For all women, being breast-fed (P=0.05), increasing cognitive ability (P=0.009), and increasing parity (P=0.001) delayed menopause.

CONCLUSIONS

This study found that the impact of weight at 2 years, parental divorce during childhood, and mother's age at menopause varied according to the women's age at menopause. There was further evidence that being breast-fed, higher childhood cognitive ability, and increasing parity delayed menopause. These results suggest the interaction of genetic and environmental factors in determining age at menopause.

Potential use of biomarkers for analyzing interpopulation and cross-cultural variability in reproductive aging

OBJECTIVE

The aims of this study were (1) to document the extent of variability in physiological aspects of reproductive aging; (2) to outline those areas where more work is needed to expand our knowledge of this variability; (3) to outline available biomarkers that can be used to measure aspects of reproductive aging, such as ovarian reserve and declining hormone levels; and (4) to note potential problems with the use of these biomarkers in cross-cultural settings.

DESIGN

Literature review of English and French publications using PubMed with no date restrictions.

RESULTS

Substantial variability exists in both cultural and physiological aspects of reproductive aging and menopause. However, the extent of variability across populations for many areas of reproductive aging needs better documentation as well as explanation of sources of this variability. Several biomarkers exist for use in cross-cultural research, including ovarian characteristics such as ovarian volume, ovarian reserve, follicular development, and atresia, and levels of hormones such as follicle-stimulating hormone, inhibin B, and anti-mullerian hormone.

CONCLUSION

We urge that further work be undertaken to evaluate and describe variability in physiological aspects of reproductive aging in cross-cultural settings. Some problems exist in the use of biomarkers to record this variability, particularly in remote settings with few logistical resources.

Prevalence of premature ovarian failure in monozygotic and dizygotic twins

BACKGROUND

Premature ovarian failure (POF) before 40 years of age from natural causes affects approximately 1% of adult women, with minor variations between ethnic groups. A recent case of ovarian transplantation between young monozygotic (MZ) twins in which one had undergone unexplained POF at 14 years has prompted a study of the prevalence of POF.

METHODS

Menopausal ages of 832 Australian and UK female twin-pairs were extracted from volunteer national twin registry databases containing medical, reproductive and lifestyle data surveyed by mail questionnaire. Surgical menopause was an exclusion criterion.

RESULTS

The prevalence of POF in both MZ and dizygotic (DZ) twins was similar in both registries and 3- to 5-fold greater than the general population at age thresholds 40 and 45 years. No specific factors were found to account for the higher risk of early menopause. Some twins of both zygosities were highly discordant for menopausal age (>or=10 years). Nevertheless, there was significant intra-twin dependence, especially for MZ twins, and the average age difference at last menses was greater in DZ twin-pairs.

CONCLUSION

Both MZ and DZ twins are at higher risk of POF. Despite some striking differences within MZ twin-pairs, menopausal ages were more concordant than for DZ twin-pairs, confirming that the timing of menopause has a heritable component.

Age at natural menopause in women exposed to diethylstilbestrol in utero

Age at natural menopause is related to several health outcomes, including cardiovascular disease and overall mortality. Age at menopause may be influenced by the number of follicles formed during gestation, suggesting that prenatal factors could influence menopausal age. Diethylstilbestrol (DES), a nonsteroidal estrogen widely prescribed during the 1950s and 1960s, is related to reproductive tract abnormalities, infertility, and vaginal cancer in prenatally exposed daughters but has not been studied in relation to age at menopause. The authors used survival analyses to estimate the risk of natural menopause in 4,210 DES-exposed versus 1,829 unexposed US women based on responses to questionnaires mailed in 1994, 1997, and 2001. DES-exposed women were 50% more likely to experience natural menopause at any given age (hazard ratio = 1.49, 95% confidence interval: 1.28, 1.74). Among women for whom dose information was complete, there were dose-response effects, with a greater than twofold risk for those exposed to >10,000 mg. The causal mechanism for earlier menopause may be related to a smaller follicle pool, more rapid follicle depletion, or changes in hormone synthesis and metabolism in DES-exposed daughters. Age at menopause has been related, albeit inconsistently, to several exposures, but, to the authors' knowledge, this is the first study to suggest that a prenatal exposure may influence reproductive lifespan.

Childhood cognitive ability and age at menopause: evidence from two cohort studies

OBJECTIVE

To investigate whether poorer cognitive ability in childhood is associated with an earlier menopause.

DESIGN

Two cohorts were included: a nationally representative British birth cohort study of 1,350 women born in March 1946 and followed up to age 54 years, and an Aberdeen cohort study of 3,465 women born in Aberdeen from 1950 to 1956 and followed up to age 44 to 50 years. Both cohorts had prospective information on childhood cognitive ability at age 7 or 8 years.

RESULTS

In both cohorts, women with lower cognitive scores in childhood reached menopause earlier than women with higher scores. With follow-up of menopause to 49 years, the hazard ratio (HR) for one standard deviation of the cognitive score was 0.80 (95% CI, 0.72-0.90) in the Aberdeen cohort and 0.84 (95% CI, 0.73-0.97) in the older 1946 birth cohort. The effect was still evident in the 1946 birth cohort with follow-up of menopause to 53 years (HR = 0.87; 95% CI, 0.79-0.95). These ratios were weakly attenuated by adjustment for potential confounding effects of lifetime socioeconomic circumstances, parity, and smoking.

CONCLUSIONS

The association between early cognitive ability and timing of menopause only partially reflects common risk factors, although residual confounding remains a possibility. Alternatively, early environmental or genetic programming may explain this association, perhaps through setting lifelong patterns of hormone release or causing transient hormonal changes at sensitive periods of development. These findings have implications for the interpretation of studies investigating an association between age at menopause and adult cognitive function.

Seasonality and seasonal affective disorder (SAD): an evolutionary viewpoint tied to energy conservation and reproductive cycles

The characteristic symptoms of SAD, including hypersomnia and weight gain, might reflect a genetically programmed attempt to conserve energy during historically predictable periods of dwindling food supply. While this basic hypothesis has obvious conceptual appeal, few authors have considered the specific positive selection pressures that might have contributed to such a process. The goal of the current paper is to further develop an evolutionary model of SAD with a focus on energy conservation in the context of seasonal reproductive cycles. To accomplish this, seasonal data on birth rates are considered from an evolutionary viewpoint. There is considerable indirect evidence that in temperate climates, the symptoms of SAD reflect a predisposition for conception to occur in late spring/early summer to ensure a peak of births in the late winter/early spring. The adaptive value of such a pattern, and its putative role in natural selection in humans, is also discussed.

Embryonic and fetal programming of physiological disorders in adulthood

In the past decade, data from numerous epidemiological studies have indicated strong inverse associations between birth weight and risk of coronary heart disease, hypertension, type 2-diabetes, and other diseases in adulthood. The "Barker hypothesis" thus postulates that a number of organ structures and functions undergo programming during embryonic and fetal life. This developmental programming determines the set points of physiological and metabolic responses in adult life. Alterations of nutrient availability during gestation may lead to developmental adaptations, via hormonal maneuvers by the embryo and fetus that readjust these set points. These adaptive measures have short-term benefits to the embryo and fetus, so that the newborn will be better prepared for the adverse environment (e.g., undernutrition). However, adequate nutritional support during postnatal life that enables catch-up growth may create metabolic conflicts that predispose the adult to aberrant physiological functions and, ultimately, increased risk of disease. It is plausible that other adverse in utero conditions, including exposure to developmental toxicants, may similarly alter adult disease susceptibility. This article provides an overview of the Barker hypothesis, its supporting evidence, the current advances in understanding the biological mechanisms underlying this phenomenon, and its implications for developmental toxicology.

Fetal origins of developmental plasticity: are fetal cues reliable predictors of future nutritional environments?

Evidence that fetal nutrition triggers permanent adjustments in a wide range of systems and health outcomes is stimulating interest in the evolutionary significance of these responses. This review evaluates the postnatal adaptive significance of fetal developmental plasticity from the perspective of life history theory and evolutionary models of energy partitioning. Birthweight is positively related to multiple metabolically costly postnatal functions, suggesting that the fetus has the capacity to distribute the burden of energy insufficiency when faced with a nutritionally challenging environment. Lowering total requirements may reduce the risk of negative energy balance, which disproportionately impacts functions that are not essential for survival but that are crucial for reproductive success. The long-term benefit of these metabolic adjustments is contingent upon the fetus having access to a cue that is predictive of its future nutritional environment, a problem complicated in a long-lived species by short-term ecologic fluctuations like seasonality. Evidence is reviewed suggesting that the flow of nutrients reaching the fetus provides an integrated signal of nutrition as experienced by recent matrilineal ancestors, which effectively limits the responsiveness to short-term ecologic fluctuations during any given pregnancy. This capacity for fetal nutrition to minimize the growth response to transient ecologic fluctuations is defined here as intergenerational "phenotypic inertia," and is hypothesized to allow the fetus to cut through the "noise" of seasonal or other stochastic influences to read the "signal" of longer-term ecologic trends. As a mode of adaptation, phenotypic inertia may help the organism cope with ecologic trends too gradual to be tracked by conventional developmental plasticity, but too rapid to be tracked by natural selection. From an applied perspective, if a trait like fetal growth is designed to minimize the effects of short-term fluctuations by integrating information across generations, public health interventions may be most effective if focused not on the individual but on the matriline.