Why do women stop reproducing before menopause? A life-history approach to age at last birth

Evolutionary biologists have long considered menopause to be a fundamental puzzle in understanding human fertility behaviour, as post-menopausal women are no longer physiologically capable of direct reproduction. Menopause typically occurs between 45 and 55 years of age, but across cultures and history, women often stop reproducing many years before menopause. Unlike age at first reproduction or even birth spacing, a woman nearing the end of her reproductive cycle is able to reflect upon the offspring she already has—their numbers and phenotypic qualities, including sexes. This paper reviews demographic data on age at last birth both across and within societies, and also presents a case study of age at last birth in rural Bangladeshi women. In this Bangladeshi sample, age at last birth preceded age at menopause by an average of 11 years, with marked variation around that mean, even during a period of high fertility. Moreover, age at last birth was not strongly related to age at menopause. Our literature review and case study provide evidence that stopping behaviour needs to be more closely examined as an important part of human reproductive strategies and life-history theory. Menopause may be a final marker of permanent reproductive cessation, but it is only one piece of the evolutionary puzzle.     

Sporadic Retinoblastoma and Parental Smoking and Alcohol Consumption before and after Conception: A Report from the Children’s Oncology Group

Background

Retinoblastoma is the most frequent tumor of the eye in children and very little is known about the etiology of non-familial (sporadic) retinoblastoma. In this study we examined whether parental tobacco smoking or alcohol consumption (pre- or post-conception) contribute to the two phenotypes (bilateral or unilateral) of sporadic retinoblastoma.

Methods

Two large multicenter case-control studies identified 488 cases through eye referral centers in the United States and Canada or through the Children’s Oncology Group. Controls (n = 424) were selected from among friends and relatives of cases and matched by age. Risk factor information was obtained via telephone interview. We employed multivariable logistic regression to estimate the effects of parental tobacco smoking and alcohol consumption on retinoblastoma.

Findings

Maternal smoking before and during pregnancy contributed to unilateral retinoblastoma risk in the child: year before pregnancy conditional Odds Ratio (OR), 8.9; 95% confidence interval (CI) 1.5–51, and unconditional OR, 2.4; 95% CI, 1.3–4.7; month before or during pregnancy, conditional OR, 3.3; 95% CI, 0.5–20.8, and unconditional OR, 2.8; 95% CI, 1.1–7.0. No association was found for maternal or paternal alcohol consumption.

Conclusion

The results of this study indicate that maternal active smoking during pregnancy may be a risk factor for sporadic retinoblastoma. Our study supports a role for tobacco exposures in embryonal tumors.     

Cursorial spiders and succession: age or habitat structure?

Summary The structure of cursorial spider assemblages was examined along a gradient of four temperature successional communities. Species diversity (H), richness (S), and evenness (J) exhibited a dichotomy between herbaceous and woody communities rather than a progressive change with community age: all three parameters were higher in the two younger fields than in the two older woodlands, which is contrary to conventional successional theory. Species importance curves were steeper in the two woody communities. The breadth of the distribution of adult body lengths was greater in the two herbaceous communities. Indices of community similarity revealed neither a successional trend nor the vegetative dichotomy. We suggest the hypothesis that habitat structure is a more important determinant of cursorial spider diversity than successional age per se, and that the switch in dominance from herbaceous to woody vegetation is the critical change. We further suggest that competition for prey is more important to cursorial spiders in early successional (herbaceous) communities, because of a switch in the limiting resource from prey in these communities to the amount of accumulating litter (a spatial resource) in older woody stands. This may explain the greater variation in adult body size of these generalist predators in the two younger communities.     

Noninvasive assessment of left ventricular and myocardial contractility in middle-aged men and women: disparate evolution above the age of 50?

End-systolic elastance (E(es)) is a frequently used index of left ventricular (LV) contractility. However, because of its inherent dependence on LV geometry, E(es) cannot be used to compare myocardial contractile state between ventricles with different geometries, which is the case in any cross-sectional study. Various normalization methods for E(es) have been proposed in the literature, but a standardized method is still lacking. In this study, we introduced a novel alternative normalization technique and compared it with three previously suggested methods. We tested all normalization methods to assess the age- and sex-related differences in myocardial contractility in a large population sample of 2,184 middle-aged (ages, 35-55 yr) untreated subjects free from overt cardiovascular disease. Ventricular contractility E(es) was determined using a previously validated noninvasive single-beat method, based on two-dimensional echocardiographic and brachial blood pressure measurements. Myocardial contractility was estimated as 1) E(es).end-diastolic volume (EDV); 2) E(es).LV mass (LVM); 3) 0.433.E(es).LVM/relative wall thickness (RWT), based on a theoretical LV model; and 4) 0.0941.E(es).LVM(0.455).RWT(-0.159), a novel semiempirical expression derived in this study. Because of the difference in their underlying assumptions, the various myocardial contractility indexes do not provide consistent information with respect to sex differences. Despite these discrepancies, it was found that myocardial contractility in women appears to be better preserved after the age of 50 yr compared with that in men. The physiological mechanisms behind this potentially clinically important phenomenon at population level require further investigation.     

Young Asian women and relationships: traditional or transitional?

This article investigates social and cultural aspects of "teenage life" among south Asian girls in Britain, particularly their experiences of relationships with boys and the extent to which they become involved in sexual activities. In-depth interviews were carried out with teenage girls and young women from Indian, Pakistani and Bangladeshi backgrounds and a comparative group of white British girls, in four schools and one college in the South and West Health Authority Region. Asian teenage girls conformed to different behavioural norms than their white peers. They were influenced by cultural traditions, religious obligations, family loyalties and community expectations. Few Asian girls became involved in relationships or sexual activities. However, once removed from the parental home, the influence of parents and their Asian community, their social and sexual behaviour changes; they experience an independence which often involves relationships and sexual activities. In contrast, white teenage girls experienced a different set of pressures which came from peers and boyfriends and accepted involvement with boys and sexual activity.     

Spontaneous micronucleus frequency and age: what are normal values?

Micronucleus frequency in epidemiological studies of human exposure has become a preferred biomarker. A generally recognized observation is that micronucleus frequency increases with age. One requirement for comparison of data, which is being generated in many countries, is some common agreement about what constitutes a typical or normal background frequency of micronuclei. This is also a requirement when examining any individual value, especially one which might be considered an outlier. A mean value for normal micronucleus frequency with age is developed via the analysis of multiple studies, all of which employed large population bases and generally were conducted with the intent of determining population values. The result is presented here, with the understanding that it may over- or under-estimate the actual values in certain populations.     

Trisomy 21 and maternal age of menopause: does reproductive age rather than chronological age influence risk of nondisjunction?

The biological basis underlying the increased risk of nondisjunction in offspring of women of advanced maternal age is not understood. We sought to test the hypothesis that maternal reproductive age (distance in time from approaching menopause) rather than chronological age is pivotal in the etiology of nondisjunction. Our results found no difference in age of menopause between women 30 years old at delivery of a child with trisomy 21 (i.e., age-related nondisjunction) compared to controls. Among women <30 years of age at delivery of a child with trisomy 21, none underwent premature menopause. Therefore, our findings fail to support the theory that reproductive age plays a major role in the etiology of nondisjunction.     

Coronary artery disease: Are men and women created equal?

Background: Ischemic heart disease in women is a difficult issue in cardiovascular medicine, mainly because of our lack of understanding of the early-stage mechanisms and symptoms. A better and earlier understanding of the pathophysiology of coronary artery disease (CAD) in women will enable us to detect ischemic heart disease earlier and prevent adverse clinical outcomes.Objectives: The aims of this article were to describe the phenomenon of ischemic heart disease in women, increase awareness of the difference between men and women in relation to ischemic heart disease, improve our understanding of the mechanisms that cause this difference, and identify new approaches for better and earlier detection and treatment of CAD in women.Methods: We conducted a search of the PubMed database for double-blind studies on the mechanistic pathways of CAD in women published in English within the past 10 years and epidemiologic studies published since 1970. Search terms included women and coronary artery disease and ischemic heart disease in women.Results: The literature search revealed 30 peer-reviewed articles pertaining to this issue. The incidence of CAD was markedly lower in women <60 years of age than in older women. After 60 years of age, the rate of CAD increased and reached the rate seen among men by the 8th decade of life. The gender difference in atherosclerosis in the coronary tree was particularly large in patients <55 years of age and remained large at older ages. The gender difference in the coronary bed was strikingly larger than in other vascular beds. Intensive risk-factor modification had a similar effect on plaque progression in both men and women. Coronary endothelial dysfunction appeared to be related to cardiovascular morbidity and mortality in women as well as in men, and because endothelial dysfunction could be modified, it appeared that the prognosis could be improved by appropriate management. A strong association was found between body mass index (BMI) and metabolic status, but only the metabolic syndrome was associated with CAD. Physical activity was independently associated with fewer risk factors, less CAD, and fewer adverse events in women; however, obesity was not associated with these outcomes.Conclusions: Results of the identified studies suggest that reduction of risk factors is a common approach to fighting heart disease in both sexes. It appears that for women, weight and BMI are not as important as previously thought, but physical exercise and fitness are very important and can change risk factors and clinical outcomes more than any other known intervention. Data suggest that global inflammation may play an important role in women and may predict cardiovascular outcome in women much better than the traditional risk factors that have been used and proved for men.     

Does early age at marriage influence gynaecological morbidities among Pakistani women?

This paper presents the prevalence of and investigates predictors for specific perceived gynaecological morbidities in Pakistani women. A total of 717 women were identified from eight squatter settlements in Karachi, Pakistan. Detailed information on demographics, contraceptive use and gynaecological morbidities was elicited. The perceived prevalence of uterine prolapse was 19.1% and that of pelvic inflammatory disease 12.8%. The prevalence of uterine prolapse (adjusted odds ratio 1.8; 95% confidence interval 1.0-3.0) was significantly higher among women who married at younger ages (< or = 16 years), independent of education, socioeconomic status and parity. That of pelvic inflammatory disease was significantly higher among those under 21 years of age (adjusted odds ratio 2.3; 95% confidence interval 1.1-4.8), independent of education, socioeconomic status and parity. Young Pakistani women report an immense burden of reproductive ill health, especially those who began sexual activity at an early age.     

Language evolution: syntax before phonology?

Phonology and syntax represent two layers of sound combination central to language''s expressive power. Comparative animal studies represent one approach to understand the origins of these combinatorial layers. Traditionally, phonology, where meaningless sounds form words, has been considered a simpler combination than syntax, and thus should be more common in animals. A linguistically informed review of animal call sequences demonstrates that phonology in animal vocal systems is rare, whereas syntax is more widespread. In the light of this and the absence of phonology in some languages, we hypothesize that syntax, present in all languages, evolved before phonology.     

Smoking and nicotine in inflammatory bowel disease: good or bad for cytokines?

Smoking has either a beneficial or harmful effect on the course and recurrence of ulcerative colitis and Crohn''s disease respectively. Transdermal application of nicotine had similar effects in ulcerative colitis and therefore was considered to be an effective basic drug which could be further developed in the search for new compounds in the treatment of acute exacerbations of corticosteroid resistant ulcerative colitis. In this communication the short-term use of nicotine in ulcerative colitis is reviewed.     

Are men and women really so different?

Distinct differences in the behaviour and preferences of men and women have conventionally been attributed to Trivers' powerful insights regarding the impact of parental investment on sexual selection and mating systems. This has spawned a huge literature about the evolutionary significance of human sex differences. But are men and women really so different? An elegant new study shows that men and women are strikingly similar in their mate preferences. Have conventional models blinded us to the obvious, and precluded the posing of far more interesting questions?     

Harvesting before a fire: How much energy and organics can Greece gain?

Mediterranean-type climate regions like Greece have to face many problems, such as fuel, wood, paper and animal food deficiencies. In addition, great amounts of money are spent every year on fire fighting. The suggested harvesting of mediterranean-type ecosystems every 10 years will contribute to a combined solution of all these problems.     

Estrogen and memory in women: how can we reconcile the findings?

Although several randomized controlled trials (RCTS) of surgically menopausal women have provided evidence that estrogen protects aspects of memory, many cross-sectional and longitudinal studies, including those from the RCT, the Women's Health Initiative Memory Study (WHIMS), have reported inconsistent information with regard to the relationship between estrogen and aspects of cognitive function. Although numerous reasons could be offered to explain these discrepancies in research findings, recent evidence from rodent, nonhuman primate, and human studies consistently suggests that one possibility may be critical to our understanding of the estrogenic effect on memory. Results of these animal and human studies indicate that the initiation of estrogen treatment at the time of menopause, or soon after ovariectomy (OVX), provides a window of opportunity for the preservation of memory in females whereas the administration of the hormone following a considerable delay in time after OVX has little or no beneficial effect on cognition. Considering the evidence that, in several organ systems, heightened disease risks accrue to a longer duration of estrogen deprivation in women, it would seem important to determine whether this is also true for brain structure and function in order to protect the quality of life for the considerable number of women who undergo a surgical menopause before their natural menopause had occurred.     

Mastering health: liberating beauty: Will the cosmetics of tomorrow be genetic?

Systems that have yet to stand the test of time carry imperfections that need to be skillfully addressed with the least amount of authoritarianism as possible. The communication and transmission of knowledge that we hold dear are essential pillars to social progress. As such, it is necessary to analyze with the greatest scientific objectivity the applications arising from the deep revolution rooted in the total sequencing of the human genome which affects all aspects of our societies. This extraordinary advance in human knowledge and the resulting technological achievements should not lend themselves to the fears or fantasies often fueled by those who criticize all scientific progress calling into question the most established dogmas. Certain supposedly scholarly analyses of the health situation with which we are currently confronted worldwide are a perfect illustration of this unfortunate trend. It is undeniable that the progress of molecular genetics has opened up a wide range of applications in many fields, affecting the well-being of humans, their mental and physical health. The apparent universal and individual interest for the most advanced genetic profile analyzing technologies is a testimony to this strong common desire to better understand one’s genetic heritage and to control their usage. Despite this movement, little attention is given to the recent advances in genetics applied to essential aspects of the social life of individuals through their inter-personal interactions. It is particularly distressing that the contributions of molecular biology and genetics to the daily well-being of individuals have not yet allowed open-access non-medical genetic testing to gain the recognition it deserves and are still viewed as recreational applications. Through an analysis of the cross influences that genetic biotechnologies have had since the beginning of the century in the fields of nutrition and cosmetics, we have tried to project ourselves into the near future which should witness major behavioral and social upheavals.