Post-reproductive Females Research Articles

Serotonin suppresses intraspecific aggression in an agrobiont spider, Pardosa pseudoannulata, without affecting predation on insects.

Spiders are an abundant group of natural enemies preying on insect pests in agroecosystem. But their potential in biological control has not been fully realized due to difficult mass production. One hindrance is the intense intraspecific aggression in spiders. Neurotransmitters such as serotonin play important roles in modulating aggression. Here, we investigated the regulatory function of serotonin (5-hydroxytryptamine [5-HT]) signaling in the intraspecific aggression in a wandering spider Pardosa pseudoannulata (Araneae, Lycosidae). The aggression was quantified with 5 escalated aggression behaviors as approach, chasing, lunging, boxing, and biting. Virgin (VG) females exhibited higher aggression levels but less 5-HT content than post-reproductive (PR) females. Systemic increase of 5-HT via 5-HT injection decreased aggression, while decrease of 5-HT via RNA interference (RNAi) of the tryptophan hydroxylase gene, increased aggression. The involvement of the four 5-HT receptors were determined via individual or combined RNAi. Co-RNAi of the three 5-HT1 genes increased overall aggression with decreased incidents of approach, chasing, lunging, and increased biting. RNAi of 5-HT1B decreased approach and increased biting, whereas RNAi of 5-HT1A or 5-HT1C did not affect aggression. RNAi of 5-HT7 decreased approach only. Therefore, different 5-HT receptor types contribute to different aspects of the inhibitory effects of 5-HT on aggression and provide several pharmacological targets for manipulating spider aggression. 5-HT injection did not affect spiders' predation on their insect prey, the brown planthopper Nilaparvata lugens. The findings reveal 1 neuronal mechanism regulating intraspecific aggression in spiders and provide an insight in developing aggression suppression strategies for spider mass rearing.

The Response of the Gut Physiological Function and Microbiome of a Wild Freshwater Fish (Megalobrama terminalis) to Alterations in Reproductive Behavior.

The fish gut microbiome is well known for its role in degrading nutrients to improve the host's digestion and absorption efficiency. In this study, we focused on the core physiological adaptability during the various reproductive stages of the black Amur bream (Megalobrama terminalis) to explore the interaction mechanisms among the fish host gut mucosal structure, gut enzyme activity, and gut microbial metabolism in the course of the host's reproductive cycle. Our findings showed that M. terminalis exhibited locomotion metabolic type (aids in sporting) in the reproductive stage, and a change to visceral metabolic type (aids in digestion) during non-reproductive and post-reproductive stage phases. The impact of metabolic type selection and energy demand during various reproductive stages on fish nutrition strategy and digestive function was substantial. Our resulted showed that mitochondria in intestinal epithelial cells of reproductive M. terminalis appeared autophagy phenomenon, and the digestive enzyme activities in the intestines of reproductive M. terminalis were lower than those in the non-reproductive and post-reproductive individuals. Moreover, these differences in nutrition strategy have a prominent impact on the gut microbiome of reproductive M. terminalis, compared to non-reproductive and post-reproductive samples. Our findings showed that reproductive females had lower levels of alpha diversity compared to non-reproductive and post-reproductive females. Our results also showed a greater functional variety and an increase in functional genes related to carbohydrate, lipid, amino acid, cofactors, and vitamin metabolic pathways in the NRS and PRS group. It is noteworthy that an enrichment of genes encoding putative enzymes implicated in the metabolism of taurine and hypotaurine was observed in the RS samples. Our findings illustrated that the stability and resilience of the gut bacterial community could be shaped in the wild fish host-microbiome interactions during reproductive life history.

Demographic and hormonal evidence for menopause in wild chimpanzees.

Among mammals, post-reproductive life spans are currently documented only in humans and a few species of toothed whales. Here we show that a post-reproductive life span exists among wild chimpanzees in the Ngogo community of Kibale National Park, Uganda. Post-reproductive representation was 0.195, indicating that a female who reached adulthood could expect to live about one-fifth of her adult life in a post-reproductive state, around half as long as human hunter-gatherers. Post-reproductive females exhibited hormonal signatures of menopause, including sharply increasing gonadotropins after age 50. We discuss whether post-reproductive life spans in wild chimpanzees occur only rarely, as a short-term response to favorable ecological conditions, or instead are an evolved species-typical trait as well as the implications of these alternatives for our understanding of the evolution of post-reproductive life spans.

Postreproductive female killer whales reduce socially inflicted injuries in their male offspring

Understanding the evolution of menopause presents a long-standing scientific challenge1,2,3-why should females cease ovulation prior to the end of their natural lifespan? In human societies, intergenerational resource transfers, for example, food sharing and caregiving, are thought to have played a key role in the evolution of menopause, providing a pathway by which postreproductive females can boost the fitness of their kin.4,5,6 To date however, other late-life contributions that postreproductive females may provide their kin have not been well studied. Here, we test the hypothesis that postreproductive female resident killer whales (Orcinus orca) provide social support to their offspring by reducing the socially inflicted injuries they experience. We found that socially inflicted injuries, as quantified by tooth rake marks, are lower for male offspring in the presence of their postreproductive mother. In contrast, we find no evidence that postreproductive mothers reduce rake marking in their daughters. Similarly, we find no evidence that either reproductive mothers or grandmothers (reproductive or postreproductive) reduce socially inflicted injuries in their offspring and grandoffspring, respectively. Moreover, we find that postreproductive females have no effect on reducing the rake marks for whales in their social unit who are not their offspring. Taken together, our results highlight that directing late-life support may be a key pathway by which postreproductive females transfer social benefits to their male offspring.

Temporal dynamics of mother-offspring relationships in Bigg's killer whales: opportunities for kin-directed help by post-reproductive females.

Age-related changes in the patterns of local relatedness (kinship dynamics) can be a significant selective force shaping the evolution of life history and social behaviour. In humans and some species of toothed whales, average female relatedness increases with age, which can select for a prolonged post-reproductive lifespan in older females due to both costs of reproductive conflict and benefits of late-life helping of kin. Killer whales (Orcinus orca) provide a valuable system for exploring social dynamics related to such costs and benefits in a mammal with an extended post-reproductive female lifespan. We use more than 40 years of demographic and association data on the mammal-eating Bigg's killer whale to quantify how mother-offspring social relationships change with offspring age and identify opportunities for late-life helping and the potential for an intergenerational reproductive conflict. Our results suggest a high degree of male philopatry and female-biased budding dispersal in Bigg's killer whales, with some variability in the dispersal rate for both sexes. These patterns of dispersal provide opportunities for late-life helping particularly between mothers and their adult sons, while partly mitigating the costs of mother-daughter reproductive conflict. Our results provide an important step towards understanding why and how menopause has evolved in Bigg's killer whales.

Estradiol-independent restoration of T-cell function in post-reproductive females.

Aging leads to a general decline in protective immunity. The most common age-associated effects are in seen T-cell mediated immune function. Adult mice whose immune systems show only moderate changes in T-cell subsets tend to live longer than age-matched siblings that display extensive T-cell subset aging. Importantly, at the time of reproductive decline, the increase in disease risks in women significantly outpace those of men. In female mice, there is a significant decline in central and peripheral naïve T-cell subsets at the time of reproductive failure. Available evidence indicates that this naïve T-cell decline is sensitive to ovarian function and can be reversed in post-reproductive females by transplantation of young ovaries. The restoration of naïve T-cell subsets due to ovarian transplantation was impressive compared with post-reproductive control mice, but represented only a partial recovery of what was lost from 6 months of age. Apparently, the influence of ovarian function on immune function may be an indirect effect, likely moderated by other physiological functions. Estradiol is significantly reduced in post-reproductive females, but was not increased in post-reproductive females that received new ovaries, suggesting an estradiol-independent, but ovarian-dependent influence on immune function. Further evidence for an estradiol-independent influence includes the restoration of immune function through the transplantation of young ovaries depleted of follicles and through the injection of isolated ovarian somatic cells into the senescent ovaries of old mice. While the restoration of naïve T-cell populations represents only a small part of the immune system, the ability to reverse this important functional parameter independent of estradiol may hold promise for the improvement of post-reproductive female immune health. Further studies of the non-reproductive influence of the ovary will be needed to elucidate the mechanisms of the relationship between the ovary and health.

Reduced neural investment in post-reproductive females of the bee Ceratina calcarta

Many insects show plasticity in the area of the brain called the mushroom bodies (MB) with foraging and social experience. MBs are paired neuropils associated with learning and memory. MB volume is typically greater in mature foragers relative to young and/or inexperienced individuals. Long-term studies show that extended experience may further increase MB volume, but long-term studies have only been performed on non-reproductive social insect workers. Here we use the subsocial bee Ceratina calcarata to test the effect of extended foraging experience on MB volume among reproductive females. Ceratina calcarata females forage to provision their immature offspring in the spring, and then again to provision their adult daughters in the late summer. We measured the volume of the MB calyces and peduncle, antennal lobes (AL), optic lobes (OL), central complex (CX), and whole brains of three groups of bees: newly emerged females, reproductive females in spring (foundresses), and post-reproductive mothers feeding their adult daughters in late summer. Post-reproductive late summer mothers had smaller MB calyces and ALs than foundresses. Moreover, among late mothers (but not other bees), wing wear, which is a measure of foraging experience, negatively correlated with both MB and OL volume. This is contrary to previously studied non-reproductive social insect workers in which foraging experience correlates postiviely with MB volume, and suggests that post-reproductive bees may reduce neural investment near the end of their lives.

Urinary neopterin of wild chimpanzees indicates that cell-mediated immune activity varies by age, sex, and female reproductive status

The study of free-living animal populations is necessary to understand life history trade-offs associated with immune investment. To investigate the role of life history strategies in shaping proinflammatory cell-mediated immune function, we analyzed age, sex, and reproductive status as predictors of urinary neopterin in 70 sexually mature chimpanzees (Pan troglodytes) at Ngogo, Kibale National Park, Uganda. In the absence of clinical signs of acute infectious disease, neopterin levels significantly increased with age in both male and female chimpanzees, as observed in humans and several other vertebrate species. Furthermore, males exhibited higher neopterin levels than females across adulthood. Finally, females with full sexual swellings, pregnant females, and post-reproductive females, the oldest individuals in our sample, exhibited higher neopterin levels than lactating females and cycling females without full swellings. Variation in females’ neopterin levels by reproductive status is consistent with post-ovulatory and pregnancy-related immune patterns documented in humans. Together, our results provide evidence of ample variation in chimpanzee immune activity corresponding to biodemographic and physiological variation. Future studies comparing immune activity across ecological conditions and social systems are essential for understanding the life histories of primates and other mammals.

Social evolution in Plio-Pleistocene hominins: Insights from hamadryas baboons and paleoecology

Reconstructions of hominin evolution have long benefited from comparisons with nonhuman primates, especially baboons and chimpanzees. The hamadryas baboon (Papio hamadryas) is arguably one of the best such models, as it exhibits both the male kin bonding and the cross-sex pair bonding thought to have been important in hominin evolution. Here we link processes of behavioral evolution in hamadryas baboons with those in a Plio-Pleistocene hominin, provisionally identified as Homo erectus (sensu lato) – a pivotal species in that its larger body and brain size and wider ranging patterns increased female costs of reproduction, increasing the importance of sociality. The combination of these higher costs of reproduction and shifts in diet and food acquisition have previously been argued to have been alleviated either via strengthening of male-female bonds (involving male provisioning and the evolution of monogamy) or via the assistance of older, post-reproductive females (leading to post-reproductive longevity in females, i.e., the grandmother hypothesis). We suggest that both arrangements could have been present in Plio-Pleistocene hominins if they lived in multilevel societies. Here we expand on our earlier scenario with two sets of recent data in support of it, (1) archaeological data from the 2 million year old Oldowan site of Kanjera South, Kenya and other sites that are suggestive of tool dependent foraging on nutrient dense resources (animal carcasses and plant underground storage organs), cooperation, and food sharing; and (2) a pattern of genetic variation in hamadryas baboons that suggests the operation of kin selection among both males and females at multiple levels of society. Taken together, these two sets of data strengthen our model and support the idea of a complex society linked by male-male, male-female, and female-female bonds at multiple levels of social organization in Plio-Pleistocene hominins.

Effects of reproduction on sexual dimorphisms in rat bone mechanics

Osteoporosis most commonly affects postmenopausal women. Although men are also affected, women over 65 are 6 times more likely to develop osteoporosis than men of the same age. This is largely due to accelerated bone remodeling after menopause; however, the peak bone mass attained during young adulthood also plays an important role in osteoporosis risk. Multiple studies have demonstrated sexual dimorphisms in peak bone mass, and additionally, the female skeleton is significantly altered during pregnancy/lactation. Although clinical studies suggest that a reproductive history does not increase the risk of developing postmenopausal osteoporosis, reproduction has been shown to induce long-lasting alterations in maternal bone structure and mechanics, and the effects of pregnancy and lactation on maternal peak bone quality are not well understood. This study compared the structural and mechanical properties of male, virgin female, and post-reproductive female rat bone at multiple skeletal sites and at three different ages. We found that virgin females had a larger quantity of trabecular bone with greater trabecular number and more plate-like morphology, and, relative to their body weight, had a greater cortical bone size and greater bone strength than males. Post-reproductive females had altered trabecular microarchitecture relative to virgins, which was highly similar to that of male rats, and showed similar cortical bone size and bone mechanics to virgin females. This suggests that, to compensate for future reproductive bone losses, females may start off with more trabecular bone than is mechanically necessary, which may explain the paradox that reproduction induces long-lasting changes in maternal bone without increasing postmenopausal fracture risk.

Cognitive behavior and sensory function were significantly influenced by restoration of active ovarian function in postreproductive mice

In mammals, the relationship between reproductive function and health has been particularly difficult to define. Previously, in old, postreproductive-aged mice, replacement of senescent ovaries with new ovaries from young, actively cycling mice increased life span. We hypothesized that the same factors that increased life span would also influence health span. In the current experiments, we tested two of the seven domains of function/health, sensory function and cognition to determine if exposure of postreproductive female mice to young transplanted ovaries influenced health span. We evaluated control female CBA/J mice at six, 13 and 16months of age. Additional mice received new (60d) ovaries at 12 or 17months of age and were subsequently evaluated at 16 or 25months of age, respectively. Evaluation of sensory function included two measures of olfactory perception; olfactory identification (buried pellet test) and olfactory discrimination (novel recognition block test). We found a significant age-related decline in olfactory identification in 16-month old mice. This decline was avoided by ovarian transplantation at 12months of age. The olfactory discrimination block test revealed an age-associated increase in time spent on both the novel and familiar blocks. This trend was reversed in 16-month old new-ovary recipients. We evaluated cognitive behavior with a burrowing behavior test. We detected a significant age-related decrease in burrowing behavior at 16months of age. This age-related decrease in burrowing behavior was prevented by ovarian transplantation at 12months of age. In summary, we have shown that cognitive behavior and sensory function, which are negatively influenced by aging, can be positively influenced or restored by re-establishment of active ovarian function in aged female mice. These findings provide strong incentive for further investigation of the positive influence of young ovaries on restoration of health in postreproductive females.

Restoration of immune and renal function in aged females by re-establishment of active ovarian function.

Proper immune functioning is necessary to maximize reproductive success. In addition, age-associated uremia in women is often associated with hypothalamic--pituitary-gonadal dysfunction. In the present experiments, we tested immune and renal function to determine if exposure of postreproductive mice to young, reproductively cycling ovaries would influence non-reproductive physiological functions. Control female CBA/J mice were evaluated at 6, 13 and 16 months of age. Additional mice received new (60-day-old) ovaries at 12 months of age and were evaluated at 16 months of age. Consequently, 6-month-old control mice and 16-month-old recipient mice both possessed 6-month-old ovaries and were reproductively cycling. A significant age-related decline in immune function (T-cell subset analysis) was found in 16-month-old mice, but was improved 64% by ovarian transplantation. Renal function (blood urea nitrogen:creatinine ratio) was also decreased with aging, but ovarian transplantation restored function to levels found in 6-month-old mice. In summary, we have shown that immune and renal function, which are negatively influenced by aging, can be positively influenced or restored by re-establishment of active ovarian function in aged female mice. These findings provide a strong incentive for further investigation of the positive influence of young ovaries on restoration of health in postreproductive females.

Do post-reproductive aged females promote maternal health? Preliminary evidence from historical populations.

Much literature argues that natural selection conserved menopause and longevity in women because those who stopped childbearing helped bolster daughters' fertility and reduce infant mortality among grandchildren. Whether the presence of grandmothers ever improved fitness sufficiently to affect longevity via natural selection remains controversial and difficult to test. The argument underlying the grandmother and associated alloparenting literature, however, leads us to the novel and testable prediction that the presence of older women in historical societies could have affected population health by reducing lethality associated with childbearing. Using historical life table data from four societies (Denmark, England and Wales, France and Sweden), we test the hypothesis that death rates among women initiating childbearing declined when the societies in which they were embedded included unexpectedly high frequencies of older women. We use time series analysis to measure the extent to which the observed likelihood of death among women aged 20-24 differs from statistically expected values when the number of older women grows or declines. In three of the four countries examined, we find an inverse relationship between the frequency of post-reproductive females in the population and odds of mortality among females at the peak of childbearing initiation. Results suggest that the presence of older women in a population may enhance population health by reducing mortality among women who face high risk of maternal death, although additional research is needed to determine if this relationship is causal.

Reproductive Conflict and the Evolution of Menopause in Killer Whales

Why females of some species cease ovulation prior to the end of their natural lifespan is a long-standing evolutionary puzzle [1-4]. The fitness benefits of post-reproductive helping could in principle select for menopause [1, 2, 5], but the magnitude of these benefits appears insufficient to explain the timing of menopause [6-8]. Recent theory suggests that the cost of inter-generational reproductive conflict between younger and older females of the same social unit is a critical missing term in classical inclusive fitness calculations (the "reproductive conflict hypothesis" [6, 9]). Using a unique long-term dataset on wild resident killer whales, where females can live decades after their final parturition, we provide the first test of this hypothesis in a non-human animal. First, we confirm previous theoretical predictions that local relatedness increases with female age up to the end of reproduction. Second, we construct a new evolutionary model and show that given these kinship dynamics, selection will favor younger females that invest more in competition, and thus have greater reproductive success, than older females (their mothers) when breeding at the same time. Third, we test this prediction using 43 years of individual-based demographic data in resident killer whales and show that when mothers and daughters co-breed, the mortality hazard of calves from older-generation females is 1.7 times that of calves from younger-generation females. Intergenerational conflict combined with the known benefits conveyed to kin by post-reproductive females canexplain why killer whales have evolved the longest post-reproductive lifespan of all non-human animals.

Manipulation of Ovarian Function Significantly Influenced Sarcopenia in Postreproductive-Age Mice.

Previously, transplantation of ovaries from young cycling mice into old postreproductive-age mice increased life span. We anticipated that the same factors that increased life span could also influence health span. Female CBA/J mice received new (60 d) ovaries at 12 and 17 months of age and were evaluated at 16 and 25 months of age, respectively. There were no significant differences in body weight among any age or treatment group. The percentage of fat mass was significantly increased at 13 and 16 months of age but was reduced by ovarian transplantation in 16-month-old mice. The percentages of lean body mass and total body water were significantly reduced in 13-month-old control mice but were restored in 16- and 25-month-old recipient mice by ovarian transplantation to the levels found in six-month-old control mice. In summary, we have shown that skeletal muscle mass, which is negatively influenced by aging, can be positively influenced or restored by reestablishment of active ovarian function in aged female mice. These findings provide strong incentive for further investigation of the positive influence of young ovaries on restoration of health in postreproductive females.

Ecological Knowledge, Leadership, and the Evolution of Menopause in Killer Whales

Summary Classic life-history theory predicts that menopause should not occur because there should be no selection for survival after the cessation of reproduction [1]. Yet, human females routinely live 30 years after they have stopped reproducing [2]. Only two other species—killer whales ( Orcinus orca ) and short-finned pilot whales ( Globicephala macrorhynchus ) [3, 4]—have comparable postreproductive lifespans. In theory, menopause can evolve via inclusive fitness benefits [5, 6], but the mechanisms by which postreproductive females help their kin remain enigmatic. One hypothesis is that postreproductive females act as repositories of ecological knowledge and thereby buffer kin against environmental hardships [7, 8]. We provide the first test of this hypothesis using a unique long-term dataset on wild resident killer whales. We show three key results. First, postreproductively aged females lead groups during collective movement in salmon foraging grounds. Second, leadership by postreproductively aged females is especially prominent in difficult years when salmon abundance is low. This finding is critical because salmon abundance drives both mortality and reproductive success in resident killer whales [9, 10]. Third, females are more likely to lead their sons than they are to lead their daughters, supporting predictions of recent models [5] of the evolution of menopause based on kinship dynamics. Our results show that postreproductive females may boost the fitness of kin through the transfer of ecological knowledge. The value gained from the wisdom of elders can help explain why female resident killer whales and humans continue to live long after they have stopped reproducing.

Ecological Knowledge, Leadership, and the Evolution of Menopause in Killer Whales

Classic life-history theory predicts that menopause should not occur because there should be no selection for survival after the cessation of reproduction [1]. Yet, human females routinely live 30 years after they have stopped reproducing [2]. Only two other species-killer whales (Orcinus orca) and short-finned pilot whales (Globicephala macrorhynchus) [3, 4]-have comparable postreproductive lifespans. In theory, menopause can evolve via inclusive fitness benefits [5, 6], but the mechanisms by which postreproductive females help their kin remain enigmatic. One hypothesis is that postreproductive females act as repositories of ecological knowledge and thereby buffer kin against environmental hardships [7, 8]. We provide the first test of this hypothesis using a unique long-term dataset on wild resident killer whales. We show three key results. First, postreproductively aged females lead groups during collective movement in salmon foraging grounds. Second, leadership by postreproductively aged females is especially prominent in difficult years when salmon abundance is low. This finding is critical because salmon abundance drives both mortality and reproductive success in resident killer whales [9, 10]. Third, females are more likely to lead their sons than they are tolead their daughters, supporting predictions of recent models [5] of the evolution of menopause based on kinship dynamics. Our results show that postreproductive females may boost the fitness of kin through the transfer of ecological knowledge. The value gained from the wisdom of elders can help explain why female resident killer whales and humans continue to live long after they have stopped reproducing.

Sex-specific distribution and diet of Platichthys flesus at the end of spawning in the northern Baltic Sea

This study examined the relationship of seascape structure, prey availability and sex on the post-spawning distribution and diet of European flounder Platichthys flesus in the northern Baltic Sea. The objectives were to determine whether: (1) wave exposure and substratum affect abundance and distribution of P. flesus, (2) diet reflects the benthic prey composition and (3) sex affects the distribution or diet of P. flesus. The results showed that P. flesus was evenly spread in the archipelago with no correlation to wave exposure. The distribution was, however, sex specific; reproductive males dominated the exposed zone and mainly post-reproductive females dominated the intermediate and sheltered zones. Platichthys flesus fed mainly on two bivalve prey species: blue mussels Mytilus edulis and Baltic tellins Macoma balthica. Hard substratum invertebrates dominated the diet in all habitats and apart from some typical soft substratum species, there was no clear link between fish feeding and the dominance structure of benthic prey. Diet was further sex specific, with females showing a broader range of diet than males. Results suggest that P. flesus is a specialist molluscivore found commonly and equally in soft- and hard-substratum habitats throughout the archipelago area. Previous studies on P. flesus in the Baltic Sea have yielded inconsistent results regarding diet and it has commonly been believed that the distribution of Baltic Sea P. flesus is linked to sand and soft substrata. The present findings emphasize the importance of including the entire range of habitats when diet and regional species distributions are assessed.

Sleep-disordered breathing during pregnancy: future implications for cardiovascular health.

Cardiovascular disease (CVD) is a common condition in postreproductive females. Key risk factors for later-life CVD include gestational hypertension (GHTN) and preeclampsia (PE). Although several risk factors of hypertension in pregnancy are well recognized, a novel risk factor that has emerged recently is sleep-disordered breathing (SDB), a condition characterized by repeated closure of the upper airway during sleep with disrupted ventilation and sleep fragmentation. In the nonpregnant population, SDB is now known to play a causal role in future CVD. The aim of this study was to propose the hypothesis that occult SDB during pregnancy may play a role in long-term CVD in women who had hypertensive disorders of pregnancy. This study is a review and synthesis of empirical evidence that links SDB to GHTN/PE and GHTN/PE to future CVD. An increasing body of evidence supports the relationship between SDB and hypertensive disorders of pregnancy via mechanisms of inflammation, oxidative stress, and endothelial dysfunction. It is well established that hypertensive disorders of pregnancy are associated with long-term risk for CVD via similar mechanisms. However, no studies have addressed the potential role of SDB in long-term outcomes of women with GHTN/PE during pregnancy. Given the suggested mechanisms that explain these associations, it is plausible that SDB during pregnancy may increase long-term cardiovascular morbidity and mortality. Pregnancy may offer a window of opportunity for identification and treatment of SDB, which could provide substantial health benefit for many years to come.

Absence of long-term effects of reproduction on longevity in the mouse model.

BackgroundMost human demographic data, particularly those on natural fertility populations, find no relationship or even a positive association between fertility and longevity. The present study aims to ascertain whether there is a trade-off between fertility and longevity in the mouse model.MethodsThe study was focused on the first litter produced by 10- to 14-wk-old hybrid (C57BL/6JIco female X CBA/JIco male) mice. A single female/male per litter was individually housed with a male/female at the age of 25 and 52 wk, respectively, until the end of reproductive life in females or natural death in males under controlled housing conditions. Post-reproductive females and virgin mice were reared until natural death. Cox regression models with forward stepwise variable selection were fitted to examine the effect of several fertility variables on expectation of survival times.ResultsVirgin females displayed higher life expectancy than virgin males. The relative risk of dying for a virgin male at a particular age was 2.116 [99% confidence interval: 1.317, 3.398] times that of a virgin female. No significant differences on expectation of survival times between virgin and mated females, and between virgin and mated males were found. Furthermore, total number of pups at weaning and total number of litters produced by a dam/stud, time interval between mating and last litter, time interval between litters, and age at last litter were not significant predictors of expectation of survival times in both mated females and mated males.ConclusionsLike in most human studies, the present study evidences no relationship between total number of offspring/litters produced by a dam/stud and expectation of survival times. Moreover, the present data are in agreement with the general phenomenon of a bias in life expectancy in favor of females.