Estradiol modulates recovery of REM sleep in a time-of-day-dependent manner

Ovarian Suppression: Early Menopause, Late Effects

PURPOSE OF REVIEW

Pre-menopausal women diagnosed with hormone receptor (HR) breast cancer are candidates for prolonged hypoestrogenism to improve cancer outcomes. However, the disease benefit eclipses the toxicities associated with ovarian function suppression (OFS), which are often under-reported.

RECENT FINDINGS

Increased risk of mortality from cardiovascular disease, bone disorders, and metabolic disorders is well reported in women with no history of cancer, after surgical oophorectomy or premature ovarian failure. Vasomotor symptoms, urogenital atrophy, weight gain, sexual dysfunction, cognitive decline, and sleep disturbances contribute to the increased non-compliance associated with OFS, especially in younger women. Balancing the toxicities of prolonged OFS with its benefits should be critically analyzed by providers when making recommendations for their patients. Supportive care to manage multi-system toxicities and to counteract the long-term impact on all-cause mortality should be emphasized by every cancer program. Future studies with OFS should incorporate patient outcomes and strategies for symptom management in addition to focusing on improving disease outcomes.

Sex and Sleep Disruption as Contributing Factors in Alzheimer's Disease

Alzheimer's disease (AD) affects more women than men, with women throughout the menopausal transition potentially being the most under researched and at-risk group. Sleep disruptions, which are an established risk factor for AD, increase in prevalence with normal aging and are exacerbated in women during menopause. Sex differences showing more disrupted sleep patterns and increased AD pathology in women and female animal models have been established in literature, with much emphasis placed on loss of circulating gonadal hormones with age. Interestingly, increases in gonadotropins such as follicle stimulating hormone are emerging to be a major contributor to AD pathogenesis and may also play a role in sleep disruption, perhaps in combination with other lesser studied hormones. Several sleep influencing regions of the brain appear to be affected early in AD progression and some may exhibit sexual dimorphisms that may contribute to increased sleep disruptions in women with age. Additionally, some of the most common sleep disorders, as well as multiple health conditions that impair sleep quality, are more prevalent and more severe in women. These conditions are often comorbid with AD and have bi-directional relationships that contribute synergistically to cognitive decline and neuropathology. The association during aging of increased sleep disruption and sleep disorders, dramatic hormonal changes during and after menopause, and increased AD pathology may be interacting and contributing factors that lead to the increased number of women living with AD.

The Effects of Hormonal Contraceptives on the Sleep of Women of Reproductive Age

Research about the effects of hormonal contraceptives on sleep has been performed but is subjected to important levels of methodological heterogeneity. Hormonal contraceptives impact sleep, but the direction of this association is not clear. Most studies describe a negative sleep profile among contraceptive users, including increased sleepiness, insomnia symptoms, decreased sleep efficiency, and a reduced overall sleep quality. Hormonal intrauterine contraceptives are associated with less negative effects. More research on the field, especially randomized controlled trials, is needed to increase the level and certainty of evidence about the effects of hormonal contraceptives on sleep.

Sex hormone dose escalation for treating abnormal sleep in ovariectomized rats: in vitro GABA synthesis in sleep-related brain areas

No data in the literature have evaluated sex hormone dose escalation for treating abnormal sleep of ovariectomized rats-nor studies on the role of sex hormones in GABA synthesis of rats' sleep-related areas. The main aim of this study was to determine the maximum tolerated dose (MTD) of estradiol (ET), progesterone (PT), and the mixture of both (EPT) to restore normal sleep in a model of menopause in rats. The second purpose was to describe the in vitro activity of glutamate decarboxylase (GAD) in sleep-related brain areas in the presence or absence of sex hormones. A weekly dose-escalation design of ET, PT, or EPT was implemented in ovariectomized rats (six per group). Dose escalation continued until the dose at which 100% of the rats exhibited a state of "complete somnolence." Doses that were not toxic or did not show side effects were considered. For in vitro experiments, sleep-related brain areas were separated and incubated with radiolabeled glutamate. Estradiol (17β-E2), progesterone (P), and pyridoxal phosphate (PLP) were added to this assay, and GAD activity was determined. Under the same conditions, a second test was carried out, but the P antagonist RU486 was added to assess the role of P in GAD activity. Ovariectomy increased periodic awakenings compared to those determined for the SHAM group. The EPT for ovariectomized rats was very effective by the fifth week in decreasing arousal and achieving a similar sleep behavior to the SHAM-control group. Rats tolerated the ET, PT, and EPT well to the maximum planned dose (0.66 mg/kg and 4.4 mg/kg, respectively). No lethal events occurred; the MTD was reached. The in vitro studies indicated that the presence of 17β-E2 plus P in the assay triggered the activity of isotype 65 GAD in all the studied brain areas. RU486 in the incubation medium blocked such activity; however, the action of isotype 67 GAD was not blocked by RU486. A dose-escalation model was determined; the MTD coincided with the maximum dose of ET and PT used. However, the EPT combination restored normal sleep in the menopause model compared to the SHAMs without toxic effects. The in vitro model demonstrated that 17β-E2 plus P presence in the assay increased the activity of GAD65 in the studied brain tissues.

The stress of losing sleep: Sex-specific neurobiological outcomes

Sleep is a vital and evolutionarily conserved process, critical to daily functioning and homeostatic balance. Losing sleep is inherently stressful and leads to numerous detrimental physiological outcomes. Despite sleep disturbances affecting everyone, women and female rodents are often excluded or underrepresented in clinical and pre-clinical studies. Advancing our understanding of the role of biological sex in the responses to sleep loss stands to greatly improve our ability to understand and treat health consequences of insufficient sleep. As such, this review discusses sex differences in response to sleep deprivation, with a focus on the sympathetic nervous system stress response and activation of the hypothalamic-pituitary-adrenal (HPA) axis. We review sex differences in several stress-related consequences of sleep loss, including inflammation, learning and memory deficits, and mood related changes. Focusing on women's health, we discuss the effects of sleep deprivation during the peripartum period. In closing, we present neurobiological mechanisms, including the contribution of sex hormones, orexins, circadian timing systems, and astrocytic neuromodulation, that may underlie potential sex differences in sleep deprivation responses.

The Influence of Steroid Hormones on Tooth Wear in Children and in Adolescents

(1) Background: From a young age, boys are more often affected by tooth wear than girls. This suggests an influence of the male sex hormone (testosterone) on the aetiology of tooth wear. The aim of the present study was to investigate the incidence of tooth wear in relation to steroid hormone levels in children. (2) Methods: 1022 test persons aged between 10 and 18 (491 male, 531 female) from the LIFE Child study underwent medical and dental examination. Tooth wear was measured through clinical inspection. Blood samples were taken to determine hormone levels (testosterone, SHBG). The level of free testosterone was calculated from the ratio of testosterone to SHBG. Using multivariable methods, the incidence of tooth wear was analyzed as a function of hormone levels, while controlling for confounders such as age, sex, social status, and orthodontic treatment. (3) Results: The incidence of tooth wear increased with age in both sexes. Boys showed significantly more often attrition facets than girls (17.5% vs. 13.2%, p < 0.001). Subjects with tooth wear showed significantly higher free testosterone levels than those without (males: p < 0.001, females: p < 0.05). After controlling for confounding variables, the risk of tooth wear increased by approximately 30.0% with each year of life (odds ratio [OR]boys = 1.29, 95% confidence interval [CI] = 1.04−1.56; [OR]girls = 1.32, 95% CI = 1.08−1.61). In addition, the risk of tooth wear increased by 6.0% per free testosterone scale score only in boys (OR = 1.06, 95% CI = 1.01−1.12). (4) Conclusions: Tooth wear is common in children and in adolescents, and it increases steadily with age in both sexes. The stronger increase and the higher prevalence among male adolescents can be explained by the additional effect of free testosterone.

The Role of Reproductive Hormones in Sex Differences in Sleep Homeostasis and Arousal Response in Mice

There are various sex differences in sleep/wake behaviors in mice. However, it is unclear whether there are sex differences in sleep homeostasis and arousal responses and whether gonadal hormones are involved in these sex differences. Here, we examined sleep/wake behaviors under baseline condition, after sleep deprivation by gentle handling, and arousal responses to repeated cage changes in male and female C57BL/6 mice that are hormonally intact, gonadectomized, or gonadectomized with hormone supplementation. Compared to males, females had longer wake time, shorter non-rapid eye movement sleep (NREMS) time, and longer rapid eye movement sleep (REMS) episodes. After sleep deprivation, males showed an increase in NREMS delta power, NREMS time, and REMS time, but females showed a smaller increase. Females and males showed similar arousal responses. Gonadectomy had only a modest effect on homeostatic sleep regulation in males but enhanced it in females. Gonadectomy weakened arousal response in males and females. With hormone replacement, baseline sleep in gonadectomized females was similar to that of intact females, and baseline sleep in gonadectomized males was close to that of intact males. Gonadal hormone supplementation restored arousal response in males but not in females. These results indicate that male and female mice differ in their baseline sleep-wake behavior, homeostatic sleep regulation, and arousal responses to external stimuli, which are differentially affected by reproductive hormones.

Relationship between hormonal contraceptives and sleep among women of reproductive age: a systematic review protocol

INTRODUCTION

The aetiology of sleep disruptions is unknown, but hormonal fluctuations during the menstrual cycle, pregnancy and menopause have been shown to potentially affect how well a woman sleeps. The aim of this systematic review was to investigate whether hormonal contraceptives are associated with a decreased quality of sleep and increased sleep duration in women of reproductive age.

METHODS

This review will analyse data from randomised controlled trials or non-randomised comparative studies investigating the association between hormonal contraceptives and sleep outcomes among women of reproductive age. Reviews addressing the same research question with similar eligibility criteria will be included. A literature search will be performed using the MEDLINE, Embase and Cochrane Central Register of Controlled Trials databases from inception to 7 March 2021. The Cochrane Collaboration's Risk of Bias for Randomised Trials V.2.0 and The Risk of Bias for Non-randomised Studies of Interventions tool will be used to assess risk of bias for each outcome in eligible studies. Two reviewers will independently assess eligibility of studies and risk of bias and extract the data. All extracted data will be presented in tables and narrative form. For sleep measures investigated by two or more studies with low heterogeneity, we will conduct random-effects meta-analysis to estimate the magnitude of the overall effect of hormonal contraceptives. If studies included in this systematic review form a connected network, a network meta-analysis will be conducted to estimate the comparative effect of different contraceptives. The Grading of Recommendations, Assessment, Development, and Evaluation approach will be used to summarise the quality of evidence. Our protocol follows the Preferred Reporting Items for Systematic Reviews and Meta-Analyses for Protocols 2015 guidelines.

ETHICS AND DISSEMINATION

Ethics approval is not required as data were sourced from previously reported studies. The findings of this review will be published in a peer-reviewed journal and presented at relevant conferences.

PROSPERO REGISTRATION NUMBER

CRD42020199958.

Estradiol Influences Adenosinergic Signaling and NREM Sleep Need in Adult Female Rats

Gonadal steroids and gender are risk factors for sleep disruptions and insomnia in women. However, the relationship between ovarian steroids and sleep is poorly understood. In rodent models, estradiol (E2) suppresses sleep in females suggesting that E2 may reduce homeostatic sleep need. The current study investigates whether E2 decreases sleep need and the potential mechanisms that govern E2 suppression of sleep. Our previous findings suggest that the median preoptic nucleus (MnPO) is a key nexus for E2 action on sleep. Using behavioral, neurochemical and pharmacological approaches, we tested whether (1) E2 influenced the sleep homeostat and (2) E2 influenced adenosine signaling in the MnPO of adult female rats. In both unrestricted baseline sleep and recovery sleep from 6-hour sleep deprivation, E2 significantly reduced non-rapid eye movement sleep (NREM)-delta power, NREM-Slow Wave Activity (NREM-SWA, 0.5-4.0Hz), and NREM-delta energy suggesting that E2 decreases homeostatic sleep need. However, coordinate with E2-induced changes in physiological markers of homeostatic sleep was a marked increase in MnPO extracellular adenosine (a molecular marker of homeostatic sleep need) during unrestricted and recovery sleep in E2-treated but not oil control animals. While these results seemed contradictory, systemically administered E2 blocked the ability of CGS-21680 (adenosine A2A receptor agonist) microinjected into the MnPO to increase NREM sleep suggesting that E2 may block adenosine signaling. Together, these findings provide evidence that E2 may attenuate the local effects of the A2A receptors in the MnPO which in turn may underlie estrogenic suppression of sleep behavior as well as changes in homeostatic sleep need.

Prenatal Kynurenine Elevation Elicits Sex-Dependent Changes in Sleep and Arousal During Adulthood: Implications for Psychotic Disorders

Dysregulation of the kynurenine pathway (KP) of tryptophan catabolism has been implicated in psychotic disorders, including schizophrenia and bipolar disorder. Kynurenic acid (KYNA) is a KP metabolite synthesized by kynurenine aminotransferases (KATs) from its biological precursor kynurenine and acts as an endogenous antagonist of N-methyl-D-aspartate and α7-nicotinic acetylcholine receptors. Elevated KYNA levels found in postmortem brain tissue and cerebrospinal fluid of patients are hypothesized to play a key role in the etiology of cognitive symptoms observed in psychotic disorders. Sleep plays an important role in memory consolidation, and sleep disturbances are common among patients. Yet, little is known about the effect of altered KP metabolism on sleep-wake behavior. We presently utilized a well-established experimental paradigm of embryonic kynurenine (EKyn) exposure wherein pregnant dams are fed a diet laced with kynurenine the last week of gestation and hypothesized disrupted sleep-wake behavior in adult offspring. We examined sleep behavior in adult male and female offspring using electroencephalogram and electromyogram telemetry and determined sex differences in sleep and arousal in EKyn offspring. EKyn males displayed reduced rapid eye movement sleep, while female EKyn offspring were hyperaroused compared to controls. We determined that EKyn males maintain elevated brain KYNA levels, while KYNA levels were unchanged in EKyn females, yet the activity levels of KAT I and KAT II were reduced. Our findings indicate that elevated prenatal kynurenine exposure elicits sex-specific changes in sleep-wake behavior, arousal, and KP metabolism.

Sex and Menstrual Phase Influences on Sleep and Memory

Purposes of Review

This review highlights the effect of sex differences in sleep mediated memory consolidation and cognitive performance. In addition, the role of menstrual cycle and the fluctuating level of sexual hormones (mainly oestrogen and progesterone) are stressed.

Recent Findings

The literature indicates that sex hormones mediate and orchestrate the differences observed in performance of females in comparison with males in a variety of tasks and can also be related to how sleep benefits cognition. Although the exact mechanism of such influence is not clear, it most likely involves differential activation of brain areas, sensitivity to neuromodulators (mainly oestrogen), circadian regulation of sleep and temperature, as well as modification of strategies to solve tasks across the menstrual cycle.

Summary

With the evidence presented here, we hope to encourage researchers to develop appropriate paradigms to study the complex relationship between menstrual cycle, sleep (its regulation, architecture and electrophysiological hallmarks) and performance in memory and other cognitive tasks.

Chronic modafinil therapy ameliorates depressive-like behavior, spatial memory and hippocampal plasticity impairments, and sleep-wake changes in a surgical mouse model of menopause

Depression, cognitive deficits, and sleep disturbances are common and often severe in menopausal women. Hormone replacement cannot effectively alleviate these symptoms and sometimes elicits life-threatening adverse reactions. Exploring effective therapies to target psychological problems is urgently needed. In this work, we developed a mouse model of menopause by bilateral ovariectomies (OVXs) and investigated whether menopausal mental symptoms can be ameliorated by psychostimulant modafinil (MOD) as well as explored the underlying mechanisms. At ~3 weeks after OVXs, mice got daily intraperitoneal administrations of MOD at the beginning of the active phase. Several behavioral tests and electroencephalogram (EEG) recordings were conducted. Electrophysiological and immunohistochemical experiments were carried out to evaluate the synaptic plasticity and neurogenesis, respectively. We found that chronic MOD administration in OVX mice significantly decreased immobility time. The spatial memory performance of OVX mice improved significantly in response to MOD administration in the Morris water-maze test. The OVX mice were characterized by an attenuation of hippocampal synaptic transmission and synaptic long-term potentiation and had fewer 5-ethynyl-2'-deoxyuridine-labeled cells in the dentate gyrus, which were restored after MOD administration. Antagonists of dopamine D₁ and D₂ receptors and GABA_A receptor agonists were involved in MOD-exerted anti-depressant actions and augments of hippocampal neurogenesis in OVX mice. Moreover, night-dosed MOD therapy significantly promoted the night-time delta-band EEG power during wakefulness and the day-time rapid eye movement sleep amount, which were significantly reduced by OVXs. Collectively, these findings suggest that MOD is a promising therapeutic candidate for menopausal women.

Neurobiological and Hormonal Mechanisms Regulating Women's Sleep

Sleep is crucial for optimal well-being, and sex differences in sleep quality have significant implications for women's health. We review the current literature on sex differences in sleep, such as differences in objective and subjective sleep measures and their relationship with aging. We then discuss the convincing evidence for the role of ovarian hormones in regulating female sleep, and survey how these hormones act on a multitude of brain regions and neurochemicals to impact sleep. Lastly, we identify several important areas in need of future research to narrow the knowledge gap and improve the health of women and other understudied populations.

Role of Ovarian Hormones in the Modulation of Sleep in Females Across the Adult Lifespan

Ovarian hormones, including 17β-estradiol, are implicated in numerous physiological processes, including sleep. Beginning at puberty, girls report more sleep complaints than boys, which is maintained throughout the reproductive life stage. Sleep problems are exacerbated during the menopausal transition, evidenced by greater risk for sleep disorders. There is emerging evidence that menopause-associated hormone loss contributes to this elevated risk, but age is also an important factor. The extent to which menopause-associated sleep disturbance persists into postmenopause above and beyond the effects of age remains unknown. Untreated sleep disturbances have important implications for cognitive health, as they are emerging as risk factors for dementia. Given that sleep loss impairs memory, an important knowledge gap concerns the role played by menopause-associated hormone loss in exacerbating sleep disturbance and, ultimately, cognitive function in aging women. In this review, we take a translational approach to illustrate the contribution of ovarian hormones in maintaining the sleep-wake cycle in younger and middle-aged females, with evidence implicating 17β-estradiol in supporting the memory-promoting effects of sleep. Sleep physiology is briefly reviewed before turning to behavioral and neural evidence from young females linking 17β-estradiol to sleep-wake cycle maintenance. Implications of menopause-associated 17β-estradiol loss is also reviewed before discussing how ovarian hormones may support the memory-promoting effects of sleep, and why menopause may exacerbate pathological aging via effects on sleep. While still in its infancy, this research area offers a new sex-based perspective on aging research, with a focus on a modifiable risk factor for pathological aging.

Sex- and Age-dependent Differences in Sleep-wake Characteristics of Fisher-344 Rats

Aging is a well-recognized risk factor for sleep disruption. The characteristics of sleep in aging include its disruption by frequent awakenings, a decline in both non-rapid eye movement (nonREM) and REM sleep amounts, and a weaker homeostatic response to sleep loss. Evidence also suggests that sleep in females is more sensitive to changes in the ovarian steroidal milieu. The Fischer-344 rats are commonly used experimental subjects in behavioral and physiological studies, including sleep and aging. Most sleep studies in Fischer-344 rats have used male subjects to avoid interactions between the estrus and sleep-waking cycles. The changes in the sleep-wake organization of female Fischer-344 rats, especially with advancing age, are not well-characterized. We determined sleep-waking features of cycling females across estrus stages. We also compared spontaneous and homeostatic sleep response profiles of young (3-4 months) and old (24-25 months) male and female Fischer-344 rats. The results suggest that: i) sleep-wake architectures across stages of estrus cycle in young females were largely comparable except for a significant suppression of REM sleep at proestrus night and an increase in REM sleep the following day; ii) despite hormonal differences, sleep-wake architecture in male and female rats of corresponding ages were comparable except for the suppression of REM sleep at proestrus night and higher nonREM delta power in recovery sleep; and iii) aging significantly affected sleep-wake amounts, sleep-wake stability, and homeostatic response to sleep loss in both male and female rats and that the adverse effects of aging were largely comparable in both sexes.

Analysis of the long‑term beneficial effects of menopausal hormone therapy on sleep quality and menopausal symptoms

A large number of menopausal women report sleep disturbances along with psychological, somatic and urogenital menopausal symptoms. The aim of this study was to evaluate the efficacy of menopausal hormonal therapy (MHT) in improving subjective sleep quality and the severity of menopausal symptoms. An institutional ethics committee approved this retrospective chart review of 342 women treated with MHT for menopausal symptoms. Standard 28-day MHT consisted of the oral administration of 2 mg estradiol daily for 14 days, followed by 2 mg estradiol and 10 mg dydrogesterone daily for the remaining 14 days. A subgroup of 14 participants with a family history of cancer and mammography scores of 3 and above, received only tibolone 2.5 mg daily. Perceived sleep quality was measured with the Pittsburgh Sleep Quality Index (PSQI), while the assessment of menopausal symptoms was performed using the Kupperman Menopause Index (KMI) and menopause rating scale (MRS). Of the 342 patients, 79 were followed-up for 3 years. Compared to the baseline scores, the mean decrease in PSQI scores was 1.53±0.29 points (P<0.0001) at 1 month, 2.21±0.187 points (P<0.0001) at 2 months and 2.26±0.6 points (P<0.0001) after 3 years of MHT. The KMI scores also decreased by a mean of 6.37±1.59 points (P<0.0001) at 1 month and by 8.73±1.92 points after 3 years (P<0.0001). The MRS scores decreased by a mean of 3.56±1.05 points (P<0.0001) at 1 month and by 4.28±2.01 points (P<0.0001) after 3 years, as compared to the baseline scores. Patients receiving tibolone MHT did not report any improvement in sleep quality (P=0.956). On the whole, the findings of this study indicate that conventional MHT has a rapid and prolonged beneficial effect on self-reported sleep quality and menopausal symptoms in women. However, further clinical studies are warranted to compare the effects of different MHT regimens.

Sex differences in sleep and sleep loss-induced cognitive deficits: The influence of gonadal hormones

Males and females can respond differentially to the same environmental stimuli and experimental conditions. Chronic sleep loss is a frequent and growing problem in many modern societies and has a broad variety of negative outcomes for health and well-being. While much has been done to explore the deleterious effects of sleep deprivation (SD) on cognition in both human and animal studies over the last few decades, very little attention has been paid to the part played by sex differences and gonadal steroids in respect of changes in cognitive functions caused by sleep loss. The effects of gonadal hormones on sleep regulation and cognitive performances are well established. Reduced gonadal function in menopausal women and elderly men is associated with sleep disturbances and cognitive decline as well as dementia, which suggests that sex steroids play a key role in modulating these conditions. Finding out whether there are sex differences in respect of the effect of insufficient sleep on cognition, and how neuroendocrine mediators influence cognitive impairment induced by SD could provide valuable insights into the best therapies for each sex. In this review, we aim to highlight the involvement of sex differences and gonadal hormone status on the severity of cognitive deficits induced by sleep deficiency in both human and animal studies.

Neuroendocrine Control of Sleep

Sleep is a phenomenon in animal behavior as enigmatic as it is ubiquitous, and one deeply tied to endocrine function. Though there are still many unanswered questions about the neurochemical basis of sleep and its functions, extensive interactions have been identified between sleep and the endocrine system, in both the endocrine system's effect on sleep and sleep's effect on the endocrine system. Unfortunately, until recent years, much research on sleep behavior largely disregarded its connections with the endocrine system. Use of both clinical studies and rodent models to investigate interactions between neuroendocrine function, including biological sex, and sleep therefore presents a promising area of further exploration. Further investigation of the neurobiological and neuroendocrine basis of sleep could have wide impact on a number of clinical and basic science fields. In this review, we summarize the state of basic sleep biology and its connections to the field of neuroendocrine biology, as well as suggest key future directions for the neuroendocrine regulation of sleep that may significantly impact new therapies for sleep disorders in women and men.

Decreased serum potassium may disturb sleep homeostasis in essential hypertensives

The aim is to investigate the association between alterations in the serum potassium (K+) concentration and sleep architecture parameters in essential hypertensives. Two hundred ninety-two hypertensives undergoing polysomnography and providing blood samples were recruited. The sleep architecture was composed of sleep stages 1 (N1), 2 (N2), 3 (N3), 4 (N4) and REM. The light sleep stage (LST) was composed of N1 + N2, and the deep sleep stage (DST) was composed of N3 + N4. The potentialrelationships between electrolytes and sleep parameters were determined via univariate and multivariate analyses. The subjects were divided into two groups via the serum K⁺ median (3.86 mmol/L). The K⁺ < 3.86 mmol/L group showed significantly decreased N1 (7.10 ± 4.55% vs 8.61 ± 5.23%, p = 0.002), LST (71.48 ± 11.33% vs 75.92 ± 17.08%, p = 0.013), and periodic leg movement during sleep related to microarousals (MA) /arousal (PLMS-A) [4 (1~10) vs 8 (3~15)/night, p < 0.001] and increased REM (17.38 ± 6.43% vs 15.37 ± 6.18%, p = 0.007) compared to the K⁺ ≥ 3.86 mmol/L group. A subdivided analysis by gender showed that these changes were more statistically significant in men than in women. Significant positive correlations were identified between K⁺ and N1 (r = 0.169, p = 0^.004), as well as PLMS-A (r = 0.222, p < 0.001) in subjects. Compared to women, a significantly strong correlation was identified between K+ and REM sleep in men (r = 0.158, p = 0.028 vs. r = 0.078, p = 0.442). Multiple linear regression analysis indicated that K+ is significantly associated with N1 in all subjects (p = 0.03) and with REM in men (p = 0.008), even after adjusting for confounders. Decreased K+ may disturb the homeostasis of the sleep architecture, and gender may interfere with their links in the hypertensive population.

Methamphetamine alters DNMT and HDAC activity in the posterior dorsal medial amygdala in an ovarian steroid-dependent manner

Methamphetamine (Meth) is a psychomotor stimulant associated with increased sexual drive and risky sexual behaviors in both men and women. Females are comparatively understudied, despite the fact that are just as likely as men to use methamphetamine. Importantly, Meth-associated sexual behaviors put female-users at a greater risk for unplanned pregnancies, and increase the risk of psychiatric co-morbidities such as depression. Our work in a rodent model has demonstrated that in the presence of the ovarian steroids, estradiol (EB) and progesterone (P), methamphetamine facilitates the activation of neurons of in the Medial Amygdala (MePD) and Ventromedial Nucleus of the Hypothalamus (VMN), nuclei that are integral to female sexual behavior. As methamphetamine has been previously associated with epigenetic changes in males, we hypothesized that methamphetamine may facilitate sexual motivation in females by modulating the amount of epigenetic enzymatic activity in the VMN and MePD. To test this hypothesis, histone deacetylase (HDAC) and DNA methyltransferase (DNMT) activity was quantitated in both the VMN and MePD in the presence and absence of methamphetamine in femalerats who were ovariectomized (OVX), or OVXed and hormone replaced with EB + P. DMNT1 and DNMT3B protein levels were also assessed. Our results show that methamphetamine alters DNMT and HDAC activity in the MePD in an ovarian steroid-dependent fashion. Both methamphetamine alone and EB + P alone significantly reduce DNMT enzymatic activity in an OVX female, but do not further decrease activity when both are given in combination. In contrast, no changes in HDAC or DNMT activity were seen in the VMN regardless of treatment, but the amount of DNMT3b after methamphetamine was significantly altered depending on the presence or absence of ovarian steroids. Taken together, these results support the hypothesis that methamphetamine induces change on an epigenetic level in female rats in both a hormone and nucleus dependent manner, and suggests epigenetic changes may play a role in methamphetamine's mechanism to facilitate the sexual motivation.

REM deprivation but not sleep fragmentation produces a sex-specific impairment in extinction

REM sleep is essential for learning and memory processes, particularly emotional learning. Manipulations of REM sleep impair learning and memory and sleep architecture is often altered following a learning experience; for example, short term REM deprivation immediately after fear conditioning results in impaired extinction. In light of research demonstrating sex-dependent differences in fear conditioning as well as differences in sleep architecture, the present study investigated the effects of short term REM deprivation on the extinction of conditioned fear in male and female rats. In addition, given evidence that sleep fragmentation, which is a consequence of REM deprivation, can negatively impact learning and memory, this manipulation was compared to REM deprivation and a control condition. Male and female rats were exposed to fear conditioning followed by 6 h of REM deprivation, sleep fragmentation, or a control condition. Two extinction sessions were conducted at 48 h intervals after conditioning. REM deprivation, but not sleep fragmentation or the control condition, impaired extinction of conditioned fear. However, this effect was seen only in male rats. This study is the first to explore the effects of sleep manipulations on memory in female rats and suggests that female rats are more resilient to the deleterious effects of REM deprivation. In addition, it demonstrates that REM deprivation but not fragmentation of sleep is responsible for impairment in extinction of conditioned fear.

Effects of hormonal contraceptives on sleep - A possible treatment for insomnia in premenopausal women

Due to the changes that took place since the 1970s, women have achieved important socioeconomic positions. Many tasks, including domestic and familiar ones, continue to be under women's responsibility, which leads to an overload work. Additionally, the female organism has its peculiarities due to hormonal changes. Adding all these factors up, women seem to be more vulnerable to stressing factors and consequently, might be prone to present several health problems. Within this scenario, one can point out insomnia as a highly prevalent disease among women, directly affecting performance and quality of life. Progesterone has an important effect over sleep, acting both as a hypnogenic and as a respiratory stimulant. Hormonal contraceptives are largely recognized among the modern society women; however, little is known about the effects of these drugs on sleep. This proposal hypothesizes that the use of hormonal contraceptives, mainly those based on progestagens could be a new therapeutic element for the treatment of insomnia and one more tool to be used to improve women´s sleep pattern and quality of life.

Acute Kynurenine Challenge Disrupts Sleep-Wake Architecture and Impairs Contextual Memory in Adult Rats

Study Objectives

Tryptophan metabolism via the kynurenine pathway may represent a key molecular link between sleep loss and cognitive dysfunction. Modest increases in the kynurenine pathway metabolite kynurenic acid (KYNA), which acts as an antagonist at N-methyl-d-aspartate and α7 nicotinic acetylcholine receptors in the brain, result in cognitive impairments. As glutamatergic and cholinergic neurotransmissions are critically involved in modulation of sleep, our current experiments tested the hypothesis that elevated KYNA adversely impacts sleep quality.

Methods

Adult male Wistar rats were treated with vehicle (saline) and kynurenine (25, 50, 100, and 250 mg/kg), the direct bioprecursor of KYNA, intraperitoneally at zeitgeber time (ZT) 0 to rapidly increase brain KYNA. Levels of KYNA in the brainstem, cortex, and hippocampus were determined at ZT 0, ZT 2, and ZT 4, respectively. Analyses of vigilance state-related parameters categorized as wake, rapid eye movement (REM), and non-REM (NREM) as well as spectra power analysis during NREM and REM were assessed during the light phase. Separate animals were tested in the passive avoidance paradigm, testing contextual memory.

Results

When KYNA levels were elevated in the brain, total REM duration was reduced and total wake duration was increased. REM and wake architecture, assessed as number of vigilance state bouts and average duration of each bout, and theta power during REM were significantly impacted. Kynurenine challenge impaired performance in the hippocampal-dependent contextual memory task.

Conclusions

Our results introduce kynurenine pathway metabolism and formation of KYNA as a novel molecular target contributing to sleep disruptions and cognitive impairments.

Sleep architecture is altered in the reserpine-induced fibromyalgia model in ovariectomized rats

Fibromyalgia (FM) is a musculoskeletal chronic pain syndrome with various concomitant symptoms like sleep disorders. FM patients are mainly women and menopause might play an important role in the altered processing of somatosensory information. Adverse effects and moderated efficacy of drugs promote treatment discontinuation by patients. Animal models of FM report pain and depression-like behaviors, but none of them have explored sleep disturbance as possible marker in the preclinic diagnostic. The aim of this study was to investigate alterations of the sleep architecture in the reserpine (RES)-induced FM model in ovarectomized (OVX) rats. The behavioral thresholds of nociceptive response in the experimental FM were analyzed in a first block using muscle pressure, tactile response and allodynia to cold stimulus. In a second block, the sleep-wake cycle was examined in a polysomnographic study. Groups (n = 8) consisted in: (a) no treatment, (b) RES vehicle, (c) RES alone, (d) RES + vehicle of fluoxetine (FLX, antidepressant reference drug), and (e) RES + FLX. Our results demonstrated that RES induced pain-related behavior (50-70%) in OVX rats and altered sleep architecture by the increase of total wake time (38%), diminution of the no-REM stage (SWS-I 33% and SWS-II 76%), and abolition of the REM sleep, effects that were partially reverted in the presence of FLX. In conclusion, our results support the face validity of the RES-induced pain-related behavior as FM model showing nociceptive behavioral responses associated to sleep alterations observed as symptoms in FM patients; thus, these evidences substantiate its usefulness to look for alternatives of treatment for FM symptoms.

Sex differences in age-related changes in the sleep-wake cycle

Age-related changes in sleep and circadian regulation occur as early as the middle years of life. Research also suggests that sleep and circadian rhythms are regulated differently between women and men. However, does sleep and circadian rhythms regulation age similarly in men and women? In this review, we present the mechanisms underlying age-related differences in sleep and the current state of knowledge on how they interact with sex. We also address how testosterone, estrogens, and progesterone fluctuations across adulthood interact with sleep and circadian regulation. Finally, we will propose research avenues to unravel the mechanisms underlying sex differences in age-related effects on sleep.

Ovarian hormones, sleep and cognition across the adult female lifespan: An integrated perspective

Loss of ovarian function in women is associated with sleep disturbances and cognitive decline, which suggest a key role for estrogens and/or progestins in modulating these symptoms. The effects of ovarian hormones on sleep and cognitive processes have been studied in separate research fields that seldom intersect. However, sleep has a considerable impact on cognitive function. Given the tight connections between sleep and cognition, ovarian hormones may influence selective aspects of cognition indirectly, via the modulation of sleep. In support of this hypothesis, a growing body of evidence indicates that the development of sleep disorders following menopause contributes to accelerated cognitive decline and dementia in older women. This paper draws from both the animal and human literature to present an integrated view of the effects of ovarian hormones on sleep and cognition across the adult female lifespan.

The middle-aged ovariectomized marmoset (Callithrix jacchus) as a model of menopausal symptoms: Preliminary evidence

Menopausal women often suffer from hot flashes and sleep disturbances that significantly impact their quality of life. Both human and animal studies suggest that loss of estrogens during menopause contribute to these symptoms. In the female rat, both core body temperature (CBT) and sleep are sensitive to 17β-estradiol (E2) levels, but important differences between the rat and the human patterns limit the interpretation of the results. The sleep and thermoregulation of the common marmoset (Callithrix jacchus) more closely resemble human patterns. However, no study to date has examined whether E2 influences sleep and thermoregulation in this species. The main goal of the present study was to investigate the suitability of the ovariectomized (OVX) marmoset for studying two major menopausal symptoms experienced by women, sleep disturbance and thermodysregulation. Two middle-aged OVX marmosets (6years old) were implanted with a telemeter that records electroencephalograms (EEG), electromyograms (EMG), and CBT. Sleep patterns and CBT were recorded under baseline, two E2 replacement (6 and 12μg/kg/day, p.o.) conditions and two E2 withdrawal conditions. Relative to both baseline and withdrawal, high E2 replacement was associated with lower nighttime CBT. In addition, fewer nighttime arousals were observed under low E2 replacement compared to baseline. Higher delta power was observed under both E2 replacement conditions suggesting enhanced sleep quality. These preliminary results suggest that E2 modulates sleep and thermoregulation in the OVX marmoset, making it a promising model for studying menopausal symptoms.

Morningness-Eveningness and Physical Activity in Adolescent Girls: Menarche as a Transition Point

This study identified trajectories of morningness-eveningness (M-E) and physical activity when chronological (i.e., time since birth) versus gynecological (i.e., time since menarche) age is used to indicate maturation. Piecewise models were fit for girls (N = 262, ages 11-19) using chronological or gynecological age as the time metric. Girls stayed up later (i.e., eveningness) as they approach menarche. After menarche no change in M-E was observed. In contrast, no change in M-E was detected with chronological age. No change in physical activity was observed before menarche, and physical activity declined after menarche. With chronological age, physical activity declined as girls got older. Gynecological age may be more appropriate than chronological age as a metric for understanding changes in M-E and physical activity.

Androgen-primed castrate males are sufficient for methamphetamine-facilitated increases in proceptive behavior in female rats

Methamphetamine (MA) is a psychomotor stimulant associated with increases in sex drive in both men and women. Women, however, are far more likely to face social disadvantages as a consequence of MA use, and their increased sexual motivation poses additional health concerns such as unplanned pregnancies. To better understand the mechanisms underlying MA-facilitated sexual motivation in females, we previously established a rodent model where a "binge"-type administration paradigm of MA to sexually receptive female rats significantly increases proceptive behavior in the presence of a sexually active, gonadally-intact male. Our previous work with this model has led us to consider whether the increases in proceptive behavior are truly indicative of increased sexual motivation, or instead a consequence of heightened motor responsivity. Here, we test whether MA-induced increases in proceptive behaviors are specific to a sexually relevant stimulus. Females' sexual, social, exploratory behaviors, and interaction times were scored during the exposure to stimulus males, including castrates, and dihydrotestosterone (DHT)-treated castrates. MA-treated females demonstrated significant increases in proceptive behaviors toward DHT-treated castrate males but not toward castrate males. While the non-MA-treated females did display proceptive behavior, there was no significant difference between behaviors elicited by DHT-CX males compared to CX males. Our results support the hypothesis that MA facilitates proceptive behavior only in response to specific, androgen mediated sexually-relevant cues.

Sex differences in sleep: impact of biological sex and sex steroids

Men and women sleep differently. While much is known about the mechanisms that drive sleep, the reason for these sex differences in sleep behaviour is unknown and understudied. Historically, women and female animals are underrepresented in studies of sleep and its disorders. Nevertheless, there is a growing recognition of sex disparities in sleep and rhythm disorders. Women typically report poorer quality and more disrupted sleep across various stages of life. Findings from clinical and basic research studies strongly implicate a role for sex steroids in sleep modulation. Understanding how neuroendocrine mediators and sex differences influence sleep is central to advancing our understanding of sleep-related disorders. The investigation into sex differences and sex steroid modulation of sleep is in its infancy. Identifying the mechanisms underlying sex and gender differences in sleep will provide valuable insights leading to tailored therapeutics that benefit each sex. The goal of this review is to discuss our current understanding of how biological sex and sex steroids influence sleep behaviour from both the clinical and pre-clinical perspective.

The Neurobiology of Sleep and Wakefulness

Cortical electroencephalographic activity arises from corticothalamocortical interactions, modulated by wake-promoting monoaminergic and cholinergic input. These wake-promoting systems are regulated by hypothalamic hypocretin/orexins, while GABAergic sleep-promoting nuclei are found in the preoptic area, brainstem and lateral hypothalamus. Although pontine acetylcholine is critical for REM sleep, hypothalamic melanin-concentrating hormone/GABAergic cells may "gate" REM sleep. Daily sleep-wake rhythms arise from interactions between a hypothalamic circadian pacemaker and a sleep homeostat whose anatomical locus has yet to be conclusively defined. Control of sleep and wakefulness involves multiple systems, each of which presents vulnerability to sleep/wake dysfunction that may predispose to physical and/or neuropsychiatric disorders.

Sleep regulation and sex hormones exposure in men and women across adulthood

This review aims to discuss how endogenous and exogenous testosterone exposures in men and estrogens/progesterone exposures in women interact with sleep regulation. In young men, testosterone secretion peaks during sleep and is linked to sleep architecture. Animal and human studies support the notion that sleep loss suppresses testosterone secretion. Testosterone levels decline slowly throughout the aging process, but relatively few studies investigate its impact on age-related sleep modifications. Results suggest that poorer sleep quality is associated with lower testosterone concentrations and that sleep loss may have a more prominent effect on testosterone levels in older individuals. In women, sex steroid levels are characterized by a marked monthly cycle and reproductive milestones such as pregnancy and menopause. Animal models indicate that estrogens and progesterone influence sleep. Most studies do not show any clear effects of the menstrual cycle on sleep, but sample sizes are too low, and research designs often inhibit definitive conclusions. The effects of hormonal contraceptives on sleep are currently unknown. Pregnancy and the postpartum period are associated with increased sleep disturbances, but their relation to the hormonal milieu still needs to be determined. Finally, studies suggest that menopausal transition and the hormonal changes associated with it are linked to lower subjective sleep quality, but results concerning objective sleep measures are less conclusive. More research is necessary to unravel the effects of vasomotor symptoms on sleep. Hormone therapy seems to induce positive effects on sleep, but key concerns are still unresolved, including the long-term effects and efficacy of different hormonal regimens.

In utero exposure to valproic acid changes sleep in juvenile rats: a model for sleep disturbances in autism

STUDY OBJECTIVES

To determine whether sleep disturbances are found in the valproic acid model of autism spectrum disorders (ASD).

DESIGN

Comparative study for sleep behavior, sleep architecture, electroencephalogram (EEG) spectral analysis, and glutamic acid decarboxylase (GAD) 65/67 protein expression in juvenile rats exposed to valproic acid (VPA), sodium salt, or saline in utero.

SETTING

N/A.

PARTICIPANTS

Juvenile (postnatal day 32) male and female Sprague-Dawley rats.

INTERVENTIONS

In utero exposure to either saline or 400 mg/kg VPA administered intraperitoneally to the dams on gestational day 12.5. On postnatal days 22-24, all rats were implanted with transmitters to record EEG and electromyogram (EMG) activity.

MEASUREMENTS AND RESULTS

During the light phase, when nocturnal animals are typically quiescent, the VPA-exposed animals spent significantly more time in wake (∼35 min) and significantly less time in non-rapid eye movement (NREM) sleep (∼26 min) compared to the saline controls. Furthermore, spectral analysis of the EEG revelled that VPA-exposed animals exhibited increased high-frequency activity during wake and rapid eye movement (REM) sleep and reduced theta power across all vigilance states. Interestingly, the gamma-aminobutyric acid (GABA)-ergic system, which modulates the induction and maintenance of sleep states, was also disrupted, with reduced levels of both GAD 65 and GAD67 in the cortical tissue of VPA-exposed animals compared to saline controls.

CONCLUSIONS

To date, the current animal models of ASD have been underutilized in the investigation of associated sleep disturbances. The VPA animal model recapitulates aspects of sleep disruptions reported clinically, providing a tool to investigate cellular and molecular dysregulation contributing to sleep disruptions in ASD.

Exploring sex and gender differences in sleep health: a Society for Women's Health Research Report

Previous attempts have been made to address sleep disorders in women; however, significant knowledge gaps in research and a lack of awareness among the research community continue to exist. There is a great need for scientists and clinicians to consider sex and gender differences in their sleep research to account for the unique biology of women. To understand the role of sex differences in sleep and the state of women's sleep health research, the Society for Women's Health Research convened an interdisciplinary expert panel of well-established sleep researchers and clinicians for a roundtable meeting. Focused discussions on basic and clinical research along with a focus on specific challenges facing women with sleep-related problems and effective therapies led to the identification of knowledge gaps and the development of research-related recommendations. Additionally, sex differences in sleep disorders were noted and discussed in the context of underlying hormonal differences. Differences in sleep behavior and sleep disorders may not only be driven by biological factors but also by gender differences in the way women and men report symptoms. Progress has been made in identifying sex and gender differences in many areas of sleep, but major research gaps in the areas of epidemiology, sleep regulation, sleep quality, diagnosis, and treatment need to be addressed. Identifying the underlying nature of sex and gender differences in sleep research has potential to accelerate improved care for both men and women facilitating better diagnosis, treatment, and ultimately prevention of sleep disorders and related comorbid conditions.

The relationship between sleep disorders and testosterone

PURPOSE OF REVIEW

This review describes evolving concepts and recent data on the relationship between serum testosterone levels and normal and disordered sleep.

RECENT FINDINGS

Sex-related differences in circadian rhythms and sleep physiology are in part due to organizational and activational effects of sex steroids. Testosterone affects the organization of circadian rhythms and the timing, but not the duration, of sleep. Increasing testosterone during puberty leads to later bedtimes. The diurnal variation in testosterone depends on sleep rather than circadian rhythm or season. Pubertal onset is heralded, well before virilization, by a luteinizing hormone level at least 3.7 U/l during sleep. Total sleep deprivation lowers testosterone, but sleep restriction only does so if it occurs in the first half of the night. The recovery of testosterone from sleep disruption is impaired in old as compared with young rodents. In men with obstructive sleep apnoea (OSA), low testosterone is related to obesity rather than the OSA itself, and improves with weight loss but inconsistently with continuous positive airway pressure (CPAP). Testosterone treatment only transiently worsens severity of OSA, which need not be considered a contraindication to its use.

SUMMARY

Testosterone treatment is unlikely to benefit sleep in men with secondary hypogonadism, for example due to obesity or depression, in contrast to the management of the underlying abnormality.

Gonadal steroid modulation of sleep and wakefulness in male and female rats is sexually differentiated and neonatally organized by steroid exposure

The paucity of clinical and preclinical studies investigating sex differences in sleep has resulted in mixed findings as to the exact nature of these differences. Although gonadal steroids are known to modulate sleep in females, less is known about males. Moreover, little evidence exists concerning the origin of these sex differences in sleep behavior. Thus, the goal of this study was to directly compare the sensitivity of sleep behavior in male and female Sprague Dawley rats to changes in the gonadal steroid milieu and to test whether the sex differences in sleep are the result of brain sexual differentiation or differences in circulating gonadal steroids. Here we report the magnitude of change in sleep behavior induced by either estradiol (E2) or testosterone (T) was greater in females compared with males, suggesting that sleep behavior in females is more sensitive to the suppressive effects of gonadal steroids. Furthermore, we demonstrated that the organizational effects of early gonadal steroid exposure result in male-like responsivity to gonadal steroids and directly alter the activity of the ventrolateral preoptic area (VLPO), an established sleep-promoting nucleus, in adult masculinized females. Moreover, the nonaromatizable androgen dihydrotestosterone did not suppress sleep in either males or females, suggesting that the T-mediated effect in females was due to the aromatization of T into E2. Together our data suggest that, like sex behavior, sex differences in sleep follow the classical organizational/activational effects of gonadal steroids.

Sex differences in circadian timing systems: implications for disease

Virtually every eukaryotic cell has an endogenous circadian clock and a biological sex. These cell-based clocks have been conceptualized as oscillators whose phase can be reset by internal signals such as hormones, and external cues such as light. The present review highlights the inter-relationship between circadian clocks and sex differences. In mammals, the suprachiasmatic nucleus (SCN) serves as a master clock synchronizing the phase of clocks throughout the body. Gonadal steroid receptors are expressed in almost every site that receives direct SCN input. Here we review sex differences in the circadian timing system in the hypothalamic-pituitary-gonadal axis (HPG), the hypothalamic-adrenal-pituitary (HPA) axis, and sleep-arousal systems. We also point to ways in which disruption of circadian rhythms within these systems differs in the sexes and is associated with dysfunction and disease. Understanding sex differentiated circadian timing systems can lead to improved treatment strategies for these conditions.