Shift work and circadian dysregulation of reproduction

Prediction of pregnancy disorders in female workers in the industrial sector

Context

As female workers face a higher risk of exposure to workplace hazards than women in general, it is imperative that measures be put in place in the workplace to ensure safe and healthy pregnancies.

Objectives

This study aimed to analyze the effects of occupational hazards in the workplace environment on the potential for pregnancy disorders experienced by female workers.

Methods

This was an analytical, observational study with a case-control design. The participants were female workers who worked in industrial environments in both formal and nonformal industries. The inclusion criteria used in this study were female workers who had been or were pregnant at the time of the study, had worked in the industrial sector for at least one year, and did not smoke or consume alcohol. The samples were collected from 144 female workers. Midwives assisted in collecting data and conducting examinations of female workers. This study was conducted in Surabaya and Sidoarjo between June and December 2020. Data were analyzed descriptively, and a multivariable logistic regression test was performed. The study was conducted in accordance with the health protocols and prevention of COVID-19.

Results

The results showed that occupational hazards in the workplace environment that affect pregnancy disorders include workload (p = 0.004, OR = 28.676 (2.979-276.076); hot working environment (p = 0.014, OR = 3.077 (1.254-7.552); strong odors (p = 0.017, OR = 7.640 (1.436-40.656); shift work (p = 0.023, OR = 8.063 (1.337-48.623); irregular shift work (p = 0.018, OR = 7.371 (1.409-38.557); and night shift work (p = 0.015, OR = 11.780 (1.605-86.450).

Conclusions

Companies are expected to pay special attention to female workers regarding various workplace controls to prevent potential pregnancy-related disorders.

Nightshift work and irregular menstrual cycle: 8-year follow-up cohort study

BACKGROUND

Irregular menstruation is a major health problem among women, although its association with nightshift work remains controversial.

AIMS

To study the association between nightshift work and irregular menstrual cycle among female workers and investigate any differences according to sleep quality, working hours or obesity.

METHODS

This study included female workers who underwent health examinations from 2012 to 2019. Nightshift work, working hours, sleep quality and menstrual cycles were assessed using self-administered questionnaires. Irregular menstrual cycle was defined as self-reported irregular or ≥36 days. Adjusted odds ratios and 95% confidence intervals (CIs) were calculated by multivariable logistic regression; adjusted hazard ratios (95% CIs) for incident irregular menstrual cycle were calculated by Cox proportional hazard models with time-dependent analysis.

RESULTS

The study participants were 87 147 in the cross-sectional study and 41 516 in the longitudinal study. After adjusting for all covariates in the cross-sectional analyses, the odds ratio for prevalent irregular menstrual cycle among female nightshift workers versus the reference was 1.26 (95% CI 1.2-1.33). In the cohort study, the adjusted hazard ratio for incident irregular menstrual cycle among nightshift workers was 1.95 (95% CI 1.61-2.35) in the period after 6 years. No significant differences were observed among subgroups stratified by sleep quality, working hours or obesity.

CONCLUSIONS

Nightshift work is associated with an increased risk of both prevalent and incident irregular menstrual cycle in female workers without significant interactions by sleep quality, working hours or obesity.

A Retrospective Review on Dysregulated Autophagy in Polycystic Ovary Syndrome: From Pathogenesis to Therapeutic Strategies

The main purpose of this article is to explore the relationship between autophagy and the pathological mechanism of PCOS, and to find potential therapeutic methods that can alleviate the pathological mechanism of PCOS by targeting autophagy. Relevant literatures were searched in the following databases, including: PubMed, MEDLINE, Web of Science, Scopus. The search terms were "autophagy", "PCOS", "polycystic ovary syndrome", "ovulation", "hyperandrogenemia", "insulin resistance", "inflammatory state", "circadian rhythm" and "treatment", which were combined according to the retrieval methods of different databases. Through analysis, we uncovered that abnormal levels of autophagy were closely related to abnormal ovulation, insulin resistance, hyperandrogenemia, and low-grade inflammation in patients with PCOS. Lifestyle intervention, melatonin, vitamin D, and probiotics, etc. were able to improve the pathological mechanism of PCOS via targeting autophagy. In conclusion, autophagy disorder is a key pathological mechanism in PCOS and is also a potential target for drug development and design.

A novel lncRNA LOC105613571 binding with BDNF in pituitary promotes gonadotropin secretion by AKT/ERK-mTOR pathway in sheep associated with prolificacy

The pituitary is a vital endocrine organ for synthesis and secretion of gonadotropic hormones (FSH and LH), and the gonadotropin showed fluctuations in animals with different fecundity. Long non-coding RNAs (lncRNAs) have been identified as regulatory factors for the reproductive process. However, the profiles of lncRNAs and their roles involved in sheep fecundity remains unclear. In this study, we performed RNA-sequencing for the sheep pituitary gland associated with different fecundity, and identified a novel candidate lncRNA LOC105613571 targeting BDNF related to gonadotropin secretion. Our results showed that expression of lncRNA LOC105613571 and BDNF could be significantly upregulated by GnRH stimulation in sheep pituitary cells in vitro. Notably, either lncRNA LOC105613571 or BDNF silencing inhibited cell proliferation while promoted cell apoptosis. Moreover, lncRNA LOC105613571 knockdown could also downregulate gonadotropin secretion via inactivation AKT, ERK and mTOR pathway. In addition, co-treatment with GnRH stimulation and lncRNA LOC105613571 or BDNF knockdown showed the opposite effect on sheep pituitary cells in vitro. In summary, BDNF-binding lncRNA LOC105613571 in sheep regulates pituitary cell proliferation and gonadotropin secretion via the AKT/ERK-mTOR pathway, providing new ideas for the molecular mechanisms of pituitary functions.

Examining the Impact of Burnout on Hospital Nurses Engaged in Shift Work: Insights From a Nationwide Cross-Sectional Study in Malaysia

Introduction

Shift workers follow nonstandard schedules that encompass overnight duty, rotational timetables, or permanent night work which can lead to misaligned core circadian physiology. Shift work has been associated with sleep deprivation, burnout, and metabolic syndrome among healthcare workers.

Objective

We aimed to examine if shift nurses working in Malaysian public hospitals are more predisposed to burnout and to determine the predictors of burnout in this profession.

Method

This national-level cross-sectional study was conducted among nurses in public hospitals in Malaysia between July and November 2019 using self-administered questionnaires. Maslach Burnout Inventory-Human Service Survey was used to determine burnout. Multistage stratified sampling was used to recruit nurses from 32 hospitals. A complex sampling analysis was performed.

Results

Among the 1,491 hospital nurses, more than half (70.8%) of them followed shift work schedules. Shift nurses were mostly below 40 years old (80.9%), diploma holders (87.2%), and of lower professional grades (64.2%). The prevalence of overall burnout, as well as the domains of emotional exhaustion and depersonalization, was higher among shift nurses (27.1%) as compared to their counterparts (22.4%). Nurses who performed more than six night shifts per month were 2.6 times more predisposed to burnout.

Conclusion

Shift work is integral to ensure round-the-clock nursing care for patients. However, nurses are increasingly faced with more shift duties due to heavy patient loads and staff shortages. Modified work schedules must be implemented to provide sufficient rest time for shift nurses to mitigate burnout. Additionally, proper human resource projection and distribution are imperative to prevent worsening burnout.

Evaluation of chronotype and sleep quality in infertile population and comparison with fertile population: a cross-sectional study

PURPOSE

Infertility is a stressful condition for couples and can affect patients' circadian rhythm and sleep quality. The goal of this study is to assess differences in chronotype and sleep quality between infertile and fertile people.

METHODS

A cross-sectional study was conducted. The infertile patient population consisted study group. Primiparous patients without any known gynecological disease who presented for routine cervical cancer screening follow-up were included in the control group. The Turkish version of the Morningness-Eveningness Questionnaire (MEQ) and Pittsburg Sleep Quality Index (PSQI) scores were evaluated between groups.

RESULTS

A total of 227 patients were assessed. There were 110 patients in the study (infertile) group and 117 patients in the control (fertile) group. The evening chronotype proportion (23.6 vs. 0.9%, p < 0.001) was higher in the infertile group. The median of MEQ score was significantly higher in the fertile patients (50, IQR = 43 - 55 vs. 56, IQR = 51 - 59; p < 0.001), and the median of PSQI score was significantly higher in the infertile patients (5, IQR = 4 - 6, vs. 4, IQR = 3 - 5; p < 0.001).

CONCLUSIONS

In this study, we found significantly worse sleep quality, and more evening chronotype in the patients with infertility.

The Role of Gut Microbiota in Gestational Diabetes Mellitus Affecting Intergenerational Glucose Metabolism: Possible Mechanisms and Interventions

The incidence of type 2 diabetes is increasing every year and has become a serious public health problem. In addition to genetic factors, environmental factors in early life development are risk factors for diabetes. There is growing evidence that the gut microbiota plays an important role in glucose metabolism, and the gut microbiota of pregnant women with gestational diabetes mellitus (GDM) differs significantly from that of healthy pregnant women. This article reviews the role of maternal gut microbiota in offspring glucose metabolism. To explore the potential mechanisms by which the gut microbiota affects glucose metabolism in offspring, we summarize clinical studies and experimental animal models that support the hypothesis that the gut microbiota affects glucose metabolism in offspring from dams with GDM and discuss interventions that could improve glucose metabolism in offspring. Given that adverse pregnancy outcomes severely impact the quality of survival, reversing the deleterious effects of abnormal glucose metabolism in offspring through early intervention is important for both mothers and their offspring.

Maternal Occupational Risk Factors and Preterm Birth: A Systematic Review and Meta-Analysis

Objective: This systematic review and meta-analysis aimed to summarize the evidence on the relationship between physical occupational risks (high physical workload, long working hours, shift work, whole-body vibrations, prolonged standing, and heavy lifting) and preterm birth. Methods: A systematic review and meta-analysis was conducted across six databases to investigate the relationship between physical occupational risks and preterm birth. Result: A comprehensive analysis of 37 studies with varying sample sizes found moderate evidence of positive associations between high physical workload, long working hours, shift work, whole-body vibration, and preterm birth. Meta-analysis showed a 44% higher risk (OR 1.44, 95% CI 1.25-1.66) for preterm birth with long working hours and a 63% higher risk (OR 1.63, 95% CI 1.03-2.58) with shift work. Conclusion: Pregnant women in physically demanding jobs, those working long hours or on shifts, and those exposed to whole-body vibration have an increased risk of preterm birth. Employers should establish supportive workplaces, policymakers implement protective measures, healthcare providers conduct screenings, and pregnant women must stay informed and mitigate these job-related risks. Systematic Review Registration: [https://www.crd.york.ac.uk/prospero/], Identifier [CRD42022357045].

First-trimester occupational exposures and hypertensive disorders of pregnancy among US nurses

BACKGROUND

Limited and conflicting data exist regarding the impact of first-trimester nursing occupational exposures on hypertensive disorders of pregnancy (HDP).

AIMS

To investigate whether first-trimester night shift work, work hours and work-related activities are associated with HDP.

METHODS

We conducted a cross-sectional analysis of 6610 women within the Nurses' Health Study II. We used multiple logistic regression to estimate the odds ratios (ORs) and 95% confidence intervals (CIs) for the relation of occupational exposures to HDP.

RESULTS

Nine per cent of respondents reported an HDP in the index pregnancy (gestational hypertension: n = 354, 5%, preeclampsia: n = 222, 3%). First-trimester fixed or rotating night shift work was not significantly associated with gestational hypertension or preeclampsia compared to day shift work only. Compared to those working 21-40 h/week, working overtime (≥41 h/week) was not associated with gestational hypertension but was associated with 43% higher odds of preeclampsia (95% CI 1.02, 2.00). For part-time work (≤20 h/week), the OR was 0.76 (95% CI 0.56, 1.02) for gestational hypertension and 0.64 (95% CI 0.43, 0.97) for preeclampsia. The odds of preeclampsia were 3% higher per additional hour worked per week (95% CI 1.01-1.04). Compared to 0-4 h spent standing or walking per day, standing or walking ≥9 h daily was associated with 32% lower odds of gestational hypertension (95% CI 0.47, 0.99) but was not significantly associated with preeclampsia. Frequency of heavy lifting was not associated with either hypertensive disorder or pregnancy.

CONCLUSIONS

Among nurses, working overtime was associated with higher odds of preeclampsia.

Sleep characteristics before assisted reproductive technology treatment predict reproductive outcomes: a prospective cohort study of Chinese infertile women

Sleep disorders affect mental and physical health. Infertile women undergoing assisted reproductive technology (ART) treatment are prone to sleep disorders. Sleep condition, its influencing factors, and the association between sleep condition and ART treatment outcomes before treatment have not been explored within a population with a large sample size. Therefore, we investigated the sleep characteristics of 1002 Chinese infertile women before ovulation induction and investigated the influencing factors (negative and positive psychological factors, demographics, and fertility characteristics). We also examined whether sleep conditions before treatment predicted reproductive outcomes. We found that 24.1% of participants reported poor sleep quality. Women with primary infertility reported poorer sleep than women with secondary infertility. Negative psychological factors, including depression, anxiety, and perceived stress were associated with poor sleep, whereas positive affect was linked with good sleep. Adverse sleep characteristics, including poor subjective sleep quality, sleep disturbances, and poor sleep efficiency, decreased the quantity and quality of oocytes retrieved, fertilization rates, and clinical pregnancy rates. This study indicates that before ART treatment, a large number of females with infertility suffer from sleep problems, which are affected by psychological factors and infertility type, and unhealthy sleep characteristics may impair treatment outcomes. Our findings highlight the importance of screening and treatment for sleep disorders before the enrollment of ART treatment in infertile women.

Impact of high-fat diet and exposure to constant light on reproductive competence of female ICR mice

Obesity and exposure to light at night are prevalent in modern society and associated with changes in physiology and behavior that can affect a female's ability to support offspring growth during pregnancy and lactation. A 2X3 factor study of ICR mice was conducted to determine the effect of diet [control (CON; 10% fat) or high fat (HF; 60% fat)] and exposure to regular 12 h light:dark cycles (LD) or continuous low (L5) or high (L100) lux of light on gestation length, birth litter size, milk composition and litter growth to lactation day 12. HF diet reduced birth litter size, but increased postnatal d 12 litter weight (P<0.05), whereas constant light tended to increase litter weight (P=0.07). Continuous light increased gestation length, altered dam feed intake, increased serum prolactin and increased final dam and mammary gland weight (P<0.05), while decreasing mammary ATP content and milk lactose (P<0.05). Correlation analysis indicated a positive relationship between final litter weight and mammary size, metabolic stores (e.g. maternal fat pad weight), kcal of feed intake, and gestation length (P<0.05). Although CON mice spent more time eating than HF dams, the calorically dense HF diet was related to greater rates of litter growth to peak lactation. Constant light circadian disrupting effects appear to be confounded by a potential long day photoperiod response exemplified by higher circulating levels of prolactin and increased body and mammary weight of females exposed to these conditions. Other model systems may be better to study the interacting effects of obesity and circadian disruption on reproductive competence.

Latitudinal and zoo specific zeitgebers influence circadian and circannual rhythmicity of behavior in captive giant pandas (Ailuropoda melanoleuca)

Introduction

The circadian clock influences many aspects of animal welfare including metabolism, breeding, and behavior. In most species, circadian clocks are internal clocks regulated by external environmental cues called zeitgebers. The most common zeitgebers are light/dark cycles, food, and temperature. However, within captive environments, animals can be housed at latitudes with different light/dark cycles than their natural habitat and most other zeitgebers are controlled by humans. The effects that modified zeitgebers have on captive animals' circadian and circannual rhythmicity is largely unknown. To explore this and potential welfare implications, we measured and analyzed observational behavioral data of zoo-housed giant pandas for one year utilizing live camera footage from six zoos across the world. The worldwide distribution of the zoos gives us the unique opportunity to investigate how housing giant pandas within and outside of their natural latitudinal range can affect circadian rhythmicity and behavior.

Methods

Focal sampling was completed for 11 giant pandas each month for 12 consecutive months to gain an estimate of one circannual cycle. Within each month, we estimated one daylight or 24 h cycle of activity/behavior by conducting 10-min observation sessions systemically each hour the pandas were visible.

Results

Zero-inflated negative binomial mixture models found that latitude is associated with activity levels, with pandas housed outside of their natural latitudinal range displaying less activity than those within their latitudinal range. Amount of daylight, temperature minimum, and temperature range were also associated with activity cycles, potentially acting as zeitgebers. An association between sexual-related and stereotypic behavioral cycles was found, with the circannual cycles fluctuating in synchrony throughout several points in a year.

Discussion

These results indicate that changes to common zeitgebers and environmental conditions can influence circadian and circannual cycles. The widespread evolution of circadian rhythms suggests an adaptive advantage to possessing one in an environment with cyclical changes, allowing species to anticipate changes in their environment and respond accordingly. Therefore, although animals are highly adaptive, creating a captive environment that mimics the environmental conditions for which the animal has evolved can encourage naturalistic cycles that ultimately aid in promoting positive welfare states and increasing chances of successful breeding and conservation.

Menstrual disturbances and its association with sleep disturbances: a systematic review

BACKGROUND

Menstrual disturbances harm women's health, and general well-being. As growing evidence highlights the relationship between sleep and menstrual disturbances, it is imperative to comprehensively examine the association between sleep and menstrual disturbance considering the multiple dimensions of sleep. This systematic review aims to identify the association between sleep and menstrual disturbances by evaluating using Buysse's sleep health framework.

METHODS

A comprehensive search of the literature was conducted in PubMed, EMBASE, psychINFO, and CINAHL to identify publications describing any types of menstrual disturbances, and their associations with sleep published between January 1, 1988 to June 2, 2022. Quality assessment was conducted using the Joanna Briggs Institute Critical Appraisal Checklist for Analytical Cross-Sectional Studies. The findings were iteratively evaluated menstrual disturbances and their association with sleep using Buysse's sleep health framework. This framework understands sleep as multidimensional concept and provides a holistic framing of sleep including Satisfaction, Alertness during waking hours, Timing of sleep, Efficiency, and Sleep duration. Menstrual disturbances were grouped into three categories: premenstrual syndrome, dysmenorrhea, and abnormal menstrual cycle/heavy bleeding during periods.

RESULTS

Thirty-five studies were reviewed to examine the association between sleep and menstrual disturbances. Premenstrual syndrome and dysmenorrhea were associated with sleep disturbances in sleep health domains of Satisfaction (e.g., poor sleep quality), Alertness during waking hours (e.g., daytime sleepiness), Efficiency (e.g., difficulty initiating/maintaining sleep), and Duration (e.g., short sleep duration). Abnormal menstrual cycle and heavy bleeding during the period were related to Satisfaction, Efficiency, and Duration. There were no studies which investigated the timing of sleep.

CONCLUSIONS/IMPLICATIONS

Sleep disturbances within most dimensions of the sleep health framework negatively impact on menstrual disturbances. Future research should longitudinally examine the effects of sleep disturbances in all dimensions of sleep health with the additional objective sleep measure on menstrual disturbances. This review gives insight in that it can be recommended to provide interventions for improving sleep disturbances in women with menstrual disturbance.

Understanding Circadian and Circannual Behavioral Cycles of Captive Giant Pandas (Ailuropoda melanoleuca) Can Help to Promote Good Welfare

Circadian and circannual cycles of behavior regulate many aspects of welfare including metabolism, breeding, and behavioral interactions. In this study, we aim to demonstrate how systematically determining circadian and circannual cycles can provide insight into animals' needs and be part of an evidence-based approach to welfare assessment. We measured and analyzed the observational behavioral data of 13 zoo-housed giant pandas (Ailuropoda melanoleuca), across life stages and between sexes, each month for one year using live camera footage from six zoos across the world. Our results indicate that life stage was associated with changes in overall activity, feeding, locomotion, and pacing, and that sex influenced scent anointing and anogenital rubbing. Overall, the circadian rhythms showed three peaks of activity, including a nocturnal peak, as seen in wild giant pandas. We also found associations between sexual-related, stereotypical/abnormal, and feeding behavior, which are possibly linked to the timing of migration of wild pandas, and elucidated the relationship between a mother and cub, finding that they concentrate maternal behaviors to mainly after closing hours. Understanding these cycle patterns can aid animal care staff in predicting changing needs throughout the day, year, and life cycle and preemptively provide for those needs to best avoid welfare concerns.

Circadian hormone secretion of enteroendocrine cells: implication on pregnancy status

The timing of food intake is a key cue for circadian rhythms in humans and animals. In response to food intake, gut hormones called incretin are produced by intestinal enteroendocrine cells in a circadian rhythm that stimulates insulin secretion and regulates body weight and energy expenditure. Pregnancy is associated with the expansion of β cells, the risk of gestational diabetes mellitus, and excessive weight gain. The timing of food intake is a good way to address metabolic complications during pregnancy. The current review focuses on the circadian rhythms and biological actions of enteroendocrine hormones and their associations with pregnancy status, specifically topics like food intake and gut circadian rhythms, the circadian secretion of enteroendocrine peptides, and the effects of these factors during pregnancy.

Gestational exposure to continuous light impairs the development of the female reproductive system in adult Wistar rat offspring

INTRODUCTION

It has been suggested that maternal exposure to constant light during the gestational period could be considered as a chronic stressor, impairing offspring development by interfering in neuroendocrine and behavior responses.

OBJECTIVE

This study aimed to evaluate whether maternal exposure to continuous light during pregnancy affects the adult reproductive system in the female offspring.

MATERIALS AND METHODS

Pregnant Wistar rats were allocated into light-dark (LD) group, exposed to light and dark photoperiod during gestation, and the light-light (LL) group, exposed to a photoperiod of constant light during gestation. After birth, pups were maintained under normal light-dark photoperiod until adulthood. At postnatal day 90, blood was collected from the female offspring, to analyze plasma luteinizing hormone (LH) and progesterone levels, and the uterus and ovaries were harvested for morphometric, histological, and oxidative stress evaluations.

RESULTS AND DISCUSSION

Female exposure to continuous light during the intrauterine period resulted in the adult reduction of LH and increased progesterone plasma levels, and uterine injuries a higher number of endometrial glands and reduced levels of antioxidant enzymes, such as glutathione reductase and glutathione S-transferase. In these experimental conditions, gestational continuous light exposure disturbs sex hormone balance and reduces the antioxidant enzymatic activity in the uterus of female offspring in adult life.

Circadian Rhythms Disrupted by Light at Night and Mistimed Food Intake Alter Hormonal Rhythms and Metabolism

Availability of artificial light and light-emitting devices have altered human temporal life, allowing 24-hour healthcare, commerce and production, and expanding social life around the clock. However, physiology and behavior that evolved in the context of 24 h solar days are frequently perturbed by exposure to artificial light at night. This is particularly salient in the context of circadian rhythms, the result of endogenous biological clocks with a rhythm of ~24 h. Circadian rhythms govern the temporal features of physiology and behavior, and are set to precisely 24 h primarily by exposure to light during the solar day, though other factors, such as the timing of meals, can also affect circadian rhythms. Circadian rhythms are significantly affected by night shift work because of exposure to nocturnal light, electronic devices, and shifts in the timing of meals. Night shift workers are at increased risk for metabolic disorder, as well as several types of cancer. Others who are exposed to artificial light at night or late mealtimes also show disrupted circadian rhythms and increased metabolic and cardiac disorders. It is imperative to understand how disrupted circadian rhythms alter metabolic function to develop strategies to mitigate their negative effects. In this review, we provide an introduction to circadian rhythms, physiological regulation of homeostasis by the suprachiasmatic nucleus (SCN), and SCN-mediated hormones that display circadian rhythms, including melatonin and glucocorticoids. Next, we discuss circadian-gated physiological processes including sleep and food intake, followed by types of disrupted circadian rhythms and how modern lighting disrupts molecular clock rhythms. Lastly, we identify how disruptions to hormones and metabolism can increase susceptibility to metabolic syndrome and risk for cardiovascular diseases, and discuss various strategies to mitigate the harmful consequences associated with disrupted circadian rhythms on human health.

The Circadian Clock, Nutritional Signals and Reproduction: A Close Relationship

The circadian rhythm, which is necessary for reproduction, is controlled by clock genes. In the mouse uterus, the oscillation of the circadian clock gene has been observed. The transcription of the core clock gene period (Per) and cryptochrome (Cry) is activated by the heterodimer of the transcription factor circadian locomotor output cycles kaput (Clock) and brain and muscle Arnt-like protein-1 (Bmal1). By binding to E-box sequences in the promoters of Per1/2 and Cry1/2 genes, the CLOCK-BMAL1 heterodimer promotes the transcription of these genes. Per1/2 and Cry1/2 form a complex with the Clock/Bmal1 heterodimer and inactivate its transcriptional activities. Endometrial BMAL1 expression levels are lower in human recurrent-miscarriage sufferers. Additionally, it was shown that the presence of BMAL1-depleted decidual cells prevents trophoblast invasion, highlighting the importance of the endometrial clock throughout pregnancy. It is widely known that hormone synthesis is disturbed and sterility develops in Bmal1-deficient mice. Recently, we discovered that animals with uterus-specific Bmal1 loss also had poor placental development, and these mice also had intrauterine fetal death. Furthermore, it was shown that time-restricted feeding controlled the uterine clock's circadian rhythm. The uterine clock system may be a possibility for pregnancy complications, according to these results. We summarize the most recent research on the close connection between the circadian clock and reproduction in this review.

The Progress of Research on Genetic Factors of Recurrent Pregnancy Loss

Recurrent pregnancy loss (RPL) is both mental and physical health problem affecting about 1-5% of women of childbearing age. The etiology of RPL is complex, involving chromosomal abnormalities, autoimmune diseases, metabolic disorders, and endometrial dysfunction. The causes of abortion are still unknown in more than 50% of these cases. With the development of science and technology, an increasing number of scholars focus on this field and find that genetic factors may play an essential role in unexplained RPL, such as embolism-related genes, immune factor-related genes, and chromosomal numeric, and structural variation. This review summarizes the genetic factors associated with RPL, including genetic mutations and genetic polymorphisms, chromosomal variants, and chromosomal polymorphisms. Many related genetic factors have been found to be demographically and geographically relevant, some of which can be used for risk prediction or screening for the etiology of RPL. However, it is difficult to predict and prevent RPL due to uncertain pathogenesis and highly variable clinical presentation. Therefore, the genetic factors of RPL still need plentiful research to obtain a more accurate understanding of its pathogenesis and to provide more detection means for the screening and prevention of RPL.

Circadian Regulation of Hormonal Timing and the Pathophysiology of Circadian Dysregulation

Circadian rhythms are endogenously generated, daily patterns of behavior and physiology that are essential for optimal health and disease prevention. Disruptions to circadian timing are associated with a host of maladies, including metabolic disease and obesity, diabetes, heart disease, cancer, and mental health disturbances. The circadian timing system is hierarchically organized, with a master circadian clock located in the suprachiasmatic nucleus (SCN) of the anterior hypothalamus and subordinate clocks throughout the CNS and periphery. The SCN receives light information via a direct retinal pathway, synchronizing the master clock to environmental time. At the cellular level, circadian rhythms are ubiquitous, with rhythms generated by interlocking, autoregulatory transcription-translation feedback loops. At the level of the SCN, tight cellular coupling maintains rhythms even in the absence of environmental input. The SCN, in turn, communicates timing information via the autonomic nervous system and hormonal signaling. This signaling couples individual cellular oscillators at the tissue level in extra-SCN brain loci and the periphery and synchronizes subordinate clocks to external time. In the modern world, circadian disruption is widespread due to limited exposure to sunlight during the day, exposure to artificial light at night, and widespread use of light-emitting electronic devices, likely contributing to an increase in the prevalence, and the progression, of a host of disease states. The present overview focuses on the circadian control of endocrine secretions, the significance of rhythms within key endocrine axes for typical, homeostatic functioning, and implications for health and disease when dysregulated. © 2022 American Physiological Society. Compr Physiol 12: 1-30, 2022.

The impact of workplace psychosocial factors on menstrual disorders and infertility: a protocol for a systematic review and meta-analysis

INTRODUCTION

Workplace environment, especially psychosocial factors at work such as job strain, workplace social support, and shift work, may affect the menstrual abnormalities and fertility of female workers. However, the association between psychosocial factors at work and menstrual abnormalities or fertility is not well understood. To address this relationship, we will conduct a systematic review and a meta-analysis of the literature that has utilized a longitudinal or prospective cohort design.

METHODS AND ANALYSIS

The inclusion criteria for this systematic review and meta-analysis are defined as follows: (P) adult female workers (over 18 years old), (E) the presence of adverse psychosocial factors at work, (C) the absence of adverse psychosocial factors at work, and (O) any menstrual cycle disorders, menstrual-related symptoms, or fertility. The MEDLINE, Embase, PsycINFO, PsycArticles, and Japan Medical Abstracts Society electronic databases will be used to search for published studies. The statistical synthesis of the studies included in the meta-analysis will be conducted to estimate pooled coefficients and 95% CIs. For the main analysis, we will synthesize measures of association between psychosocial factors at work and menstrual-related disorders/symptoms. At least three eligible studies will have to be gathered to conduct a meta-analysis; otherwise (i.e., if only one or two studies will be eligible and included), the results will be presented in a narrative table. We will use the Risk of Bias in Non-randomized Studies of Interventions (ROBINS-I) to determine the quality of selected studies. To assess meta-bias, Egger's test, along with a funnel plot, will be used to check for publication bias. Lastly, we will examine heterogeneity using the χ² test with Cochran's Q statistic and I².

ETHICS AND DISSEMINATION

The results and findings will be submitted and published in a scientific peer-reviewed journal and will be disseminated broadly to researchers and policymakers interested in the translatability of scientific evidence into good practices.

SYSTEMATIC REVIEW REGISTRATION

The study protocol was registered at the UMIN registry (registration number: UMIN000039488). The registration date is on 14 Feb 2020. URL: https://upload.umin.ac.jp/cgi-bin/ctr/ctr_view_reg.cgi?recptno=R000044704.

Effects of Sleep Disorders and Circadian Rhythm Changes on Male Reproductive Health: A Systematic Review and Meta-analysis

Objectives: The purpose of this study was to elucidate the relationship between sleep disorders and male reproductive health, and to explore the underlying mechanisms via a systematic review and meta-analysis.

Methods: PubMed, Embase, The Cochrane library, Web of Science, Scopus databases were searched to collect clinical research on the effects of sleep disorders on male semen parameters from inception to February 24, 2022. RevMan 5.4 was used for meta-statistical analysis. Stata16 software was used to detect publication bias.

Results: The results of meta-analysis showed that sleep disorders were associated with reduced total sperm count (mean difference (MD) = −27.91, 95% CI = (−37.82, −18.01), p < 0.001), reduced sperm concentration (MD = −5.16, 95% CI = (−9.67, −0.65), p = 0.02), reduced progressive motility (MD = −2.94, 95% CI = (−5.28, −0.59), p = 0.01), and reduced normal morphology (MD = −0.52, 95% CI = (−0.80, −0.24), p < 0.001). However, there is no significant association between sleep disorders and semen volume/reproductive hormones. Further bioinformatics mining revealed that related clock genes (PER1, PER2, CRY2, NR1D1 and NPAS2) were down-regulated in non-obstructive azoospermia patients.

Conclusion: In conclusion, current evidence suggests that sleep disorders have a negative impact on male reproductive health, and its underlying mechanism may be related to circadian rhythm disorders. However, the relationship between sleep disorders and reproductive hormone levels has not been found. Due to the limited number and quality of included studies, the above findings need to be validated by more high-quality studies.

A Cross-Sectional, Exploratory Study on the Impact of Night Shift Work on Midwives’ Reproductive and Sexual Health

Background: Shift work is the basis for health care system functioning. The non-standard schedules enforce abrupt changes in the timing of sleep and light-dark exposure. It can contribute to the increased risk of various medical conditions, including reproductive and sexual health issues. The purpose of the study was to assess the impact of shift work with night shifts on midwives’ reproductive and sexual health. Methods: This cross-sectional, exploratory study included 520 midwives. A descriptive questionnaire was distributed in person (414) and online (106) from July 2019 to May 2020. We used the Female Sexual Function Index (PL-FSFI) standardized questionnaire and proprietary research tools (applicable to demographic and social data and reproductive health). All statistical calculations were performed with the IBM SPSS 23 statistical package. Results: Shift work affects midwives’ reproductive and sexual health. Midwives working night shifts are more likely to experience reproductive problems and sexual dysfunctions. The most pronounced differences are observed in the experience of infertility and the number of miscarriages. PL-FSFI results clearly showed the adverse impact of working shifts including night shifts on functioning in various dimensions of sexual health. Conclusion: Shift work negatively affects reproductive and sexual health and causes work-life conflict experience. It is necessary to develop procedures that minimize shift rotation and implement work schedules that allow for recuperation or rest and ensure proper family and social life.

Environmental disruption of reproductive rhythms

Reproduction is a key biological function requiring a precise synchronization with annual and daily cues to cope with environmental fluctuations. Therefore, humans and animals have developed well-conserved photoneuroendocrine pathways to integrate and process daily and seasonal light signals within the hypothalamic-pituitary-gonadal axis. However, in the past century, industrialization and the modern 24/7 human lifestyle have imposed detrimental changes in natural habitats and rhythms of life. Indeed, exposure to an excessive amount of artificial light at inappropriate timing because of shift work and nocturnal urban lighting, as well as the ubiquitous environmental contamination by endocrine-disrupting chemicals, threaten the integrity of the daily and seasonal timing of biological functions. Here, we review recent epidemiological, field and experimental studies to discuss how light and chemical pollution of the environment can disrupt reproductive rhythms by interfering with the photoneuroendocrine timing system.

Shift and night work during pregnancy and preterm birth-a cohort study of Swedish health care employees

BACKGROUND

Previous studies of preterm birth (PTB) concerning night work have been inconclusive and partly limited by imprecise data on working schedules. This study investigated the risk of PTB in relation to detailed, registry-based data on working hours.

METHODS

In a register-based prospective cohort study, we identified 4970 singleton births with information on PTB from the Swedish Medical Birth Register of health care employees in Stockholm. Day-by-day information on working hours 2008-16 was obtained from a computerized employee register. Odds ratios (ORs) of PTB according to work hour characteristics were analysed by logistic regression adjusted for mother's age, stature, body mass index (BMI), parity, smoking habits, education, profession and country of birth.

RESULTS

There was an increased risk of PTB among those who frequently worked night shifts (>25 times) [OR, 1.62; 95% confidence interval (CI), 1.03-2.53] and who ever worked ≥3 consecutive night shifts (OR, 1.43; 95% CI, 1.03-1.99) during the first trimester. Frequently (> 8 times) working 3 or more consecutive nights, and frequently (>18 times) having quick returns from night shifts (<28 h) during the first trimester showed 3-4 fold increased risk of PTB. Moreover, working frequent (>20 times) long shifts (≥10 h) (OR 1.63; 95% CI, 1.07-2.49) during the first trimester and working any Week >40 h (OR 2.05; 95% CI, 1.31-3.22) during the third trimester were associated with PTB.

CONCLUSIONS

In this cohort of Swedish health care employees with registry-based data on working hours, night work, especially working frequent consecutive nights, and quick returns from night shifts during the first trimester were associated with increased risk of PTB among pregnant women.

Men's Sleep Quality and Assisted Reproductive Technology Outcomes in Couples Referred to a Fertility Clinic: A Chinese Cohort Study

BACKGROUND

Poor sleep quality has been linked to lower semen quality, but it is unclear whether this result in decreased fertility. To address this question, we retrospectively evaluated the relationship between men's sleep quality and treatment outcomes in subfertile couples receiving assisted reproductive technology (ART).

PATIENT ENROLLMENT AND METHODS

From September 2017 to November 2019, 282 subfertile couples referred to a Chinese fertility clinic and eligible for ART procedures were enrolled in our study. Sociodemographic characteristics, life habits, and sleep habits in the year prior to ART were recorded. Sleep quality was measured using the Pittsburgh Sleep Quality Index (PSQI). We first divided the patients into two groups based on sleep quality (good sleep: PSQI < 5 and poor sleep: PSQI ≥ 5). Then, the ART outcomes (fertilization rate, good quality embryo rate, implantation rate, positive pregnancy rate, clinical pregnancy rate, live birth rate, miscarriage rate, and birth weight) of each group were analyzed. Finally, multivariate linear and logistic regression analysis were used to examine the relationship between sleep quality (discrete variable or dichotomous variable) and ART outcomes.

RESULTS

The participants in the poor sleep group showed a lower fertilization rate of 60.13% (543/903) when compared with 67.36% for the good sleep group (902/1339), P < 0.001. The global PSQI score had a significant influence on birth weight (β, -63.81; 95% CI, -119.91- -8.52; P = 0.047), and live birth rate (OR, 0.88; 95% CI, 0.78- 0.99; P = 0.047) after adjusting for the interfering factors. Men's sleep quality was unrelated to good quality embryos rate, implantation rate, positive pregnancy rate, clinical pregnancy rate, or miscarriage rate.

CONCLUSION

Men's sleep quality was positively associated with fertilization rate, birth weight, and live birth rate among couples undergoing ART.

The potential impacts of circadian rhythm disturbances on male fertility

A circadian rhythm is an internalized timing system that synchronizes the cellular, behavioral, and physiological processes of organisms to the Earth's rotation. Because all physiological activities occur at a specific time, circadian rhythm disturbances can lead to various pathological disorders and diseases. Growing evidence has shown that the circadian clock is tightly connected to male fertility, and circadian perturbations contribute to infertility. The night shiftwork, insufficient sleep, and poor sleep quality are common causes of circadian disturbances, and many studies have reported that they impair sperm quality and increase the risk of male infertility. However, research on the impacts of light, body temperature, and circadian/circannual rhythms is relatively lacking, although some correlations have been demonstrated. Moreover, as the index of sperm quality was diverse and study designs were non-uniform, the conclusions were temporarily inconsistent and underlying mechanisms remain unclear. A better understanding of whether and how circadian disturbances regulate male fertility will be meaningful, as more scientific work schedules and rational lifestyles might help improve infertility.

Sleep, psychological distress, and clinical pregnancy outcome in women and their partners undergoing in vitro or intracytoplasmic sperm injection fertility treatment

OBJECTIVES

To explore the prevalence of poor sleep quality in couples undergoing fertility treatment and study possible associations.

PARTICIPANTS

163 women and 132 partners receiving in vitro (IVF) or intracytoplasmic sperm injection (ICSI) fertility treatment.

SETTING

Three public Danish fertility clinics.

DESIGN AND MEASUREMENTS

Participants completed the Pittsburgh Sleep Quality Index (PSQI) at three time-points as part of a larger RCT. Additional data from patient records and questionnaires were included to evaluate possible associations with treatment protocol type, psychological distress, and pregnancy outcome.

RESULTS

Mean PSQI global scores before treatment were 8.1 (standard deviation = 2.3), with 91% of participants having PSQI scores > 5, indicating poor sleep quality. Scores did not differ between women and their partners and did not change during treatment. Statistically significant associations were found between sleep quality and depressive symptoms and state anxiety (p < .001). No difference in PSQI scores was found between protocol types. While there was a trend towards higher clinical pregnancy rates among women with good sleep quality (PSQI ≤ 5 = 72.7%, PSQI 6-10 = 52.6% and PSQI ≥ 11 = 42.3%), the differences did not reach statistical significance (p = .10-.21).

CONCLUSIONS

Poor sleep quality is a prevalent problem among couples undergoing fertility treatment and is associated with psychological distress and possibly with pregnancy outcomes. Success rates after fertility treatment remain moderate, and poor sleep quality, a potentially modifiable factor, could be relevant to screen for and treat among couples undergoing fertility treatment. The high prevalence of poor sleep quality calls for further investigation.

Night shift work undertaken by women and fertility treatment interact to increase prevalence of urogenital anomalies in children

OBJECTIVE

To investigate the role of maternal night shift work in occurrence of urogenital anomalies in offspring, considering a possible interaction with mode of conception.

METHODS

A population-based cohort comprising births in South Australia (1986-2002) was produced via linkage of fertility clinic records, perinatal and birth defects data. This study concerned first births to women in paid employment (n=98 103). Potential exposure to night shift was imputed by applying a job-exposure matrix to recorded occupation. Associations were examined using logistic regression, first for nurses and other night shift workers separately, then combined. An interaction term for night shift work and mode of conception was included in all models, while adjusting for covariates.

RESULTS

Associations were similar for nurses and other night shift workers, although only statistically significant for the former when considered separately. A multiplicative interaction was supported: for natural conceptions, maternal night shift work was not associated with offspring urogenital anomalies (OR=0.99, 95% CI 0.84 to 1.15); where a birth arose from fertility treatment, urogenital anomalies were significantly higher among births to all night shift workers compared with day workers (OR=2.07, 95% CI 1.20 to 3.55). This was not due to differences in the type of fertility treatment received.

CONCLUSIONS

Women in occupations that probably involved night shift did not have offspring with increased prevalence of urogenital anomalies if they conceived naturally. When night shift workers conceived with fertility treatment, the prevalence of urogenital anomalies was elevated. Possibly these women had the greatest exposure to night shift work, or least tolerance for this work schedule, or heightened sensitivity to hormonal aspects of fertility treatment.

In Silico, In Vitro, and In Vivo Analysis Identifies Endometrial Circadian Clock Genes in Recurrent Implantation Failure

CONTEXT

Previous work has demonstrated the role of the circadian clock in ovarian steroid hormone synthesis and attributed embryo implantation failure associated with arrhythmic circadian clock genes to insufficient ovarian-derived progesterone synthesis. Research on expression of core circadian clock genes in the endometrium itself and possible roles in compromised endometrial receptivity and recurrent implantation failure (RIF) are limited.

OBJECTIVE

We aimed to assess the core circadian clock gene profiling in human endometrium across the menstrual cycle and the possible gene interaction networks in the endometrial receptivity of window of implantation (WOI) as well as RIF.

METHODS

The study was initially an in silico study, with confirmatory lab-based data from primary human endometrial stromal cells (hESCs) as well as endometrial biopsies obtained from 60 women undergoing gynecological surgery in a clinical research center. The study included 30 RIF women and 30 age-matched and body mass index-matched controls.

RESULTS

Initial data mining and bioinformatics analysis of human endometrial microarray datasets across the menstrual cycle and between RIF women versus controls demonstrated the varied expression of core circadian clock genes across menstrual cycle, including the key role of PER2 in WOI and RIF. A PER2-centered network was investigated in the regulation of endometrial receptivity. We also confirmed the evidently increased mRNA expression of SHTN1, RXFP1, KLF5, and STEAP4 in the endometrium of RIF women, displaying the same trend as PER2 did, without any changes in MT1E and FKBP5. Treatment of PER2 siRNA in hESCs verified the positive regulation of PER2 to SHTN1, KLF5, and STEAP4.

CONCLUSION

Aberrant expression of endometrial PER2 might contribute to impaired endometrial receptivity and development of RIF via regulating SHTN1, KLF5, and STEAP4.

Evaluation of the effect of shift working and sleep quality on semen parameters in men attending infertility clinic

We aimed to evaluate the effect of shift work on semen parameters together with the effect of sleep quality in men attending infertility clinic. The participants were divided into two groups as follows: 104 shift worker men (Group 1) and 116 nonshift worker men (Group 2). Groups were compared in terms of semen parameters, Depression Anxiety Stress Scale-21 (DASS-21), and Pittsburg Sleep Quality Index (PSQI) scores. A higher rate of oligozoospermia and poor sleep quality and a lower mean normal morphology percentage was observed in shift workers than nonshift workers (p = .006, .039 and .036 respectively). In addition, a positive correlation was seen between sleep duration and sperm concentration, while a negative correlation was found between sleep latency and total sperm count. Shift working together with high PSQI score was also a significant association with oligozoospermia when controlling for the other variables of age, total testosterone, DASS-21 stress score, smoking and varicocele (OR = 2.11, 95% CI 1.03-4.34 and OR = 1.18, 95% CI 1.01-1.39 respectively). In this study, infertile shift workers had a lower percentage of normal morphology and higher rates of oligozoospermia and poor sleep quality. Considering that shift workers have lower sleep quality, it seems that shift working negatively affects the circadian rhythm.

Perceived stress and sleep quality before oocyte pick-up, embryo transfer, and pregnancy test in women receiving in vitro fertilization treatment

BACKGROUND

Infertility is a major health problem that affects both the family and the community. Women receiving infertility treatment may suffer from stress and even experience sleep disturbance. Sleep quality is an important factor of human health and well-being. Sleep disturbances tend to occur among infertile women during in vitro fertilization treatment. Many studies have focused on the stress and sleep quality associated with their treatment in infertile women. However, few studies have investigated factors linked to their sleep disturbances.

OBJECTIVE

This study investigated the relationship between perceived stress and sleep quality before oocyte pick-up, in vitro fertilization-embryo transfer, and pregnancy test in women receiving in vitro fertilization treatment.

MATERIAL AND METHODS

This prospective, longitudinal study was conducted between January and May 2020. One hundred fifty-seven women receiving infertility treatment were included in the study. A personal information form, the Perceived Stress Scale (PSS), and the Pittsburgh Sleep Quality Index (PSQI) were used to collect data.

RESULTS

The relationship between the Perceived Stress Scale scores and the Pittsburgh Sleep Quality Index scores in all stages of infertility treatment was found to be positively significant at the p < .001 significance level.

CONCLUSION

Perceived stress level was high in women throughout the infertility treatment. Our study suggested that sleep quality was impaired as stress increased.

TRIAL REGISTRATION

70904504/38.

Circadian Deregulation as Possible New Player in Pollution-Induced Tissue Damage

Circadian rhythms are 24-h oscillations driven by a hypothalamic master oscillator that entrains peripheral clocks in almost all cells, tissues and organs. Circadian misalignment, triggered by industrialization and modern lifestyles, has been linked to several pathological conditions, with possible impairment of the quality or even the very existence of life. Living organisms are continuously exposed to air pollutants, and among them, ozone or particulate matters (PMs) are considered to be among the most toxic to human health. In particular, exposure to environmental stressors may result not only in pulmonary and cardiovascular diseases, but, as it has been demonstrated in the last two decades, the skin can also be affected by pollution. In this context, we hypothesize that chronodistruption can exacerbate cell vulnerability to exogenous damaging agents, and we suggest a possible common mechanism of action in deregulation of the homeostasis of the pulmonary, cardiovascular and cutaneous tissues and in its involvement in the development of pathological conditions.

From Environmental to Possible Occupational Exposure to Risk Factors: What Role Do They Play in the Etiology of Endometriosis?

Endometriosis is a gynecological disorder characterized by the presence of endometrial stroma and glands outside the uterine cavity. A systematic review of the literature was conducted to clarify, starting from environmental exposure data, whether possible occupational risk factors may correlate with the onset of the disease. The guidelines for reporting systematic reviews of the “PRISMA” statement were followed and two databases, Scopus and PubMed, were used. Of the 422 studies selected with specific keywords, 32 publications were eligible, 28 of which referred to chemical agents and 4 related to night work. Conflicting data emerged among these studies. Although some compounds seemed to be more involved than others in the onset of endometriosis. Association with exposure to organochlorine compounds is the most supported by the epidemiological data, while other pesticide exposure did not show any clear correlation. Likewise, the hypothesis of a correlation with perfluoroalkyls exposure is not currently supported by data. The involvement of metals as risk factors has not been confirmed, while the role of night work, in the case of long service, seems to play an etiological role. In order to clarify the potential occupational risk of endometriosis development, well-designed studies are needed to evaluate the potential association between chemical compounds and disease etiology.

Impact of Circadian Desynchrony on Spermatogenesis: A Mini Review

The purpose of this mini review is to provide data about pre-clinical and clinical evidence exploring the impact of circadian desynchrony on spermatogenesis. Several lines of evidence exist demonstrating that disruption of circadian rhythms may interfere with male fertility. Experimental knock-out or knock-down of clock genes, physiologically involved in the regulation of circadian rhythms, are associated with impairments of fertility pathways in both animal and human models. Moreover, disruption of circadian rhythms, due to reduction of sleep duration and/or alteration of its architecture can negatively interfere in humans with circulating levels of male sexual hormones as well as with semen parameters. Unfortunately, current evidence remains low due to study heterogeneity.

Shiftwork and Light at Night Negatively Impact Molecular and Endocrine Timekeeping in the Female Reproductive Axis in Humans and Rodents

Shiftwork, including work that takes place at night (nightshift) and/or rotates between day and nightshifts, plays an important role in our society, but is associated with decreased health, including reproductive dysfunction. One key factor in shiftwork, exposure to light at night, has been identified as a likely contributor to the underlying health risks associated with shiftwork. Light at night disrupts the behavioral and molecular circadian timekeeping system, which is important for coordinated timing of physiological processes, causing mistimed hormone release and impaired physiological functions. This review focuses on the impact of shiftwork on reproductive function and pregnancy in women and laboratory rodents and potential underlying molecular mechanisms. We summarize the negative impact of shiftwork on female fertility and compare these findings to studies in rodent models of light shifts. Light-shift rodent models recapitulate several aspects of reproductive dysfunction found in shift workers, and their comparison with human studies can enable a deeper understanding of physiological and hormonal responses to light shifts and the underlying molecular mechanisms that may lead to reproductive disruption in human shift workers. The contributions of human and rodent studies are essential to identify the origins of impaired fertility in women employed in shiftwork.

Genipin improves reproductive health problems caused by circadian disruption in male mice

BACKGROUND

Circadian rhythm disruption impacts a wide range of physiological processes, including fertility. However, the effect of circadian disruption on male spermatogenesis and fertility, and treatments for these effects have been largely unexplored at the molecular level.

METHODS

In this study, we examined the effects of genipin on improving the reproductive health problems caused by circadian disruption. Three groups of animals were fed under different conditions: control group (normal T cycle with saline), group of shortened T cycles (Light/Dark = 4 hours/4 hours) with saline, and a group of shortened T cycles with genipin by oral gavage. The male fertility was evaluated by fertility study and pups parameters analysis after successful sexual behavior and mating with female mice. We sacrificed the treated animals after 5 or 10 weeks and collected the testis, sperm and serum for histological analysis, sperm motility assay, and serum hormone detection, respectively. Furthermore, the effect of genipin was assessed by detection of progesterone secretion and steroidogenic key proteins expression, including StAR and CYP11A1, in mouse Leydig tumor MLTC-1 cells.

RESULTS

Male mice exposed to shortened light-dark cycles, much shorter than 24 hours, had reduced fertility with decreased sperm concentrations and sperm motility. Male mice under circadian disruption have reduced testis size and abnormal morphology, leading to lower fertility rates, reduced litter size and pup body weight. Treatment with exogenous genipin, a natural plant-derived compound, alleviated circadian disruption-induced damage to fertility and spermatogenesis and normalized testosterone, dihydrotestosterone (DHT), and androstenedione (ASD) levels in the male mice. The levels of key proteins involved in steroidogenesis, StAR and CYP11A1, were reduced in mouse testes after the circadian disruption, but genipin treatment restored the reduction. The mRNA expression of SRD5A1, which encodes an androgen synthesis enzyme, was also upregulated by genipin treatment. Furthermore, genipin treatment showed a positive effect on steroidogenesis in MLTC-1 cells, resulting in an increase in hormone secretion and the upregulation of StAR and CYP11A1.

CONCLUSIONS

Our results showed an association between circadian disruption and reproductive health problems in male mice and indicated that treatments with genipin have positive effects on the reproductive health of male mice with circadian rhythm disorders.

Night Shift Among Women: Is It Associated With Difficulty Conceiving a First Birth?

Background: Asynchrony in circadian processes alters many physiological systems, including female reproduction. Thus, there are possible reproductive consequences of night shift work for women including menstrual irregularity, endometriosis, and prolonged time to conception. This study examined whether women who worked night shift were more likely than those who did not to require fertility treatment to conceive a first birth, whether they had specific infertility diagnoses, and if such relationships were age-specific. Methods: In a retrospective data linkage study of 128,852 primiparous women, fertility treatment data were linked to the state perinatal registry for South Australia (1986-2002). Potential exposure to night shift work was assessed using a job-exposure matrix. First, the association between night shift work and fertility treatment was assessed among (1) all women, then (2) women in paid employment, using logistic regression. Interactions between age and shift work status were also examined. Secondly, among women who conceived with fertility treatment, we assessed associations between night shift work and type of infertility diagnosis. Potential confounders were considered in all analyses. Results: Among women ≤35 years, night shift workers were more likely to require fertility treatment (all: OR = 1.40, 95% CI 1.19-1.64; in paid employment: OR = 1.27, 95% CI 1.08-1.50). There were no associations among women >35 years. Ethnicity, socioeconomic status and smoking did not affect these results. Among women who underwent fertility treatment, night shift workers were more likely than day workers to have menstrual irregularity (OR = 1.42, 95% CI 1.05-1.91) or endometriosis (OR = 1.34, 95% CI 1.00-1.80). Conclusions: Night shift work may contribute to increased need for fertility treatment in younger women. This increased risk may reflect young women's vulnerability in terms of poor tolerance of night shift work, and/or lack of control and choice about shift schedule.

Rapid Jetlag Resetting of Behavioral, Physiological, and Molecular Rhythms in Proestrous Female Mice

A gradual adaptation to a shifted light-dark (LD) cycle is a key element of the circadian clock system and believed to be controlled by the central circadian pacemaker, the suprachiasmatic nucleus (SCN). Endocrine factors have a strong influence on the regulation of the circadian clock network and alter acute photic responses of the SCN clock. In females, endocrine function depends on the stage of the ovarian cycle. So far, however, little is known about the effect of the estrous cycle on behavioral and molecular responses to shifts in the LD rhythm. Based on this, we investigated whether estrous state affects the kinetics of phase shift during jetlag in behavior, physiology, and molecular clock rhythms in the SCN and in peripheral tissues. Female mice exposed to an advanced LD phase at proestrous or metestrous showed different phase-shift kinetics, with proestrous females displaying accelerated adaptation in behavior and physiology. Constant darkness release experiments suggest that these fast phase shifts do not reflect resetting of the SCN pacemaker. Explant experiments on SCN, adrenal gland, and uterus confirmed this finding with proestrous females showing significantly faster clock phase shifts in peripheral tissues compared with the SCN. Together, these findings provide strong evidence for an accelerated adaptation of proestrous compared with metestrous females to new LD conditions that is accompanied by rapid behavioral, physiological, and molecular rhythm resetting. Not only do these findings open up a new avenue to understand the effect of estrous cycle on the clock network under changing environmental conditions but also imply a greater susceptibility in proestrous females.

Chrononutrition during Pregnancy: A Review on Maternal Night-Time Eating

Evidence from women working night shifts during pregnancy indicates that circadian rhythm disruption has the potential to adversely influence pregnancy outcomes. In the general population, chronodisruption with the potential to affect pregnancy outcomes may also be seen in those with high energy intakes in the evening or at night. However, maternal night eating during pregnancy remains understudied. This narrative review provides an overview of the prevalence, contributing factors, nutritional aspects and health implications of night eating during pregnancy. We derived evidence based on cross-sectional studies and longitudinal cohorts. Overall, night eating is common during pregnancy, with the estimated prevalence in different populations ranging from 15% to 45%. The modern lifestyle and the presence of pregnancy symptoms contribute to night eating during pregnancy, which is likely to coexist and may interact with multiple undesirable lifestyle behaviors. Unfavorable nutritional characteristics associated with night eating have the potential to induce aberrant circadian rhythms in pregnant women, resulting in adverse metabolic and pregnancy outcomes. More research, particularly intervention studies, are needed to provide more definite information on the implications of night eating for mother-offspring health.

Meta-Analysis Comparing Menstrual Regularity and Dysmenorrhea of Women Working Rotating Shifts and Fixed Day Shifts

Background: Rotating shift work can cause abnormalities in their endocrine system. We conducted a meta-analysis to gain a better understanding of the differences between women working rotating shifts and fixed day shifts in menstrual regularity and dysmenorrhea. Methods: We searched for studies containing relevant keywords that were published between 1990 and 2019 in the Cochrane Library, EBSCO (including the Cumulative Index to Nursing and Allied Health Literature [CINAHL]), MEDLINE, and ProQuest. Data analysis was performed using the software package Comprehensive Meta-Analysis (CMA) Version 3.0. Results: A total of 14 studies met our selection criteria. The pooled odds ratio (OR) comparing the menstrual irregularity of women working rotating shifts and fixed day shifts was 1.35 (95% confidence interval [CI]: 1.28-1.42, p < 0.001). The pooled OR of the women aged 30 years or older was 1.35 (95% CI: 1.28-1.42, p < 0.001); and for the women under 30 years old, the pooled OR was 1.66 (95% CI: 1.13-2.44, p = 0.010). The pooled OR comparing the dysmenorrhea occurrence among women working rotating shifts and fixed day shifts was 1.51 (95% CI: 0.87-2.62, p = 0.139). The pooled OR of the women aged 30 years or older was 2.35 (95% CI: 1.63-3.39, p < 0.001); and for the women under 30 years old, the pooled OR was 1.20 (95% CI: 0.61-2.33, p = 0.601). Conclusions: The results indicate that regardless of age, women working rotating shifts were more likely to experience menstrual irregularity than those working fixed day shifts. With regard to dysmenorrhea, among women aged 30 years or older, those working rotating shifts were also more likely to experience dysmenorrhea than those working fixed day shifts.

Hypertensive disorders of pregnancy are associated with dysmenorrhea in early adulthood: A cohort study

AIM

Hypertensive disorders of pregnancy (HDP) are serious conditions that occur in 5-10% of pregnancies. Maternal factors, such as maternal age, obesity, and renal disease, have been described as risk factors. In order to extract the background lifestyle and gynecological characteristics for HDP, we conducted a prospective cohort study.

METHODS

Pregnant participants were administered a questionnaire on characteristics, menstrual abnormalities and lifestyle factors. The women were followed individually until 1-month postpartum. We used medical records to examine the relationship between menstrual abnormalities and the onset of HDP.

RESULTS

We collected data from 193 pregnant women, and excluding 3 who had miscarriage, examined the records of 190. A total of 26 patients developed HDP, of which 10 had early-onset HDP and 16 had late-onset HDP. Although there was no significant association between HDP and dysmenorrhea just prior to pregnancy, there was a significant increase in the incidence of HDP in patients who experienced dysmenorrhea around the age of 20 years (odds ratio 4.362 [95% CI 1.61-11.81]).

CONCLUSION

We found that patients with a history of dysmenorrhea around the age of 20 years have a significantly higher risk of developing HDP. Although dysmenorrhea in young adulthood is ameliorated, it may become apparent as a perinatal disease when a physical load such as pregnancy is applied.

Associations of plasma hypocretin-1 with metabolic and reproductive health: Two systematic reviews of clinical studies

The hypocretin system consists of two peptides hypocretin-1 and hypocretin-2 (HCRT1 and HCRT2). Hypocretin-containing neurons are located in the posterior and lateral hypothalamus, and have widespread projections throughout the brain and spinal cord. In addition to its presence in the cerebrospinal fluid (CSF), peripheral HCRT1 has been detected in plasma. Robust experimental evidence demonstrates functions of hypothalamic-originated HCRT1 in regulation of multiple biological systems related to sleep-wake states, energy homeostasis and endocrine function. In contrast, HCRT1 studies with human participants are limited by the necessarily invasive assessment of CSF HCRT1 to patients with underlying morbidity. Regulation by HCRT1 of energy homeostasis and reproduction in animals suggests similar regulation in humans and prompts these two systematic reviews. These reviews translate prior experimental findings from animal studies to humans and examine associations between HCRT1 and: 1) metabolic risk factors; 2) reproductive function in men, women and children. A total of 21 studies and six studies met the inclusion criteria for the two searches, respectively. Research question, study design, study population, assessments of HCRT1, reproductive, cardiometabolic data and main findings were extracted. Associations between HCRT1, metabolic and reproductive function are inconsistent. Limitations of studies and future research directions are outlined.

Night Shift Work and Fecundability in Late Reproductive-Aged African American Women

Background: We estimated the association between night shift work and fecundability among African American women. Methods: Black Women's Health Study participants (n = 560) aged 30-45 years reported their history of night shift work in 2005. Time to pregnancy for all pregnancies resulting in a livebirth was reported in 2011. We estimated the fecundability ratio (FR) and 95% confidence interval (CI) using proportional probabilities regression, accounting for multiple observations of individual women using generalized estimating equations. Results: We observed 4,417 months of pregnancy attempt time resulting in 390 births. After adjustment for covariates, women who reported ever working night shifts had 20% lower fecundability compared with those who never reported night shift work (FR = 0.80, 95% CI: 0.59-1.04). The FR for women reporting night shift work with a frequency of ≥1 time per month and a duration of ≥2 years was 0.65 (95% CI: 0.47-0.94) relative to women reporting no shift work. We observed a decrease in fecundability associated with ever working night shifts (FR = 0.74, 95% CI: 0.56-0.96) among women aged ≥35 years, but not among younger women (FR = 1.33, 95% CI: 0.78-2.28). Conclusion: A history of working night shifts was associated with reduced fecundability among older reproductive-aged African American women attempting pregnancy.

Circadian Clock and OxInflammation: Functional Crosstalk in Cutaneous Homeostasis

Circadian rhythms are biological oscillations that occur with an approximately 24 h period and optimize cellular homeostasis and responses to environmental stimuli. A growing collection of data suggests that chronic circadian disruption caused by novel lifestyle risk factors such as shift work, travel across time zones, or irregular sleep-wake cycles has long-term consequences for human health. Among the multiplicity of physiological systems hypothesized to have a role in the onset of pathologies in case of circadian disruption, there are redox-sensitive defensive pathways and inflammatory machinery. Due to its location and barrier physiological role, the skin is a prototypical tissue to study the influence of environmental insults induced OxInflammation disturbance and circadian system alteration. To better investigate the link among outdoor stressors, OxInflammation, and circadian system, we tested the differential responses of keratinocytes clock synchronized or desynchronized, in an in vitro inflammatory model exposed to O₃. Being both NRF2 and NF-κB two key redox-sensitive transcription factors involved in cellular redox homeostasis and inflammation, we analyzed their activation and expression in challenged keratinocytes by O₃. Our results suggest that a synchronized circadian clock not only facilitates the protective role of NRF2 in terms of a faster and more efficient defensive response against environmental insults but also moderates the cellular damage resulting from a condition of chronic inflammation. Our results bring new insights on the role of circadian clock in regulating the redox-inflammatory crosstalk influenced by O₃ and possibly can be extrapolated to other pollutants able to affect the oxinflammatory cellular processes.

Impact of Circadian Disruption on Female Mice Reproductive Function

In female mammals, cycles in reproductive function depend both on the biological clock synchronized to the light/dark cycle and on a balance between the negative and positive feedbacks of estradiol, whose concentration varies during oocyte maturation. In women, studies report that chronodisruptive environments such as shiftwork may impair fertility and gestational success. The objective of this study was to explore the effects of shifted light/dark cycles on both the robustness of the estrous cycles and the timing of the preovulatory luteinizing hormone (LH) surge in female mice. When mice were exposed to a single 10-hour phase advance or 10-hour phase delay, the occurrence and timing of the LH surge and estrous cyclicity were recovered at the third estrous cycle. By contrast, when mice were exposed to chronic shifts (successive rotations of 10-hoursour phase advances for 3 days followed by 10-hour phase delays for 4 days), they exhibited a severely impaired reproductive activity. Most mice had no preovulatory LH surge at the beginning of the chronic shifts. Furthermore, the gestational success of mice exposed to chronic shifts was reduced, because the number of pups was 2 times lower in shifted than in control mice. In conclusion, this study reports that exposure of female mice to a single phase shift has minor reproductive effects, whereas exposure to chronically disrupted light/dark cycles markedly impairs the occurrence of the preovulatory LH surge, leading to reduced fertility.

Role of core circadian clock genes in hormone release and target tissue sensitivity in the reproductive axis

Precise timing in hormone release from the hypothalamus, the pituitary and ovary is critical for fertility. Hormonal release patterns of the reproductive axis are regulated by a feedback loop within the hypothalamic-pituitary-gonadal (HPG) axis. The timing and rhythmicity of hormone release and tissue sensitivity in the HPG axis is regulated by circadian clocks located in the hypothalamus (suprachiasmatic nucleus, kisspeptin and GnRH neurons), the pituitary (gonadotrophs), the ovary (theca and granulosa cells), the testis (Leydig cells), as well as the uterus (endometrium and myometrium). The circadian clocks integrate environmental and physiological signals to produce cell endogenous rhythms generated by a transcriptional-translational feedback loop of transcription factors that are collectively called the "molecular clock". This review specifically focuses on the contribution of molecular clock transcription factors in regulating hormone release patterns in the reproductive axis, with an emphasis on the female reproductive system. Specifically, we discuss the contributions of circadian rhythms in distinct neuronal populations of the female hypothalamus, the molecular clock in the pituitary and its overall impact on female and male fertility.

Pregnancy, childbirth, and puerperium outcomes in female firefighters in Korea

Background

Female firefighters are exposed to hazardous environmental (chemical and physical) and working (shift work, psychological, and ergonomic factors) conditions that have reported or are suspected of adverse effects on reproductive health. However, no previous studies have reported on pregnancy, childbirth, and puerperium outcomes (PCPOs) in female firefighters.

Methods

The present study compared hospital admissions for PCPOs, based on 10th revision of the International Statistical Classification of Diseases and Related Health Problems (ICD-10) codes, among Korean female firefighters with those of the general Korean population. Standardized admission ratios (SARs) and their 95% confidence intervals (CIs) were calculated.

Results

The study population included 1,766 female firefighters. Total follow-up duration was 9,659 person-years. Compared to the general female population, the female firefighters' SARs were higher in all admissions for PCPOs (SAR, 1.92; 95% CI: 1.79–2.05); pregnancy and abortive outcomes (SAR, 1.56; 95% CI: 1.12–2.12); other maternal disorders predominantly related to pregnancy (SAR, 2.65; 95% CI: 1.99–3.46); maternal care related to the fetus, amniotic cavity, and possible delivery problems (SAR, 2.13; 95% CI: 1.74–2.57); labor and delivery complications (SAR, 1.55; 95% CI: 1.15–2.06); delivery (SAR, 1.94; 95% CI: 1.80–2.08); and complications predominantly related to puerperium (SAR, 4.68; 95% CI: 2.02–9.23).

Conclusion

The results of this study showed high SARs in all and specific subcategories of PCPOs in female firefighters.

Melatonin and Female Reproduction: An Expanding Universe

For more than a half century the hormone melatonin has been associated with vertebrate reproduction, particularly in the context of seasonal breeding. This association is due in large measure to the fact that melatonin secretion from the pineal gland into the peripheral circulation is a nocturnal event whose duration is reflective of night length, which of course becomes progressively longer during winter months and correspondingly shorter during the summer months. The nocturnal plasma melatonin signal is conserved in essentially all vertebrates and is accessed not just for reproductive rhythms, but for seasonal cycles of metabolic activities, immune functions, and behavioral expression. A vast literature on melatonin and vertebrate biology has accrued over the past 60 years since melatonin's discovery, including the broad topic of animal reproduction, which is far beyond the scope of this human-focused review. Although modern humans in the industrialized world appear in general to have little remaining reproductive seasonality, the relationships between melatonin and human reproduction continue to attract widespread scientific attention. The purpose of this chapter is to draw attention to some newer developments in the field, especially those with relevance to human fertility and reproductive medicine. As the vast majority of studies have focused on the female reproductive system, a discussion of the potential impact of melatonin on human male fertility will be left for others.

Melatonin alleviates circadian system disruption induced by chronic shifts of the light-dark cycle in Octodon degus

Modern 24-h society lifestyle is associated with experiencing frequent shifts in the lighting conditions which can negatively impact human health. Here, we use the degus, a species exhibiting diurnal and nocturnal chronotypes, to: (a) assess the impact of chronic shifts of the light:dark (LD) cycle in the animal's physiology and behaviour and (b) test the therapeutic potential of melatonin in enhancing rhythmicity under these conditions. Degus were subjected to a "5d + 2d" LD-shifting schedule for 19 weeks. This protocol aims to mimic lighting conditions experienced by humans during shift work: LD cycle was weekly delayed by 8h during 5 "working" days (Morning, Afternoon and Night schedule); during weekends (2 days), animals were kept under Morning schedule. After 9 weeks, melatonin was provided daily for 6h in the drinking water. The "5d + 2d" shifting LD schedule led to a disruption in wheel-running activity (WRA) and body temperature (Tb) rhythms which manifested up to three separate periods in the circadian range. This chronodisruption was more evident in nocturnal than in diurnal degus, particularly during the Afternoon schedule when a phase misalignment between WRA and Tb rhythms appeared. Melatonin treatment and, to a lesser extent, water restriction enhanced the 24-h component, suggesting a potential role in ameliorating the disruptive effects of shift work.