Evidence for a relationship between chronotype and reproductive function in women

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.

Associations of chronotype and insomnia with menstrual problems in newly employed nurses at university hospitals in the Republic of Korea

Background

Dysmenorrhea and menstrual cycle changes occur in women working shifts. Circadian rhythm disruption and sleep disturbances associated with shift work leads to health problems. We identified chronotypes and the occurrence of insomnia among newly employed university hospital nurses and investigated the association of these factors with menstrual problems.

Methods

We conducted pre-placement health examinations for shift workers using self-reported questionnaires between 2018 and 2020. A total of 463 nurses were included in the study. Sociodemographic data, shift work experience, and information on insomnia were collected from health examination data. In addition, details regarding chronotype, dysmenorrhea, irregular and abnormal menstrual cycles, amenorrhea, and contraceptive use were obtained from the questionnaire. Multiple logistic regression analysis was performed to study the association between chronotype, insomnia, and menstrual problems after controlling for age, body mass index, contraceptive use, amenorrhea, and prior shift work.

Results

The prevalence rates of dysmenorrhea, irregular menstrual cycles, and longer menstrual cycles were 23.8%, 14.9%, and 4.1%, respectively. The risk of dysmenorrhea increased in the evening-type (odds ratio [OR]: 3.209; 95% confidence interval [CI]: 1.685-6.113) and those with insomnia (OR: 1.871; 95% CI: 1.074-3.261). Additionally, the risk of an irregular menstrual cycle (OR: 2.698; 95% CI: 1.167-6.237) increased in the evening-type, and the risk of a longer menstrual cycle (OR: 4.008; 95% CI: 1.354-11.864) increased in individuals with insomnia.

Conclusions

Our findings suggest that dysmenorrhea is promoted in the evening-type and insomnia individuals. There may be an increased risk of irregular menstrual cycles among evening-type nurses and an increased risk of longer menstrual cycles among those with insomnia. Therefore, factors such as evening-type and insomnia should be considered for the prevention of menstrual problems in women performing shift work.

Chronotype and sleep duration interact to influence time to pregnancy: Results from a New York City cohort

STUDY OBJECTIVE

To study associations between nighttime sleep characteristics and time to pregnancy.

METHODS

Pregnant people age ≥18 years and<18 weeks' gestation were recruited from 3 New York University Grossman School of Medicine affiliated hospitals in Manhattan and Brooklyn (n = 1428) and enrolled into the New York University Children's Health and Environment Study. Participants in the first trimester of pregnancy were asked to recall their time to pregnancy and their sleep characteristics in the 3 months before conception.

RESULTS

Participants who reported sleeping<7 hours per night tended to have shorter time to pregnancy than those who slept 7-9 hours per night (adjusted fecundability odds ratio = 1.16, 95% confidence interval: 0.94, 1.41). Participants with a sleep midpoint of 4 AM or later tended to have longer time to pregnancy compared with those with earlier sleep midpoints (before 4 AM) (adjusted fecundability odds ratio = 0.88, 95% confidence interval: 0.74, 1.04). When stratified by sleep midpoint, sleeping<7 hours was significantly associated with shorter time to pregnancy only among those whose sleep midpoint was before 4 AM (adjusted fecundability odds ratio = 1.33, 95% confidence interval: 1.07, 1.67).

CONCLUSIONS

The association of sleep duration with time to pregnancy was modified by chronotype, suggesting that both biological and behavioral aspects of sleep may influence fecundability.

Changes in menstrual cycle length and in sleep-wake behaviors during COVID-19 related lockdown in Israel

COVID-19 related lockdowns changed our life. Studies report that young women are more susceptible to lockdown-induced adverse effects and stress. As stress and menstrual cycle are associated, we hypothesized that menstrual cycle length might change during lockdown. We examined menstrual cycle length, and sleep-wake behaviors during lockdown in Israel. Participants were 97 women in their fertile years who used Tempdrop fertility sensor™ to track cycles. Data were collected before, during and after lockdown in Israel. Our main finding is that lockdown was associated with changes in menstrual cycle length of most participants, with either increased of decreased length. Changes were reversed when lockdown was terminated. Sleep duration increased during lockdown but we found no relationship between sleep and menstrual cycle. We suggest these findings contribute to the understanding of the relationship between stress, sleep, and menstrual cycle. Further studies should explore the sources for differential effects in sub-groups of women.

Preconception sleep duration, sleep timing, and shift work in association with fecundability and live birth among women with a history of pregnancy loss

OBJECTIVE

To evaluate the associations between preconception sleep characteristics and shift work with fecundability and live birth.

DESIGN

Secondary analysis of the Effects of Aspirin in Gestation and Reproduction study, a preconception cohort.

SETTING

Four US academic medical centers.

PATIENT(S)

Women aged 18-40 with a history of 1-2 pregnancy losses who were attempting to conceive again.

INTERVENTION(S)

Not applicable.

MAIN OUTCOME MEASURES(S)

We evaluated baseline, self-reported sleep duration, sleep midpoint, social jetlag, and shift work among 1,228 women who were observed for ≤6 cycles of pregnancy attempts to ascertain fecundability. We ascertained live birth at the end of follow up via chart abstraction. We estimated fecundability odds ratios (FORs) using discrete, Cox proportional hazards models and risk ratios (RRs) for live birth using log-Poisson models.

RESULT(S)

Sleep duration ≥9 vs. 7 to <8 hours (FOR: 0.81, 95% confidence interval [CI], 0.61; 1.08), later sleep midpoints (3rd tertile vs. 2nd tertile: FOR: 0.85; 95% CI, 0.69, 1.04) and social jetlag (continuous per hour; FOR: 0.93, 95% CI: 0.86, 1.00) were not associated with reduced fecundability. In sensitivity analyses, excluding shift workers, sleep duration ≥9 vs. 7 to <8 hours (FOR: 0.62; 95% CI, 0.42; 0.93) was associated with low fecundability. Night shift work was not associated with fecundability (vs. non-night shift work FOR: 1.17, 95% CI, 0.96; 1.42). Preconception sleep was not associated with live birth.

CONCLUSION(S)

Overall, there does not appear to be a strong association between sleep characteristics, fecundability, and live birth. Although these findings may suggest weak and imprecise associations with some sleep characteristics, our findings should be evaluated in larger cohorts of women with extremes of sleep characteristics.

CLINICAL TRIAL REGISTRATION NUMBER

Clinicaltrials.gov NCT00467363.

Influence of chronotype on the incidence and severity of perinatal depression in the "Life-ON" study

BACKGROUND

Perinatal depression (PND) is a severe complication of pregnancy, but there are no established risk factors predicting the disease. Evening chronotype has been associated with unhealthy lifestyle habits and adverse outcomes during pregnancy. In this study, we aimed to clarify whether chronotype can predict symptoms and/or occurrence of PND.

METHODS

Two hundred ninety-nine women were followed-up from the first trimester of pregnancy until 6 months postpartum. Chronotype was assessed at baseline using the MEQ, while mood was repeatedly assessed by depression rating scales (EPDS, HDRS, MADRS). The influence of time and chronotype on EPDS, HDRS and MADRS, was estimated by constructing multilevel linear mixed regression models. A Cox proportional-hazard regression model was built to evaluate the association between chronotype and incidence of depression.

RESULTS

Chronotype modulated PND symptom severity depending on time of assessment, with evening chronotypes having a higher risk for developing PND symptoms, as assessed by EPDS, at postpartum visits V4 (5-12 days) and V5 (19-26 days). These also had less healthy lifestyle habits and were more likely to suffer from gestational diabetes mellitus and undergo cesarean delivery as compared to other chronotypes.

LIMITATIONS

Only a minority of women were classified as evening chronotypes. The long follow-up phase of the study led to missing data.

CONCLUSIONS

Pregnant evening chronotypes show unhealthy lifestyle habits and sociodemographic characteristics commonly associated with a higher risk for PND. They also have a higher risk of developing PND symptoms in the first month after delivery. Chronotype should therefore be routinely assessed during pregnancy to identify women potentially at risk for developing PND.

Human fertility and sleep disturbances: A narrative review

INTRODUCTION

Many factors may be hidden behind the global fertility decline observed in Western countries. Alongside the progressively increased age of infertile couples, environmental and behavioural factors, including non-optimal lifestyle habits, should be considered. Among these, sleep disorders have been suggested to be linked to human fertility.

METHODS

This is a narrative review, describing first sleep physiology, its disturbances, and the tools able to quantify sleep dysfunction. Then, we consider all available studies aimed at investigating the connection between sleep disorders and human fertility, providing a comprehensive view on this topic.

RESULTS

Forty-two studies investigating the relationship between sleep habits and human reproduction were included. All the published evidence was grouped according to the aspect of human fertility considered, i.e. i) female reproductive functions, ii) male reproductive functions, iii) natural conception and iv) assisted reproduction. For each of the sub-groups considered, the connection between sleep dysregulation and human fertility was classified according to specific sleep characteristics, such as sleep duration, quality, and habits. In addition, possible physio-pathological mechanisms proposed to support the link between sleep and fertility were summarized.

CONCLUSION

This review summarizes the most relevant findings about the intricate and still largely unknown network of molecular pathways involved in the regulation of circadian homeostasis, to which sleep contributes, essential for reproductive physiology. Thus, many mechanisms seem correlate sleep disorders to reproductive health, such as adrenal activation, circadian dysregulation, and genetic influences. This review highlights the need to properly designed trials on the topic.

Sleep Behavior and Self-Reported Infertility: A Cross-Sectional Analysis Among U.S. Women

OBJECTIVE

To investigate the associations between sleep behaviors and female infertility.

METHODS

We conducted a cross-sectional study composed of 2175 U.S. women 18-44 years of age from the National Health and Nutrition Examination Survey (NHANES) (2015-2018). Bedtime/waketime and sleep duration were extracted from the sleep disorder questionnaire. Self-reported infertility was defined as a binary variable based on the participants' response to the question, "Have you ever attempted to become pregnant over a period of at least a year without becoming pregnant?". Multivariate logistic regression analyses were done to explore the relationship between sleep behaviors and female infertility.

RESULTS

Bedtime (OR=1.24; 95% CI, 1.10-1.40, P = 0.001) and waketime (OR=1.14; 95% CI, 1.01-1.28, P = 0.037) were associated with infertility. Waketime of 08:00 was the inflection point, above which the probability of infertility increased rapidly (OR=1.41; 95% CI, 1.11-1.79, P = 0.004). Sleep-wake behavior was significantly associated with infertility (OR=1.34; 95% CI, 1.16-1.53, P < 0.001) and participants with early-bed/early-rise behavior had the lowest risk.

CONCLUSIONS

Among U.S. women 18-44 years of age, bedtime and waketime were significantly linearly and non-linearly correlated with infertility, respectively. Early-bed/early-rise behavior was associated with the lowest infertility rate. Further study is needed because the timing of sleep behaviors are modifiable factors and could be a novel strategy to cope with infertility.

Impact of sleep on female and male reproductive functions: a systematic review

OBJECTIVE

To evaluate the association of sleep parameters on female and male reproductive functions.

DESIGN

Systematic review.

SETTING

Not applicable.

PATIENT(S)

Female and male individuals, either healthy or infertile.

INTERVENTION(S)

Relevant articles were identified according to the The Preferred Reporting Items for Systematic Reviews and Meta-analyses recommendations in the PubMed and EMBASE databases from January 1, 2000 to June 8, 2020.

MAIN OUTCOME MEASURE(S)

The association between sleep and ovary function, spermatic function, natural fertility, and in vitro fertilization (IVF) outcomes was assessed.

RESULT(S)

A total of 33 studies that looked at the association between sleep and either ovary function (n = 10), spermatic function (n = 12), natural fertility (n = 5), or IVF outcomes (n = 6) were included. Overall, female and male fertility, as well as IVF outcomes may be affected by short sleep duration, evening chronotype, or shift/night work schedules. However, the results were hardly comparable due to the heterogeneous study methodologies used.

CONCLUSION(S)

Sleep may be an original and innovative parameter to consider in the reproduction field. Further investigation is needed to elucidate how sleep and fertility are interrelated and how sleep might constitute a useful modifiable target in infertility management.

Chronotype, social jetlag, and time perspective

The phase of entrainment (chronotype) is known to be associated with time perspective (TP), suggesting that the state of circadian system is involved in the long-term planning of human life. However, little is known regarding the influence of circadian misalignment on long-term planning ability. The aim of this study was to investigate the association between social jetlag (SJL) and TP. A total of 1064 schoolchildren and university students (mean age ± standard deviation, 19.2 ± 2.9 years; range, 15-25 years; females, 71.7%) from four cities in the Russian Federation located between 56.9 and 61.7 degrees North completed the Munich ChronoType Questionnaire, the Pittsburgh Sleep Quality Index, the Seasonal Pattern Assessment Questionnaire, and Zimbardo Time Perspective Inventory. Study participants also indicated personal data (age, sex, height weight, place of residence, and achievements). A multiple regression analysis with stepwise inclusion of predictors in the model was performed to evaluate associations between time perspective characteristics (dependent variables) and predictor variables. The change in R² was used as the measure of effect size. Chronotype was found to be a moderate predictor of future TP (B = 0.034; ΔR² = 0.037). In addition, sleep quality was found to be a moderate predictor of past negative (B = 0.043; ΔR² = 0.074), present fatalistic (B = 0.021; ΔR² = 0.035), and deviation from balanced TP (B = 0.034; ΔR² = 0.066). Mood seasonality was a moderate predictor of present hedonistic TP (B = 0.016; ΔR² = 0.038), and social jetlag was a weak predictor of present fatalistic (B = 0.052; ΔR² = 0.019), future (B = -0.033; ΔR² = 0.004), and deviation from balanced TP (B = 0.047; ΔR² = 0.012). In conclusion, this study found a weak but significant association between social jetlag and TP in adolescents and young adults.

Morning chronotype is a protective factor against chemotherapy-induced hot flashes in premenopausal women with breast cancer

PURPOSE

Adjuvant chemotherapy in patients with breast cancer often causes hot flashes, impairing quality of life. However, the chronobiological or psychiatric factors associated with the development of chemotherapy-induced hot flashes (CIHFs) remain undetermined. The purpose of this study was to investigate whether chronotype was associated with the incidence of CIHFs.

METHODS

A total of 119 premenopausal women with non-metastatic breast cancer awaiting adjuvant chemotherapy after surgery without hot flashes were included. The presence of CIHF was defined as having moderate to severe hot flashes, as measured by the subscale of hot flashes in the Menopause Rating Scale, at 4 weeks after the completion of chemotherapy. Chronotype (Morning/Intermediate/Evening) was assessed with the Composite Scale of Morningness before adjuvant chemotherapy. To examine the association between chronotype and CIHF, we built logistic regression models, adjusting for age, body mass index, sleep quality, and radiation therapy.

RESULTS

CIHF occurred in 50.4% of participants. Morning type was inversely associated with CIHF (reference: Intermediate type, odds ratio [OR], 0.37; 95% confidence interval [CI], 0.16-0.94; p = 0.040) in the univariate model, and the association remained significant (OR, 0.37; CI, 0.13-0.96; p = 0.045) after adjusting for age, body mass index, sleep quality, and radiation therapy.

CONCLUSIONS

Morning chronotype is a protective factor against the development of CIHF in patients with breast cancer. Chronotypes should be assessed and considered in the prediction and management of CIHF.

Eveningness associates with smoking and sleep problems among pregnant women

Sleep problems during pregnancy impair maternal health and increase the risk for adverse pregnancy outcome. The circadian preference toward eveningness has been associated with sleep problems in previous studies. Here, we studied whether evening-type women had more sleep problems during their pregnancy, as compared with other chronotypes, in a sample consisting of 1653 pregnant women from the Finnish CHILD-SLEEP Birth Cohort. Chronotype was assessed with a shortened version of the morningness-eveningness questionnaire. Pregnant evening-type women reported more sleep problems, including troubles of falling asleep (OR = 3.4, p < 0.0001), poor sleep quality (OR = 2.9, p < 0.01) and daily tiredness (OR = 3.2, p < 0.0001) than the morning-type women, even after controlling for sleep duration and sleep deprivation. They had higher scores on Epworth Sleepiness Scale (p < 0.05), Basic Nordic Sleep Questionnaire (p < 0.0001) and Global Seasonality Score (p < 0.01) and were also more often smokers, also during pregnancy (p < 0.001) and reported poorer general health (p < 0.001) than the morning-type women. They also reported having had more sleep problems during their childhood (OR = 1.5, p < 0.05) and adolescence (OR = 2.0, p < 0.001) than the morning-type women. Our results indicate that eveningness is associated with more sleep problems and unhealthy life habits during pregnancy.

Women would like their partners to be more synchronized with them in their sleep-wake rhythm

Men sleep shorter and go to bed and get up later than women, thus they are later chronotypes. This difference between the sexes is most pronounced between puberty and menopause indicating the possibility that morningness is subject to sexual dimorphism related to reproductive aspects. The objective of the study was to compare the sleep-wake behavior of women with their actual partners and with their preferred partners. As a hypothesis, we expect some assortment in mating concerning chronotype (with the actual partner), but we also expect a higher synchronization with a preferred ideal partner. 167 women were analyzed in this study (mean age: 23.0 ± 2.57 (SD) years). Mated women were earlier chronotypes than their partners (t = -2.051, p = .042, d = .34) but the difference was small (11:02 min ± 1:04 min). The results of the present study showed women preferring a partner synchronized to their own sleep-wake-rhythm more than their actual partners were. The above result was true either for single facets of the sleep-wake rhythm (e.g. bed time, sleep onset) or for midpoint of sleep on free days - an indicator of actual chronotype: women's and their partners' correlation of midpoint of sleep was lower (r = .513) than women's and their ideal partners' correlation (r = .855). Amongst various sleep-wake measures, women particularly preferred a partner going to bed at the same time. Assortative mating according to sleep-wake rhythm exists, but women for long-term pair-bonds would like their partners far more synchronized.