Bed-Sharing in Couples Is Associated With Increased and Stabilized REM Sleep and Sleep-Stage Synchronization

The effects of daylight duration on the multiple sleep latency test (MSLT) results: A pilot study

OBJECTIVE

MSLT results are known to be affected by multiple factors including sleep time, frequency of nighttime arousals, and medications intake. Although being the main synchronizer of sleep and wakefulness, daylight duration effects on MSLT have not been examined. Burlington, Vermont, USA experiences great variations in daylight duration, ranging from 8 h 50 min to 15 h 33 min of daylight. The aim of this study was to test the hypothesis that there would be photoperiod duration effects on MSLTs performed during short daylight (short daylight studies, SDS) vs. long daylight (long daylight studies, LDS) from 2013 to 2023 in our sleep laboratory.

METHODS

We identified and analyzed 37 SDS (daylight 530-560 min) and 36 LDS (daylight 903-933 min) from our database. Groups of SDS and LDS results were compared using non-paired student T test, Chi-Square and non-parametric Mann Whitney U Test.

RESULTS

Average daylight duration was 15 h 18 ± 14.6 min for LDS and 8 h 57 ± 18 min for SDS. Two groups did not differ in terms of the age, gender, BMI and race of patients studied. Mean total sleep time and sleep efficiency during PSG preceding MSLT, and MSLT mean sleep onset latency did not significantly differ for the two groups. However, SDS MSLT naps had significantly more sleep onset REM periods (SOREMP), and distribution of the number of SOREMP captured during MSLT was different for SDS and LDS groups. Differences of SDS and LDS results did not relate to sleep architecture of the overnight PSG as analysis of sleep and REM latency and relative percentages of N1, N2, REM, and N3 was not significantly different between SDS and LDS. The two groups showed difference in arousal indexes during N1 and REM sleep.

CONCLUSIONS

Daylight duration may impact MSLT results and should probably be accounted for in MSLT interpretation. Attention to photoperiod could be considered in MSLT guidelines, if our results are replicated in larger samples.

Attachment and sleep quality in adults: A multilevel meta-analysis of actor and partner effect

Within the context of sleep, attachment is hypothesized to play a central role in regulating bedtime affect and arousal. While previous studies have suggested a link between attachment and sleep quality, a meta-analysis specifically examining this association in adults has been lacking. To address this gap, we conducted a series of multilevel meta-analyses of 28 studies on this topic. Our results indicated a correlation between attachment anxiety and an individual's own sleep quality (r = -0.16, p < 0.001), as well as their partner's sleep quality (r = -0.10, p < 0.05). There was also a negative correlation between attachment avoidance and an individual's sleep quality (r = -0.15, p < 0.001) as well as their partner's sleep quality (r = -0.16, p < 0.01). Additionally, the relationships were moderated by several variables, including age, sleep measurement, and gender. Further analysis indicated that attachment anxiety was associated with poorer subjective sleep quality (PSQI) (r = -0.23, p < 0.001), longer sleep latency (r = -0.10, p < 0.05), increased wakefulness after sleep onset (r = -0.09, p < 0.05), and greater daytime sleepiness (r = -0.20, p < 0.01). Attachment avoidance was associated with poorer self-reported sleep quality (PSQI) (r = -0.16, p < 0.001), longer time to fall asleep (r = -0.15, p < 0.05), and increased daytime sleepiness (r = -0.15, p < 0.05). In summary, the findings of the current study supported the association between attachment insecurity and poorer sleep quality in both individuals and their partners. These findings hold important implications for future interventions aimed at improving sleep quality by addressing attachment-related concerns.

Development of the Couples' Sleep Conflict Scale: A new tool to assess conflict around sleep in romantic relationships

OBJECTIVE

The purpose of this study was to evaluate the psychometric properties of the Couples' Sleep Conflict Scale, a new measure designed to identify the extent of conflict around sleep in romantic relationships.

METHODS

Data from an individual sample (N = 158) and dyadic sample (N = 143 mixed-gender couples) in romantic relationships were used to examine the psychometric properties of the Couples' Sleep Conflict Scale, including internal consistency, convergent and divergent validity, and whether the factor structure differed between couples with concordant and discordant chronotypes.

RESULTS

Results revealed that the Couples' Sleep Conflict Scale fit a 1-factor solution of 5 items, a summed or mean score can be used, and that it is reliable for both men and women. In addition, more relational sleep conflict was associated with both their own and their partners' poorer sleep hygiene, worse sleep quality, and more daytime sleepiness as well as more general relationship conflict, lower relationship satisfaction, and higher anxious and avoidant attachment. Finally, we found partial measurement invariance for factor loadings, intercepts, and latent variable variances between couples with concordant vs. discordant chronotypes.

CONCLUSION

The Couples' Sleep Conflict Scale is a brief measure that can be used in both research and in health care settings to examine how sleep-related conflict can affect both sleep and relationship quality among couples.

Parents' Sleep Multi-Trajectory Modelling from 3 to 36 Months Postpartum in the SEPAGES Cohort

Objective

We investigated maternal and paternal sleep evolution from 3 to 36 months postpartum, their interrelations and predictors in the SEPAGES cohort.

Methods

Sleep information (night sleep duration [NSD], weekend daytime sleep duration [DSD] and subjective sleep loss [SSL]) was collected by self-administered questionnaires at 3, 18, 24 and 36 months postpartum in the SEPAGES French cohort that included 484 mothers and 410 fathers. Group-based multi-trajectory modelling was used to identify maternal, paternal and couple sleep multi-trajectory groups among 188 couples reporting sleep data for at least 2 time points. Multinomial logistic regression was used to assess associations between parental sleep multi-trajectories and early characteristics such as sociodemographic, chronotypes, child sex, birth seasonality or breastfeeding duration.

Results

We identified three maternal (M1-M3), paternal (F1-F3) and couple (C1-C3) sleep multi-trajectory groups with similar characteristics: a group with short NSD and high SSL prevalence (M1, F2, C2), a group with long NSD but medium SSL prevalence (M2, F3, C3) and a group with long NSD and low SSL prevalence (M3, F1, C1). Mothers with the shortest NSD (M1) were less likely to have a partner with long NSD (F2). As compared with long NSD and low SSL prevalence (C1), couples with short NSD and high SSL prevalence (C2) were less likely to have had a first child born in the autumn and fathers in C2 had a later chronotype.

Conclusion

We identified distinct sleep multi-trajectory groups for mothers, fathers and couples from 3- to 36-month postpartum. Sleep patterns within couples were homogeneous.

Neurophysiological and behavioral synchronization in group-living and sleeping mice

Social interactions profoundly influence animal development, physiology, and behavior. Yet, how sleep-a central behavioral and neurophysiological process-is modulated by social interactions is poorly understood. Here, we characterized sleep behavior and neurophysiology in freely moving and co-living mice under different social conditions. We utilized wireless neurophysiological devices to simultaneously record multiple individuals within a group for 24 h, alongside video acquisition. We first demonstrated that mice seek physical contact before sleep initiation and sleep while in close proximity to each other (hereafter, "huddling"). To determine whether huddling during sleep is a motivated behavior, we devised a novel behavioral apparatus allowing mice to choose whether to sleep in close proximity to a conspecific or in solitude, under different environmental conditions. We also applied a deep-learning-based approach to classify huddling behavior. We demonstrate that mice are willing to forgo their preferred sleep location, even under thermoneutral conditions, to gain access to social contact during sleep. This strongly suggests that the motivation for prolonged physical contact-which we term somatolonging-drives huddling behavior. We then characterized sleep architecture under different social conditions and uncovered a social-dependent modulation of sleep. We also revealed coordination in multiple neurophysiological features among co-sleeping individuals, including in the timing of falling asleep and waking up and non-rapid eye movement sleep (NREMS) intensity. Notably, the timing of rapid eye movement sleep (REMS) was synchronized among co-sleeping male siblings but not co-sleeping female or unfamiliar mice. Our findings provide novel insights into the motivation for physical contact and the extent of social-dependent plasticity in sleep.

To Sleep Dreaming Medals: Sleep Characteristics, Napping Behavior, and Sleep-Hygiene Strategies in Elite Track-and-Field Athletes Facing the Olympic Games of Tokyo 2021

PURPOSE

Few data are available on sleep characteristics of elite track-and-field athletes. Our study aimed to assess (1) differences in sleep between sexes and among different track-and-field disciplines, (2) the effect of individualized sleep-hygiene strategies on athletes' sleep parameters, and (3) daytime nap characteristics in track-and-field athletes.

METHODS

Sleep characteristics of 16 elite Olympic-level track-and-field athletes (male: n = 8; female: n = 8) were assessed during the preseason period, at baseline (T0), and during the in-season period, after the adoption of individualized sleep-hygiene strategies (T1). Sleep parameters were objectively monitored by actigraphy for a minimum of 10 days, for each athlete, at both T0 and T1. A total of 702 nights were analyzed (T0 = 425; T1 = 277).

RESULTS

Female athletes displayed better sleep efficiency (88.69 [87.69-89.68] vs 91.72 [90.99-92.45]; P = .003, effect size [ES]: 0.44), lower sleep latency (18.99 [15.97-22.00] vs 6.99 [5.65-8.32]; P < .001, ES: 0.65), higher total sleep time (07:03 [06:56-07:11] vs 07:18 [07:10-07:26]; P = .030, ES: 0.26), earlier bedtime (00:24 [00:16-00:32] vs 00:13 [00:04-00:22]; P = .027, ES: 0.18), and lower nap frequency (P < .001) than male athletes. Long-distance runners had earlier bedtime (00:10 [00:03-00:38] vs 00:36 [00:26-00:46]; P < .001, ES: 0.41) and wake-up time (07:41 [07:36-07:46] vs 08:18 [08:07-08:30]; P < .001, ES: 0.61), higher nap frequency, but lower sleep efficiency (88.79 [87.80-89.77] vs 91.67 [90.95-92.38]; P = .013, ES: 0.44), and longer sleep latency (18.89 [15.94-21.84] vs 6.69 [5.33-8.06]; P < .001, ES: 0.67) than athletes of short-term disciplines. Furthermore, sleep-hygiene strategies had a positive impact on athletes' total sleep time (429.2 [423.5-434.8] vs 451.4 [444.2-458.6]; P < .001, ES: 0.37) and sleep latency (14.33 [12.34-16.32] vs 10.67 [8.66-12.68]; P = .017, ES: 0.19).

CONCLUSIONS

Sleep quality and quantity were suboptimal at baseline in Olympic-level track-and-field athletes. Large differences were observed in sleep characteristics between sexes and among different track-and-field disciplines. Given the positive effect of individualized sleep-hygiene strategies on athlete's sleep, coaches should implement sleep education sessions in the daily routine of top-level athletes.

Concordance in parent-child and sibling actigraphy-measured sleep: Evidence among early adolescent twins and primary caregivers

STUDY OBJECTIVES

Growing evidence suggests concordance between parent and youth sleep. However, no known study has simultaneously examined concordance among siblings' sleep patterns. This study investigated daily and average concordance in (1) parent-youth and (2) sibling actigraphy-measured sleep, as well as the degree to which sibling concordance varied by sleeping arrangements.

METHODS

516 twin siblings (Mage = 10.74, 51% female; 30% monozygotic (MZ) twin pairs, 37% same-sex dizygotic pairs (DZ-ss), 33% opposite-sex DZ pairs (DZ-os)) and their primary caregivers (Mage = 40.59, 95% female) wore wrist-based accelerometers for 7 consecutive nights to measure sleep duration, efficiency, midpoint time, and latency. Primary caregivers also reported on demographics, youth pubertal status, and room-sharing. Two-level multilevel models were estimated to examine daily and average concordance in parent-youth and sibling sleep.

RESULTS

Daily concordance was observed between parent and youth sleep duration and midpoint; average concordance was found for sleep duration, midpoint, and latency. Within sibling dyads, daily and average concordance was evident across all sleep parameters (duration, efficiency, midpoint, latency), with generally stronger concordance patterns for MZ than DZ twin pairs, and for twins who shared a room with their co-twin.

CONCLUSIONS

This is the first known study to document concordance among parent-youth and siblings' actigraphy-measured sleep within the same study (i.e., triad). Our findings can help inform the development of family-level interventions targeting daily and overall sleep hygiene.

Marital status and living apart affect sleep quality in male military personnel: a study of the China's Navy during COVID-19

Background

Marital status is a robust sociodemographic predictor of sleep. Having to live apart from spouse may have different implications than those of cohabitants or singles, especially in military personnel. Further research on this group will help provide knowledge in advance and facilitate early targeted interventions.

Methods

An online questionnaire study was conducted from July to November 2021. A total of 1,832 male military personnel completed the questionnaire. The marital status was measured by a self-reported single choice question. Pittsburgh sleep quality index (PSQI), Epworth Sleepiness Scale (ESS) and The Dysfunctional Beliefs and Attitudes about sleep scale (DBAS-16) were used to measure sleep-related outcomes. Inverse probability weighting (IPW) was applied to reduce the effects of confounding. Logistic regression was used to analyze the relationship between marital status and sleep and explore the impact of living together or not.

Results

After inverse probability weighting, the prevalence of poor sleep quality, sleepiness and dysfunctional beliefs were 16.1, 20.1 and 7.1%, respectively. One-way ANOVA results for the means of both groups were statistically significantly different, except for the sleep latency and sleep disturbance dimensions of PSQI. Participants who were married were more likely to have poor sleep quality (OR: 1.408, 95% CI: [1.10, 1.80]), to have daytime sleepiness (OR: 1.560, 95% CI: [1.27, 1.92]) and to develop dysfunctional beliefs and attitudes (OR: 2.497, 95% CI: [1.65, 3.80]) than those who were unmarried. Further analysis showed that the odds of developing poor sleep quality and DBAS in participants who married but living apart were significantly bigger than those unmarried (OR: 1.548 and 3.991, respectively.), while there were no significant differences in the odds of daytime sleepiness (OR: 0.738, p = 0.050). Age was a protective factor for the development of bad sleep outcomes, while family economic was an independent risk factor.

Conclusion

Marital status appear important for sleep quality, daytime sleepiness and sleep beliefs. The effect of living apart or not should be considered separately as an important predictor of sleep.

Recent Progress in Long-Term Sleep Monitoring Technology

Sleep is an essential physiological activity, accounting for about one-third of our lives, which significantly impacts our memory, mood, health, and children's growth. Especially after the COVID-19 epidemic, sleep health issues have attracted more attention. In recent years, with the development of wearable electronic devices, there have been more and more studies, products, or solutions related to sleep monitoring. Many mature technologies, such as polysomnography, have been applied to clinical practice. However, it is urgent to develop wearable or non-contacting electronic devices suitable for household continuous sleep monitoring. This paper first introduces the basic knowledge of sleep and the significance of sleep monitoring. Then, according to the types of physiological signals monitored, this paper describes the research progress of bioelectrical signals, biomechanical signals, and biochemical signals used for sleep monitoring. However, it is not ideal to monitor the sleep quality for the whole night based on only one signal. Therefore, this paper reviews the research on multi-signal monitoring and introduces systematic sleep monitoring schemes. Finally, a conclusion and discussion of sleep monitoring are presented to propose potential future directions and prospects for sleep monitoring.

Comparing Sleep in Shared and Individual Rooms During Training Camps in Elite Youth Soccer Players: A Short Report

CONTEXT

Athletes' sleep is the most important recovery strategy and has received growing attention. However, athletes may experience sleep disruptions due to numerous factors, such as training and competition workloads, travel, changes in sleep-wake schedules, and sleeping environments. They often spend nights in unfamiliar hotels, and sharing a bed, room, or both with another person might affect sleep duration and quality.

OBJECTIVE

To analyze the effect of sleeping in shared (SRs) versus individual (IRs) rooms on objective and subjective sleep and on slow-wave-sleep-derived cardiac autonomic activity during an official training camp in elite youth soccer players. Training and match workloads were characterized.

DESIGN

Observational case study.

SETTING

Hotel accommodations.

PATIENTS OR OTHER PARTICIPANTS

Thirteen elite male youth soccer players.

RESULTS

Players slept longer in IRs than in SRs (+1:28 [95% CI = 1:18, 1:42] hours:minutes; P < .001). Sleep efficiency was higher in IRs than in SRs (+12% [95% CI = 10%, 15%]; P < .001), whereas sleep latency was shorter in IRs than in SRs (-3 [95% CI = -15, -4] minutes; P < .001). Subjective sleep quality was lower in IRs than in SRs (-2 [-3 to -2] arbitrary units; P < .001). No differences were found for slow-wave-sleep-derived cardiac autonomic activity or for training or match workloads between training camps.

CONCLUSIONS

During soccer training camps, sleep may be affected by whether the athlete is in an SR versus an IR.

The Effect of Chronic Disease and Mental Health on Sleep Quality among Migrant Elderly Following Children in Weifang City, China

Few studies have focused on the sleep quality among migrant elderly following children (MEFC). This study aimed to investigate the effects of chronic disease and mental health on the sleep quality of MEFC in Weifang, China. A cross-sectional study was conducted by multi-stage cluster random sampling, and in total 613 participants were enrolled. Sleep quality and mental health were assessed by the Pittsburgh Sleep Quality Index (PSQI) and the Depression, Anxiety, and Stress Scale (DASS-21), respectively. Chronic disease was assessed by the question "how many chronic diseases do you have?" A descriptive analysis and chi-square test were used to describe participants' sociodemographic variables, chronic disease, mental health, and sleep quality. The relationship between chronic disease, mental health, and sleep quality was explored by establishing binary logistic regression models. The results showed that 18.3% of MEFC's sleep quality was poor. MEFCs who were male were more likely to report good sleep quality. MEFCs who have similar monthly family income compared with others around, with multimorbidity, depression, and anxiety were more likely to report poor sleep quality. Nearly 1/5 of MEFCs were having poor sleep quality in this study. Results indicated that chronic diseases, depression, and anxiety were risk factors for the sleep quality of MEFC. Implications for the government, communities, and families of MEFC were given for improving their sleep quality.

Affective Experience and Regulation via Sleep, Touch, and "Sleep-Touch" Among Couples

Touch associated with sleep (sleep-touch; reported physical contact during or shortly before/after sleep) is underexplored as a distinct contributor to affect regulatory processes associated with adult sleep. Given the affect-regulating effects of interpersonal touch, we theorized that among healthy co-sleeping adults, sleep-touch would add to sleep-related effects on affective "resetting," resulting in the experience of calmer, more regulated states. We studied 210 married heterosexual couples (aged 20-67 years, 79% non-Hispanic white, 13% Latinx) assigned 14 days of twice-daily (morning/evening) sleep/mood diaries. Multilevel daily (within-couple) mediation analyses showed that as hypothesized, more reported sleep-touch was associated with happier/calmer and less angry/irritable morning mood. In turn, happier/calmer mood was associated with greater enjoyment of time with spouse (for both spouses). Sleep-touch also was linked directly to both evening positive spousal events and enjoyment ratings. Sleep-touch was associated indirectly with fewer negative spousal events and less spouse-related stress via less angry/irritable morning mood (both spouses). Further, wives' sleep-touch was related to happier/calmer husband mood and evening enjoyment; husbands' sleep-touch was unrelated to wives' reports. All associations with sleep-touch were present while accounting for subjective sleep quality, prior evening mood, non-sleep-related physical affection, day in study, and weekend versus weekday. We speculate that among relatively healthy satisfied couples, physical touch during and surrounding sleep may add to sleep's restorative and affect-regulatory functions, suggesting a pathway through which co-sleeping can improve affect regulation and ultimately relationships and health.

The moderating role of gender in the association between quality of social relationships and sleep

To determine whether the association between perceived social support or strain in close relationships and sleep outcomes varies by gender. Participants were selected from the Biomarker projects of either the MIDUS II or MIDUS Refresher study if they were in a married-or married-like relationship and shared a bed with their partner (N = 989). A subsample also participated in a seven-day sleep study (n = 282). Perceived social support and strain from partner, family, and friends were examined by self-report questionnaires. We used the Pittsburgh Sleep Quality Index, sleep daily diary, and actigraphy to measure both subjective and objective sleep. Social support and strain were both associated with sleep outcomes. Specifically, higher social support was associated with fewer daily reports of light sleep and feeling more rested in the morning, while higher social strain was associated with higher clinical sleep disturbance. For women, but not men, social support was significantly associated with lower daily sleep disturbance while perceived social strain was significantly associated with higher daily sleep disturbance, lighter sleep, feeling less rested in the morning, lower sleep efficiency, and longer sleep onset latency. Mainly among women, social support and strain are associated with an important transdiagnostic health outcome-sleep-which may have implications for a wide range of health disparities. Interpersonal stressors may increase health risks differently for women compared to men and one mechanism that may link social relationships to long-term health outcomes is sleep.

Evening light environments can be designed to consolidate and increase the duration of REM-sleep

Evening exposure to short-wavelength light has disruptive effects on circadian rhythms and sleep. These effects can be mitigated by blocking short-wavelength (blue) frequencies, which has led to the development of evening blue-depleted light environments (BDLEs). We have previously reported that residing 5 days in an evening BDLE, compared with residing in a normal indoor light environment of similar photopic lux, advances circadian rhythms and increases the duration of rapid eye movement (REM) sleep in a randomized cross-over trial with twelve healthy participants. The current study extends these findings by testing whether residing in the evening BDLE affects the consolidation and microstructure of REM sleep in the same sample. Evening BDLE significantly reduces the fragmentation of REM sleep (p = 0.0003), and REM sleep microarousals in (p = 0.0493) without significantly changing REM density or the latency to first REM sleep episode. Moreover, the increased accumulation of REM sleep is not at the expense of NREM stage 3 sleep. BDLE further has a unique effect on REM sleep fragmentation (p = 0.0479) over and above that of circadian rhythms phase-shift, indicating a non-circadian effect of BDLE. If these effects can be replicated in clinical populations, this may have a therapeutic potential in disorders characterized by fragmented REM sleep.

Socio-Ecological Context of Sleep: Gender Differences and Couples' Relationships as Exemplars

PURPOSE OF REVIEW

We summarized recent findings on insufficient sleep and insomnia, two prominent sleep issues that impact public health. We demonstrate the socio-ecologial impact of sleep health with findings on gender and couples' relationships as exemplars.

RECENT FINDINGS

Robust gender differences in sleep duration and insomnia are due to biological and socio-ecological factors. Gender differences in insufficient sleep vary by country of origin and age whereas gender differences in insomnia reflect minoritized identities (e.g., sexual, gender). Co-sleeping with a partner is associated with longer sleep and more awakenings. Gender differences and couples' sleep were affected by intersecting social and societal influences, which supports a socio-ecological approach to sleep. Recent and seminal contributions to sleep health highlight the importance of observing individual sleep outcomes in a socio-ecological context. Novel methodology, such as global measures of sleep health, can inform efforts to improve sleep and, ultimately, public health.

Loneliness in older parents: marital transitions, family and social connections, and separate bedrooms for sleep

OBJECTIVES

This research innovatively analyzed the marital transitions (i.e., divorce and widowhood) of older Taiwanese parents, their sleep problems and spousal specific characteristics (i.e., separate bedrooms for sleep and marital relationships) as well as their social and family connections, all of which were simultaneously reflected in emotional and social domains of loneliness.

METHODS

Data are from 1645 older parents from Northern Taiwan. Loneliness was assessed by a De Jong-Gierveld short scale with emotional and social domains. We conducted multivariate logistic regression to examine the associations of marital transitions and family/social connections regarding sleep problems and psychological well-being with loneliness in social and emotional domains. Besides sleep problems and individual socioeconomic status, we included data on couples' sleeping arrangements and marital relationships.

RESULTS

Social loneliness was significantly associated with being divorced (AOR = 1.80, 95% CI 1.13-2.86) and living alone (AOR = 1.50, 95% CI 1.02-2.23). In contrast, strong family cohesion and frequent weekly contact with friends were associated with lower social loneliness. Married parents who slept in separate bedrooms were more likely than bed-sharing couples to feel emotional and social loneliness, despite adjusting for their sleep problems. Furthermore, satisfactory spousal relationships significantly decreased the magnitude of associations in the social domain.

DISCUSSION

Our findings support significant associations between loneliness in later life and major marital transitions, family and social connections and sleep problems which differ in social and emotional domains. Independent of relationship satisfaction, separate bedrooms relate to higher risks of emotional loneliness in older adults.

Romantic Love and Sleep Variations: Potential Proximate Mechanisms and Evolutionary Functions

This article provides a narrative review of what is known about romantic love and sleep variations and provides possible explanations for the association. Romantic love and sleep are described using a comprehensive, unifying framework advocated by Tinbergen. We summarise the findings of studies investigating the relationship between romantic love and sleep. Sleep variations are associated with romantic love in adolescents and young adults. We then detail some proximate mechanisms that may contribute to sleep variations in people experiencing romantic love before considering potential evolutionary functions of sleep variations in people experiencing romantic love. The relationship between symptoms of psychopathology and sleep variations in people experiencing romantic love is described. With the current state of knowledge, it is not possible to determine whether sleep variations associated with romantic love are adaptations or by-products of romantic love. We conclude by proposing areas for future research.

Couple Relationships Are Associated With Increased REM Sleep-A Proof-of-Concept Analysis of a Large Dataset Using Ambulatory Polysomnography

Background/Objectives: Rapid Eye Movement (REM) sleep is associated with memory consolidation and several health effects including stress response, mental health, and longevity. Recently, it has been shown that regularly co-sleeping couples have increased and stabilized REM sleep when co-sleeping as compared to sleeping individually. However, it remained unclear whether this is due to a specific effect of altering the usual sleeping environment by partner deprivation or due to a generalizable REM-sleep promoting effect of couple relationships. The present study aims to clarify this ambiguity. Methods: Married or never married individuals were taken from the Sleep Heart Health Study (n = 5,804) and matched regarding sociodemographic and health parameters. Matching was done using propensity score matching (1:1, nearest neighbor) and resulted in two groups of n = 69 each (married vs. never married). After confirmation of successful matching, samples were compared regarding REM sleep and other polysomnographic parameters (paired Students t-tests or Wilcoxon signed-rank tests). Results: Married individuals showed significantly higher levels of total and relative REM sleep as compared to never married individuals (all p's ≤ 0.003). Neither other sleep stages nor REM-sleep fragmentation differed between groups (all p's ≥ 0.29). Results regarding number of sleep cycles were ambiguous. Conclusion: This is the first between-subjects study to show that couple relationships are associated with increased REM sleep. This finding represents a necessary (but not sufficient) condition for the previously hypothesized self-enhancing feedback loop of REM sleep and sociality as well as for REM-sleep promotion as a mechanism through which couple relationships prevent mental illness.

Self-control or social control - what determines sleep hygiene in bed-sharing couples?

Objectives:

To investigate intimate partners’ impact on sleep hygiene with focus on the temporal dimension and differential predictors of sleep hygiene in co-sleepers and individual sleepers.

Material and Methods:

Habitual co-sleepers and individual sleepers (n=102) completed a cross-sectional, self-report, in-lab, digital survey on sleep hygiene, habitual sleeping arrangement, self-control, depressiveness, and sociodemographic parameters.

Results:

The relationship between sleeping arrangement and sleep hygiene in co-sleepers was time-dependent with an initial steep incline and a subsequent plateau at approximately one year of co-sleeping routine. Co-sleepers with more than one year of unaltered sleeping arrangement had significantly better sleep hygiene than co-sleepers with less than one-year or individual sleepers. More than one-year continuity of the sleeping arrangement moreover robustly predicted sleep hygiene in co-sleepers whereas self-control was the dominant predictor in individual sleepers.

Conclusion:

Amongst others, our findings support the idea that insomnia treatment could be improved by becoming sensitive to the habitual sleeping arrangement.

Sleep Consolidation, Sleep Problems, and Co-Sleeping: Rethinking Normal Infant Sleep as Species-Typical

Infants evolved in the context of close contact (including co-sleeping). Evolutionary context is rarely considered in psychological infant sleep research, and Western sleep researchers make assumptions about what optimal "normal" infant sleep is and how to achieve early, deep, infant sleep consolidation and avoid infant sleep problems. However, an evolutionary and anthropological view of infant sleep as species-typical recognizes that human evolution likely prepared the infant brain for optimal development within its evolutionary context - co-sleeping. Thus, "normal" infant sleep, sleep consolidation, and sleep problems should all be understood within the framework of co-sleeping infants, not the historically new-phenomenon of solitary-sleeping infants. Much work needs to be done in order to understand "normal" infant sleep as species-typical and how adaptive infants are to environments that stray from their evolutionary norm.