Night-to-night associations between light exposure and sleep health.

Previous research has demonstrated that exposure to light preceding and during sleep is associated with poor sleep, but most research to date has utilized either experimental or cross-sectional designs. The current study expands upon prior studies by using a microlongitudinal design that examines the night-to-night associations between light and sleep health in a diverse sample of adults (pre-registered at osf.io/k5zgv). US adults aged 18-87 years from two parent studies (N = 124) wore an actiwatch for up to 10 nights. Light variables estimated from actigraphy include both average exposure and time above light threshold of 10 (TALT10 ) and 40 (TALT40 ) lux both during sleep and for the 1-hr preceding sleep. Actigraphy-based sleep variables included sleep offset, duration, percentage and fragmentation index. Higher average light exposure during sleep was associated with a later sleep-offset time, lower sleep percentage and higher fragmentation index (all p < 0.01). More minutes of TALT10 during sleep was associated with later sleep timing, lower sleep percentage and higher fragmentation index (all p < 0.01), and greater TALT40 during sleep was associated with lower sleep percentage. Light exposure was not related to sleep duration. In summary, greater light exposure during sleep was related to poorer sleep continuity and later wake time. The lack of association between light and sleep duration may be the result of compensating for sleep disruption by delaying wake time. Multi-level interventions to consistently reduce light levels during sleep should be considered.

The theory of planned behaviour and sleep opportunity: An ecological momentary assessment.

Many American adolescents and adults report that they are not meeting sleep duration recommendations. Although insufficient sleep duration can occur due to factors outside an individual's direct control, many individuals choose to restrict their own sleep. The theory of planned behaviour (TPB) offers a framework to study this phenomenon. Recent research efforts have used the TPB to study sleep and have demonstrated success predicting sleep-related intentions and behaviour but have failed to consider volitional sleep behaviour or consider between- and within-person differences. The present study used an intensive longitudinal design to test how constructs of the TPB relate to nightly sleep opportunity. Healthy college students (N = 79) participated in a weeklong study in which they completed four ecological momentary assessment signals per day that measured their attitudes, subjective norms, perceived behavioural control, and intentions relating to their nocturnal sleep opportunity. Participants wore an actiwatch each night of the study to measure their sleep opportunity. Mixed linear models found that both intentions and perceived behavioural control were significant predictors of subsequent sleep opportunity, and that perceived behaviour control was the strongest within-day predictor of intentions. Results demonstrate that within-person changes in perceived behavioural control and intentions predict subsequent sleep opportunity and provide insight into the potential refinement of sleep promotion efforts.

Temporal Associations Between Daytime Napping and Nocturnal Sleep: An Exploration of Random Slopes.

BACKGROUND: Restricting daytime naps is a common sleep hygiene recommendation to improve nocturnal sleep, but research on whether napping is related to sleep is mixed. The current literature is limited in that day level, bidirectional associations have not been tested in college students, and existing studies have not sufficiently examined the role of individual differences in these daily associations. PURPOSE: The current study addressed these limitations by assessing the temporal associations between self-reported daytime nap duration and objectively assessed nocturnal sleep, and whether these associations were moderated by chronotype or nap frequency, in college students. METHODS: Participants (N = 384) self-reported nap duration and wore an actiwatch to measure nocturnal sleep for 14 consecutive days and nights. Mixed linear models were used to test the daily associations between daytime nap duration and total sleep time (TST), sleep onset latency (SOL), sleep efficiency (SE), and wake after sleep onset (WASO). In addition, random slope modeling was used to test whether these associations significantly varied between participants. RESULTS: Longer nap duration was significantly associated with greater WASO, lower SE, and longer SOL. Shorter TST, shorter WASO, and greater SE were related to longer next-day nap duration. CONCLUSIONS: There were several significant associations between daytime napping and nocturnal sleep, and nap frequency significantly moderated the association between TST and next-day nap duration. Future research should test daily and contextual moderators of daytime napping and nocturnal sleep, which could refine sleep hygiene efforts by identifying individuals for whom recommendations would be most helpful.

Bidirectional Relations Between Daily Stress and Sleep Among Black Emerging Adults.

BACKGROUND: Black adults experience higher levels of stress and more dysfunctional sleep patterns compared to their White peers, both of which may contribute to racial disparities in chronic health conditions. Dysfunctional sleep patterns are also more likely in emerging adults compared to other age groups. Daily stress-sleep relations in Black emerging adults are understudied. PURPOSE: This study used ecological momentary assessment (EMA) and wrist-worn actigraphy to examine bidirectional associations between daily stress and sleep among Black emerging adults. METHODS: Black college freshmen (N = 50) completed an EMA protocol (i.e., five EMA prompts/day) and wore an accelerometer for 7 days. The first EMA prompt of each day assessed sleep duration and quality. All EMA prompts assessed stress. Wrist-worn actigraphy assessed nocturnal sleep duration, sleep onset latency, sleep efficiency, and waking after sleep onset. RESULTS: At the within-person level, stress experienced on a given day was not associated with any sleep metrics that night (p > .05). On evenings when actigraphy-based sleep duration was shorter (B = -0.02, p = .01) and self-reported sleep quality was poorer (B = -0.12, p = .02) than usual, stress was greater the following day. At the between-person level, negative bidirectional relations existed between stress and actigraphy-based waking after sleep onset (stress predicting sleep: B = -0.35, p = .02; sleep predicting stress: B = -0.27, p = .04). CONCLUSIONS: Among Black emerging adults, associations between daily sleep and stress vary at the between- and within-person level and are dependent upon the sleep metric assessed. Future research should compare these relations across different measures of stress and different racial/ethnic groups to better understand health disparities.

The effect of caffeine abstinence on sleep among habitual caffeine users with poor sleep.

Caffeine is the most widely used psychoactive substance in the world and is known to disrupt healthy sleep. However, very few studies have directly tested the effect of caffeine abstinence on sleep, and these have yielded inconsistent findings. The purpose of the present study was to examine changes in sleep following caffeine abstinence and examine the extent to which characteristics of habitual caffeine use moderated this change. Participants included 66 healthy, young adults with habitual caffeine use and poor sleep. During the 2-week baseline, sleep was assessed using wrist actigraphy and daily caffeine use was assessed with bedtime diaries. Eligible participants then completed 1 week of caffeine abstinence, during which sleep was measured with wrist actigraphy. Multilevel models found no significant differences between either mean levels or growth trajectories of total sleep time or sleep efficiency between baseline and caffeine abstinence. Mean levels of sleep onset latency also did not differ between baseline and caffeine abstinence. A small but significant quadratic effect was observed, such that sleep onset latency decreased during the first few days of caffeine abstinence, then increased to levels above baseline. Characteristics of caffeine use did not moderate changes in sleep between baseline and caffeine abstinence. These data suggest that abstaining from caffeine may not result in long-term sleep improvement for habitual caffeine users, which contradicts the common sleep health recommendation. The present findings encourage more rigorous investigation of the effectiveness of caffeine restriction on sleep.

Intraindividual Variability of Sleep Opportunity Attitudes, Perceived Norms, Perceived Behavioral Control, and Intentions.

BACKGROUND: Recent research has used the theory of planned behavior (TPB) to predict sleep. However, this research has focused on between-person effects and has failed to capture the intraindividual variability of sleep-related attitudes, subjective norms, perceived behavioral control, and intentions. PURPOSE: The current study sought to characterize the between- and within-day patterns of these constructs. METHODS: Participants (N = 79) completed a 1 week ecological momentary assessment protocol in which they reported their attitudes, subjective norms, perceived behavioral control, and intentions toward nightly sleep opportunity four times per day. RESULTS: Analyses revealed both between- and within-day variability of these constructs, with perceived behavioral control and intentions demonstrating greater variability than attitudes and subjective norms. Mixed linear models revealed that attitudes and subjective norms significantly increased throughout the week, while perceived behavioral control and intentions significantly decreased throughout the day. CONCLUSIONS: The between- and within-day patterns of the TPB constructs highlight important methodological considerations and provide insight into the potential refinement of sleep promotion efforts.

The Process of Developing a Sleep Health Improvement Plan: a Lab-Based Model of Self-Help Behavior.

BACKGROUND: Although self-help strategies to improve sleep are widely accessible, little is known about the ways in which individuals interact with these resources and the extent to which people are successful at improving their own sleep based on sleep health recommendations. The present study developed a lab-based model of self-help behavior by observing the development of sleep health improvement plans (SHIPs) and examining factors that may influence SHIP development. METHOD: Sixty healthy, young adults were identified as poor sleepers during one week of actigraphy baseline and recruited to develop and implement a SHIP. Participants viewed a list of sleep health recommendations through an eye tracker and provided information on their current sleep health habits. Each participant implemented their SHIP for 1 week during which sleep was assessed with actigraphy. RESULTS: Current sleep health habits, but not patterns of visual attention, predicted SHIP goal selection. Sleep duration increased significantly during the week of SHIP implementation. CONCLUSIONS: Findings indicate that the SHIP protocol is an effective strategy for observing self-help behavior and examining factors that influence goal selection. The increase in sleep duration suggests that individuals may be successful at extending their own sleep, though causal mechanisms have not yet been established. This study presents a lab-based protocol for studying self-help sleep improvement behavior and takes an initial step toward gaining knowledge required to improve sleep health recommendations.

Application of health behaviour theory to sleep health improvement.

Although sleep hygiene is often used for broad sleep health promotion efforts, sleep hygiene education programmes are largely ineffective. These programmes are limited by their lack of a theoretical foundation. Health behaviour theory (HBT) has been used for decades to successfully predict and modify many health behaviours, but its use in the study of sleep health is rare. The purpose of this review is threefold. First, four dominant HBTs will be introduced. Second, the brief literature on HBT and sleep health will be reviewed. Lastly, a translational research agenda will be proposed. The present review concludes that HBT shows potential in both the prediction and modification of sleep health, and that there are several short- and long- term research goals to advance these efforts.

Daily Associations Between Sleep and Physical Activity.

BACKGROUND: Research has demonstrated a correlational relationship between sleep and physical activity, though this work has been largely cross sectional and fails to demonstrate temporal relationships. The purpose of this study was to test the daily, bidirectional relationships between sleep and physical activity, and whether this varied between weekdays and weekend days. METHOD: Fifty-four healthy, young adults wore a Fitbit Flex to measure sleep and physical activity during a 6-day study period. RESULTS: Mixed linear models revealed that physical activity did not predict subsequent night's sleep. However, on nights when participants had longer than their own average total sleep time, and greater than their own average wake after sleep onset, this predicted less physical activity the following day. CONCLUSION: Results suggest that, in healthy young adults, physical activity may not promote healthier subsequent sleep, but sleep duration and continuity influence physical activity in their own way. Young adults may respond differently to health promotion efforts, and a greater understanding of these temporal associations can enhance the efficacy of these efforts.

Sleep and eating disorders among adults enrolled in a commercial weight loss program: associations with self-report and objective sleep measures.

PURPOSE: Some research suggests that eating disorders are related to poor sleep health. To increase knowledge on the relation between sleep and eating disorders, we used a multi-method approach to examine associations between sleep, chronotype, and eating disorder psychopathology. METHODS: We investigated associations between ED psychopathology, both diagnostic categories (ascertained through self-report data) and dimensional measures, and self-report and ambulatory measures of sleep. Adults currently enrolled in a commercial weight loss program completed self-report measures as well as 1 week of ambulatory sleep monitoring and sleep diaries. RESULTS: Participants with full- or sub-threshold bulimia nervosa and binge eating disorder reported significantly lower subjective sleep health and greater eveningness. Additionally, greater severity of eating disorder psychopathology was associated with lower subjective sleep health and greater eveningness. Eating disorder psychopathology was generally not related to objective sleep measures. Regarding diary measures, global eating disorder psychopathology was negatively correlated with subjective reports of feeling rested. CONCLUSION: Eating disorder psychopathology is associated with participants' subjective sense of sleep quality, but appears to have little relation to objective sleep characteristics. Level of evidence Level V, descriptive study.

Racial Disparities in Sleep: Potential Mediation by Discrimination and Psychological Distress.

Previous research has demonstrated that experiences of discrimination contribute to racial disparities in sleep, and that psychological distress mediates these relationships. However, previous research has not included race as part of the mediation pathway and has had limited dimensions of sleep health and psychological mediators. In the current study, we examine serial mediation pathways by which race and sleep health are mediated through discrimination and subsequently through psychological distress (i.e., depressive symptoms, chronic stress, and loneliness). Data were from the 2010 wave of the Health Retirement Study (HRS). The analytic sample (n = 7,749) included Black and White participants who were included in the enhanced face-to-face interview in 2010 and who completed the psychosocial questionnaire. Race was reported as either Black or White. Sleep health was assessed with a 4-item questionnaire. Depressive symptoms were assessed with the shortened CES-D, chronic stress via the ongoing chronic stressor scale, and loneliness via the UCLA loneliness scale. Covariates were included in all serial mediation models. Relative to White participants, Black participants reported increased experiences of discrimination, which was associated with increased psychological distress, and poorer sleep health. Findings demonstrate the significant adverse impact that discrimination has on both psychological well-being and sleep health.

Daily relations between nap occurrence, duration, and timing and nocturnal sleep patterns in college students.

OBJECTIVE/DESIGN: Sleep patterns change during college, and students may nap to compensate for lost sleep. Despite the increased prevalence of napping among students, few studies have investigated daily relations between napping and nocturnal sleep, as well as how timing of naps and nocturnal sleep might influence one another. The present study used daily diaries to capture the occurrence, timing, and duration of napping and relation to nocturnal sleep. SETTING/PARTICIPANTS: Daily diary data, collected for 4-7 days, from 654 college students from a mid-sized midwestern university (81.5% female). MEASUREMENT: Participants reported nightly sleep durations, bedtimes, and wake times as well as nap durations and nap start times. RESULTS: Multilevel modeling (MLM) and multi-level logistic regressions revealed bidirectional relations between nocturnal sleep and napping. Regarding nocturnal sleep and its relation to next day napping, nocturnal sleep (including shorter duration and later bedtime) was associated with increased odds of napping and longer napping the following day. Shorter sleep duration was also associated with taking an earlier nap, while later bedtime was associated with a later nap the following day. Regarding napping and its association with same-night nocturnal sleep, taking a nap was associated with longer sleep duration that night, however, later nap start times and longer nap durations were associated with later bedtimes that night. CONCLUSIONS: Findings provide evidence for bidirectional associations between napping and nocturnal sleep. Future studies are needed to explore how naps could be optimized to promote nocturnal sleep among college students, as well as for whom naps might be most beneficial.

Big 5 personality traits and intraindividual variability in sleep duration, continuity, and timing.

OBJECTIVES: The personality traits of conscientiousness and neuroticism have been consistently linked to mean-level, self-reported sleep duration and continuity. The present study expands this literature by using actigraphy sleep assessment to examine how personality is related to both mean-level and the intraindividual variability in sleep duration, continuity, and timing. DESIGN: One-week ecological sleep assessment. SETTING: The research was conducted at a mid-size Midwestern university. Actigraphy data were collected at participants' homes. PARTICIPANT: The study had a sample size of 358 college-aged participants. MEASUREMENTS: Sleep duration, continuity, and timing were assessed for 7 consecutive nights using actigraphy. Participants also completed a self-report assessment of personality. RESULTS: Conscientiousness and extraversion emerged as the key personality predictors of sleep outcomes. Higher conscientiousness was associated with longer average sleep duration and earlier timing, as well as higher consistency in total sleep time. Higher extraversion was associated with later bedtimes, less total sleep time, and more variability in their sleep timing. Neuroticism, agreeableness, and openness to experience were not significantly related to sleep. CONCLUSION: The study's results highlight the importance of personality in sleep research, with implications for sleep health promotion efforts.

U.S. masters track participation reveals a stable sex difference in competitiveness.

It is well established that men are more likely than women to engage in direct competition, but it is unclear if this reflects social structural conditions or evolved predispositions. These hypotheses can be addressed by quantifying competitiveness in sports and testing if the sex difference is decreasing over time in the U.S., a society where social roles have converged. Study 1 assessed participation and the occurrence of relatively fast performances by masters runners (40-74 years old) at recent road races and track meets. Fast performances occurred over 20 times more often at track meets than at road races. Women comprised 55% of finishers at roads races but only 15-28% of finishers at track meets. Thus, the sex difference in masters track participation can serve as a measure of the sex difference in competitiveness. Study 2 used data from national championship meets and yearly rankings lists to test whether the sex difference in masters track participation decreased from 1988-2012. The sex difference decreased overall, but there was no evidence of change since the late 1990s. Therefore, the sex difference in the willingness to engage in direct sports competition appears to reflect both social structural conditions and evolved predispositions.