Evaluating Accuracy in Five Commercial Sleep-Tracking Devices Compared to Research-Grade Actigraphy and Polysomnography.

The development of consumer sleep-tracking technologies has outpaced the scientific evaluation of their accuracy. In this study, five consumer sleep-tracking devices, research-grade actigraphy, and polysomnography were used simultaneously to monitor the overnight sleep of fifty-three young adults in the lab for one night. Biases and limits of agreement were assessed to determine how sleep stage estimates for each device and research-grade actigraphy differed from polysomnography-derived measures. Every device, except the Garmin Vivosmart, was able to estimate total sleep time comparably to research-grade actigraphy. All devices overestimated nights with shorter wake times and underestimated nights with longer wake times. For light sleep, absolute bias was low for the Fitbit Inspire and Fitbit Versa. The Withings Mat and Garmin Vivosmart overestimated shorter light sleep and underestimated longer light sleep. The Oura Ring underestimated light sleep of any duration. For deep sleep, bias was low for the Withings Mat and Garmin Vivosmart while other devices overestimated shorter and underestimated longer times. For REM sleep, bias was low for all devices. Taken together, these results suggest that proportional bias patterns in consumer sleep-tracking technologies are prevalent and could have important implications for their overall accuracy.

Emotional memory consolidation during sleep is associated with slow oscillation-spindle coupling strength in young and older adults.

Emotional memories are processed during sleep; however, the specific mechanisms are unclear. Understanding such mechanisms may provide critical insight into preventing and treating mood disorders. Consolidation of neutral memories is associated with the coupling of NREM sleep slow oscillations (SOs) and sleep spindles (SPs). Whether SO-SP coupling is likewise involved in emotional memory processing is unknown. Furthermore, there is an age-related emotional valence bias such that sleep consolidates and preserves reactivity to negative but not positive emotional memories in young adults and positive but not negative emotional memories in older adults. If SO-SP coupling contributes to the effect of sleep on emotional memory, then it may selectively support negative memory in young adults and positive memory in older adults. To address these questions, we examined whether emotional memory recognition and overnight change in emotional reactivity were associated with the strength of SO-SP coupling in young (n = 22) and older (n = 32) adults. In younger adults, coupling strength predicted negative but not positive emotional memory performance after sleep. In contrast, coupling strength predicted positive but not negative emotional memory performance after sleep in older adults. Coupling strength was not associated with emotional reactivity in either age group. Our findings suggest that SO-SP coupling may play a mechanistic role in sleep-dependent consolidation of emotional memories.

Early childhood naps initiate emotional memory processing in preparation for enhanced overnight consolidation.

Early childhood naps support emotional memory, but benefits are only observed after overnight sleep. Whether emotional memory consolidation occurs during naps, or whether napping only prepares memories for overnight consolidation is unknown. We investigated whether naps protect emotional memories from interference, indicating consolidation. Between 2018 and 2020, 63 children in western Massachusetts preschools (30 female, 33 male; 33-67 months; 23.8% Hispanic, 87.3% White) learned faces paired with negative or neutral descriptions, followed by nap or wake. Before delayed recognition, half completed an interference task. Without interference, napping benefited recognition. With interference, children recognized fewer negative faces post-nap (compared to wake), with overnight sleep attenuating this difference. Results suggest that naps initially destabilize emotional memories, possibly reflecting partial processing that promotes long-term consolidation.

Influence of naps on sedentary time and physical activity in early childhood.

The objective was to determine if, in preschool-aged children, (1) nap habituality is associated with sedentary time and physical activity (movement behaviors), (2) nap physiology is associated with movement behaviors, and (3) if missing a nap, compared to taking a nap, affects movement behaviors on the same day and subsequent day. A within-subjects (44 children; 4.2 ± 0.6 years; 55.6% female), at-home study examined two experimental conditions (one afternoon each of nap- and wake-promotion with order counterbalanced) one week apart. Movement behaviors were derived from wrist-worn actigraphy (12.1 ± 3.1 days). Average movement behaviors were calculated from the overall study period with experimental days excluded. Movement behaviors were also extracted for the same day and the subsequent day of the two experimental conditions. Polysomnography was recorded during the nap-promoted condition. Children were classified as non-, intermediate-, or habitual-nappers. Although average movement behaviors were different between nap habituality groups, differences were not significant. There were no associations between movement behaviors and nap sleep stages, and no effects for nap condition or condition by nap habituality on same or next day movement behaviors. Findings do not suggest that naps and movement behaviors are related in children. Although a single missed nap was not detrimental to same or next day movement behaviors, future studies should explore effects of multiple days of subsequent nap restriction to examine potential cumulative effects.

Temporal Associations between Actigraphy-Measured Daytime Movement Behaviors and Nap Sleep in Early Childhood.

The purpose of this micro-longitudinal study was to explore daily associations between daytime movement behaviors (sedentary time and physical activity) and nap sleep in young children. In 298 children (age = 51.0 ± 9.6 months, 43.6% female), wrist-based actigraphy (mean wear time = 10 days) assessed sedentary time, total physical activity, and provided an estimate of nap sleep duration and efficiency. Multilevel logistic and linear regression models were used to examine temporal within-person relations between wake behaviors and nap sleep, and adjusted for overnight sleep duration between days of interest, age, sex, and socioeconomic status. Movement behaviors were not related to the likelihood of next-day napping, but when children were less sedentary (OR = 0.96; p < 0.001) or more active (OR = 1.01; p = 0.001) in the morning, they were more likely to nap that same day. Movement behaviors were not associated with nap sleep duration or efficiency. Conversely, on days children napped, they were less sedentary (B = -2.09, p < 0.001) and more active (B = 25.8, p < 0.001) the following day. Though napping and movement behaviors had some reciprocal relations, effect sizes in the present study were small. Further studies should examine children with more diverse sleep health and from different childcare settings.

Contributions of memory and brain development to the bioregulation of naps and nap transitions in early childhood.

The transition from multiple sleep bouts each day to a single overnight sleep bout (i.e., nap transition) is a universal process in human development. Naps are important during infancy and early childhood as they enhance learning through memory consolidation. However, a normal part of development is the transition out of naps. Understanding nap transitions is essential in order to maximize early learning and promote positive long-term cognitive outcomes. Here, we propose a novel hypothesis regarding the cognitive, physiological, and neural changes that accompany nap transitions. Specifically, we posit that maturation of the hippocampal-dependent memory network results in more efficient memory storage, which reduces the buildup of homeostatic sleep pressure across the cortex (as reflected by slow-wave activity), and eventually, contributes to nap transitions. This hypothesis synthesizes evidence of bioregulatory mechanisms underlying nap transitions and sheds new light on an important window of change in development. This framework can be used to evaluate multiple untested predictions from the field of sleep science and ultimately, yield science-based guidelines and policies regarding napping in childcare and early education settings.

A Systematic Review of the Relationships Between Physical Activity and Sleep in Early Childhood.

The aim of this systematic review was to examine the associations between physical activity and sleep in children aged less than 6 years. Articles were included if participants were primarily aged less than 6 years and study designs were observational or experimental. Study characteristics were extracted, and the Grading Recommendations Assessment, Development and Evaluation framework was used to assess study quality. Thirty-six studies (16 sleep, 16 physical activity, and three fitness outcomes) from 18 countries reported in 29 articles were included. The majority of sleep and physical activity outcome studies reported mixed effects with very low to low quality of evidence. Fitness outcome studies were limited, and therefore, evidence was insufficient. The high prevalence of mixed and null results could be related to study limitations. Importantly, this review points to the critical need for higher quality studies of sleep and physical activity in young children, which would support health recommendations and intervention strategies for healthier child development.

Relations between sleep patterns early in life and brain development: A review.

Sleep supports healthy cognitive functioning in adults. Over the past decade, research has emerged advancing our understanding of sleep's role in cognition during development. Infancy and early childhood are marked by unique changes in sleep physiology and sleep patterns as children transition from biphasic to monophasic sleep. Growing evidence suggests that, during development, there are parallel changes in sleep and the brain and that sleep may modulate brain structure and activity and vice versa. In this review, we survey studies of sleep and brain development across childhood. By summarizing these findings, we provide a unique understanding of the importance of healthy sleep for healthy brain and cognitive development. Moreover, we discuss gaps in our understanding, which will inform future research.

Fear of Cancer Recurrence and Sleep in Couples Coping With Early-Stage Breast Cancer.

BACKGROUND: Fear of cancer recurrence (FCR) and sleep disturbance are common in cancer survivors. Yet, little research has examined their relationship, and even less is known about what links may exist between these variables among the intimate partners of cancer survivors. PURPOSE: This study examines the relationship between FCR and sleep disturbance in breast cancer survivors and their partners. Using daily sleep data collected at two distinct periods early in survivorship-the completion of adjuvant treatment and the first post-treatment mammogram-higher survivor and partner FCR was hypothesized to predict greater sleep disturbance. METHODS: Breast cancer survivors and intimate partners (N = 76 couples; 152 individuals) each reported sleep duration, sleep quality, sleep onset latency, and wake after sleep onset each morning of two 21-day sleep diary bursts during the first year post-diagnosis. Three validated measures formed latent FCR factors for survivors and partners, which were used to predict average daily sleep. RESULTS: Across both sleep diary bursts, survivor FCR was associated with their own reduced sleep duration, reduced sleep quality, and greater sleep onset latency. Survivor FCR was also associated with their partners' reduced sleep quality and greater sleep onset latency. Partner FCR was associated with their own reduced sleep duration, reduced sleep quality, and greater sleep onset latency. Partner FCR was also associated with survivors' reduced sleep quality. CONCLUSIONS: Findings revealed intrapersonal and interpersonal associations between FCR and sleep disturbance, addressing gaps in knowledge on FCR and an outcome with known short- and long-term implications for health and mortality.

Sleep enhances reconsolidation-based strengthening of visuospatial memories.

Consolidated memories can be returned to a labile state upon reactivation. The re-stabilization of reactivated memories, or reconsolidation, can allow for change in previously established memories. Given the role of sleep in the initial consolidation of memories, sleep may be important for reconsolidation as well. However, effects of sleep on reconsolidation and specific aspects of sleep that may contribute are unclear. Here, participants learned 30 picture-location pairs. After overnight sleep, initial consolidation was tested. Following either one day (Experiment 1) or one week (Experiment 2), participants were tested again to reactivate their memory and then learned 30 novel picture-location pairs. Control groups (Experiment 1) received no reactivation prior to new learning. Twelve hours later, after daytime wakefulness or overnight sleep, participants completed a final memory test. Sleep participants underwent polysomnography between reactivation and final tests. In Experiment 1, reactivation led to preservation of memory compared to no reactivation. Sleep was associated with less post-reactivation memory decline than waking, with memory preservation positively related to time spent in non-rapid-eye movement sleep. In Experiment 2, sleep was associated with greater post-reactivation memory improvement than waking, with improvement positively related to sigma activity. These results suggest sleep enhances reconsolidation-based strengthening of episodic memories.

Temporal relationships between device-derived sedentary behavior, physical activity, and sleep in early childhood.

STUDY OBJECTIVES: Understanding the ideal composition of a child's day requires a better understanding of the relations between wake behaviors (sedentary behavior [SB], physical activity [PA]) and sleep. Here, we examine between- and within-person temporal associations between daytime wake behaviors and overnight sleep in early childhood, an important age when healthy behaviors are initiated and 24-hour behaviors are largely determined by caregivers. METHODS: Daily, repeated measures of wake behavior and overnight sleep were assessed via wrist-worn actigraphy (mean = 9 days/nights) in 240 children (50.8 ± 9.8 months). Multilevel models with lagged effects were used to examine the temporal associations between wake and overnight sleep measures and adjusted for daily nap duration, age, sex, and socioeconomic status. RESULTS: Between-person associations for sleep outcomes were negative between moderate-to vigorous-intensity PA (MVPA) and total activity for sleep efficiency (SE). Between-person associations for wake outcomes were positive between sleep duration and light PA, and negative between SE and both MVPA and total PA. When children obtained higher SE relative to their individual average, they were more likely to engage in less SB and greater MVPA and total PA the next day. CONCLUSIONS: Generally, days with greater activity or sleep were not associated with greater subsequent sleep or PA. Most subsequent behaviors were not influenced by children achieving higher activity or sleep relative to their individual average levels, although higher SE was beneficially associated with next day wake behaviors. Future analyses with young children should consider within-person associations and could investigate lagged effects beyond one day.

The memory benefits of two naps per day during infancy: A pilot investigation.

In infancy, sleep occurs in multiple nap and overnight bouts that change developmentally in quantity and distribution. Though studies suggest that infant memory benefits from a single nap, no work has assessed the relative benefits of different naps (morning vs. afternoon), nor how multiple naps support memory across the day. We investigated the memory benefit of a morning nap, relative to morning wake, and the effect of these intervals on afternoon nap function in 9-month-olds (n = 15). Infants participated in two within-subjects conditions (separated by 1-2 weeks). In the Nap-Nap condition, infants took their morning and afternoon naps; in the Wake-Nap condition, infants were kept awake during morning naptime, but napped unrestricted in the afternoon. Before each nap/wake interval, infants completed an imitation memory task, with memory assessed again shortly after the nap/wake interval. In the Nap-Nap condition, infants showed memory retention across morning and afternoon naps. In contrast, infants tended to forget items learned across morning wake in the Wake-Nap condition. Moreover, morning wake was associated with a significant decline in post-nap retention of items learned in the afternoon. Furthermore, relations between nap slow-wave activity (SWA) and memory varied across naps, with SWA either not predicting (morning naps) or positively predicting (afternoon naps) memory change in the Nap-Nap condition, but negatively predicting afternoon memory change in the Wake-Nap condition. We conclude that two naps per day (rather than one) aids memory at 9 months, and that skipping the morning nap may moderate relations between afternoon nap physiology and memory.

Ageing-related changes in nap neuroscillatory activity are mediated and moderated by grey matter volume.

Ageing-related changes in grey matter result in changes in the intensity and topography of sleep neural activity. However, it is unclear whether these findings can be explained by ageing-related differences in sleep pressure or circadian influence. The current study used high-density electroencephalography to assess how grey matter volume differences between young and older adults mediate and moderate neuroscillatory activity differences during a midday nap following a motor sequencing task. Delta, theta, and sigma amplitude were reduced in older relative to young adults, especially over frontocentral scalp, leading to increases in relative delta frontality and relative sigma lateral centroposteriority. Delta reductions in older adults were mediated by grey matter loss in frontal medial cortex, primary motor cortex, thalamus, caudate, putamen, and pallidum, and were moderated by putamen grey matter volume. Theta reductions were mediated by grey matter loss in primary motor cortex, thalamus, and caudate, and were moderated by putamen and pallidum grey matter volume. Sigma changes were moderated by putamen and pallidum grey matter volume. Moderation results suggested that across frequencies, young adults with more grey matter had increased activity, whereas older adults with more grey matter had unchanged or decreased activity. These results provide a critical extension of previous findings from overnight sleep in a midday nap, indicating that they are not driven by sleep pressure or circadian confounds. Moreover, these results suggest brain regions associated with motor sequence learning contribute to sleep neural activity following a motor sequencing task.

Sleep and Coping in Early Childhood During the COVID-19 Pandemic.

Sleep disturbances in early childhood are associated with mood and anxiety disorders. Children also exhibit sleep disruptions, such as nighttime awakenings, nightmares, and difficulties falling asleep, in conjunction with adverse events and stress. Prior studies have examined independently the role of sleep on adaptive processing, as well as the effects of stress on sleep. However, how childhood sleep and children's adaptive behavior (i.e., coping strategies) bidirectionally interact is currently less known. Using a within-subjects design and actigraphy-measured sleep from 16 preschool-aged children (Mage = 56.4 months, SD = 10.8, range: 36-70 months), this study investigated how prior sleep patterns relate to children's coping during a potentially stressful event, the COVID-19 pandemic, and how prior coping skills may influence children's sleep during the pandemic. Children who woke earlier had greater negative expression both before and during the pandemic. During the pandemic, children slept longer and woke later on average compared to before the pandemic. Additionally, for children engaged in at-home learning, sleeping longer was associated with less negative expression. These findings highlight how sleep behaviors and coping strategies are related, and the stability of this relationship under stress.

Encoding and consolidation of motor sequence learning in young and older adults.

Sleep benefits motor memory consolidation in young adults, but this benefit is reduced in older adults. Here we sought to understand whether differences in the neural bases of encoding between young and older adults contribute to aging-related differences in sleep-dependent consolidation of an explicit variant of the serial reaction time task (SRTT). Seventeen young and 18 older adults completed two sessions (nap, wake) one week apart. In the MRI, participants learned the SRTT. Following an afternoon interval either awake or with a nap (recorded with high-density polysomnography), performance on the SRTT was reassessed in the MRI. Imaging and behavioral results from SRTT performance showed clear sleep-dependent consolidation of motor sequence learning in older adults after a daytime nap, compared to an equal interval awake. Young adults, however, showed brain activity and behavior during encoding consistent with high SRTT performance prior to the sleep interval, and did not show further sleep-dependent performance improvements. Young adults did show reduced cortical activity following sleep, suggesting potential systems-level consolidation related to automatization. Sleep physiology data showed that sigma activity topography was affected by hippocampal and cortical activation prior to the nap in both age groups, and suggested a role of theta activity in sleep-dependent automatization in young adults. These results suggest that previously observed aging-related sleep-dependent consolidation deficits may be driven by aging-related deficiencies in fast learning processes. Here we demonstrate that when sufficient encoding strength is reached with additional training, older adults demonstrate intact sleep-dependent consolidation of motor sequence learning.

Physical Activity, Fitness, School Readiness, and Cognition in Early Childhood: A Systematic Review.

BACKGROUND: Early childhood is an important age for brain and cognitive development. Given the support of physical activity and fitness on cognition and academic performance in older children, more research has emerged recently focusing on younger children. In this systematic review, the authors review the relations between physical activity/fitness and academic-related (ie, school readiness and cognitive) outcomes in early childhood. METHODS: A search was conducted from PubMed, PsycINFO, Web of Science, ERIC databases, and reference lists for articles that had participants aged less than 6 years were written in English, and were in peer-reviewed journals. Articles were excluded if the design was a case study or case series report. The Grading Recommendations Assessment, Development and Evaluation framework was followed to assess the quality of evidence by study design. RESULTS: Sixty-eight articles reporting on 72 studies (29 observational and 43 experimental) were included. The majority of study effects were mixed, and the quality of evidence varied from very low to low. CONCLUSIONS: A clear consensus about the role of physical activity and fitness on academic-related outcomes in early childhood is still lacking given the high heterogeneity in methodological approaches and overall effects. Additional high-quality studies are needed to determine what specific dosages of physical activity are impactful at this age.

Bedsharing in Early Childhood: Frequency, Partner Characteristics, and Relations to Sleep.

Bedsharing (sharing a bed with others during sleep) in early childhood (3-5 years old) is common across Western and non-Western societies alike. Though prior work indicates that bedsharing may relate to impairments in child sleep quantity or quality, the majority of studies conducted in young children are limited to parent-child bedsharing and rely almost exclusively on caregiver reports to measure child sleep. Here, the authors endeavored to gain further insights into the diversity of bedsharing practices among children in the United States, including how different bedsharing partners (caregivers, siblings) might impact actigraphy-derived measures of children's sleep. Using a sample of 631 children ages 2:9 to 5:11 years, we found that over 36% of children bedshared in some form overnight, with approximately 22% bedsharing habitually. In a subset of children for whom actigraphy measures were collected (n = 337), children who bedshared habitually (n = 80) had significantly shorter overnight sleep, later sleep and wake times, and longer naps than solitary sleepers (n = 257), even when controlling for socioeconomic status. Despite supplementing their shorter overnight sleep with longer naps, habitually bedsharing children had significantly shorter 24-hr sleep time than did solitary sleepers, though differences in sleep efficiency were nonsignificant for all sleep periods. Additionally, sleep efficiency, onset latency, and duration did not differ between children who habitually bedshared with siblings versus those who habitually bedshared with parents. The present results add to prior work examining family contextual correlates of sleep differences in early childhood and provide a more objective account of relations between bedsharing and child sleep.

Unhealthy Diet Is Associated With Poor Sleep in Preschool-Aged Children.

Unhealthy dietary choices are associated with poor sleep in children through adults. Yet, how diet and sleep are related in early childhood, when diet is reliant on parent choices around food availability, is unknown. The authors aimed to explore how frequency of fruit, vegetable, fast food, and soda consumption are associated with preschool children's sleep quality. They also considered how parenting factors may impact the relationship between children's sleep and diet. Actigraphy data were collected from 383 children 33-70 months old. Caregivers reported on child food and beverage frequency, demographics, and health items. Parenting strategies were assessed using the Parenting Scale. Multiple linear regression was used to examine associations between sleep and dietary measures with socioeconomic status, race-ethnicity, physical activity, and body mass index as covariates. Shorter nap duration was associated with more frequent consumption of fruits and vegetables (B = -3.6, p = .03). Shorter nighttime and 24-hr sleep durations were associated with more frequent consumption of fast food (B = -6.5, p = .01; B = -5.8, p = .01). Shorter nighttime sleep and later sleep onset were associated with more frequent soda consumption (B = -9.2, p = .01; B = 0.23, p = .001). Use of ineffective parenting strategies was negatively associated with fruit and vegetable consumption (r = -.29, p = .01) and positively associated with soda consumption (r = .25, p = .02) but was unrelated to sleep measures. Thus, ineffective parenting strategies may underlie child access to unhealthy foods, which, in turn, contributes to poor sleep. Encouraging healthier dietary habits and educating caregivers on how to reinforce such practices may lead to better sleep outcomes in early childhood.

Sleep and human cognitive development.

Emerging studies across learning domains have shed light on mechanisms underlying sleep's benefits during numerous developmental periods. In this conceptual review, we survey recent studies of sleep and cognition across infancy, childhood, and adolescence. By summarizing recent findings and integrating across studies with disparate approaches, we provide a novel understanding of sleep's role in human cognitive function. Collectively, these studies point to an interrelation between brain development, sleep, and cognition. Moreover, we point to gaps in our understanding, which inform the agenda for future research in developmental and sleep science.

Parents' Nonstandard Work and Children's Sleep: The Mediating Role of Bedtime Routines.

OBJECTIVE: The present study examined if caregivers' long work hours or shift work are related to children's sleep duration through the disruption of bedtime routines. METHOD: Work hours and schedules, bedtime routines and sleep (actigraph assessments) were examined in a sample of 250 caregivers and their preschool children. RESULTS: Results revealed that consistent bedtime routines mediated the relationship between caregiver's work and children's sleep, such that longer hours and shift work predicted fewer routines that, in turn, predicted less child sleep. CONCLUSION: These results point to the crucial role of bedtime routines as a promising point of intervention for working parents. While caregivers may not be able to change their work hours or schedules, they can create more stable and consistent bedtime routines to mitigate the negative effects of their work on children's sleep.