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Lou S, Hu S, Chen Y, Zhao K, Zhou Y, Hou J, Liang L, Sun H. Benefits of napping habits in healthy adults: Maintaining alerting performance and cortisol levels change within 90 min of habitual napping time. Sleep Med 2024; 119:214-221. [PMID: 38703605 DOI: 10.1016/j.sleep.2024.04.021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/09/2023] [Revised: 04/04/2024] [Accepted: 04/14/2024] [Indexed: 05/06/2024]
Abstract
BACKGROUND Napping is garnering increased attention as a strategy for adults to sustain alertness and alleviate stress in contemporary society. The nuances of napping habits are emerging as an independent factor influencing the extent of individual benefits. This study aimed to demonstrate the long-term benefits of napping and explore the impact of napping habits on individual alertness, as well as whether this effect was correlated with cortisol levels. METHODS The study involved 80 healthy adults categorized into two groups based on self-reported napping habits: habitual nappers (n = 49) and non-habitual nappers (n = 31). Karolinska Sleepiness Scale (KSS), psychomotor vigilance task (PVT), and saliva collection were performed every 30 min within 90 min in the absence of napping during the afternoon dip. The measurements were analyzed using repeated measures ANOVA and Pearson correlation analyses. RESULTS There was an interaction between groups and time in reaction speed and lapse number of PVT and cortisol (all p < 0.05). Post hoc analysis found that habitual nappers maintained higher objective alertness and experienced more significant increases in cortisol over time (all p < 0.05). The cortisol levels at sleepiness time were negatively associated with the slowest 10 % reaction speed of PVT in non-habitual nappers (r = -0.409, p = 0.022). CONCLUSION Under the premise of mitigating the impacts of acute nap deprivation on sleep homeostasis and rhythm, napping habits emerge as a potential factor influencing the ability of individuals to sustain heightened alertness.
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Affiliation(s)
- Sijia Lou
- Peking University Sixth Hospital, Peking University Institute of Mental Health, NHC Key Laboratory of Mental Health (Peking University), National Clinical Research Center for Mental Disorders (Peking University Sixth Hospital), Beijing, 100191, China
| | - Sifan Hu
- Peking University Sixth Hospital, Peking University Institute of Mental Health, NHC Key Laboratory of Mental Health (Peking University), National Clinical Research Center for Mental Disorders (Peking University Sixth Hospital), Beijing, 100191, China
| | - Yun Chen
- Peking University Sixth Hospital, Peking University Institute of Mental Health, NHC Key Laboratory of Mental Health (Peking University), National Clinical Research Center for Mental Disorders (Peking University Sixth Hospital), Beijing, 100191, China
| | - Kangqing Zhao
- Peking University Sixth Hospital, Peking University Institute of Mental Health, NHC Key Laboratory of Mental Health (Peking University), National Clinical Research Center for Mental Disorders (Peking University Sixth Hospital), Beijing, 100191, China
| | - Yingying Zhou
- Peking University Sixth Hospital, Peking University Institute of Mental Health, NHC Key Laboratory of Mental Health (Peking University), National Clinical Research Center for Mental Disorders (Peking University Sixth Hospital), Beijing, 100191, China
| | - Jianjun Hou
- Peking University Health Science Center, Beijing, 100191, China
| | - Lining Liang
- Peking University Health Science Center, Beijing, 100191, China
| | - Hongqiang Sun
- Peking University Sixth Hospital, Peking University Institute of Mental Health, NHC Key Laboratory of Mental Health (Peking University), National Clinical Research Center for Mental Disorders (Peking University Sixth Hospital), Beijing, 100191, China.
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Kurtoğlu A, Eken Ö, Aydın E, Çar B, Nobari H. The impact of strategic napping on peak expiratory flow and respiratory function in young elite athletes. BMC Sports Sci Med Rehabil 2024; 16:41. [PMID: 38336766 PMCID: PMC10854142 DOI: 10.1186/s13102-024-00842-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2023] [Accepted: 02/08/2024] [Indexed: 02/12/2024]
Abstract
Respiratory health is a critical determinant of athletic performance, and the utilization of restorative strategies, such as strategic napping, may offer a competitive edge to athletes. This study investigates the effects of nap duration on the respiratory function of young elite athletes who have achieved top rankings national competitions. Participants engage in three test sessions with varying nap durations: no nap (N0), a 25-minute nap (N25), and a 45-minute nap (N45), with a minimum 72-hour interval between sessions. Respiratory parameters including Forced Vital Capacity (FVC), Forced Expiratory Volume in one second (FEV1), FEV1/FVC ratio, Peak Expiratory Flow rate (PEF), Forced Expiratory Flow at 25-75% of FVC (FEF25-75%), and Forced Expiratory Time (FET) are assessed. Results reveal a significant enhancement in PEF values following a 45-minute nap (N45) compared to the no-nap control (N0) [F1 - 11=7.356, p =.004, ηp2 = 0.401, (95% CI for difference: -1.56 to - 0.056)], indicating a potential positive influence of napping on maximum expiratory flow rate and, consequently, athletes' respiratory performance. While no significant changes are observed in other respiratory parameters across different nap durations, these findings underscore the potential benefits of strategic napping in optimizing respiratory health in young elite athletes.
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Affiliation(s)
- Ahmet Kurtoğlu
- Department of Coaching Education, Faculty of Sport Science, Bandirma Onyedi Eylul University, Balıkesir, 10200, Turkey
| | - Özgür Eken
- Department of Physical Education and Sport Teaching, Faculty of Sports Sciences, Inonu University, Malatya, 44280, Turkey
| | - Engin Aydın
- Department of Pediatrics, Zeynep Kamil Maternity and Children's Disease Training and Research Hospital, University of Health Sciences, Istanbul, 34668, Turkey
| | - Bekir Çar
- Department of Physical Education and Sport Teaching, Faculty of Sport Sciences, Bandirma Onyedi Eylul University, Balıkesir, 10200, Turkey
| | - Hadi Nobari
- Faculty of Sport Sciences, University of Extremadura, Cáceres, 10003, Spain.
- Department of Exercise Physiology, Faculty of Educational Sciences and Psychology, University of Mohaghegh Ardabili, Ardabil, 56199-11367, Iran.
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3
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Xu Z, Chang Y, Guo F, Wang C, Chai N, Zheng M, Fang P, Zhu Y. The restoration ability of a short nap after sleep deprivation on the brain cognitive function: A dynamic functional connectivity analysis. CNS Neurosci Ther 2024; 30:e14413. [PMID: 37605612 PMCID: PMC10848048 DOI: 10.1111/cns.14413] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2022] [Revised: 04/07/2023] [Accepted: 08/05/2023] [Indexed: 08/23/2023] Open
Abstract
AIMS The brain function impairment induced by sleep deprivation (SD) is temporary and can be fully reversed with sufficient sleep. However, in many cases, long-duration recovery sleep is not feasible. Thus, this study aimed to investigate whether a short nap after SD is sufficient to restore brain function. METHODS The data of 38 subjects, including resting state functional magnetic resonance imaging data collected at three timepoints (before SD, after 30 h of SD, and after a short nap following SD) and psychomotor vigilance task (PVT) data, were collected. Dynamic functional connectivity (DFC) analysis was used to evaluate changes in brain states among three timepoints, and four DFC states were distinguished across the three timepoints. RESULTS Before SD, state 2 (a resting-like FC matrix) was dominant (48.26%). However, after 30 h SD, the proportion of state 2 dramatically decreased, and state 3 (still resting-like, but FCs were weakened) became dominant (40.92%). The increased proportion of state 3 positively correlated with a larger PVT "lapse" time. After a nap, the proportions of states 2 and 3 significantly increased and decreased, respectively, and the change in proportion of state 2 negatively correlated with the change in PVT "lapse" time. CONCLUSIONS Taken together, the results indicated that, after a nap, the cognitive function impairment caused by SD may be reversed to some extent. Additionally, DFC differed among timepoints, which was also associated with the extent of cognitive function impairment after SD (state 3) and the extent of recovery therefrom after a nap (state 2).
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Affiliation(s)
- Ziliang Xu
- Department of Radiology, Xijing HospitalFourth Military Medical UniversityXi'anChina
| | - Yingjuan Chang
- Department of Radiology, Xijing HospitalFourth Military Medical UniversityXi'anChina
| | - Fan Guo
- Department of Radiology, Xijing HospitalFourth Military Medical UniversityXi'anChina
| | - Chen Wang
- Department of Radiology, Xijing HospitalFourth Military Medical UniversityXi'anChina
| | - Na Chai
- Department of Radiology, Xijing HospitalFourth Military Medical UniversityXi'anChina
| | - Minwen Zheng
- Department of Radiology, Xijing HospitalFourth Military Medical UniversityXi'anChina
| | - Peng Fang
- Department of Military Medical PsychologyFourth Military Medical UniversityXi'anChina
| | - Yuanqiang Zhu
- Department of Radiology, Xijing HospitalFourth Military Medical UniversityXi'anChina
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Aksamaz S, Mölle M, Akinola EO, Gromodka E, Bazhenov M, Marshall L. Single closed-loop acoustic stimulation targeting memory consolidation suppressed hippocampal ripple and thalamo-cortical spindle activity in mice. Eur J Neurosci 2024; 59:595-612. [PMID: 37605315 PMCID: PMC11214843 DOI: 10.1111/ejn.16116] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2022] [Revised: 06/20/2023] [Accepted: 07/24/2023] [Indexed: 08/23/2023]
Abstract
Brain rhythms of sleep reflect neuronal activity underlying sleep-associated memory consolidation. The modulation of brain rhythms, such as the sleep slow oscillation (SO), is used both to investigate neurophysiological mechanisms as well as to measure the impact of sleep on presumed functional correlates. Previously, closed-loop acoustic stimulation in humans targeted to the SO Up-state successfully enhanced the slow oscillation rhythm and phase-dependent spindle activity, although effects on memory retention have varied. Here, we aim to disclose relations between stimulation-induced hippocampo-thalamo-cortical activity and retention performance on a hippocampus-dependent object-place recognition task in mice by applying acoustic stimulation at four estimated SO phases compared to sham condition. Across the 3-h retention interval at the beginning of the light phase closed-loop stimulation failed to improve retention significantly over sham. However, retention during SO Up-state stimulation was significantly higher than for another SO phase. At all SO phases, acoustic stimulation was accompanied by a sharp increase in ripple activity followed by about a second-long suppression of hippocampal sharp wave ripple and longer maintained suppression of thalamo-cortical spindle activity. Importantly, dynamics of SO-coupled hippocampal ripple activity distinguished SOUp-state stimulation. Non-rapid eye movement (NREM) sleep was not impacted by stimulation, yet preREM sleep duration was effected. Results reveal the complex effect of stimulation on the brain dynamics and support the use of closed-loop acoustic stimulation in mice to investigate the inter-regional mechanisms underlying memory consolidation.
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Affiliation(s)
- Sonat Aksamaz
- Institute of Experimental and Clinical Pharmacology,
University of Lübeck, Lübeck, Germany
- University Medical Center Schleswig-Holstein,
Lübeck, Germany
| | - Matthias Mölle
- University Medical Center Schleswig-Holstein,
Lübeck, Germany
- Center of Brain, Behavior and Metabolism, Lübeck,
Germany
| | - Esther Olubukola Akinola
- Institute of Experimental and Clinical Pharmacology,
University of Lübeck, Lübeck, Germany
- University Medical Center Schleswig-Holstein,
Lübeck, Germany
| | - Erik Gromodka
- Institute of Experimental and Clinical Pharmacology,
University of Lübeck, Lübeck, Germany
| | - Maxim Bazhenov
- Department of Medicine, University of California San Diego,
La Jolla, CA, USA
| | - Lisa Marshall
- Institute of Experimental and Clinical Pharmacology,
University of Lübeck, Lübeck, Germany
- University Medical Center Schleswig-Holstein,
Lübeck, Germany
- Center of Brain, Behavior and Metabolism, Lübeck,
Germany
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5
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Li J, Zhang X, Zhou Y. The sustained attention characteristics of flight crews on exempt and non-exempt flights. Chronobiol Int 2023; 40:926-937. [PMID: 37434407 DOI: 10.1080/07420528.2023.2235011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2022] [Revised: 07/04/2023] [Accepted: 07/05/2023] [Indexed: 07/13/2023]
Abstract
We analyzed the characteristics of sustained attention changes in flight crews during exempt and non-exempt flights. Fourteen pilots (aged 30-43 y) participated in this study, with seven involved in each flight type, all of which were intercontinental (China to North America). Pilots completed continuous performance tests (CPT) at the required flight stages without compromising safety while on duty. No significant differences in sleep and sustained attention emerged between the exempt and non-exempt flight crews. Pilots' fatigue was highest in the early morning hours. Their general stability of efficiency increased during the day and decreased at night. Non-exempt flight crews appeared to sacrifice reaction rate to improve accuracy. Exempt crews appeared to increase their test proficiency. The task stability time of the non-exempt flight crews was better than that of the exempt ones. Short-term stability was better for exempt inbound flights rather than for outbound ones. Pilots were more prone to error runs as their total time awake increased, especially on non-exempt flights. The addition of crew members to exempt flights, allowance for more in-flight rest shifts, and over-stop rest on non-exempt flights may alleviate pilot fatigue and preserve alertness.
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Affiliation(s)
- Jingqiang Li
- Safety Science and Engineering College, Civil Aviation University of China, Tianjin, China
- Research Institute of Civil Aviation Safety, Civil Aviation University of China (CAUC), Tianjin, China
| | - Xining Zhang
- Safety Science and Engineering College, Civil Aviation University of China, Tianjin, China
- Research Institute of Civil Aviation Safety, Civil Aviation University of China (CAUC), Tianjin, China
| | - Yanru Zhou
- Safety Science and Engineering College, Civil Aviation University of China, Tianjin, China
- Research Institute of Civil Aviation Safety, Civil Aviation University of China (CAUC), Tianjin, China
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6
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Campbell IG, Zhang ZY, Grimm KJ. Sleep restriction effects on sleep spindles in adolescents and relation of these effects to subsequent daytime sleepiness and cognition. Sleep 2023; 46:zsad071. [PMID: 36916319 PMCID: PMC10413429 DOI: 10.1093/sleep/zsad071] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2022] [Revised: 02/13/2023] [Indexed: 03/15/2023] Open
Abstract
STUDY OBJECTIVES Limiting spindle activity via sleep restriction could explain some of the negative cognitive effects of sleep loss in adolescents. The current study evaluates how sleep restriction affects sleep spindle number, incidence, amplitude, duration, and wave frequency and tests whether sleep restriction effects on spindles change across the years of adolescence. The study determines whether sleep restriction effects on daytime sleepiness, vigilance, and cognition are related to changes in sleep spindles. METHODS In each year of this 3-year longitudinal study, 77 participants, ranging in age from 10 to 16 years, each completed three different time in bed (TIB) schedules: 7, 8.5, or 10 hours in bed for 4 consecutive nights. A computer algorithm detected and analyzed sleep spindles in night four central and frontal electroencephalogram. Objective and self-reported daytime sleepiness and cognition were evaluated on the day following the 4th night. RESULTS For 7 versus 10 hours TIB average all-night frontal and central spindle counts were reduced by 35% and 32%, respectively. Reducing TIB also significantly decreased spindle incidence in the first 5 hours of non-rapid eye movement sleep, produced small but significant reductions in spindle amplitude, and had little to no effect on spindle duration and spindle wave frequency. Sleep restriction effects did not change with age. The reductions in spindle count and incidence were related to daytime sleepiness on the following day but were not related to working memory. CONCLUSIONS The sleep loss effects on daytime functioning in adolescents are partially mediated by reduced sleep spindles impacting daytime sleepiness.
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Affiliation(s)
- Ian G Campbell
- Department of Psychiatry and Behavioral Sciences, University of California Davis, Sacramento, CA, USA
| | - Zoey Y Zhang
- Department of Psychiatry and Behavioral Sciences, University of California Davis, Sacramento, CA, USA
| | - Kevin J Grimm
- Department of Psychology, Arizona State University, Tempe, AZ, USA
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7
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Horger MN, DeMasi A, Allia AM, Scher A, Berger SE. The unique contributions of day and night sleep to infant motor problem solving. J Exp Child Psychol 2023; 226:105536. [PMID: 36116316 DOI: 10.1016/j.jecp.2022.105536] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2022] [Revised: 08/07/2022] [Accepted: 08/08/2022] [Indexed: 10/14/2022]
Abstract
The current study sought to tease apart the unique contributions of napping and nighttime sleep to infant learning, specifically in the context of motor problem solving. We challenged 54 walking infants to solve a novel locomotor problem at three time points-training, test, and follow-up the next morning. One group of infants napped during the delay between training and test. Another group did not sleep during the delay. A third group received the test immediately after training with no delay. Only the Nap group's strategy choices continued to improve through the follow-up session, suggesting that daytime sleep has an active role in strengthening otherwise fragile memory. Although group did not affect strategy maintenance, walk experience did, suggesting that task difficulty may shape the impact of sleep on learning. Thus, day sleep and night sleep make independent contributions to the consolidation of motor problem-solving strategies during infancy.
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Affiliation(s)
- Melissa N Horger
- Graduate Center, City University of New York, New York, NY 10016, USA
| | - Aaron DeMasi
- Graduate Center, City University of New York, New York, NY 10016, USA
| | - Angelina M Allia
- College of Staten Island, City University of New York, Staten Island, NY 10314, USA
| | - Anat Scher
- University of Haifa, Haifa 3498838, Israel
| | - Sarah E Berger
- Graduate Center, City University of New York, New York, NY 10016, USA; College of Staten Island, City University of New York, Staten Island, NY 10314, USA.
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Zhang H, Zhang L, Chen C, Zhong X. Association between daytime napping and cognitive impairment among Chinese older population: a cross-sectional study. Environ Health Prev Med 2023; 28:72. [PMID: 37989282 PMCID: PMC10685077 DOI: 10.1265/ehpm.23-00031] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2023] [Accepted: 09/30/2023] [Indexed: 11/23/2023] Open
Abstract
BACKGROUND Both napping and nighttime sleep duration have been reported to be associated with cognitive function in older adults, whereas little is known about the association between daytime napping and cognitive impairment in different nighttime sleep duration subgroups. This study aimed to explore the correlation between daytime napping and cognitive impairment across nighttime sleep duration subgroups. METHODS A cross-sectional study was conducted by using the fourth survey of China Health and Retirement Longitudinal Study (CHARLS). We utilized the Mini-Mental State Examination (MMSE) scale to define cognitive impairment, and the daytime napping and nighttime sleep duration was self-reported by individuals. We applied the Restricted Cubic Spline (RCS) to analysis the dose-response relationships between daytime napping and cognitive impairment. And the multivariate Logistic Regression Model (LRM) was performed to evaluate the association of daytime napping and cognitive impairment. RESULTS A total of 3,052 individuals were included, of which 769 were cognitive impairment. The RCS showed there were non-linear association between daytime napping and cognitive impairment in all participants group and longer nighttime sleep duration subgroup (PNon-linear < 0.05, PDaytime napping < 0.05). The LRM revealed no napping (OR = 1.62, 95%CI 1.14-2.30) and excessive napping (1.64 95%CI 1.09-2.48) were related to cognitive impairment in longer nighttime sleep duration subgroup. CONCLUSIONS Daytime napping had nonlinear association with cognitive impairment in Chinese elderly population. No napping and excessive daytime napping (>90 minutes) were related to cognitive impairment in participants with 7 and more hours nighttime sleep duration.
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Affiliation(s)
- Hong Zhang
- Department of Health Statistics, School of Public Health, Chongqing Medical University, Chongqing 400016, PR China
| | - Lijuan Zhang
- Department of Health Statistics, School of Public Health, Chongqing Medical University, Chongqing 400016, PR China
| | - Chen Chen
- Department of Health Statistics, School of Public Health, Chongqing Medical University, Chongqing 400016, PR China
| | - Xiaoni Zhong
- Department of Health Statistics, School of Public Health, Chongqing Medical University, Chongqing 400016, PR China
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Leong RLF, Lo JC, Chee MWL. Systematic review and meta-analyses on the effects of afternoon napping on cognition. Sleep Med Rev 2022; 65:101666. [PMID: 36041284 DOI: 10.1016/j.smrv.2022.101666] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2021] [Revised: 06/09/2022] [Accepted: 06/21/2022] [Indexed: 10/15/2022]
Abstract
Naps are increasingly considered a means to boost cognitive performance. We quantified the cognitive effects of napping in 60 samples from 54 studies. 52 samples evaluated memory. We first evaluated effect sizes for all tests together, before separately assessing their effects on memory, vigilance, speed of processing and executive function. We next examined whether nap effects were moderated by study features of age, nap length, nap start time, habituality and prior sleep restriction. Naps showed significant benefits for the total aggregate of cognitive tests (Cohen's d = 0.379, CI95 = 0.296-0.462). Significant domain specific effects were present for declarative (Cohen's d = 0.376, CI95 = 0.269-0.482) and procedural memory (Cohen's d = 0.494, CI95 = 0.301-0.686), vigilance (Cohen's d = 0.610, CI95 = 0.291-0.929) and speed of processing (Cohen's d = 0.211, CI95 = 0.052-0.369). There were no significant moderation effects of any of the study features. Nap effects were of comparable magnitude across subgroups of each of the 5 moderators (Q values = 0.009 to 8.572, p values > 0.116). Afternoon naps have a small to medium benefit over multiple cognitive tests. These effects transcend age, nap duration and tentatively, habituality and prior nocturnal sleep.
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Affiliation(s)
- Ruth L F Leong
- Centre for Sleep and Cognition, Yong Loo Lin School of Medicine, National University of Singapore, Singapore.
| | - June C Lo
- Centre for Sleep and Cognition, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
| | - Michael W L Chee
- Centre for Sleep and Cognition, Yong Loo Lin School of Medicine, National University of Singapore, Singapore.
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10
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Weiss JT, Donlea JM. Roles for Sleep in Neural and Behavioral Plasticity: Reviewing Variation in the Consequences of Sleep Loss. Front Behav Neurosci 2022; 15:777799. [PMID: 35126067 PMCID: PMC8810646 DOI: 10.3389/fnbeh.2021.777799] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2021] [Accepted: 12/16/2021] [Indexed: 12/13/2022] Open
Abstract
Sleep is a vital physiological state that has been broadly conserved across the evolution of animal species. While the precise functions of sleep remain poorly understood, a large body of research has examined the negative consequences of sleep loss on neural and behavioral plasticity. While sleep disruption generally results in degraded neural plasticity and cognitive function, the impact of sleep loss can vary widely with age, between individuals, and across physiological contexts. Additionally, several recent studies indicate that sleep loss differentially impacts distinct neuronal populations within memory-encoding circuitry. These findings indicate that the negative consequences of sleep loss are not universally shared, and that identifying conditions that influence the resilience of an organism (or neuron type) to sleep loss might open future opportunities to examine sleep's core functions in the brain. Here, we discuss the functional roles for sleep in adaptive plasticity and review factors that can contribute to individual variations in sleep behavior and responses to sleep loss.
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Affiliation(s)
- Jacqueline T. Weiss
- Department of Neurobiology, David Geffen School of Medicine at University of California, Los Angeles, Los Angeles, CA, United States
- Neuroscience Interdepartmental Program, University of California, Los Angeles, Los Angeles, CA, United States
| | - Jeffrey M. Donlea
- Department of Neurobiology, David Geffen School of Medicine at University of California, Los Angeles, Los Angeles, CA, United States
- *Correspondence: Jeffrey M. Donlea
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Botonis PG, Koutouvakis N, Toubekis AG. The impact of daytime napping on athletic performance - A narrative review. Scand J Med Sci Sports 2021; 31:2164-2177. [PMID: 34559915 DOI: 10.1111/sms.14060] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2021] [Revised: 09/15/2021] [Accepted: 09/21/2021] [Indexed: 11/28/2022]
Abstract
Mid-day napping has been recommended as a countermeasure against sleep debt and an effective method for recovery, regardless of nocturnal sleep duration. Herein, we summarize the available evidence regarding the influence of napping on exercise and cognitive performance as well as the effects of napping on athletes' perceptual responses prior to or during exercise. The existing studies investigating the influence of napping on athletic performance have revealed equivocal results. Prevailing findings indicate that following a normal sleep night or after a night of sleep loss, a mid-day nap may enhance or restore several exercise and cognitive performance aspects, while concomitantly provide benefits on athletes' perceptual responses. Most, but not all, findings suggest that compared to short-term naps (20-30 min), long-term ones (>35-90 min) appear to provide superior benefits to the athletes. The underlying mechanisms behind athletic performance enhancement following a night of normal sleep or the restoration after a night of sleep loss are not clear yet. However, the absence of benefits or even the deterioration of performance following napping in some studies is likely the result of sleep inertia. The present review sheds light on the predisposing factors that influence the post-nap outcome, such as nocturnal sleep time, mid-day nap duration and the time elapsed between the end of napping and the subsequent testing, discusses practical solutions and stimulates further research on this area.
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Affiliation(s)
- Petros G Botonis
- School of Physical Education and Sports Science, National and Kapodistrian University of Athens, Athens, Greece
| | - Nickos Koutouvakis
- School of Physical Education and Sports Science, National and Kapodistrian University of Athens, Athens, Greece
| | - Argyris G Toubekis
- School of Physical Education and Sports Science, National and Kapodistrian University of Athens, Athens, Greece
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12
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Tandoc MC, Bayda M, Poskanzer C, Cho E, Cox R, Stickgold R, Schapiro AC. Examining the effects of time of day and sleep on generalization. PLoS One 2021; 16:e0255423. [PMID: 34339459 PMCID: PMC8328323 DOI: 10.1371/journal.pone.0255423] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2021] [Accepted: 07/16/2021] [Indexed: 12/26/2022] Open
Abstract
Extracting shared structure across our experiences allows us to generalize our knowledge to novel contexts. How do different brain states influence this ability to generalize? Using a novel category learning paradigm, we assess the effect of both sleep and time of day on generalization that depends on the flexible integration of recent information. Counter to our expectations, we found no evidence that this form of generalization is better after a night of sleep relative to a day awake. Instead, we observed an effect of time of day, with better generalization in the morning than the evening. This effect also manifested as increased false memory for generalized information. In a nap experiment, we found that generalization did not benefit from having slept recently, suggesting a role for time of day apart from sleep. In follow-up experiments, we were unable to replicate the time of day effect for reasons that may relate to changes in category structure and task engagement. Despite this lack of consistency, we found a morning benefit for generalization when analyzing all the data from experiments with matched protocols (n = 136). We suggest that a state of lowered inhibition in the morning may facilitate spreading activation between otherwise separate memories, promoting this form of generalization.
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Affiliation(s)
- Marlie C. Tandoc
- Department of Psychology, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Mollie Bayda
- Department of Psychiatry, Beth Israel Deaconess Medical Center / Harvard Medical School, Boston, Massachusetts, United States of America
- Department of Psychology, University of California-Los Angeles, Los Angeles, California, United States of America
| | - Craig Poskanzer
- Department of Psychiatry, Beth Israel Deaconess Medical Center / Harvard Medical School, Boston, Massachusetts, United States of America
- Department of Psychology and Neuroscience, Boston College, Chestnut Hill, Massachusetts, United States of America
| | - Eileen Cho
- Department of Psychiatry, Beth Israel Deaconess Medical Center / Harvard Medical School, Boston, Massachusetts, United States of America
| | - Roy Cox
- Department of Psychiatry, Beth Israel Deaconess Medical Center / Harvard Medical School, Boston, Massachusetts, United States of America
- Department of Sleep and Cognition, Netherlands Institute for Neuroscience, Amsterdam, The Netherlands
| | - Robert Stickgold
- Department of Psychiatry, Beth Israel Deaconess Medical Center / Harvard Medical School, Boston, Massachusetts, United States of America
| | - Anna C. Schapiro
- Department of Psychology, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
- Department of Psychiatry, Beth Israel Deaconess Medical Center / Harvard Medical School, Boston, Massachusetts, United States of America
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13
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Leong RLF, Yu N, Ong JL, Ng ASC, Jamaluddin SA, Cousins JN, Chee NIYN, Chee MWL. Memory performance following napping in habitual and non-habitual nappers. Sleep 2021; 44:6031654. [PMID: 33313925 PMCID: PMC8193563 DOI: 10.1093/sleep/zsaa277] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2020] [Revised: 11/16/2020] [Indexed: 11/14/2022] Open
Abstract
Study Objectives Afternoon naps benefit memory but this may depend on whether one is a habitual napper (HN; ≥1 nap/week) or non-habitual napper (NN). Here, we investigated whether a nap would benefit HN and NN differently, as well as whether HN would be more adversely affected by nap restriction compared to NN. Methods Forty-six participants in the nap condition (HN-nap: n = 25, NN-nap: n = 21) took a 90-min nap (14:00–15:30 pm) on experimental days while 46 participants in the Wake condition (HN-wake: n = 24, NN-wake: n = 22) remained awake in the afternoon. Memory tasks were administered after the nap to assess short-term topographical memory and long-term memory in the form of picture encoding and factual knowledge learning respectively. Results An afternoon nap boosted picture encoding and factual knowledge learning irrespective of whether one habitually napped (main effects of condition (nap/wake): ps < 0.037). However, we found a significant interaction for the hippocampal-dependent topographical memory task (p = 0.039) wherein a nap, relative to wake, benefitted habitual nappers (HN-nap vs HN-wake: p = 0.003) compared to non-habitual nappers (NN-nap vs. NN-wake: p = 0.918). Notably for this task, habitual nappers’ performance significantly declined if they were not allowed to nap (HN-wake vs NN-wake: p = 0.037). Conclusions Contrary to concerns that napping may be disadvantageous for non-habitual nappers, we found that an afternoon nap was beneficial for long-term memory tasks even if one did not habitually nap. Naps were especially beneficial for habitual nappers performing a short-term topographical memory task, as it restored the decline that would otherwise have been incurred without a nap. Clinical Trial Information NCT04044885.
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Affiliation(s)
- Ruth L F Leong
- Centre for Sleep and Cognition, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
| | - Nicole Yu
- Centre for Sleep and Cognition, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
| | - Ju Lynn Ong
- Centre for Sleep and Cognition, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
| | - Alyssa S C Ng
- Centre for Sleep and Cognition, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
| | - S Azrin Jamaluddin
- Centre for Sleep and Cognition, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
| | - James N Cousins
- Donders Institute for Brain, Cognition & Behaviour, Radboud University Medical Centre, EN, Nijmegen, The Netherlands
| | - Nicholas I Y N Chee
- Centre for Sleep and Cognition, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
| | - Michael W L Chee
- Centre for Sleep and Cognition, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
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14
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Zhou Y, Chen Q, Luo X, Li L, Ru T, Zhou G. Does Bright Light Counteract the Post-lunch Dip in Subjective States and Cognitive Performance Among Undergraduate Students? Front Public Health 2021; 9:652849. [PMID: 34164367 PMCID: PMC8215386 DOI: 10.3389/fpubh.2021.652849] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2021] [Accepted: 04/19/2021] [Indexed: 11/24/2022] Open
Abstract
The post-lunch dip in alertness and performance was widely experienced during the early afternoon. Taking a short nap was documented as a practical strategy for habitual nappers to counteract the decline of alertness and performance. Yet, it remains unknown whether bright light exposure in the early afternoon working hours could alleviate the performance deficits caused by a post-lunch nap loss for habitual nappers. Seventeen undergraduate students who had a long-term habit of taking a post-lunch nap were assigned to three interventions: (1) a short nap + normal indoor light (100 lx, 4,000 K at eye level); (2) no nap + normal indoor light, and (3) no nap + blue-enriched bright light (1,000 lx, 6,500 K at eye level), in which subjective alertness (Karolinska Sleepiness Scale, KSS), mood (Positive and Negative Affect Schedule, PANAS), and task performance in sustained attention (psychomotor vigilance test, PVT), response inhibition (go/no-go task), and working memory (paced visual serial addition test, PVSAT) were measured. Results showed that a post-lunch nap deprivation significantly increased subjective sleepiness and negative mood and impaired performance in PVT and PVSAT, while exposure to bright blue-enriched white light vs. normal indoor light in the early afternoon significantly relieved such negative effects on mood, sleepiness, and performance in PVSAT; subjective positive mood and performance in PVT and go/no-go task remained unaffected with light intervention. These findings suggested that bright blue-enriched white light exposure could be a potential strategy for those who are suffering from drowsiness and low working memory following a habitual midday nap loss.
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Affiliation(s)
- Ying Zhou
- Lab of Lighting and Physio-Psychological Health, National Center for International Research on Green Optoelectronics, South China Normal University, Guangzhou, China.,Guangdong Provincial Key Laboratory of Optical Information Materials and Technology & Institute of Electronic Paper Displays, South China Academy of Advanced Optoelectronics, South China Normal University, Guangzhou, China
| | - Qingwei Chen
- Lab of Lighting and Physio-Psychological Health, National Center for International Research on Green Optoelectronics, South China Normal University, Guangzhou, China.,Guangdong Provincial Key Laboratory of Optical Information Materials and Technology & Institute of Electronic Paper Displays, South China Academy of Advanced Optoelectronics, South China Normal University, Guangzhou, China
| | - Xue Luo
- School of Psychology, South China Normal University, Guangzhou, China
| | - Le Li
- Lab of Lighting and Physio-Psychological Health, National Center for International Research on Green Optoelectronics, South China Normal University, Guangzhou, China.,Guangdong Provincial Key Laboratory of Optical Information Materials and Technology & Institute of Electronic Paper Displays, South China Academy of Advanced Optoelectronics, South China Normal University, Guangzhou, China
| | - Taotao Ru
- Lab of Lighting and Physio-Psychological Health, National Center for International Research on Green Optoelectronics, South China Normal University, Guangzhou, China.,Guangdong Provincial Key Laboratory of Optical Information Materials and Technology & Institute of Electronic Paper Displays, South China Academy of Advanced Optoelectronics, South China Normal University, Guangzhou, China
| | - Guofu Zhou
- Lab of Lighting and Physio-Psychological Health, National Center for International Research on Green Optoelectronics, South China Normal University, Guangzhou, China.,Guangdong Provincial Key Laboratory of Optical Information Materials and Technology & Institute of Electronic Paper Displays, South China Academy of Advanced Optoelectronics, South China Normal University, Guangzhou, China
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15
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Cousins JN, Teo TB, Tan ZY, Wong KF, Chee MWL. Sleep after learning aids the consolidation of factual knowledge, but not relearning. Sleep 2021; 44:5920204. [PMID: 33035340 PMCID: PMC7953205 DOI: 10.1093/sleep/zsaa210] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2020] [Revised: 09/22/2020] [Indexed: 12/04/2022] Open
Abstract
Study Objectives Sleep strengthens and reorganizes declarative memories, but the extent to which these processes benefit subsequent relearning of the same material remains unknown. It is also unclear whether sleep-memory effects translate to educationally realistic learning tasks and improve long-term learning outcomes. Methods Young adults learned factual knowledge in two learning sessions that were 12 h apart and separated by either nocturnal sleep (n = 26) or daytime wakefulness (n = 26). Memory before and after the retention interval was compared to assess the effect of sleep on consolidation, while memory before and after the second learning session was compared to assess relearning. A final test 1 week later assessed whether there was any long-term advantage to sleeping between two study sessions. Results Sleep significantly enhanced consolidation of factual knowledge (p = 0.01, d = 0.72), but groups did not differ in their capacity to relearn the materials (p = 0.72, d = 0.10). After 1 week, a numerical memory advantage remained for the sleep group but was no longer significant (p = 0.21, d = 0.35). Conclusions Reduced forgetting after sleep is a robust finding that extends to our ecologically valid learning task, but we found no evidence that sleep enhances relearning. Our findings can exclude a large effect of sleep on long-term memory after 1 week, but hint at a smaller effect, leaving open the possibility of practical benefits from organizing study sessions around nocturnal sleep. These findings highlight the importance of revisiting key sleep-memory effects to assess their relevance to long-term learning outcomes with naturalistic learning materials.
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Affiliation(s)
- James N Cousins
- Centre for Cognitive Neuroscience, Duke-NUS Medical School, Singapore.,Donders Institute for Brain, Cognition & Behaviour, Radboud University Medical Centre, Nijmegen, The Netherlands
| | - Teck Boon Teo
- Centre for Cognitive Neuroscience, Duke-NUS Medical School, Singapore.,Centre for Sleep and Cognition, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
| | - Zhi Yi Tan
- Centre for Cognitive Neuroscience, Duke-NUS Medical School, Singapore
| | - Kian F Wong
- Centre for Cognitive Neuroscience, Duke-NUS Medical School, Singapore.,Centre for Sleep and Cognition, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
| | - Michael W L Chee
- Centre for Cognitive Neuroscience, Duke-NUS Medical School, Singapore.,Centre for Sleep and Cognition, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
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16
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Splitting sleep between the night and a daytime nap reduces homeostatic sleep pressure and enhances long-term memory. Sci Rep 2021; 11:5275. [PMID: 33674679 PMCID: PMC7935993 DOI: 10.1038/s41598-021-84625-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2020] [Accepted: 02/12/2021] [Indexed: 11/09/2022] Open
Abstract
Daytime naps have been linked with enhanced memory encoding and consolidation. It remains unclear how a daily napping schedule impacts learning throughout the day, and whether these effects are the same for well-rested and sleep restricted individuals. We compared memory in 112 adolescents who underwent two simulated school weeks containing 8 or 6.5 h sleep opportunities each day. Sleep episodes were nocturnal or split between nocturnal sleep and a 90-min afternoon nap, creating four experimental groups: 8 h-continuous, 8 h-split, 6.5 h-continuous and 6.5 h-split. Declarative memory was assessed with picture encoding and an educationally realistic factual knowledge task. Splitting sleep significantly enhanced afternoon picture encoding and factual knowledge under both 6.5 h and 8 h durations. Splitting sleep also significantly reduced slow-wave energy during nocturnal sleep, suggesting lower homeostatic sleep pressure during the day. There was no negative impact of the split sleep schedule on morning performance, despite a reduction in nocturnal sleep. These findings suggest that naps could be incorporated into a daily sleep schedule that provides sufficient sleep and benefits learning.
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