Observing changes in human functioning during induced sleep deficiency and recovery periods

Individual Sleep Problems Are Associated With an Accelerated Decline in Multiple Cognitive Functions in Older Adults

Poor sleep is a known risk factor of cognitive disorders, but the role of individual sleep problems in age-related cognitive changes remains unclear. This study used two complementary statistical models to estimate nonlinear trajectories of decline in four domains of cognitive functioning in the age period between 55 and 100 years depending on the severity of problems with falling asleep, night awakenings, and early morning awakenings, and short/long sleep duration. The sample included 5132 older adults (M = 67 years, 48% male) from the Longitudinal Aging Study Amsterdam (LASA), assessed 4-10 times every 2-3 years. Sleep problems were self-reported, and cognitive functioning was measured with the 15-Word test (reflecting episodic memory as immediate and delayed recall), Coding task (information processing speed) and Mini-mental State Examination/MMSE (global cognition). Data were analysed using quadratic and piecewise changepoint mixed models. The piecewise models provided more precise and interpretable findings. Decline in information processing speed accelerated significantly earlier in participants with short sleep duration (regression coefficient (B) = -2.3[95% confidence interval (CI): -3.86; -0.81]; p < 0.01) and faster with more severe early morning awakenings (B = -0.07 [-0.1; -0.03]; p < 0.01). Decline in immediate recall accelerated earlier in those with short sleep (B = -2.8 [-4.44; -1.14]; p < 0.01) and severe problems with falling asleep (B = -1.22 [-2.06; -0.39]; p = 0.01). Decline in delayed recall was faster with long sleep (B = -0.06 [-0.08;-0.03]; p < 0.01). Decline in global cognition accelerated faster in those with short/long sleep duration (B = -0.07 [-0.13; -0.01]/-0.10 [-0.18; -0.03]; p < 0.01) and severe night awakenings (B = -0.04 [-0.07;-0.02]; p < 0.01). To conclude, this study showed that some sleep problems can differentially predict earlier acceleration of deterioration in specific cognitive functions in older adults.

Age-Specific Functional Connectivity Changes After Partial Sleep Deprivation Are Correlated With Neurocognitive and Molecular Signatures

BACKGROUND

This study aimed to investigate age-specific alterations in functional connectivity after sleep deprivation (SD) and decode brain functional changes from neurocognitive and transcriptomic perspectives.

METHODS

Here, we examined changes in global and regional graph measures, particularly regional network strength (RNS), in 41 young participants and 36 older participants with normal sleep and after 3 h of SD. Additionally, by utilizing cognitive probabilistic maps from Neurosynth and gene expression data from the Allen Human Brain Atlas, we applied partial least-squares regression analysis to identify the neurocognitive and transcriptional correlates of these RNS changes.

RESULTS

After SD, older participants exhibited decreased RNS in the default mode network (DMN) and dorsal attention network, with increased RNS in the visual network. Young participants also showed decreased RNS in the DMN, notably in the left inferior parietal lobe, left dorsolateral prefrontal cortex, and left posterior cingulate cortex. In young participants, SD-induced RNS changes significantly correlated with cognitive processes such as "attention," "cognitive control," and "working memory," while in older participants, they correlated with "learning," "focus," and "decision." Gene-category enrichment analysis indicated that specific genes related to signal transduction, ion channels, and immune signaling might influence SD pathophysiology by affecting functional connectivity in young participants.

CONCLUSIONS

This study elucidates shared and age-specific brain functional network alterations associated with SD, providing a neurocognitive and molecular basis for understanding the underlying pathophysiology.

Sleep Patterns and Human Brain Health

It is a widely held opinion that sleep is important for human brain health. Here we examine the evidence for this view, focusing on normal variations in sleep patterns. We discuss the functions of sleep and highlight the paradoxical implications of theories seeing sleep as an adaptive capacity versus the theory that sleep benefits clearance of metabolic waste from the brain. We also evaluate the proposition that sleep plays an active role in consolidation of memories. Finally, we review research on possible effects of chronic sleep deprivation on brain health. We find that the evidence for a causal role of sleep in human brain health is surprisingly weak relative to the amount of attention to sleep in science and society. While there are well-established associations between sleep parameters and aspects of brain health, results are generally not consistent across studies and measures, and it is not clear to what extent alterations in sleep patterns represent symptoms or causes. Especially, the proposition that long sleep (>8 hours) in general is beneficial for long-term brain health in humans seems to lack empirical support. We suggest directions for future research to establish a solid foundation of knowledge about a role of sleep in brain health based on longitudinal studies with frequent sampling, attention to individual differences, and more ecologically valid intervention studies.

Biometrically measured sleep in medical students as a predictor of psychological health and academic experiences in the preclinical years

BACKGROUND

Student wellness is of increasing concern in medical education. Increased rates of burnout, sleep disturbances, and psychological concerns in medical students are well documented. These concerns lead to impacts on current educational goals and may set students on a path for long-term health consequences.

METHODS

Undergraduate medical students were recruited to participate in a novel longitudinal wellness tracking project. This project utilized validated wellness surveys to assess emotional health, sleep health, and burnout at multiple timepoints. Biometric information was collected from participant Fitbit devices that tracked longitudinal sleep patterns.

RESULTS

Eighty-one students from three cohorts were assessed during the first semester of their M1 preclinical curriculum. Biometric data showed that nearly 30% of the students had frequent short sleep episodes (<6 hours of sleep for at least 30% of recorded days), and nearly 68% of students had at least one episode of three or more consecutive days of short sleep. Students that had consecutive short sleep episodes had higher rates of stress (8.3%) and depression (5.4%) symptoms and decreased academic efficiency (1.72%).

CONCLUSIONS

Biometric data were shown to significantly predict psychological health and academic experiences in medical students. Biometrically assessed sleep is poor in medical students, and consecutive days of short sleep duration are particularly impactful as it relates to other measures of wellness. Longitudinal, biometric data tracking is feasible and can provide students the ability to self-monitor health behaviors and allow for low-intensity health interventions.

Preliminary examination of orexin receptor antagonism with suvorexant in individuals with Methamphetamine use disorder: a case series study

Background: No FDA-approved medications for methamphetamine (MA) use disorder (MUD) are available. Suvorexant (SUVO), a dual orexin receptor antagonist that is FDA approved for insomnia treatment, reduces MA self-administration and MA-induced reinstatement responding in preclinical studies. SUVO may also reduce MA use by targeting substance use risk factors, including insomnia, stress, cue reactivity, and craving. This case series study assessed the (1) feasibility and safety of administering suvorexant in a sample of individuals with MUD; and (2) preliminary effects of suvorexant on objective and subjective measures of sleep, stress, and cue reactivity/craving. Method: Participants (n = 3) were randomized to receive 1 week of SUVO or placebo using a within-subject, crossover design with a 1-week washout period between doses. Participants completed self-report (sleep quality, stress), behavioral (cold pressor task), and physiological measures (heart rate, electroencephalogram) during all three weeks. Participants wore a Fitbit to monitor sleep throughout the study. Results: Participants completed all study visits and tasks. One report of severe drowsiness and of severe headache were made; no other severe side effects were associated with SUVO. SUVO improved total sleep time and resulted in lower resting-state alpha power, but was mixed for subjective sleep quality. SUVO administration was associated with increased overall brain reactivity to cues that was not specific to MA cues and also reduced stress, though self-reported stress demonstrated mixed results. Conclusion: Suvorexant was safe and tolerable in a MUD sample. Future research may benefit from investigating SUVO in a well-controlled study with a larger sample.

A systematic and meta-analytic review of the impact of sleep restriction on memory formation

Modern life causes a quarter of adults and half of teenagers to sleep for less than is recommended (Kocevska et al., 2021). Given well-documented benefits of sleep on memory, we must understand the cognitive costs of short sleep. We analysed 125 sleep restriction effect sizes from 39 reports involving 1234 participants. Restricting sleep (3-6.5 hours) compared to normal sleep (7-11 hours) negatively affects memory formation with a small effect size (Hedges' g = 0.29, 95 % CI = [0.13, 0.44]). We detected no evidence for publication bias. When sleep restriction effect sizes were compared with 185 sleep deprivation effect sizes (Newbury et al., 2021) no statistically significant difference was found, suggesting that missing some sleep has similar consequences for memory as not sleeping at all. When the analysis was restricted to post-encoding, rather than pre-encoding, sleep loss, sleep deprivation was associated with larger memory impairment than restriction. Our findings are best accounted for by the sequential hypothesis which emphasises complementary roles of slow-wave sleep and REM sleep for memory.

Metabolic and vascular imaging markers for investigating Alzheimer's disease complicated by sleep fragmentation in mice

Background

Sleep problem is a common complication of Alzheimer's disease (AD). Extensive preclinical studies have been performed to investigate the AD pathology. However, the pathophysiological consequence of AD complicated by sleep problem remains to be further determined.

Purpose

To investigate brain metabolism and perfusion in an AD mouse model complicated by sleep problem, and subsequently identify potential imaging markers to better understand the associated pathophysiology.

Methods

We examined the oxygen extraction fraction (OEF), cerebral metabolic rate of oxygen (CMRO2), and cerebral blood flow (CBF) using state-of-the-art MRI techniques in a cohort of 5xFAD model mice. Additionally, neuroinflammation, indicated by activated microglia, was assessed using histology techniques. Sleep fragmentation (SF) was utilized as a representative for sleep problems.

Results

SF was associated with significant increases in OEF (P = 0.023) and CMRO2 (P = 0.029), indicating a state of hypermetabolism. CBF showed a significant genotype-by-sleep interaction effect (P = 0.026), particularly in the deep brain regions such as the hippocampus and thalamus. Neuroinflammation was primarily driven by genotype rather than SF, especially in regions with significant interaction effect in CBF measurements.

Conclusion

These results suggest that brain metabolism and perfusion measurements are promising markers for studying the co-pathogenesis of AD and SF.

Adverse childhood experiences among doctor of pharmacy students

OBJECTIVE

Adverse Childhood Experiences (ACEs) have demonstrated negative impact on physical, emotional, and cognitive health outcomes. This study aimed to assess prevalence of ACEs among Doctor of Pharmacy (PharmD) students, and their associations with mental health, substance use, academic performance, and sleep patterns.

METHODS

A cross-sectional survey was conducted on PharmD students at a private University. ACE scores, mental health history, substance use, academic performance, and sleep habits were self-reported. Descriptive statistics and chi-square tests were used for analysis.

RESULTS

From 54 participants across all cohorts of students in the curriculum (response rate: 19%), 48% reported ≥4 ACEs. A majority of students reported having been diagnosed with or sought treatment for depression (56%) or anxiety (67%), while 42.9% reported a history of contemplating suicide. Participants with ACE scores of ≥4 were more likely to have sought treatment for depression, any mental health condition, contemplated suicide, or used alcohol for mental health purposes. No differences in academic performance based on ACE scores were found.

CONCLUSION

High numbers of ACEs were common and linked to mental illness, suicidality, and use of alcohol for mental health purposes. While no direct academic impact was found in this small sample size, adopting a trauma-informed approach is crucial to supporting student well-being. Further research in this area is needed to optimize interventions to support academic and professional success among students with ≥4 ACEs.

Sleep Architecture Patterns in Critically Ill Patients and Survivors of Critical Illness: A Retrospective Study

Rationale: Sleep abnormalities are very frequent in critically ill patients during and after intensive care unit (ICU) stays. Their mechanisms are poorly understood. The odds ratio product (ORP) is a continuous metric (range, 0.0-2.5) of sleep depth measured in 3-second intervals and derived from the relationship of powers of different electroencephalographic frequencies to one another. When expressed as the percentage of epochs within 10 ORP deciles covering the entire ORP range, it provides information about the mechanism(s) of abnormal sleep. Objectives: To determine ORP architecture types in critically ill patients and survivors of critical illness who had previously undergone sleep studies. Methods: Nocturnal polysomnograms from 47 unsedated critically ill patients and 23 survivors of critical illness at hospital discharge were analyzed. Twelve critically ill patients were monitored also during the day, and 15 survivors underwent subsequent polysomnography 6 months after hospital discharge. In all polysomnograms, each 30-second epoch was characterized by the mean ORP of the 10 3-second epochs. The number of 30-second epochs with mean ORP within each of 10 ORP deciles covering the entire ORP range (0.0-2.5) was calculated and expressed as a percentage of total recording time. Thereafter, each polysomnogram was characterized using a two-digit ORP type, with the first digit (range, 1-3) reflecting increasing degrees of deep sleep (ORP < 0.5, deciles 1 and 2) and the second digit (range, 1-3) reflecting increasing degrees of full wakefulness (ORP > 2.25, decile 10). Results from patients were compared with those from 831 age- and gender-matched community dwellers free of sleep disorders. Results: In critically ill patients, types 1,1 and 1,2 (little deep sleep and little or average full wakefulness) dominated (46% of patients). In the community, these types are uncommon (<15%) and seen primarily in disorders that preclude progression to deep sleep (e.g., very severe obstructive sleep apnea). Next in frequency (22%) was type 1,3, consistent with hyperarousal. Day ORP sleep architecture was similar to night results. Survivors had similar patterns, with little improvement after 6 months. Conclusions: Sleep abnormalities in critically ill patients and survivors of critical illness result primarily from stimuli that preclude progression to deep sleep or from the presence of a hyperarousal state.

Sleep and memory: The impact of sleep deprivation on transcription, translational control, and protein synthesis in the brain

In countries around the world, sleep deprivation represents a widespread problem affecting school-age children, teenagers, and adults. Acute sleep deprivation and more chronic sleep restriction adversely affect individual health, impairing memory and cognitive performance as well as increasing the risk and progression of numerous diseases. In mammals, the hippocampus and hippocampus-dependent memory are vulnerable to the effects of acute sleep deprivation. Sleep deprivation induces changes in molecular signaling, gene expression and may cause changes in dendritic structure in neurons. Genome wide studies have shown that acute sleep deprivation alters gene transcription, although the pool of genes affected varies between brain regions. More recently, advances in research have drawn attention to differences in gene regulation between the level of the transcriptome compared with the pool of mRNA associated with ribosomes for protein translation following sleep deprivation. Thus, in addition to transcriptional changes, sleep deprivation also affects downstream processes to alter protein translation. In this review, we focus on the multiple levels through which acute sleep deprivation impacts gene regulation, highlighting potential post-transcriptional and translational processes that may be affected by sleep deprivation. Understanding the multiple levels of gene regulation impacted by sleep deprivation is essential for future development of therapeutics that may mitigate the effects of sleep loss.

A narrative review of occupational scheduling that impacts fatigue and recovery relevant to veterinarian well-being

Background

Sleep insufficiency is a worldwide affliction with serious implications for mental and physical health. Occupational factors play a large role in determining sleep habits. Healthcare workers are particularly susceptible to job-mediated sleep insufficiency and inadequate rest in general. Little is published on sleep practices among veterinarians, and overall recognition of the impacts of inadequate rest within the veterinary profession is poor.

Objectives and procedures

This review describes occupational factors affecting sufficiency of rest and recovery, reviews veterinary-specific and relevant adjacent literature pertaining to sleep patterns, and discusses potential solutions for addressing occupational schedules contributing to sleep insufficiency and inadequate rest. Online databases were searched to extract contemporary literature pertaining to sleep, insufficient rest, and occupational factors, with a focus on veterinary medicine and other healthcare sectors.

Results

Occupational factors leading to inadequate rest among healthcare workers include excessive workloads, extended workdays, cumulative days of heavy work hours, and after-hours on-call duty. These factors are prevalent within the veterinary profession and may contribute to widespread insufficient rest and the resulting negative impacts on health and well-being among veterinarians.

Conclusion and clinical relevance

Sufficient sleep quantity and quality are critical to physical and mental health and are negatively affected by many aspects of the veterinary profession. Critical review of current strategies employed in clinical practice is essential to promote professional fulfillment, health, and well-being among veterinarians.

Role of astrocytes in sleep deprivation: accomplices, resisters, or bystanders?

Sleep plays an essential role in all studied animals with a nervous system. However, sleep deprivation leads to various pathological changes and neurobehavioral problems. Astrocytes are the most abundant cells in the brain and are involved in various important functions, including neurotransmitter and ion homeostasis, synaptic and neuronal modulation, and blood-brain barrier maintenance; furthermore, they are associated with numerous neurodegenerative diseases, pain, and mood disorders. Moreover, astrocytes are increasingly being recognized as vital contributors to the regulation of sleep-wake cycles, both locally and in specific neural circuits. In this review, we begin by describing the role of astrocytes in regulating sleep and circadian rhythms, focusing on: (i) neuronal activity; (ii) metabolism; (iii) the glymphatic system; (iv) neuroinflammation; and (v) astrocyte-microglia cross-talk. Moreover, we review the role of astrocytes in sleep deprivation comorbidities and sleep deprivation-related brain disorders. Finally, we discuss potential interventions targeting astrocytes to prevent or treat sleep deprivation-related brain disorders. Pursuing these questions would pave the way for a deeper understanding of the cellular and neural mechanisms underlying sleep deprivation-comorbid brain disorders.

A narrative review of the impact of work hours and insufficient rest on job performance

OBJECTIVE

This review discusses the scientific evidence regarding effects of insufficient rest on clinical performance and house officer training programs, the associations of clinical duty scheduling with insufficient rest, and the implications for risk management.

STUDY DESIGN

Narrative review.

METHODS

Several literature searches using broad terms such as "sleep deprivation," "veterinary," "physician," and "surgeon" were performed using PubMed and Google scholar.

RESULTS

Sleep deprivation and insufficient rest have clear and deleterious effects on job performance, which in healthcare occupations impacts patient safety and practice function. The unique requirements of a career in veterinary surgery, which may include on-call shifts and overnight work, can lead to distinct sleep challenges and chronic insufficient rest with resultant serious but often poorly recognized impacts. These effects negatively impact practices, teams, surgeons, and patients. The self-assessment of fatigue and performance effect is demonstrably untrustworthy, reinforcing the need for institution-level protections. While the issues are complex and there is no one-size-fits-all approach, duty hour or workload restrictions may be an important first step in addressing these issues within veterinary surgery, as it has been in human medicine.

CONCLUSION

Systematic re-examination of cultural expectations and practice logistics are needed if improvement in working hours, clinician well-being, productivity, and patient safety are to occur.

CLINICAL SIGNIFICANCE (OR IMPACT)

A more comprehensive understanding of the magnitude and consequence of sleep-related impairment better enables surgeons and hospital management to address systemic challenges in veterinary practice and training programs.

Neural consequences of chronic sleep disruption

Recent studies in both humans and animal models call into question the completeness of recovery after chronic sleep disruption. Studies in humans have identified cognitive domains particularly vulnerable to delayed or incomplete recovery after chronic sleep disruption, including sustained vigilance and episodic memory. These findings, in turn, provide a focus for animal model studies to critically test the lasting impact of sleep loss on the brain. Here, we summarize the human response to sleep disruption and then discuss recent findings in animal models examining recovery responses in circuits pertinent to vigilance and memory. We then propose pathways of injury common to various forms of sleep disruption and consider the implications of this injury in aging and in neurodegenerative disorders.

Sleep deprivation and recovery sleep affect healthy male resident’s pain sensitivity and oxidative stress markers: The medial prefrontal cortex may play a role in sleep deprivation model

Sleep is essential for the body’s repair and recovery, including supplementation with antioxidants to maintain the balance of the body’s redox state. Changes in sleep patterns have been reported to alter this repair function, leading to changes in disease susceptibility or behavior. Here, we recruited healthy male physicians and measured the extent of the effect of overnight sleep deprivation (SD) and recovery sleep (RS) on nociceptive thresholds and systemic (plasma-derived) redox metabolism, namely, the major antioxidants glutathione (GSH), catalase (CAT), malondialdehyde (MDA), and superoxide dismutase (SOD). Twenty subjects underwent morning measurements before and after overnight total SD and RS. We found that one night of SD can lead to increased nociceptive hypersensitivity and the pain scores of the Numerical Rating Scale (NRS) and that one night of RS can reverse this change. Pre- and post-SD biochemical assays showed an increase in MDA levels and CAT activity and a decrease in GSH levels and SOD activity after overnight SD. Biochemical assays before and after RS showed a partial recovery of MDA levels and a basic recovery of CAT activity to baseline levels. An animal study showed that SD can cause a significant decrease in the paw withdrawal threshold and paw withdrawal latency in rats, and after 4 days of unrestricted sleep, pain thresholds can be restored to normal. We performed proteomics in the rat medial prefrontal cortex (mPFC) and showed that 37 proteins were significantly altered after 6 days of SD. Current findings showed that SD causes nociceptive hyperalgesia and oxidative stress, and RS can restore pain thresholds and repair oxidative stress damage in the body. However, one night of RS is not enough for repairing oxidative stress damage in the human body.

Weekend sleep after early and later school start times confirmed a model-predicted failure to catch up sleep missed on weekdays

Background

Many people believe they sleep for longer time on weekend nights to make up for sleep lost on weekdays. However, results of simulations of risetimes and bedtimes on weekdays and weekends with a sleep–wake regulating model revealed their inability to prolong weekend sleep. In particular, they predicted identical durations of weekend sleep after weeks with relatively earlier and relatively later risetime on weekdays. In the present study, this paradoxical prediction was empirically confirmed.

Methods

Times in bed were calculated from weekday and weekend risetimes and bedtimes in pairs of samples of students with early and later school start time and in subsets of samples from 7 age groups with weekday risetime earlier and later than 7:00 a.m.

Results

Among 35 pairs of students, mean age ± standard deviation was 14.5 ± 2.9 years and among the age group samples, 21.6 ± 14.6 years. As predicted by the simulations, times in bed on weekends were practically identical in the samples with early and later school start time and in two subsets with earlier and later weekday risetime.

Conclusions

The model-based simulations of sleep times can inform an individual about an amount of irrecoverable loss of sleep caused by an advance shift of wakeups on weekdays.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11325-022-02648-5.

Altered distribution of resting periods of daily locomotor activity in patients with delayed sleep phase disorder

Delayed sleep phase disorder (DSPD) and mood disorders have a close relationship. However, the shared mechanisms by DSPD and mood disorders have not been well-elucidated. We previously found that micro-fluctuations in human behaviors are organized by robust statistical laws (behavioral organization), where the cumulative distributions of resting and active period durations take a power-law distribution form and a stretched exponential functional form, respectively. Further, we found that the scaling exponents of resting period distributions significantly decreased in major depressive disorder (MDD). In this study, we hypothesized that DSPD had similar characteristics of the altered behavioral organization to that of MDD. Locomotor activity data were acquired for more than 1 week from 17 patients with DSPD and 17 age- and gender-matched healthy participants using actigraphy. We analyzed the cumulative distributions of resting and active period durations in locomotor activity data and subsequently derived fitting parameters of those distributions. Similar to patients with MDD, we found that resting period distributions took a power-law form over the range of 2-100 min, with significantly lower values of scaling exponents γ in patients with DSPD compared with healthy participants. The shared alteration in γ suggests the existence of similar pathophysiology between DSPD and MDD.