Digital biomarkers are gaining interest as proxy markers for mental health, as they enable passive and continuous data collection. However, the association between digital biomarkers of health and anxiety, both generalized anxiety disorder and anxiety symptoms, remains unknown. This systematic review and meta-analysis examined the association between digital biomarkers of health obtained from wrist-worn wearables and anxiety in adults. Systematic literature searches were conducted across 6 databases, including unpublished gray literature. The final search was done on September 21, 2025. Cross-sectional or longitudinal studies investigating the association between digital biomarkers from wrist-worn wearables and anxiety were eligible. Studies using inferential statistics or machine learning methods were both eligible. Studies were excluded if participants received diagnoses of neurodegenerative disorders or physical health conditions. Two risk-of-bias tools were used: the National Heart, Lung, and Blood Institute assessment tool for inferential statistical studies, and the modified version of the Quality Assessment of Diagnostic Accuracy Studies-2 for machine learning studies. Whenever possible, effect sizes were combined across studies, for each digital biomarker of health separately, using random-effects meta-analyses. Sensitivity analyses were performed to assess whether results differed according to anxiety type (state or trait) and age group. Otherwise, studies were synthesized narratively. A total of 44 studies from 42 articles were eligible. Among these, 36 studies used inferential statistical approaches for analysis (21 reporting sleep characteristics, 8 reporting physical activity, 2 reporting heart rate variability, and 5 reporting more than 1 type), and 8 studies used machine learning approaches. Sample size ranged from 17 to 170,320. Meta-analyses on 4 sleep metrics found no associations: sleep efficiency (Fisher z=-0.07, 95% CI -0.14 to 0.002; P=.06; PI -0.19 to 0.05), wake after sleep onset (Fisher z=0.13, 95% CI -0.04 to 0.30; P=.11; PI -0.15 to 0.41), total sleep time (Fisher z=0.009, 95% CI -0.01 to 0.03; P=.28; PI -0.02 to 0.03), and sleep onset latency (Fisher z=0.04, 95% CI -0.07 to 0.15; P=.08; PI -0.19 to 0.27). Qualitative syntheses revealed that lower physical activity levels and higher heart rate were associated with greater anxiety symptoms. Machine learning studies using wrist-worn wearable data alone showed varied performance, with predictive performance improving when wearable data were combined with other data sources. This is the first review to synthesize evidence from inferential statistical (mostly fair quality) and machine learning studies examining association between wearable-derived digital biomarkers and anxiety. Meta-analyses found no associations between sleep metrics and anxiety. Although based on limited studies, lower physical activity levels and elevated heart rate were associated with greater anxiety symptoms. Digital biomarkers may be more useful when integrated with other data sources (eg, self-report and clinical data) rather than used as stand-alone screening tools. PROSPERO CRD42023409995; https://www.crd.york.ac.uk/PROSPERO/view/CRD42023409995.

Association between obstructive sleep apnea and metabolic profiles across sleep stages in pediatrics.

A phase 3, multicenter, double-blind, randomized, placebo-controlled clinical trial of lemborexant in adults with insomnia disorder.

The impact of mind-body and aerobic exercises on subjective and objective sleep quality in middle-aged and older adults: A systematic review and meta-analysis of randomized controlled trials.

Efficacy and safety of daridorexant for the treatment of insomnia disorder in women of menopausal transition age: Insights from a randomized controlled trial.

Caregiver outcomes related to sleep disturbances in persons living with cognitive impairment.

Individual sleep/wake patterns can be characterized by the intraindividual mean (iM) and variability (iSD), which captures night-to-night fluctuations. Most accelerometry-based sleep studies assess 7-14 nights, which may be insufficient for reliable variability estimates. This pre-registered, large cohort study quantifies how many nights are needed for reliable sleep iM and iSD estimates using accelerometry. Participants (n= 10 412, Mage= 37.75±10.65, 50.00% women) wore a validated, wrist-worn biometric device (WHOOP) for one year (3 700 492 person-nights). Total sleep time (TST), sleep onset, midsleep, sleep offset, wake after sleep onset (WASO), and sleep percentage were estimated. Reliability correlation coefficients compared reference values (calculated from all 363 nights) with 2-362 consecutive nights randomly selected per participant, with r> .80 considered reliable. 95% limits of agreement were calculated using the Bland-Altman method. Reliable iM estimates (r > .80) were achieved with 2-7 nights of data, depending on the sleep metric: TST (7 nights), sleep-onset and midsleep (3), sleep-offset and sleep percentage (4), WASO (5). In contrast, reliable iSD estimates required substantially more nights: TST (43 nights), sleep-onset (44), midsleep and sleep-offset (41), sleep percentage (62), and WASO (65). iSDs estimated from 7-14 nights showed poor reliability (r = .50-.67) and wide 95% limits of agreement (e.g., TST: ±50.5min for 7 nights). Findings highlight the importance of tailoring study periods to the specific sleep metric of interest. Longer monitoring periods may improve diagnostic consistency and inform evidence-based recommendations for sleep assessments in clinical and research settings.

Background Sleep disturbances are common in people with dementia and nightly prescribed psychotropic drugs, such as sedatives or antidepressants, can increase risks such as injury, inactivity, and behavioral symptoms. Treatment decisions currently rely on periodic, proxy-rated questionnaires that may miss important daily fluctuations in sleep and activity. We explore whether sensing technologies provide insights into distinct differences in sleep characteristics and activity levels in nursing home residents with dementia who are prescribed nightly psychotropic drugs for sleep disturbances. Methods Forty-seven participants were recruited from four nursing homes in Bergen, Norway, and stratified according to prescribed nightly psychotropic drug use for sleep disturbance: 1) none, 2) medications with short half-lives, 3) medications with long half-lives. Garmin Vivoactive5 and Venu3, Vital Things Somnofy sleep monitor, and traditional questionnaires (Physical Self Maintenance Scale and Neuropsychiatric Inventory-Nursing Home version) were used for data collection. Digital metrics included Euclidean Norm Minus One (ENMO; day/night/24-h), Sleep Regulatory Index (SRI), Sleep Efficiency (SE), Total Sleep Time (TST), Sleep Fragmentation Index (SFI), and no presence (time out of bed). Results Thirty participants (73–100 years old) were included for analysis. Groups taking psychotropic medications were awake for longer periods (WASO: chi 2 = 8.7, p = 0.01) and had poorer sleep regularity (SRI: chi 2 = 20.6, p = 0.0001). Participants taking psychotropic drugs had less physical activity (day/night/24-h ENMO), with greatest differences between those on medications with a long half-life (day: chi 2 = 9.48, p = 0.009; night: chi 2 = 12.83, p = 0.002; 24-h: chi 2 = 8.23, p = 0.02) and those not on nightly psychotropic medications. Conclusion The digital biomarkers collected using the selected sensing technologies offered nuanced information regarding sleep behaviors and physical activity levels, providing detailed distinction between the groups. Sensing technologies may be a promising companion to the currently used proxy-rated assessment tools for sleep disturbance and physical activity levels for people with dementia residing in nursing homes.

Reduced rapid-eye movement (REM) sleep has been linked to increased mortality in the general population. We investigated whether diminished REM sleep is associated with higher mortality in adults with coronary artery disease (CAD) and obstructive sleep apnea (OSA). This secondary analysis of the RICCADSA trial included 356 revascularized CAD patients with OSA (apnea-hypopnea index [AHI] ≥ 15 events/h) and total sleep time (TST) ≥ 240min on baseline polysomnography. Reduced REM sleep was defined as the lowest quartile of REM percentage. Cox proportional hazards models assessed the association between reduced REM sleep and mortality over a median 4.7-year follow-up. The lowest REM quartile corresponded to 8.7% of TST. Participants with reduced REM sleep (n = 86) were older (66.0 ± 8.1 vs. 63.0 ± 8.0 years; p = 0.035), had higher BMI (29.8 ± 4.6 vs. 28.7 ± 3.8kg/m²; p = 0.010), shorter TST (369 ± 77 vs. 497 ± 69min; p < 0.001), less slow-wave sleep (5.2 ± 7.0% vs. 8.1 ± 10.0%; p = 0.007), and higher AHI (54.4 ± 26.3 vs. 35.6 ± 20.1 events/h; p < 0.001) than those with REM ≥ 8.7% (n = 270). Mortality was 12.8% in the reduced REM group versus 4.4% in the higher REM group (p = 0.006). Reduced REM sleep independently predicted mortality (hazard ratio 2.39; 95% CI 1.03-5.56; p = 0.043) after adjustment for age, sex, BMI, and CPAP allocation. Further adjustment for TST, slow-wave sleep, baseline AHI, coronary bypass surgery, atrial fibrillation, and REM-AHI interaction did not alter the association. Reduced REM sleep independently predicted higher all-cause mortality in revascularized CAD patients with OSA. Identifying diminished REM sleep may help identify particularly vulnerable patients.

Slow-wave activity (0.5-4Hz electroencephalographic activity) during non-rapid eye movement sleep is consistently associated with better cognitive performance in older adults. Slow-wave activity is known to regulate synaptic plasticity and may thereby mitigate excitotoxicity and accumulation of Alzheimer's pathology. Paradoxically, longer total sleep times in older adults are often associated with poorer cognition and general health. Conventional behavioral sleep treatments robustly increase sleep efficiency and sleep time, but do not consistently enhance slow-wave activity and have shown only subtle effects on cognition. Thus, enhancement of slow-wave activity may be a critical target for sleep-based cognitive enhancement. The Alzheimer's Pathways Sleep Study (ALPS) uses a novel time-in-bed (TiB) restriction intervention designed to increase slow-wave activity through homeostatic sleep drive and assesses improvements in measures of excitotoxic hippocampal hyperactivation, plasma levels of amyloid beta (Aβ), and overnight memory retention. ALPS is a randomized controlled trial designed to increase slow-wave activity behaviorally in older adults with poor sleep. Target enrollment is 116 participants aged 65-85. Participants are randomized to a TiB restriction intervention or an attention-matched control intervention. Participants randomized to TiB restriction follow a sleep schedule restricting their TiB to 85% of their habitual TiB for 4 weeks. The control group follows their habitual TiB for 4 weeks. Both groups are monitored with diary, actigraphy, check-in calls, and sleepiness ratings over the 4weeks. The primary outcomes for four specific aims are (1) absolute power in the slow oscillation (0.5-1Hz) range during non-rapid eye movement sleep, (2) hippocampal activation during memory encoding, (3) plasma Aβ1-42, and (4) overnight word pair memory retention. Here we describe how the ALPS intervention is administered, the protocols and scripts implemented to maximize adherence and safety, and outcomes measured to test the proposed conceptual model linking slow-wave activity with excitotoxic hyperactivation, Alzheimer's pathophysiology, and memory performance. Behavioral enhancement of homeostatic sleep drive through TiB restriction is a promising approach to improve memory performance and Alzheimer's pathophysiology. Safety measures, as described here, should be implemented to minimize risks associated with TiB restriction. ClinicalTrials.gov NCT05138848. Registered on December 1, 2021.

Abstract Background: Cancer-related cognitive difficulties (CRCD) is prevalent and distressing for breast cancer survivors and commonly co-occurs with insomnia. Although sleep tracking has become increasingly common in oncology settings, little is known about how sleep patterns influence cognition in cancer survivors. Therefore, we aim to characterize the associations between subjective and objective sleep continuity and cognition in breast cancer survivors with insomnia and CRCD. Methods: This analysis includes baseline data from a trial conducted among 260 breast cancer survivors with insomnia (Insomnia Severity Index score ≥8) and self-reported CRCD. This analysis is limited to trial participants who completed sleep tracking measures, including the Consensus Sleep Diary (CSD) and Actiwatch or FitBit smart watch (WA). Sleep continuity measures included wake after sleep onset (WASO), number of awakenings (NWAK), time spent in bed (TIB), total sleep time (TST), and sleep efficiency (SE). Subjective cognition was assessed by Functional Assessment of Cancer Therapy-Cognition Perceived Cognitive Impairment domain (FACT-Cog PCI), while objective cognition was assessed by Hopkins Verbal Learning Test-Revised (HVLT-R) Delayed Recall normed T-score. Multivariate linear regression modeling was used to explore associations between sleep continuity and cognition. All models included adjustments from covariates: chemotherapy use, cancer stage, race, and education. Results: Among 158 participants, the average age [range] was 57 [28-83] and 21.5% were nonwhite. None of the sleep metrics collected from either the CSD or WA were significantly associated with subjective cognition (all p &amp;gt; .05). In data collected by CSD, greater WASO was significantly associated with worse objective cognition (Coef. = -.243, p = .003, 95% CI [-0.135, -0.028]) and higher SE was significantly associated with better objective cognition (Coef. = .209, p = .011, 95% CI [0.054, 0.422]). In data collected by WA, greater NWAK was significantly associated with worse objective cognition (Coef. = -.298, p = .010, 95% CI [-0.294, -0.042]). Conclusion: Measured and reported sleep continuity was not significantly associated with subjective cognition, but sleep fragmentation, measured by both sleep diary and smart watch, was significantly associated with worse objective cognition in breast cancer survivors with comorbid insomnia and CRCD. Interventions targeting sleep could be used to promote cognitive health during breast cancer survivorship. Citation Format: K. Lampson, X. Li, A. Yang, S. N. Garland, J. C. Root, T. A. Ahles, J. J. Mao. Association Between Sleep Continuity and Cognition in Breast Cancer Survivors: A Cross-Sectional Study [abstract]. In: Proceedings of the San Antonio Breast Cancer Symposium 2025; 2025 Dec 9-12; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2026;32(4 Suppl):Abstract nr PS1-05-18.

ABSTRACT Objectives: To examine correlations among sleep, internalizing symptoms, and academic performance among undergraduate students. Methods: A sample of undergraduate students (N = 255) at a comprehensive public university in the U.S. wore a Fitbit activity band for three weeks to track their sleep via actigraphy. Average total sleep time, circadian midpoint, and sleep efficiency metrics, as well as intraindividual variability in those metrics, were used. Participants also completed a subjective sleep quality questionnaire and self-assessments of depression and anxiety symptoms. Academic performance (i.e., GPA) was gathered from the university registrar’s office. Results: There were mostly near-zero relations among actigraphy sleep metrics, academic performance, and internalizing symptoms in the sample. However, there were significant correlations among subjective sleep quality and internalizing symptoms. Conclusion: Contrary to our hypotheses, students who slept little, poorly, or with night-to-night variability, as measured by wearable actigraphy, did not have elevated symptoms of anxiety and depression, nor poorer academic performance.

Disordered sleep is a common reason individuals report using cannabis, yet the physiological effects of Δ9-tetrahydrocannabinol (Δ9-THC) on sleep and autonomic regulation remain incompletely understood. Early studies reported acute sleep-promoting effects of Δ9-THC, but chronic use has been associated with disrupted sleep and possible cardiovascular risk. This feasibility and mechanistic pilot study examined the influence of acute Δ9-THC administration on sleep and cardiac parasympathetic activity in adults with and without regular cannabis use. Nine individuals with regular cannabis use (> 3× per week) and nine individuals with minimal cannabis exposure (no use within the previous year and < 10 lifetime exposures) underwent 2 weeks of actigraphy-verified sleep stabilisation before a three-night, single-blind laboratory protocol including an acclimatisation night, a placebo night, and a 10 mg oral Δ9-THC dosing night. During at-home monitoring, individuals who regularly used cannabis (permitted adlibitum cannabis use) had shorter total sleep time and greater sleep disruption than the no cannabis use group (p < 0.05). In laboratory polysomnography revealed that Δ9-THC increased sleep latency, slow wave sleep (p < 0.05), EEG spectral power across frequency bands (p < 0.05), and attenuated delta power dissipation in the first half of the night (DrugxSleephour, p < 0.05). Δ9-THC also markedly reduced heart rate variability across time- (p < 0.01) and frequency-domain (p < 0.05) metrics. These findings demonstrate the feasibility and tolerability of controlled in-laboratory Δ9-THC administration following sleep stabilisation among adults who regularly use cannabis and those with minimal exposure, and provide preliminary mechanistic evidence that acute Δ9-THC before bedtime increases cortical activation and reduces cardiac parasympathetic activity during sleep.

ABSTRACT Background A new health monitoring device called Fitbit Charge 6 has appeared on the Vietnamese market. This study aimed to evaluate the consistency between Fitbit Charge 6 and structured interview questions in measuring sleep quality among breastfeeding mothers. Research design and methods A cross-sectional study utilizing random convenience sampling was conducted in Ho Chi Minh City, Vietnam, involving 208 breastfeeding women one month postpartum. The participants used the Fitbit Charge 6 device continuously for four days and three nights to gather daily sleep information; then, they were administered a structured sleep questionnaire via home interviews. Results The correlation between the total sleep time (TST) recorded by both the device and interview was weak (r = 0.28), as was the correlation for short nap duration (r = 0.25). The agreement between the Fitbit Sleep Score and sleep satisfaction from the questionnaire was 79.9%, with a notably low kappa coefficient (0.02), indicating a lack of strong agreement. Conclusion The Fitbit Charge 6 did not show reliable correlation with the subjective sleep data reported by one-month postpartum breastfeeding women. Further research employing rigorous comparative studies is necessary to assess the validity and reliability of sleep data collection methods for this demographic.

Chronic Insomnia Disorder (ID) is characterized by hyperarousal, a key pathophysiological feature. While Cognitive-Behavioral Therapy for Insomnia (CBT-I) is the first-line treatment, its physiological effects on sleep-related hyperarousal remain underexplored. This study assessed the impact of CBT-I on cortical hyperarousal using quantitative EEG (qEEG) during non-REM (NREM) sleep, with the delta/beta ratio as the primary outcome. Secondary aims included evaluating changes in sleep stability and exploring phenotypic differences in treatment response. Ninety-eight ID patients across five centers completed a 6-8-week CBT-I program. Pre-and post-treatment assessments included polysomnography (PSG), sleep diaries, and Insomnia Severity Index (ISI). Cortical hyperarousal was indexed by the NREM delta/beta ratio; sleep stability (Sstab) was derived from a transition probability matrix. Patients were categorized as insomnia with short (ISSD) or normal sleep duration (INSD) based on PSG-derived total sleep time (median TST = 347.3 min). CBT-I significantly improved ISI and sleep parameters (sleep onset latency, wake after sleep onset, time in bed, sleep efficiency) in both self-reported and PSG, with smaller effects in the latter. qEEG analyses revealed a significant increase in the delta/beta ratio post-CBT-I (baseline:13.4 ± 4.9, end-of-treatment:14.6 ± 5.9; p = 0.002), indicating reduced cortical hyperarousal, with no center effects. Sstab improved significantly (p = 0.005), though it was not correlated with delta/beta changes. ISSD showed greater delta/beta improvements than INSD (p = 0.014), suggesting phenotypic differences. CBT-I reduces cortical hyperarousal in ID, as reflected by increased delta/beta ratio. The dissociation from sleep stability suggests distinct mechanisms. These findings support qEEG biomarkers as valuable tools for understanding the neurophysiological mechanisms of insomnia treatment and guiding precision medicine approaches.

Neurofibromatosis type 1 (NF1) is a common autosomal dominant disorder resulting from pathogenic variants in the NF1 gene. Preclinical studies suggest the NF1 gene regulates sleep and circadian processes, yet objective human data is limited. Characterizing sleep disturbances, sleep-related biomarkers, and their relationships to neurodevelopmental outcomes, may identify potential novel therapeutic targets in children with NF1. This study aimed to compare sleep-wake profiles, circadian rhythmicity and melatonin production in children with NF1 compared to typically developing controls, and to examine relationships between sleep outcomes, cognition, and behavior. In this cross-sectional study children aged 6-16 years with NF1 were recruited and compared to controls. Actigraphy data over one week were used to derive nine sleep-wake rhythm variables. Overnight urinary 6-sulfatoxymelatonin (aMT6s) served as marker of melatonin secretion. Neuropsychological and subjective assessment of sleep were also examined. Compared to controls, children with NF1 had lower aMT6s secretion, which was significantly associated with significantly longer sleep latency. Children with NF1 also had greater sleep irregularity and reduced total sleep time. Cluster analysis revealed four distinct sleep profiles in NF1: (1) delayed sleep onset, (2) night-wakers, (3) generalized sleep difficulties, and (4) normal sleep patterns. Greater sleep disturbance was associated with lower adaptive functioning, elevated behavioral difficulties and poorer cognition in NF1. The current findings highlight the importance of sleep assessment in this group and suggest that altered sleep and circadian regulation are related to the broader neurodevelopmental phenotype in NF1.

This network meta-analysis of randomized controlled trials (RCTs) aimed to investigate which hypnotics are associated with the most favorable sleep architecture and respiratory outcomes in adults with obstructive sleep apnea. Primary outcomes included total sleep time (TST) and apnea-hypopnea index (AHI) during TST. Other outcomes were rapid eye movement (REM) sleep time, latency to persistent sleep (LPS), wake after sleep onset (WASO), sleep efficiency (SE), AHI during non-REM or REM sleep, mean peripheral oxygen saturation (SpO2) during TST, mean SpO2 nadir during TST, arousal index (AI), all-cause discontinuation, adverse event-related discontinuation, and incidence of individual adverse events. Effect sizes with 95% confidence intervals were calculated. This systematic review included 32 RCTs (n = 1871, average age = 51.60 years, 62.52% male, mean AHI = 23.60). Our network meta-analysis evaluated brotizolam, daridorexant, eszopiclone, flurazepam, lemborexant, nitrazepam, ramelteon, temazepam, triazolam, zaleplon, zolpidem, zopiclone, and placebo. Compared with placebo, lemborexant increased TST, REM sleep time, and SE and decreased LPS and WASO, whereas both daridorexant and zolpidem increased TST and SE and decreased WASO. These three medications demonstrated respiratory safety and discontinuation profiles similar to those of placebo. Eszopiclone increased TST and SE and decreased LPS, WASO, AHI during TST, and AI, but its effects on LPS, WASO, AHI during TST, and AI disappeared in the sensitivity analysis, excluding continuous positive airway pressure titration studies. Our network meta-analysis identified different effects of various hypnotics on sleep architecture and respiratory parameters; however, the lack of data prevented a formal synthesis of subjective outcomes. Therefore, these results should be interpreted with caution in clinical practice.

Executive functioning (EF) deficits are frequently observed in preterms. EF development is linked to the prefrontal cortex and sleep-regulating homeostatic processes. As sleep is an essential driver of early brain maturation, curtailment of sleep in the NICU may be unfavorable. This study examined whether neonatal sleep behavior influences EF at 2 years corrected age in preterm children. 76 preterm infants ( < 34 weeks gestation and/or 1500 g) underwent overnight polysomnography before discharge. Sleep stages-Total Sleep Time, Active Sleep (AS), Quiet Sleep (QS) and Transitional Sleep-were quantified using an automated sleep algorithm. EF was assessed at 2 years corrected age, focusing on spatial working memory, cognitive flexibility, and inhibitory control. General linear models were used, adjusting for confounders. More Total Sleep Time was significantly associated with higher overall EF scores, and the subtest for spatial working memory. AS and QS durations were influenced by postmenstrual age. Longer AS bouts were linked to increased Total Sleep Time. However, individual AS or QS percentages were not directly associated with EF. Higher levels of Transitional Sleep were related to lower EF performance. Neonatal sleep duration is positively associated with better EF outcomes at 2 years. Protecting sleep in the NICU may support early brain development and executive functioning. This study links objective neonatal sleep measurements-using polysomnography and automated sleep staging-with later executive functioning development in preterm children. Neonatal sleep duration, particularly Total Sleep Time, is positively associated with executive functioning at 2 years in children born preterm. This study highlights neonatal sleep as a potential early marker of altered brain development. The findings support the importance of protecting and improving sleep in the NICU as a possible modifiable factor that could enhance early brain maturation and neurodevelopment.

Background/Objectives: Sleep is an important factor for recovery and performance in endurance sports, yet its role in ultra-endurance events remains unclear due to extreme physical and cognitive demands and disrupted sleep patterns. This systematic review aimed to analyze the role of sleep in physical and cognitive performance in ultra-endurance athletes. Methods: This systematic review followed PRISMA guidelines. A comprehensive search was conducted in May 2025 across PubMed/Medline, Embase, SPORTDiscus, and Web of Science. Two researchers independently screened, selected, extracted, and assessed data quality using the JBI tools (PROSPERO ID: CRD420251042220). Results: Of 424 articles, 16 met inclusion criteria, totaling data from 1389 athletes. Regarding physical performance, better outcomes were associated with no or less sleep during competition (TST), extended sleep the night before, and increased time in light sleep. In contrast, longer wake time, lower sleep quality, greater sleepiness during competition, and higher sleep efficiency were linked to poorer performance. Cognitive performance was positively associated with pre-race sleep quality and mid-race naps. Conversely, greater accumulated sleep before testing was linked to worse cognitive outcomes. Conclusions: Sleep, particularly total sleep time (TST), plays an important role in ultra-endurance performance, although this relationship may be non-linear and influenced by race context and individual strategies. Pre-race and intra-race sleep strategies such as napping and extended sleep may benefit performance. Further rigorous and longitudinal studies are needed to clarify sleep's impact on performance and recovery in ultra-endurance contexts.

Gut microbiota, sleep quality, and cognitive function in adults: A systematic review.