Study ObjectivesTo investigate if glucose homeostasis was impaired during recurrent periods of sleep restriction and recovery, and if the impairment was moderated by sleep duration variability across nights.MethodsIn this 16-day laboratory-based study, 48 healthy young adults underwent two baseline nights of 8-h time-in-bed (TIB), followed by two cycles of “weekday” sleep opportunity manipulation (control group’s TIB: 8-h/night; stable short sleep group: 6-h/night; variable short sleep group: 8-, 4-, 8-, 4-, and 6-h from the first to fifth night) and “weekend” recovery (all groups: 8-h/night). Plasma glucose and insulin concentrations during fasting and oral glucose tolerance tests (OGTTs) were measured at the end of baseline and each manipulation period.ResultsNo significant group×day interaction on glucose or insulin outcomes was found (p > .15). At 2-h post-glucose load, the control group’s glucose levels remained relatively stable in all OGTTs (p > .08), although their insulin levels increased from baseline (p < .02) probably due to sedentariness in the laboratory. The stable short sleep group also showed increased insulin levels in the first week (p = .02), but their glucose levels still increased from baseline (p = .02; Cohen’s dz = 0.39). Importantly, in both weeks of sleep restriction, the variable short sleep group failed to significantly elevate their insulin levels (p > .30); hence, their glucose levels increased from baseline (p < .01, dz ≥ 0.99) more prominently than the stable short sleep group.ConclusionsGlucose homeostasis was impaired in healthy young adults after recurrent periods of sleep restriction. Variable and stable short sleep schedules may impair glucose tolerance to different extents and in different pathways.Clinical TrialPerformance, Mood, and Brain and Metabolic Functions During Different Sleep Schedules (STAVAR), https://www.clinicaltrials.gov/study/NCT04731662, NCT04731662.Statement of SignificanceSimulating two consecutive work weeks, our study showed that weekday sleep restriction led to decreased glucose tolerance despite intervening weekend recovery sleep. The extents and presentations of glucose tolerance depended on the variability in night-to-night sleep duration: the stable short sleep group experienced early signs of insulin resistance with compensatory insulin hypersecretion and small elevation in glucose concentrations, while the variable short sleep group experienced possible beta cell functional impairment, resulting in an absence of significant compensatory insulin hypersecretion and prominent increases in glucose levels. Critically, having a time-in-bed within the age-specific recommended range every night appeared to be the only way to optimize glucose tolerance, thereby minimizing the risk for type 2 diabetes mellitus.

Insomnia is highly prevalent among postmenopausal women and is associated with adverse health outcomes, highlighting the need to identify modifiable determinants of sleep. Diet and sleep are interrelated; however, few studies have evaluated longitudinal associations of complete dietary patterns with incident insomnia in postmenopausal women. This study evaluates prospective associations of established diet quality metrics with insomnia in the Women's Health Initiative Observational Study (WHI-OS). The WHI-OS enrolled 93 676 postmenopausal women from across the United States. Alternate Mediterranean (aMed) diet and Dietary Approaches to Stop Hypertension (DASH) diet quality scores were quantified from a Food Frequency Questionnaire at baseline and dichotomized scores using a data-driven approach. Insomnia was assessed at baseline and Year 3 using the WHI Insomnia Rating Scale. Multivariable logistic regression models adjusted for sociodemographic, lifestyle, and health factors evaluated associations of baseline diet quality with incident insomnia and longitudinal insomnia status (stable/new onset insomnia vs. stable absence/remission of insomnia). Among women without insomnia at baseline (n = 50 644), good vs. poor diet quality at baseline was associated with lower risk for incident insomnia at 3-year follow-up (OR [95% CI], aMed: 0.925 [0.879-0.974], p=.003; DASH: 0.937 [0.891-0.985], p=.01]). In longitudinal analyses (n = 74 513), greater baseline adherence to aMed and DASH diets related to 6.3% (0.903-0.971) and 8.5% (0.883-0.948) lower odds, respectively, of having stable or new onset insomnia over 3 years (both p<.005). Better diet quality predicts lower insomnia risk in postmenopausal women. Clinical trials are needed to determine whether strategies to enhance diet quality improve insomnia symptoms. The Women's Health Initiative Observational Study is registered on Clinicaltrials.gov #NCT00000611: https://clinicaltrials.gov/study/NCT00000611.

Sleep is essential for memory consolidation, yet its role in implicit visuomotor memory remains poorly understood. Rapid eye movement (REM) sleep, particularly its Phasic and Tonic sub-states, may contribute to this process. This study revisits data from Viczko etal. (2018) to examine Phasic and Tonic REM characteristics and electroencephalography activity in implicit visuomotor memory consolidation using the Serial Reaction Time Task. Participants trained on an implicit visuomotor sequence and were tested post-training, after a sleep/wake interval, and 1 week later. Polysomnography was used to analyze sleep architecture, focusing on REM sub-states. Electroencephalography data during REM were assessed for theta power (~4-8Hz) using event-related spectral perturbation. Eye movements were categorized into Phasic or Tonic REM, with task-specific regional activity examined over frontal (Fz) and motor areas (C4). Increases in total REM sleep and Tonic REM sleep duration were observed during the experimental compared to the control night. Changes in Tonic REM sleep correlated with motor representation speed post-sleep. Event-related spectral perturbation analysis revealed enhanced theta power time-locked to Phasic and Tonic REM eye movements, with regionally specific task-related increases over Fz and C4 (but not contralaterally). Findings suggest Tonic REM stabilizes visuomotor memory, with theta oscillations serving as electrophysiological markers of consolidation. Task-specific theta increases highlight regional specificity of memory processing during sleep. This study underscores the roles of REM sub-states in implicit visuomotor memory consolidation and the need to further explore sleep sub-states.

Isolated rapid eye movement (REM) sleep behavior disorder (iRBD) is an early manifestation of alpha-synuclein-related neurodegenerative diseases (NDD). There is an average delay in iRBD diagnosis of 9 years from the onset of symptoms, showing that we need easier methods of detection to improve access to specialist care and potential disease-modifying clinical trials. We designed a 3-step approach to detect iRBD in a community of older adults (≥50 years) in Tasmania, Australia, using home-based video-polysomnography (vPSG). The Tasmania-London (TASLON) protocol for iRBD detection comprised 3 key steps: participants completed an online iRBD screening question; those who screened positive were invited to undertake the TASLON iRBD Screening Interview by telephone; a sample then completed a home-based vPSG based on iRBD screening risk level. A total of 2891 participants (mean [SD] age 64 [7.7] years; 74% female) without any known NDD were recruited from throughout Tasmania. 267 (9%; age 63 [7.7] years; 55% female) were identified as having "probable" RBD through positive online screening; 87 (33%) agreed to complete the clinical screening interview; 47 (55%) underwent home-based vPSG; and 21 (45%; age 68 [7] years; 52% female) were found to have iRBD. The TASLON protocol is a feasible method of improving timely access to iRBD diagnoses in the community. It streamlines the path to vPSG by identifying those at highest risk of iRBD, thus improving access to diagnostic testing and clinical trial opportunities for those who otherwise may not have been identified. Statement of Significance The TASLON protocol offers a novel, community-based approach to early detection of isolated REM sleep behavior disorder (iRBD), a precursor to alpha-synuclein-related neurodegenerative diseases (NDD). By streamlining the path to home-based video-polysomnography (vPSG), bypassing the need for hospital/laboratory-based vPSG, this method addresses a critical delay in iRBD diagnosis, especially for populations with limited access to specialist sleep centers. This study highlights the feasibility and preliminary results of the TASLON protocol in detecting new cases of iRBD in the community. This holds potential to reduce inequity of access to early interventions and may improve patient outcomes in NDD through enhanced access to specialist care and clinical trials. Future work should focus on extending this approach and exploring its applicability in broader populations to aid access to earlier diagnosis.

Study ObjectivesThe boundaries between narcolepsy type 1 (NT1), narcolepsy type 2 (NT2), and idiopathic hypersomnia (IH) and the evolution of these diseases over time are poorly understood. This retrospective cohort single-center study with a cross-sectional follow-up aims to assess changes of diagnosis and test findings over time.MethodsRetrospective and cross-sectional data collection: We assessed demographic characteristics, symptoms, sleep–wake tests, and diagnosis changes in patients with NT1, NT2, or IH seen at the Bern Sleep–Wake Epilepsy center between 2000 and 2021. In addition, we obtained information about changes in symptoms and diagnosis by contacting patients seen between 2005 and 2017 by telephone. The two data sources were combined to analyze the frequency of diagnosis changes.ResultsA total of 214 patients (NT1 n = 122, NT2 n = 37, IH n = 55) were included. In 17% (30/179) of patients with follow-up, the diagnosis changed during the observational period. The most unstable diagnosis was NT2 (17/30, 57%), most commonly transitioning to NT1 (n = 5) and IH (n = 9). Five patients with IH went into remission. NT1 was mostly stable (104/107). We confirmed a poor retest reliability of the MSLT in patients with NT2 and IH.ConclusionsFrequent diagnosis changes in patients with NT2 and IH challenge the current diagnostic criteria, in addition, IH can remit.

This study investigated the associations between changes in sleep dimensions, cognitive transition, and incident dementia. Using data from the UK Biobank (UKB) and the China Health and Retirement Longitudinal Study (CHARLS), we systematically investigated longitudinal changes in eight distinct sleep dimensions, including sleep duration, chronotype, and napping, etc. Cognitive transitions were assessed through changes in standardized cognitive test scores in the UKB and categorized cognitive states (normal cognition, mild cognitive impairment [MCI], and probable dementia) in CHARLS. We used generalized linear models for cognitive scores, logistic regression for cognitive status transitions, and Cox models for dementia risk associated with changes in sleep dimensions. A total of 8994 and 14 720 participants were involved in the change-to-change analyses and change-to-dementia analyses, respectively. Compared to individuals who maintained their original sleep dimensions, those who changed their sleep duration to the optimal range (7-8h/day) or shifted chronotype to morningness exhibited higher overall cognitive scores (β = 0.15, p= .037; β = 0.23, p= .011). Conversely, transitioning to non-optimal sleep duration (OR = 1.07, p= .034) or declining overall sleep quality (OR = 1.06, p= .006) increased the risk of cognitive decline from normal baseline. Napping cessation increased the risk of MCI progression to dementia (OR = 1.16, p= .001). Transitioning to non-optimal sleep duration (HR = 1.82, p= .005) and discontinuing napping (HR = 2.13, p= .015) were associated with a higher incident of all-cause dementia. Maintaining optimal or optimizing sleep duration, preserving napping habits, and transitioning to a morning chronotype are essential for dementia prevention.