Clocks & Sleep, Volume 8, Issue 1 (March 2026) – 14 articles

The role of body position during sleep, particularly the supine position, is now recognized as an important factor in the development of sleep-disordered breathing such as snoring, apnea, and hypopnea. This pilot study aimed to evaluate the efficacy of a new wearable vibrotactile device (SoftSleep) in reducing sleep time in the supine position without negatively affecting total sleep duration or perceived sleep quality. This pilot study included 20 healthy volunteers. Sleep was monitored over two consecutive nights: the first night without positional therapy (PT) and the second night using a PT device. The primary outcome measures were total sleep time, sleep duration in the supine position, number of position changes, and subjective sleep quality (using the modified Pittsburgh Sleep Quality Index). Use of SoftSleep showed a significant reduction in the mean proportion of sleep in the supine position from 56.01% to 7.84% (p < 0.001). Total sleep time did not change significantly (7:39 ± 1:33 vs. 7:42 ± 1:19; p > 0.05). A moderate increase in the number of position changes was not accompanied by a deterioration in subjective sleep quality: 90% of participants rated their sleep with the device as very good or fairly good. Only three participants reported brief awakenings, which did not affect their overall perception of nighttime rest. These results indicate that the SoftSleep device effectively promotes sleep in a non-supine position without altering sleep quality or subjective perception of sleep. The high tolerability of the device confirms its potential for further clinical evaluation in patients with positional sleep apnea. Full article

Sleep is a fundamental biological process essential for physical, cognitive, and mental health, yet sleep disorders remain underrecognized in primary care. Given the central role of primary care physicians (PCPs) in early identification and management, this study aimed to assess sleep and sleep disorder knowledge among PCPs working within the Primary Health Care Corporation in Qatar. A cross-sectional study was conducted using the validated 30-item Assessment of Sleep Knowledge in Medical Education (ASKME) questionnaire, alongside demographic and clinical practice variables. The primary outcomes were the overall ASKME percentage score and participants achieving adequate sleep knowledge (≥60%). A total of 110 PCPs were included in the analysis. The mean overall ASKME score was 56.5%, and 44.5% of participants achieved adequate sleep knowledge. Knowledge was highest in circadian sleep–wake regulation and basic sleep principles, and lowest in common sleep disorders, sleep architecture, and the effects of drugs and alcohol on sleep. In multivariable logistic regression, years of clinical experience was the only factor independently associated with adequate sleep knowledge. These findings indicate persistent gaps in clinically relevant sleep knowledge among PCPs and underscore the need for targeted sleep education within primary care to support early and effective management of sleep disorders. However, the achieved sample size was substantially smaller than the initially calculated target of 260, limiting statistical power; therefore, the non-significant findings may reflect a Type II error, and the regression analyses should be interpreted with caution. Full article

Background/Objectives: There are limited data on the dynamic changes in daily composition of movement behaviors (sleep; moderate-to-vigorous physical activity, MVPA; light physical activity, LPA; and sedentary time, SED) and their associations with body weight in postpartum women. The purpose of this study was to examine associations of reallocating time in one behavior to another with body weight, at different times in the first year postpartum. Methods: The study included 86 women who delivered a singleton infant at ≥37 weeks gestation. Physical activity and sleep were measured via actigraphy in early, mid-, and late postpartum. Body weight was measured at each timepoint. Isotemporal substitution models were used to examine the association of reallocating ten minutes of one behavior (MVPA, LPA, SED, or sleep) to another, with body weight. Results: Participants spent most of their day in SED (~52–53%), followed by sleep (~30%), LPA (~12–13%), and then MVPA (~2%) throughout the first year postpartum. In early and mid-postpartum, but not late postpartum, reallocating 10 min of MVPA to LPA, SED, or sleep was associated with lower body weight (range: 3.07–4.03 kg lower). In early and late postpartum, reallocating 10 min of SED to LPA was associated with a lower body weight (4.03 kg and 1.04 kg, respectively). In participants who slept ≥7 h per day, reallocating sleep to LPA in early postpartum, and MVPA time to LPA in mid-postpartum was associated with lower body weight. In those who slept <7 h, no significant associations with body weight were found when reallocating time from one behavior to another. Conclusions: Encouraging LPA throughout the postpartum period may be beneficial for weight loss, and having enough sleep may be especially important for early to mid-postpartum. Future research examining the impact of changes in LPA on body weight in the postpartum period are needed, along with postpartum specific 24 h movement guidelines. Full article

Sleep disorders and primary headache syndromes frequently coexist, and accumulating evidence suggests that this relationship is bidirectional and biologically mediated rather than coincidental. Patients with migraine, tension-type headache, and cluster headache commonly report poor sleep quality, insomnia symptoms, and irregular sleep patterns, while individuals with sleep disorders such as insomnia, obstructive sleep apnea, restless legs syndrome, and narcolepsy experience a higher prevalence, severity, and chronification of headache disorders. This narrative review synthesizes current clinical, epidemiologic, and translational evidence supporting shared neurobiological mechanisms linking sleep and headache disorders. We focus on five major overlapping pathways: dopaminergic dysfunction, iron deficiency, hypothalamic and circadian dysregulation, central sensitization, and neuroinflammation. Evidence from population-based studies, clinical cohorts, neuroimaging, genetic research, and experimental models demonstrates that these mechanisms converge within hypothalamic, brainstem, and trigeminovascular circuits that regulate arousal, pain processing, and homeostasis. Conditions such as insomnia, obstructive sleep apnea, restless legs syndrome, and circadian disruption not only exacerbate headache burden but may act as modifiable risk factors that promote headache onset and progression. Recognizing sleep disorders as integral components of headache pathophysiology has important clinical implications, emphasizing the need for systematic sleep assessment and targeted sleep interventions as part of comprehensive headache management strategies. Full article

The circadian clock enables organisms to anticipate daily recurring events and synchronize their internal rhythms with environmental cues, such as light, aligning with the day/night cycle. Central to the molecular mechanisms of the circadian clock and light sensing are the Period (Per) 1 and 2 genes. While the roles of Per2 in astrocytes and neurons have been characterized, the specific contributions of Per1 remain less understood. Previous research has shown that Per2 in neurons, but not astrocytes, influences phase shifts, whereas the regulation of the circadian period involves Per2 in both cell types. In this study, we investigated the role of Per1 in neurons and astrocytes in modulating the circadian period and phase shifts. Using an Aschoff Type I protocol (constant darkness) combined with 15 min light pulses at circadian times (CT) 10, 14, and 22, we found that the absence of Per1 in neurons—but not in astrocytes—significantly affected both the circadian period and phase advance shifts in response to light at CT22. Full article

Sleep banking, i.e., preemptively obtaining extra sleep prior to anticipated sleep loss, has been proposed as a strategy to reduce the cognitive and physiological consequences of sleep deprivation. However, our understanding remains incomplete regarding the effectiveness of preemptive sleep extension in enhancing resilience to sleep loss. A comprehensive literature search was conducted using PubMed, MEDLINE, and Embase for studies published between 2004 and 2025. Following a comprehensive literature search, we identified 12 studies meeting the inclusion criteria—seven primary experimental trials comprising approximately 140 participants, predominantly healthy young adults aged 18–39 years. We evaluated the effects of sleep banking on cognitive performance, mood, physiological parameters, and real-world outcomes. Included studies encompassed experimental laboratory trials, observational research, and field studies in occupational and athletic settings. Although the number of studies on sleep banking remains limited, experimental evidence demonstrates that preemptive sleep extension improves objective alertness and vigilance during subsequent sleep restriction or total sleep deprivation. Individuals who obtained additional sleep exhibited fewer attentional lapses, faster reaction times, and improved mood, although subjective sleepiness often remained high. Preliminary field evidence suggests that preemptive sleep extension enhances workplace safety, reduces errors, and improves sustained attention in shift workers. In athletic contexts, sleep banking has been associated with improved physical endurance and reaction speed. Importantly, this review primarily addresses the homeostatic dimension of sleep regulation (Process S); circadian factors (Process C), including chronotype, social jetlag, and circadian timing of sleep extension and testing, were not systematically addressed in the included studies and represent important limitations of the current evidence base. Overall, sleep banking appears to be a viable strategy for enhancing resilience to acute sleep loss. It confers measurable benefits in performance, cognitive function, and physiological markers, supporting its application in high-demand occupations and competitive environments. Although it does not fully eliminate subjective fatigue, sleep banking may serve as a valuable complement to other fatigue mitigation strategies for anticipated short-term sleep loss. Full article

Sleep and circadian research in real-life environments is challenging but essential. This study presents the design and implementation of a data-collection protocol in a highly challenging real-life setting over 56 days, examining both researchers’ and participants’ perspectives on its strengths, limitations, and key challenges, and highlighting the lessons learned relevant to future studies in similar contexts. Thirty military submariners completed a questionnaire after the 56-day pre-mission, mission, and post-mission data collection to assess their views on the study and each task. Compliance with measurements (questionnaires, diaries, actigraphy, and blood collections) was quantified and correlated with participants’ answers. Mean global satisfaction was 3.57 ± 0.77 (0–5 scale) and declined across study phases, with a significant change only in the post-mission phase (p < 0.001). Higher work satisfaction correlated with better global study satisfaction (ρ = 0.396; p = 0.030). Diaries were rated the most burdensome task, while blood collections generated the most polarized responses. Compliance with continuous measurements was high, but these also decreased in the third phase of the study, significantly for actigraphy (p < 0.001), although without clear predictors, including satisfaction. In this extreme setting, satisfaction and compliance declined significantly in the final phase of the study, without clear predictive factors. Having different engagement strategies for different work shifts is also an important consideration for future studies. Full article

Light exposure profoundly influences human emotions and physiology. Yet, adolescents spend considerable time under artificial indoor lighting. Reduced daytime light exposure delays the circadian clock, negatively affecting sleep, cognition, and mood. This pilot study examined whether 470–490 nm enhanced LED lighting modulates mood, sleep quality, and attention among 65 male Korean high school students (mean age = 15.4 years) who participated in a two-week intervention. Both groups were exposed to natural daylight, but the experimental group additionally used LED lighting enriched in the 470–490 nm wavelength range, whereas the control group used LED lighting without modified spectral characteristics. Students were exposed to the assigned lighting from 08:00 to 17:00 during regular school hours for two consecutive weeks. To evaluate the effects of the two-week intervention, pre- and post-assessments included the Beck Depression Inventory (BDI-II), the Richards–Campbell Sleep Questionnaire (RCSQ), the Epworth Sleepiness Scale (ESS), the Perceived Stress Scale (PSS), and the Frankfurter Attention Inventory (FAIR), administered twice at each assessment point. The linear mixed-effect model showed a significant time × group interaction for line errors in the first FAIR trial (F (1, 52) = 5.21, p = 0.027, η² partial = 0.09), suggesting a greater relative reduction in attentional errors in the experimental group compared with the control group. No significant effects were observed for sleep- or mood-related outcomes. These results indicate the potential relevance of wavelength-optimized lighting in educational settings where sustained attention is critical. Future studies with larger samples and longer interventions are required to confirm and extend these findings. Full article

Insomnia symptoms are very common among psychiatric inpatients and can increase the risk of suicide in this population. However, little is known about how psychiatrists and nurses manage insomnia symptoms in psychiatric inpatients. This study aimed to investigate the views, opinions, and experiences of psychiatrists and nurses regarding inpatients’ sleep complaints in a Swiss psychiatric hospital. This qualitative study used individual semi-structured interviews with a purposive sample of psychiatrists and nurses working in a Swiss psychiatric hospital. Interviews were audio-recorded, transcribed verbatim, and analysed manually using inductive thematic analysis. Ten participants (six psychiatrists and four nurses) were interviewed. Three overarching themes were identified: identifying and classifying sleep complaints, the decision-making process, and the actions taken to respond to the complaint. Insomnia symptoms were approached by psychiatrists and nurses in a highly heterogeneous, non-evidence-based manner, with a lack of adaptation of CBT-I leading to overmedication. This heterogeneity may be explained by the diversity of underlying problems associated with insomnia symptoms, the lack of hospital-specific guidelines, and the fact that current guidelines focus mainly on chronic insomnia and do not fully account for the complexity of psychiatric inpatients. Full article

We investigated the effects of Continuous Positive Airway Pressure (CPAP) on blood pressure (BP) and vigilance in taxi drivers with obstructive sleep apnea (OSA). This pilot study recruited taxi drivers aged ≥60 years to undergo polysomnography. Those diagnosed with OSA underwent 6 months of CPAP therapy. Baseline and follow-up assessments included 24 h ambulatory blood pressure monitoring (ABPM) and the psychomotor vigilance test (PVT). Among the 32 participants, 22 (68.8%) were diagnosed with OSA (median age 63.0 [62.0–65.0] years; 21 males). The average CPAP adherence was 3.1 ± 2.3 h per night, with 23.5% using CPAP for more than 4 h per night. There were no significant changes in 24 h mean systolic ABPM (125.9 [116.8–134.9] mmHg to 126.0 [118.3–133.7] mmHg; p = 0.93) or reaction times measured by PVT (2.0 [0.0–3.0] lapses to 2.0 [1.0–3.0] lapses; p = 0.82) after CPAP therapy. A high prevalence of OSA was observed among taxi drivers. CPAP adherence was suboptimal and did not result in significant improvements in BP or vigilance. Full article

Background. Exposure to artificial light at night can lead to circadian disruption and health risks. It can cause mood swings, confusion, and depression. The aim of this cross-sectional study was to assess the relationship between the illuminance of urban lighting and the health of residents. Methods: This study was carried out among residents of two similar towns, one with typical street lighting and a Dark Sky Park characterized by reduced lighting. A total of 272 respondents participated in this study. A self-administered questionnaire and the WHOQOL-BREF were used among the respondents. Results. People living in the Dark Sky Park were more likely to be satisfied with their sleep (p < 0.001). In fact, 58.7% of Dark Sky Park residents reported no sleep problems. In the control town, only 49.25% did (p = 0.04). The sleep duration was similar in the two towns, but Dark Sky Park residents were statistically less likely to use sleeping pills and window blinds. People exposed to typical street lighting at night reported suffering from eye diseases, cardiovascular diseases, and mood changes more often than those living in the Dark Sky Park. The environmental and physical quality of life, as measured by the WHOQOL-BREF, were significantly higher in the Dark Sky Park residents than in the control town (p < 0.05). Conclusions. People living in places with limited illuminance declare better health and a higher quality of life in the physical and environmental domains. Full article

Late-night feeding, defined in the present review as feeding after 8:00 pm when evening insulin secretion and sensitivity are low, is increasingly prevalent in Western society and is recognized as a disruptor of metabolic homeostasis. Yet health problems related to late-night feeding are largely ignored in time-restricted feeding studies that generally do not extend past an 8:00 pm feeding window. This paper proposes a novel cascade linking late-night hyperglycemia with sleep disturbances and nasal congestion mediated by renal sodium retention, increased plasma osmolarity, and stress hormone release by hypothalamic–pituitary–adrenal axis activation. The narrative describes the circadian decline in insulin sensitivity, which amplifies postprandial glucose surges following late-night feeding. Elevated glucose levels drive renal glucose reabsorption via sodium–glucose cotransporters, promoting sodium retention independent of insulin. Increased sodium retention raises extracellular osmolarity, activating hypothalamic osmoreceptors and stimulating the hypothalamic–pituitary–adrenal axis. Cortisol release promotes alertness, while fluid retention and mucosal edema contribute to nasal congestion and early waking. Supine fluid redistribution during sleep further exacerbates airway narrowing, increasing the risk of sleep fragmentation and obstructive sleep apnea. The present paper fills a gap in current time-restricted feeding literature by integrating renal, osmotic, and neuroendocrine pathways that may be overlooked as underlying mechanisms of dysregulated glucose control and hormone dysfunction. Reviewed evidence suggests that symptoms such as nocturnal congestion and sleep disruption are not merely incidental to late-night feeding but frame late night feeding as a risk factor with underlying physiological stressors that could contribute to cardiometabolic risk. Full article