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Clocks & Sleep

Clocks & Sleep is a peer-reviewed, open access journal that investigates a wide range of sleep related topics and is published quarterly online by MDPI.
The Australasian Chronobiology Society, Society for Light, Rhythms, and Circadian Health, and Swiss Society of Sleep Research, Sleep Medicine and Chronobiology are affiliated with Clocks & Sleep and their society members receive a discount on the article processing charges.

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All Articles (368)

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.

16 March 2026

Total sleep time on the first night (blue bars) and the second night (red bars). h = hours; min = minutes.

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.

12 March 2026

Flowchart of study participant recruitment.

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.

7 March 2026

Impact of reallocating 10 min of one behavior to another on body weight (kg) at early, mid-, and late postpartum. The regression coefficients are from Isotemporal Substitution Models at each time point and represent the estimated change in body weight (kg) for a 10 min substitution of one behavior for another behavior.

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.

27 February 2026

Bidirectional interaction between sleep and headache disorders, with the shared mechanistic overlap.

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Clocks & Sleep - ISSN 2624-5175