דו״ח מאומת

The effects of local body cooling on thermal comfort and sleep quality in a hot environment were investigated in an experiment with 16 male subjects. Sleep quality was evaluated subjectively, using questionnaires completed in the morning, and objectively, by analysis of electroencephalogram (EEG) signals that were continuously monitored during the sleeping period. Compared with no cooling, the largest improvement in thermal comfort and sleep quality was observed when the back and head (neck) were both cooled at a room temperature of 32°C. Back cooling alone also improved thermal comfort and sleep quality, although the effects were less than when cooling both back and head (neck). Mean sleep efficiency was improved from 84.6% in the no cooling condition to 95.3% and 92.8%, respectively, in these conditions, indicating good sleep quality. Head (neck) cooling alone slightly improved thermal comfort and subjective sleep quality and increased Stage N3 sleep, but did not otherwise improve sleep quality. The results show that local cooling applied to large body sections (back and head) could effectively maintain good sleep and improve thermal comfort in a hot environment.…

PMID: 28960513

Ambient temperature and the bedding thermal resistance are two key factors affecting sleepers' thermal comfort. Six duvets with thermal resistance of 3.81, 5.12, 6.19, 7.81, 8.75 and 8.93 clo were included to investigate the effects of duvet thermal resistance on the sleep thermal comfort zone. Six males and six females were enrolled in a whole night sleep experiment, and the ambient temperature of the sleep room was adjusted to be thermally comfortable. Skin temperature, bed climate temperature and sleep stages were all acquired. Subjective evaluations including thermal perception and sleep quality were also assessed through questionnaires. The results indicated that increasing the thermal resistance of duvets widened the thermal comfort zone of ambient temperature, with the highest thermal resistance ranging from 8.2 to 17.7 °C and the lowest from 16.4 to 22.2 °C. The upper and lower temperature limits of the comfort zone did not significantly differ in their effect on sleep quality. The recommended bed climate temperature for comfortable sleep would be in the small range of 30-33 °C, and a good quality of sleep can be guaranteed in the scenario.…

PMID: 37748286

Environmental high temperatures can strongly affect sleep. Our aim was to assess the protective effect of a High Heat Conductivity Mattress topper (HHCM) on sleep duration and quality during one night's exposure to heat. HHCM efficacy was studied in a randomised double-blind crossover design in fifteen healthy young active subjects by overnight polysomnography in a temperature-controlled sleep laboratory, during 4 nights: 2 nights at 22°C (HHCM and Control Mattress, CM) and 2 nights at 32°C (HHCM and CM). Core body temperature (CBT), skin, room and mattress toppers surface temperatures were continuously recorded. We observed interactions between temperature and mattress conditions. At 22°C, we did not show any beneficial effect of HHCM compared to CM on sleep duration, but a longer N3 sleep stage duration (p = 0.03) and higher slow oscillation spectral density (p = 0.03). Heat night exposure (32°C) induced a decrease in total sleep time (TST) (-24.8 ± 7.1 min, p = 0.02), rapid eye movement (REM) duration (p = 0.03), sleep efficiency (p = 0.04), delta power spectral density (p = 0.03) and an increase of wake after sleep onset (p = 0.03) and transition between stages rate (p = 0.02). At 32°C, in comparison to CM, HHCM induced higher TST (+21.4 ± 16.1 min, p = 0.04), sleep efficiency (p = 0.04), REM duration (p = 0.03), and lower awakening duration (p = 0.03). These effects were associated with lower skin temperature and CBT. In conclusion, HHCM improves sleep quality and has a protective effect on CBT and sleep patterns during heat exposure in active healthy subjects. It could be a countermeasure for promoting sleep in particular during heat waves.…

PMID: 40704570

Sleep is influenced by environmental factors, and hot ambient temperature undermines sleep quality. Considering the global warming, it becomes increasingly important to keep bedroom temperature cool in the summer. Today, two electrical cooling systems are available: convection and radiant. Convection air cooling system supplies cooled air-flow. Radiant cooling system cools the room through radiation from the cooled surfaces, moisture condensation on which is prevented by reheated refrigeration cycle system. The present study was a randomized, cross-over trial setting room air temperature at 26 ℃ to compare subjective and objective quality of sleep between convection and radiant cooling in 7 healthy women. Subjective and objective quality of sleep were assessed by Oguri-Shirakawa-Azumi Sleep Inventory and EEG-based sleep parameters, respectively. Compared with convection cooling, radiant cooling provided lower relative humidity and air flow. Refreshness, one of the 4 indices of subjective quality of sleep, was higher with radiant cooling. Among the EEG-based sleep parameters, sleep efficiency was higher and sleep latency was shorter with radiant cooling. In spite of similar ambient room temperature, difference in cooling (radiant vs. convection) and/or dehumidifying (ordinary air conditioning vs. reheated refrigeration cycle) method provided difference in thermal comfort affecting subjective and objective quality of sleep.…

PMID: 41062732

<h4>Introduction</h4>Caffeine is the most widely consumed psychoactive stimulant worldwide and acts primarily through antagonism of adenosine A1 and A2A receptors, thereby reducing sleep pressure and promoting wakefulness. Although its alerting and performance-enhancing effects are well established, its influence on sleep-related electroencephalography (EEG) has been investigated across diverse paradigms with substantial methodological heterogeneity. This systematic and mechanistic review aimed to synthesize human evidence on how caffeine affects sleep architecture, quantitative sleep EEG, and neurophysiological markers of sleep homeostasis, and to interpret these findings within current models of adenosine-mediated sleep-wake regulation.<h4>Materials and methods</h4>A systematic search of PubMed/MEDLINE, Web of Science, Scopus, Embase, PsycINFO, ResearchGate, and Google Scholar was conducted for studies published between January 1980 and January 2026, with the final search performed on 10 January 2026. Eligible studies were original human investigations examining caffeine exposure or administration and reporting sleep-related EEG outcomes, including polysomnographic sleep staging, spectral EEG analyses, or other EEG-derived sleep metrics. Two reviewers independently screened records and assessed eligibility, with disagreements resolved by consensus. Data on study design, participant characteristics, caffeine interventions, EEG methodology, and outcomes were extracted using a predefined form. Risk of bias was evaluated using the RoB 2 and ROBINS-I tools. Owing to marked heterogeneity across studies, findings were synthesized narratively within a mechanistic interpretive framework.<h4>Results</h4>Thirty-two studies were included. Across highly heterogeneous paradigms-including acute bedtime or evening dosing, daytime or repeated caffeine use before nocturnal sleep, administration during prolonged wakefulness followed by recovery sleep, withdrawal protocols, and ambulatory/home EEG monitoring-the most consistent finding was suppression of low-frequency NREM EEG activity, particularly slow-wave activity and the lowest delta frequencies. Caffeine frequently increased faster EEG activity, including sigma/spindle and beta ranges, producing a lighter, more aroused, and more wake-like sleep EEG profile. These effects were especially prominent during early-night NREM sleep and in recovery sleep after sleep deprivation, where caffeine attenuated the expected homeostatic rebound in low-frequency power. REM-related effects were less consistent, but some studies reported delayed REM timing and subtler alterations in REM EEG. Emerging evidence further suggests that caffeine increases EEG complexity and shifts sleep dynamics toward a more excitation-dominant state. Several studies indicated that quantitative EEG measures were more sensitive than conventional sleep-stage variables in detecting caffeine-related sleep disruption. Dose, timing, habitual caffeine use, withdrawal state, age, circadian context, and adenosinergic genetic variation, particularly involving ADORA2A, moderated the magnitude of effects. We also highlighted the connection between current results and sports and sports science.<h4>Conclusions</h4>Caffeine reliably alters the neurophysiological architecture of human sleep in a direction consistent with reduced sleep depth and weakened homeostatic recovery. The overall evidence supports a mechanistic model centered on adenosine receptor antagonism, attenuation of sleep-pressure build-up and expression, and a shift toward greater cortical arousal during sleep. Sleep EEG appears to be a sensitive marker of these effects, often revealing physiological disruption even when conventional sleep architecture changes are modest. Future research should prioritize larger and more diverse samples, pharmacokinetic and pharmacogenetic characterization, and ecologically valid high-resolution sleep monitoring to clarify the real-world and functional consequences of caffeine-induced EEG changes.…

PMID: 42075032

<h4>Objectives</h4>To examine coffee consumption patterns and their associations with sleep quality indicators among Saudi youth, and to identify independent predictors of poor sleep outcomes using multivariate regression.<h4>Methods</h4>A cross-sectional study was conducted among 1458 consenting Saudi youth (aged 16-30 years) using an online questionnaire adapted from the Pittsburgh Sleep Quality Index (PSQI). Chi-square tests examined associations between coffee consumption patterns (type, timing, pre-bedtime cessation) and sleep variables. Binary logistic regression identified independent predictors of late bedtime (sleeping after midnight), adjusting for demographic covariates.<h4>Results</h4>The sample was predominantly female (69.4%, n = 1012) and aged 18-22 years (65.7%, n = 958). Evening/night-time coffee consumption was a strong independent predictor of sleeping after midnight (OR = 3.04, 95% CI: 2.30-4.02, p < 0.001), adjusting for cessation strategy, sex, age, and student status. Chi-square analyses confirmed that coffee consumption timing showed highly significant associations with bedtime patterns (χ² = 57.806, p < 0.001), sleep duration (χ² = 42.759, p < 0.001), and daytime sleep behaviours (χ² = 27.247, p < 0.001). Pre-bedtime cessation timing was significantly associated with bedtime patterns (χ² = 73.075, p < 0.001) and nighttime awakenings (χ² = 28.912, p = 0.007).<h4>Conclusions</h4>Temporal aspects of coffee consumption demonstrate stronger and more consistent associations with sleep quality than coffee type selection. Evening coffee use is an independent risk factor for delayed sleep timing. Strategic timing interventions may be more effective than content-based restrictions for improving sleep health in Saudi youth.…

PMID: 42170230

BACKGROUND: This study aimed to determine the frequency and amount of consumption of caffeine-containing foods among adults in active employment and to examine the relationship between total daily caffeine intake and sleep quality. METHODS: This cross-sectional study included 428 working adults aged 19–50 years. Caffeine intake was assessed using a quantitative consumption frequency form created by the researchers, while sleep quality was assessed using the Pittsburgh Sleep Quality Index (PSQI). Statistical analyses involved appropriate parametric and nonparametric tests, as well as correlation and multiple linear regression models. RESULTS: The participants’ average daily caffeine intake was 262.5 [144.0-411.0] mg. The primary sources of caffeine were black coffee (filter/Americano), black tea, and Turkish coffee. Participants with poor sleep quality (71.7%) consumed significantly more caffeine daily than those with good sleep quality. A positive and significant correlation was observed between caffeine intake and PSQI scores. Regression analysis indicated that caffeine consumption, was a significant independent predictor of poor sleep quality (β = 0.147, p = 0.003), particularly affecting sleep duration and disturbances. CONCLUSION: These results suggest that caffeine intake is a significant lifestyle factor independently associated with sleep quality, and a comprehensive evaluation of consumption sources could benefit public health. Future research should also focus on the timing of caffeine consumption and incorporate objective sleep measures.…

PMID: 42026645

To assess the effects of magnesium bisglycinate supplementation on insomnia symptoms in healthy adults reporting poor sleep quality. This randomized, double-blind, placebo-controlled trial enrolled 155 adults aged 18-65 years with self-reported poor sleep quality. Participants were randomly assigned to either magnesium bisglycinate supplementation (250 mg elemental magnesium, daily) or placebo capsules. Sleep quality was assessed using the Insomnia Severity Index (ISI) and additional psychological questionnaires at baseline and multiple time points throughout the study. Generalized linear mixed models (GLMM) adjusted for baseline ISI scores, age, sex, body mass index, and occupation were applied. The magnesium bisglycinate group showed a significantly greater reduction in ISI scores compared to the placebo group from baseline to Week 4 (-3.9 [95% CI: -5.8 to -2.0] vs -2.3 [95% CI: -4.1 to -0.4], respectively; p = 0.049). The effect size was small (Cohen's d = 0.2), indicating a modest benefit. Exploratory analyses suggested notably greater improvements among participants reporting lower baseline dietary magnesium intake, potentially indicating a subgroup of high responders. No significant differences were observed in other psychological outcomes. Magnesium bisglycinate supplementation modestly improved insomnia severity in adults reporting poor sleep quality. Future research should include objective sleep assessments, longer intervention periods, and better characterization of potential high responders by systematically assessing baseline dietary magnesium intake and status. Effect of magnesium bisglycinate supplementation on sleep and fatigue parameters in healthy adults reporting poor sleep quality; https://drks.de/search/en/trial/DRKS00031494 DRKS-ID: DRKS00031494.…

PMID: 40918053

Magnesium (Mg²⁺) is the fourth most abundant cation in the human body and a critical cofactor in hundreds of enzymatic reactions that regulate energy metabolism, neuromuscular function, cardiovascular health, bone integrity, immune defense, and psychological well-being. Despite its essential roles, magnesium deficiency remains common worldwide, driven by inadequate dietary intake, chronic diseases, medication use, and lifestyle factors. Low magnesium status is associated with hypertension, type 2 diabetes, osteoporosis, migraines, depression, and chronic inflammation, whereas sufficient intake supports cardiometabolic resilience, skeletal strength, neurological stability, and healthy aging. This review synthesizes current evidence on magnesium metabolism, physiological functions, and the health consequences of deficiency, and it summarizes global status with attention to biomarker limitations, widespread suboptimal intake, and key demographic and lifestyle determinants. It also discusses dietary sources, supplementation, and innovative approaches such as food fortification, personalized nutrition, and improved diagnostic strategies. The evidence highlights magnesium as a modifiable factor with potential to lessen the burden of chronic diseases. Recognizing magnesium deficiency as a pressing but underappreciated public health issue, this article underscores the need for integrated strategies to optimize magnesium balance at both individual and population levels.…

PMID: 41305676

Although sleep is a key element in adolescent development, teens are spending increasing amounts of time online with health risks related to excessive use of electronic media (computers, smartphones, tablets, consoles…) negatively associated with daytime functioning and sleep outcomes. Adolescent sleep becomes irregular, shortened and delayed in relation with later sleep onset and early waking time due to early school starting times on weekdays which results in rhythm desynchronization and sleep loss. In addition, exposure of adolescents to the numerous electronic devices prior to bedtime has become a great concern because LEDs emit much more blue light than white incandescent bulbs and compact fluorescent bulbs and have therefore a greater impact on the biological clock. A large number of adolescents move to evening chronotype and experience a misalignment between biological and social rhythms which, added to sleep loss, results in e.g. fatigue, daytime sleepiness, behavioral problems and poor academic achievement. This paper on adolescent circadian disruption will review the sensitivity of adolescents to light including LEDs with the effects on the circadian system, the crosstalk between the clock and the pineal gland, the role of melatonin, and the behavior of some adolescents(media use, alcohol consumption, binge drinking, smoking habits, stimulant use…). Lastly, some practical recommendations and perspectives are put forward. The permanent social jet lag resulting in clock misalignment experienced by a number of adolescents should be considered as a matter of public health.…

PMID: 28487255

Exposure to blue light at bedtime, suppresses melatonin secretion, postponing the sleep onset and interrupting the sleep process. Some smartphone manufacturers have introduced night-mode functions, which have been claimed to aid in improving sleep quality. In this study, we evaluate the impact of blue light filter application on decreasing blue light emissions and improving sleep quality. Participants in this study recorded the pattern of using their mobile phones through a questionnaire. In order to evaluate sleep quality, we used a PSQI questionnaire. Blue light filters were used by 9.7% of respondents, 9.7% occasionally, and 80% never. The mean score of PSQI was more than 5 in 54.10% of the participants and less than 5 in 45.90%. ANOVA test was performed to assess the relationship between using blue light filter applications and sleep quality (p-value = 0.925). The findings of this study indicate a connection between the use of blue light filter apps and habitual sleep efficiency in the 31-40 age group. However, our results align only to some extent with prior research, as we did not observe sustained positive effects on all parameters of sleep quality from the long-term use of blue light filtering apps. Several studies have found that blue light exposure can suppress melatonin secretion, exacerbating sleep problems. Some studies have reported that physical blue light filters, such as lenses, can affect melatonin secretion and improve sleep quality. However, the impact of blue light filtering applications remains unclear and debatable. Using smartphones before bedtime and being exposed to its blue light can make it harder to fall asleep and disrupt your sleep. Some smartphone makers have introduced a night mode feature claiming it can help improve your sleep. In this study, we wanted to find out if using these blue light filters on smartphones really makes a difference. We asked people how often they used blue light filters on their phones and also had them fill out a questionnaire about their sleep quality. Only about 10% of people said they used blue light filters regularly, another 10% used them occasionally, and the majority, around 80%, never used them. When we looked at the results, more than half of the participants had sleep scores higher than 5, indicating they might have sleep problems. Less than half had sleep scores lower than 5, suggesting better sleep quality. We used some statistical tests to see if using blue light filters had any link to sleep quality, and the results showed that there was only a connection between the use of blue light filter apps and habitual sleep efficiency in the 31–40 age group. Our findings matched what other studies have found before, that using blue light filters on smartphones may not significantly help improve sleep. So, while it might be a good idea to limit smartphone use before bed, using a blue light filter app may not be the magic solution for better sleep.…

PMID: 38461462

The timing of sleep is under the control of the circadian clock, which uses light to entrain to the external light-dark cycle. A combination of genetic, physiological and environmental factors produces individual differences in chronotype (entrained phase as manifest in sleep timing). A mismatch between circadian and societal (e.g., work) clocks leads to a condition called social jetlag, which is characterized by changing sleep times over work and free days and accumulation of sleep debt. Social jetlag, which is prevalent in late chronotypes, has been related to several health issues. One way to reduce social jetlag would be to advance the circadian clock via modifications of the light environment. We thus performed two intervention field studies to describe methods for decreasing social jetlag. One study decreased evening light exposure (via blue-light-blocking glasses) and the other used increased morning light (via the use of curtains). We measured behaviour as well as melatonin; the latter in order to validate that behaviour was consistent with this neuroendocrinological phase marker of the circadian clock. We found that a decrease in evening blue light exposure led to an advance in melatonin and sleep onset on workdays. Increased morning light exposure advanced neither melatonin secretion nor sleep timing. Neither protocol led to a significant change in social jetlag. Despite this, our findings show that controlling light exposure at home can be effective in advancing melatonin secretion and sleep, thereby helping late chronotypes to better cope with early social schedules.…

PMID: 30506899

In modern society, delayed sleep patterns among schoolchildren present challenges to academic attendance and performance. The impact of nighttime light exposure, especially blue wavelength light, on sleep delay has long been acknowledged. We investigated the effects of using partial blue light blocking glasses (JINS Screen Lens Heavy [40% cut]) on salivary melatonin levels, sleep patterns, sleep circadian phase, and daytime behavior in 39 male schoolchildren aged 10-12 who regularly wear glasses for myopia. Participants alternated between blue light blocking and standard clear lens glasses, both providing vision correction, for three hours before their habitual bedtime. The study was conducted over five weeks using a crossover design with two-week glasses-wearing sessions and a one-week washout interval between conditions. While blue light blocking glasses did not influence salivary melatonin levels, they significantly advanced the sleep phase (bedtime: 22.03 ± 0.08h vs. 22.13 ± 0.09h, p = 0.040, sleep onset: 22.26 ± 0.08h vs. 22.36 ± 0.10h, p = 0.041). The effects were more pronounced in the second week and accompanied by reduced irritability and disruptive behavior during daytime. Our results suggest that wearing blue light blocking glasses before bedtime may advance the sleep phase and improve daytime behavior in schoolchildren under real-world living conditions, warranting further mechanistic investigation.…

PMID: 41166315