Head cooling during sleep improves sleep quality in the luteal phase in female university students: A randomized crossover-controlled pilot study

Does body cooling facilitated by bedding compared to control condition improve sleep among adults (18-64 years old)? A systematic review and meta-analysis

INTRODUCTION

The relationship between blood distribution, body temperature, and sleep/wakefulness states is still unclear. The aim of the present study is to systematically review the potential beneficial effects of bedding strategies (e.g., mattress, mattress topper or pillow) on body cooling and night-time sleep.

MATERIAL & METHODS

This systematic review with meta-analysis searched PubMed, ScienceDirect and Web of Science, from inception until March 4, 2024. We included randomized controlled trials aiming to investigate any type of bedding that induced body cooling compared to habitual sleep environment on sleep parameters in healthy adults. Two reviewers independently extracted data, appraised risk of bias by Cochrane tool, and estimated the mean differences between groups with 95% confidence interval. Meta-analyses and proportional meta-analyses were performed depending on the type of variable. The certainty of evidence was assessed using the Grades of Recommendation, Assessment, Development and Evaluation system.

RESULTS

From 3454 articles screened, 9 studies met the inclusion criteria. Overall, with the certainty of the evidence ranging from very low to low we found no differences between groups on sleep onset latency, sleep efficiency, sleep proportion spent in each sleep stage (i.e. N1, N2, N3 and REM), wake after sleep onset, and total sleep time. Results could be interpreted with caution due to high heterogeneity in the estimated effects.

CONCLUSION

With uncertainty of evidence, that ranged from very low to low, different bedding strategies had no effects on night-time sleep characteristics; however, the studies included into the qualitative synthesis suggested an effect of different bedding strategies on body cooling (i.e., lower core body temperature, p < 0.05) from an acute perspective. Future studies on various forms of bedding interventions susceptible to favour and maintain sleep through a positive body thermal effect are highly warranted.

PROSPERO REGISTRATION

CRD42021275369.

The Effect of Superficial Heat-Cold Application on the Sleep Quality of Patients With Restless Leg Syndrome: A Systematic Review and Meta-Analysis

AIM

The present study was conducted to determine the effect of the superficial heat-cold application on the sleep quality of patients with restless leg syndrome.

DESIGN

This study was a systematic review and meta-analysis.

METHODS

In the present study, the electronic databases Scopus, ProQuest, Web of Science, PubMed, SID and Google Scholar were searched from their inception to September 2023. The quality of included studies was evaluated through the Cochrane Collaboration's Risk of Bias Tool, and finally, a meta-analysis was conducted by calculating standardised mean differences (SMDs).

RESULTS

The meta-analysis results revealed that superficial heat-cold application improved sleep quality in patients with RLS (SMD = 0.685, 95% CI: 0.421-0.950). The meta-regression results showed that as the temperature increased, the intervention was more effective in improving sleep quality (β = 0.0182, 95% CI: 0.0096-0.0268, p < 0.05). Moreover, the effectiveness of the intervention in improving the sleep quality of patients with RLS reduced significantly as the duration of intervention in each session (β = -0.031, 95% CI: -0.059 to -0.001, p < 0.05) as well as participants' age increased (β = -0.013, 95% CI: -0.024 to -0.001, p = 0.0259).

PATIENT OR PUBLIC CONTRIBUTION

This research showed that superficial heat-cold application had the capability to improve the sleep quality of patients with restless leg syndrome. In addition, in this study, settings were suggested according to which the maximum effectiveness of the intervention could be achieved.

Periocular Skin Warming Promotes Sleep Onset Through Heat Dissipation From Distal Skin in Patients With Insomnia Disorder

STUDY OBJECTIVES

Periocular skin warming before bedtime has been demonstrated to improve subjective sleep initiation in healthy adults with sleep difficulties scored six or higher in the Pittsburgh Sleep Questionnaire Index. This study aimed to investigate the effects of periocular skin warming on sleep initiation and thermoregulation processes in patients with insomnia disorder.

METHODS

Participants included those with sleep difficulty (n = 22) and those with insomnia disorder (n = 16). Individuals from both groups were assessed at baseline (habitual sleep-wake schedule) and after two intervention conditions (use of a warming eye mask or a sham eye mask before habitual bedtime). The subjective and electroencephalographic sleep onset latency, along with proximal and distal skin temperature after periocular skin warming, were evaluated.

RESULTS

Periocular skin warming reduced objective sleep onset latency in independently of the group. Foot temperature and foot-proximal temperature gradient after getting into bed increased with periocular skin warming in independently of the group. However, the increase in hand temperature was observed only in the insomnia disorder group. Periocular skin warming also increased the normalized high frequency component of heart rate variability in independently of the group. The reduction of objective sleep onset latency was strongly associated with heat dissipation from the foot skin region.

CONCLUSION

These results suggest that periocular skin warming promotes sleep initiation by enhancing heat dissipation from the distal skin regions in individuals with sleep difficulty and insomnia disorder. Periocular skin warming could thus be a novel non-pharmacological therapy for insomnia disorder.

Assessment of bladder function for stabilizing urinary volume overnight with recording of brain waves (ABSORB study)

OBJECTIVES

The bladder urothelium is not always impermeable. During sleep, the bladder might absorb urine in healthy individuals who sleep through the night. This study aimed to determine whether the bladder absorbs urine by using a method other than ultrasonic scanning and to simultaneously evaluate sleeping conditions.

METHODS

Eleven participants (five males, six females) aged 20 to 49 years without lower urinary tract symptoms or urination while sleeping were enrolled. Bladder volume was estimated by studying the relationship between dilution and absorbance of indigo carmine dissolved in urine. A 12F Foley catheter was inserted into the bladder before sleep. Urine samples (5 mL) were extracted at 2, 3, 4, 5, and 6 am sleep stages were monitored with a single-channel portable electroencephalograph device.

RESULTS

The estimated bladder volume at 6 am and voided volume immediately after rising were significantly correlated (Spearman's ρ = 0.62, P = .046). Eight participants (three males, five females) showed an absorption pattern of the estimated bladder volume change. In a male participant, the blue dye's strength gradually decreased until 4 am (estimated 859 mL) and increased from 5 am (estimated 455 mL). In another, the blue dye's strength increased at 4 am (estimated 449 mL) vs at 3 am (estimated 757 mL). In all participants, electroencephalograph data demonstrated that sleep was maintained despite having a full bladder.

CONCLUSIONS

The bladder absorbs urine and maintains an approximate volume of functional bladder capacity during sleep to avoid incontinence and maintain sleep in adults due to an urge to void urine during the sleep cycle.

Effect of Chronotype on Sleep Quality in a Laboratory Setting

Sleep is undoubtedly important for human health as insufficient sleep has been associated with a plethora of diseases. Adequate sleep assessment is critical in clinical and research settings, however current sleep assessment protocols fail to account for circadian rhythms, despite the fact that sleep is a well-recognized circadian process.

PURPOSE

The purpose of this study was to determine if circadian parameters, such as chronotype, influence sleep quality in a sleep laboratory setting.

METHODS

In order to investigate this, twenty participants (10 men and 10 women) aged 18-31 years old had their sleep recorded by electroencephalography in a sleep lab. Participants also complete surveys which provided data on chronotype, social jet lag and subjective sleep quality. Participants were allowed to self-select sleep time for the study, and sleep discrepancy, defined as the difference between reported and experienced mid-sleep, was determined.

RESULTS

Interestingly, results indicated a significant correlation between self-reported sleep quality and social jet lag, with those who typically experience more social jet lag being more satisfied with their sleep during the study (r = 0.549, p = 0.012). In addition, when participants were separated into groups based on chronotype, sleep discrepancy and social jet lag, sizeable differences were noted for parameters such as sleep onset latency, number of awakenings, and percent of time spent in REM sleep.

CONCLUSION

These results suggest circadian parameters serve as predictors of both subjective and objective sleep quality, and thus illuminates a necessity for these parameters to be taken into account in the assessment and research of sleep.