Patterns and reliability of children's skin temperature prior to and during sleep in the home setting

Enhanced conductive body heat loss during sleep increases slow-wave sleep and calms the heart

Substantial evidence suggests that the circadian decline of core body temperature (CBT) triggers the initiation of human sleep, with CBT continuing to decrease during sleep. Although the connection between habitual sleep and CBT patterns is established, the impact of external body cooling on sleep remains poorly understood. The main aim of the present study is to show whether a decline in body temperatures during sleep can be related to an increase in slow wave sleep (N3). This three-center study on 72 individuals of varying age, sex, and BMI used an identical type of a high-heat capacity mattress as a reproducible, non-disturbing way of body cooling, accompanied by measurements of CBT and proximal back skin temperatures, heart rate and sleep (polysomnography). The main findings were an increase in nocturnal sleep stage N3 (7.5 ± 21.6 min/7.5 h, mean ± SD; p = 0.0038) and a decrease in heart rate (- 2.36 ± 1.08 bpm, mean ± SD; p < 0.0001); sleep stage REM did not change (p = 0.3564). Subjects with a greater degree of body cooling exhibited a significant increase in nocturnal N3 and a decrease in REM sleep, mainly in the second part of the night. In addition, these subjects showed a phase advance in the NREM-REM sleep cycle distribution of N3 and REM. Both effects were significantly associated with increased conductive inner heat transfer, indicated by an increased CBT- proximal back skin temperature -gradient, rather than with changes in CBT itself. Our findings reveal a previously far disregarded mechanism in sleep research that has potential therapeutic implications: Conductive body cooling during sleep is a reliable method for promoting N3 and reducing heart rate.

How staying in a gymnasium affects sleep and bed climate in children

BACKGROUND

We investigated the relationship between sleep, ambient climate, and bed climate in school-aged children during a one-night stay in a simulated shelter in a gymnasium to demonstrate the effect of ambient climate, and bed climate on sleep.

METHODS

We obtained measurements during a one-night stay in a school gymnasium (C), days before C (BC), on the day after (A1), and on the second day after C (A2) in 13 healthy school-aged children during summer. Sleep was evaluated using an actigraph, and the temperature and humidity of the bedrooms in the participants' homes and in the gymnasium were monitored for 3 days before and after C. The bed climate of the chest and foot areas was measured for two nights before and after C. The participants were asked to report on their subjective sleep estimations and thermal sensations two nights before and after C.

RESULTS

The ambient temperature in C was significantly higher than that in BC at the initial 180 min, while it significantly decreased compared to A1 and A2 in the last 100 min. The ambient humidity was significantly higher in both C and BC compared to A1 and A2. The sleep efficiency index decreased significantly in C (43±4.8%) compared to other conditions. Sleep time was significantly shorter in C than in other conditions during the initial 195 min. The increase in the bed climate temperature of the chest area in C was significantly delayed compared to that in the other conditions, around the initial 30 min after the lights were off. Subjective estimation revealed that in C, 85% of the participants were out of their sleeping bag at sleep onset, and their sleep was disturbed by heat (77%).

CONCLUSIONS

Our study revealed that the disturbed sleep patterns observed with children in a simulated shelter may be related to a delayed increase in bed climate temperature in the chest area. This delayed increase could be related to the children not entering the sleeping bag and a delayed chest skin temperature increase during the sleep onset period.

Functional links between thermoregulation and sleep in children with neurodevelopmental and chronic health conditions

The bi-directional relationship between sleep and wake is recognized as important for all children. It is particularly consequential for children who have neurodevelopmental disorders (NDDs) or health conditions which challenge their sleep and biological rhythms, and their ability to maintain rhythms of participation in everyday activities. There are many studies which report the diverse reasons for disruption to sleep in these populations. Predominantly, there is focus on respiratory, pharmaceutical, and behavioral approaches to management. There is, however, little exploration and explanation of the important effects of body thermoregulation on children's sleep-wake patterns, and associated behaviors. Circadian patterns of sleep-wake are dependent on patterns of body temperature change, large enough to induce sleep preparedness but remaining within a range to avoid sleep disturbances when active thermoregulatory responses against heat or cold are elicited (to maintain thermoneutrality). Additionally, the subjective notion of thermal comfort (which coincides with the objective concept of thermoneutrality) is of interest as part of general comfort and associated behavioral responses for sleep onset and maintenance. Children's thermoregulation and thermal comfort are affected by diverse biological functions, as well as their participation in everyday activities, within their everyday environments. Hence, the aforementioned populations are additionally vulnerable to disruption of their thermoregulatory system and their capacity for balance of sleep and wakefulness. The purpose of this paper is to present hitherto overlooked information, for consideration by researchers and clinicians toward determining assessment and intervention approaches to support children's thermoregulation functions and promote their subjective thermal comfort, for improved regulation of their sleep and wake functions.

Skin Temperatures of Back or Neck Are Better Than Abdomen for Indication of Average Proximal Skin Temperature During Sleep of School-Aged Children

PURPOSE

The tight association between sleep, body temperature regulation, and patterns of skin temperature change highlights the necessity for accurate and valid assessment of skin temperatures during sleep. With increased interest in this functional relationship in infants and children, it is important to identify where to best measure proximal skin temperature and whether it is possible to reduce the number of sites of measures, in order to limit the experimental effects in natural settings. Thus, the aim of this study was to determine the most suitable single skin temperature sites for representation of average proximal skin temperature during sleep of school aged children.

METHODS

Statistical analyses were applied to skin temperature data of 22 children, aged 6 to 12 years, measured over four consecutive school nights in their home settings, to compare single site measures of abdomen, back, neck, forehead and subclavicular skin temperatures (local temperatures) with average proximal skin temperatures.

RESULTS

Abdomen and forehead skin temperatures were significantly different (respectively higher and lower) to the other local proximal temperatures and to average proximal skin temperatures. Moreover, the time pattern of forehead temperature was very different from that of the other local temperatures.

CONCLUSIONS

Local forehead and abdomen skin temperatures are least suitable as single site representations of average proximal skin temperatures in school aged children when considering both the level and the time course pattern of the temperature across the night. Conversely, back and neck temperatures provide most fitting representation of average proximal skin temperatures.

Sleep and thermoregulation

In homeothermic animals sleep preparatory behaviours often promote thermal efficiency, including warmth-seeking, adopting particular postures (curling up, head tucking) and nest building, all promoting warmer skin microclimates. Skin warmth induces NREM sleep and body cooling via circuitry that connects skin sensation to the preoptic hypothalamus. Coupling sleep induction and lower body temperature could serve to minimise energy expenditure or allow energy reallocation. Cooling during NREM sleep may also induce transcriptional changes in genes whose products facilitate housekeeping functions or measure the time spent sleeping.

A hot topic for health: Results of the Global Sauna Survey

OBJECTIVE

Sauna-bathing is an ancient tradition that is gaining popularity across the world as a wellness tool. There is a growing body of medical evidence supporting the role of saunas, or whole-body thermotherapy, as a form of treatment for a range of health issues. However, the demographics, motivations and experiences of current sauna bathers have not yet been explored on a global scale. This study is designed to explore these themes.

DESIGN

An online 71-item questionnaire compiling information on the individual characteristics, sauna-related habits and perceived health and wellness experiences of regular sauna bathers was conducted from October 2016 to October 2017. The validated 'SF-12' quality of life scoring tool was incorporated into the questionnaire to measure physical and mental indicators of well-being.

RESULTS

Of 572 logins recorded, 482 valid responses were generated. Both men (51.3%) and women (48.7%) were represented, and respondents were predominantly well-educated (81.8%), non-smoking (90.6%), regularly-exercising (78.8%) individuals of normal-to-overweight status (87.1%) who sauna-bathed approximately 1-2 times per week. The key reasons indicated by respondents for sauna-bathing included relaxation/stress reduction, pain relief and socializing. Nearly a third of respondents reported medical conditions and of this subset, those with back/musculoskeletal pain and mental issues cited the greatest improvements in their conditions with sauna-bathing. Of all respondents, 83.5% reported sleep benefits after sauna use. Analysis of well-being scores after stratifying respondents into three groups by sauna-bathing frequency (group I: <5 times per month; group II: 5-15 times per month; group III: >15 times per month) revealed group II respondents had slightly higher mental well-being scores (Kruskal-Wallis testing: H = 6.603 > ꭔ2 of 5.991, p = 0.0368, df = 2 with post hoc analysis using Mann-Whitney U test: p = 0.016) as compared to respondents who were sauna-bathing less frequently (group I). No respective differences were detected between the physical well-being scores of any of the three groups. Adverse reactions to sauna-bathing were recorded as mostly minor (93.1%), including primarily symptoms of dizziness, dehydration and headache. However, there were two reports (0.3%) of chest pain and eye irritation requiring hospitalization.

CONCLUSIONS

This cross-sectional study documents that sauna-bathing participants, particularly those from Finland, Australia and the United States, are motivated to use saunas predominantly for relaxation, reporting health benefits especially around mental well-being and sleep, with relatively few adverse effects. While these results reinforce some of the known health benefits of sauna bathing, they indicate that further research and better dissemination of existing evidence is needed to fully develop the sauna's potential as a therapeutic intervention.

Distal skin vasodilation in sleep preparedness, and its impact on thermal status in preterm neonates

OBJECTIVE

Prior to sleep onset in human adults, distal body temperatures change progressively from wakefulness levels (low skin temperatures and a high core temperature) to sleep levels (high skin temperatures and a low core temperature) due to distal skin vasodilation and greater body cooling. It is not known whether this sleep preparedness exists in preterm neonates, even though sleep has a key role in neonatal health and neurodevelopment. The present study's objectives were to determine whether sleep preparedness (as observed in adults) can be evidenced in preterm neonates, and to assess repercussions on thermal stress.

METHODS

During a 12-h night-time polysomnography session, skin temperatures (recorded with an infrared camera), sleep, and wakefulness episodes were measured in 18 nine-day-old preterm neonates.

RESULTS

Fifteen wakefulness episodes were considered. Our results highlighted significant pre-sleep distal skin vasodilation (mainly at the foot: an increase of 0.38 °C in the 20 min preceding sleep onset) for the first time in preterm neonates. This vasodilation occurred even though (1) most factors known to influence pre-sleep vasodilation in adults were not present in these neonates, and (2) the neonates were nursed in a nearly constant thermal environment. The vasodilatation-related increase in body heat loss corresponded to a 0.15°C/h fall in mean body temperature (calculated using partitional calorimetry).

CONCLUSION

Compensation for this body heat loss and the maintenance of body homeothermia would require a 4% increase in metabolic heat production. In neonates, this type of energy expenditure cannot be maintained for a long period of time.

Sleep in children with neurodevelopmental difficulties

Sleep disorders in children with neurodevelopmental disorders are complex and reflect underlying genetic/biological and behavioural components. The sleep disorders are the same as in the typically developing child, although there may be some modifications to the presentation or the frequency depending on the phenotype. Consideration of the known phenotypes and environmental issues are important in defining management strategies. Despite this complexity, defined behavioural strategies with good sleep hygiene can have a significant effect on the sleep problem and on parental management of the behaviours.