Sleeping in an Inclined Position to Reduce Snoring and Improve Sleep: In-home Product Intervention Study.

BACKGROUND: Accurately and unobtrusively testing the effects of snoring and sleep interventions at home has become possible with recent advances in digital measurement technologies. OBJECTIVE: The aim of this study was to examine the effectiveness of using an adjustable bed base to sleep with the upper body in an inclined position to reduce snoring and improve sleep, measured at home using commercially available trackers. METHODS: Self-reported snorers (N=25) monitored their snoring and sleep nightly and completed questionnaires daily for 8 weeks. They slept flat for the first 4 weeks, then used an adjustable bed base to sleep with the upper body at a 12-degree incline for the next 4 weeks. RESULTS: Over 1000 nights of data were analyzed. Objective snoring data showed a 7% relative reduction in snoring duration (P=.001) in the inclined position. Objective sleep data showed 4% fewer awakenings (P=.04) and a 5% increase in the proportion of time spent in deep sleep (P=.02) in the inclined position. Consistent with these objective findings, snoring and sleep measured by self-report improved. CONCLUSIONS: New measurement technologies allow intervention studies to be conducted in the comfort of research participants' own bedrooms. This study showed that sleeping at an incline has potential as a nonobtrusive means of reducing snoring and improving sleep in a nonclinical snoring population.

Characteristics of Children Likely to Have Spontaneous Resolution of Obstructive Sleep Apnea: Results from the Childhood Adenotonsillectomy Trial (CHAT).

OBJECTIVE: To evaluate if cardiopulmonary coupling (CPC) calculated sleep quality (SQI) may have a role in identifying children that may benefit from other intervention than early adenotonsillectomy (eAT) in management of obstructive sleep apnea (OSA). METHODS: A secondary analysis of electrocardiogram-signals (ECG) and oxygen saturation-data (SpO2) collected during polysomnography-studies in the prospective multicenter Childhood Adenotonsillectomy Trial (CHAT) to calculate CPC-SQI and apnea hypopnea index (AHI) was executed. In the CHAT, children 5-9 years with OSA without prolonged oxyhemoglobin desaturations were randomly assigned to adenotonsillectomy (eAT) or watchful waiting with supportive care (WWSC). The primary outcomes were to document change in attention and executive function evaluated with the Developmental Neuropsychological Assessment (NEPSY). In our analysis, children in the WWSC-group with spontaneous resolution of OSA (AHIObstructive < 1.0) and high-sleep quality (SQI ≥ 75) after 7-months were compared with children that showed residual OSA. RESULTS: Of the 227 children randomized to WWSC, 203 children had available data at both baseline and 7-month follow-up. The group that showed resolution of OSA at month 7 (n = 43, 21%) were significantly more likely to have high baseline SQI 79.96 [CI95% 75.05, 84.86] vs. 72.44 [CI95% 69.50, 75.39], p = 0.005, mild OSA AHIObstructive 4.01 [CI95% 2.34, 5.68] vs. 6.52 [CI95% 5.47, 7.57], p= 0.005, higher NEPSY-attention-executive function score 106.22 [CI95% 101.67, 110.77] vs. 101.14 [CI95% 98.58, 103.72], p = 0.038 and better quality of life according to parents 83.74 [CI95% 78.95, 88.54] vs. 77.51 [74.49, 80.53], p = 0.015. The groups did not differ when clinically evaluated by Mallampati score, Friedman palate position or sleep related questionnaires. CONCLUSIONS: Children that showed resolution of OSA were more likely to have high-SQI and mild OSA, be healthy-weight and have better attention and executive function and quality of life at baseline. As this simple method to evaluate sleep quality and OSA is based on analyzing signals that are simple to collect, the method is practical for sleep-testing, over multiple nights and on multiple occasions. This method may assist physicians and parents to determine the most appropriate therapy for their child as some children may benefit from WWSC rather than interventions. If the parameters can be used to plan care a priori, this would provide a fundamental shift in how childhood OSA is diagnosed and managed.

Sleep spindle and slow wave frequency reflect motor skill performance in primary school-age children.

BACKGROUND AND AIM: The role of sleep in the enhancement of motor skills has been studied extensively in adults. We aimed to determine involvement of sleep and characteristics of spindles and slow waves in a motor skill in children. HYPOTHESIS: We hypothesized sleep-dependence of skill enhancement and an association of interindividual differences in skill and sleep characteristics. METHODS: 30 children (19 females, 10.7 ± 0.8 years of age; mean ± SD) performed finger sequence tapping tasks in a repeated-measures design spanning 4 days including 1 polysomnography (PSG) night. Initial and delayed performance were assessed over 12 h of wake; 12 h with sleep; and 24 h with wake and sleep. For the 12 h with sleep, children were assigned to one of three conditions: modulation of slow waves and spindles was attempted using acoustic perturbation, and compared to yoked and no-sound control conditions. ANALYSES: Mixed effect regression models evaluated the association of sleep, its macrostructure and spindles and slow wave parameters with initial and delayed speed and accuracy. RESULTS AND CONCLUSIONS: Children enhance their accuracy only over an interval with sleep. Unlike previously reported in adults, children enhance their speed independent of sleep, a capacity that may to be lost in adulthood. Individual differences in the dominant frequency of spindles and slow waves were predictive for performance: children performed better if they had less slow spindles, more fast spindles and faster slow waves. On the other hand, overnight enhancement of accuracy was most pronounced in children with more slow spindles and slower slow waves, i.e., the ones with an initial lower performance. Associations of spindle and slow wave characteristics with initial performance may confound interpretation of their involvement in overnight enhancement. Slower frequencies of characteristic sleep events may mark slower learning and immaturity of networks involved in motor skills.

Modulation of γ and spindle-range power by slow oscillations in scalp sleep EEG of children.

Deep sleep is characterized by slow waves of electrical activity in the cerebral cortex. They represent alternating down states and up states of, respectively, hyperpolarization with accompanying neuronal silence and depolarization during which neuronal firing resumes. The up states give rise to faster oscillations, notably spindles and gamma activity which appear to be of major importance to the role of sleep in brain function and cognition. Unfortunately, while spindles are easily detectable, gamma oscillations are of very small amplitude. No previous sleep study has succeeded in demonstrating modulations of gamma power along the time course of slow waves in human scalp EEG. As a consequence, progress in our understanding of the functional role of gamma modulation during sleep has been limited to animal studies and exceptional human studies, notably those of intracranial recordings in epileptic patients. Because high synaptic density, which peaks some time before puberty depending on the brain region (Huttenlocher and Dabholkar, 1997), generates oscillations of larger amplitude, we considered that the best chance to demonstrate a modulation of gamma power by slow wave phase in regular scalp sleep EEG would be in school-aged children. Sleep EEG was recorded in 30 healthy children (aged 10.7 ± 0.8 years; mean ± s.d.). Time-frequency analysis was applied to evaluate the time course of spectral power along the development of a slow wave. Moreover, we attempted to modify sleep architecture and sleep characteristics through automated acoustic stimulation coupled to the occurrence of slow waves in one subset of the children. Gamma power increased on the rising slope and positive peak of the slow wave. Gamma and spindle activity is strongly suppressed during the negative peak. There were no differences between the groups who received and did not receive acoustic stimulation in the sleep parameters and slow wave-locked time-frequency analysis. Our findings show, for the first time in scalp EEG in humans, that gamma activity is associated with the up-going slope and peak of the slow wave. We propose that studies in children provide a uniquely feasible opportunity to conduct investigations into the role of gamma during sleep.

Sleep, vigilance, and thermosensitivity.

The regulation of sleep and wakefulness is well modeled with two underlying processes: a circadian and a homeostatic one. So far, the parameters and mechanisms of additional sleep-permissive and wake-promoting conditions have been largely overlooked. The present overview focuses on one of these conditions: the effect of skin temperature on the onset and maintenance of sleep, and alertness. Skin temperature is quite well suited to provide the brain with information on sleep-permissive and wake-promoting conditions because it changes with most if not all of them. Skin temperature changes with environmental heat and cold, but also with posture, environmental light, danger, nutritional status, pain, and stress. Its effect on the brain may thus moderate the efficacy by which the clock and homeostat manage to initiate or maintain sleep or wakefulness. The review provides a brief overview of the neuroanatomical pathways and physiological mechanisms by which skin temperature can affect the regulation of sleep and vigilance. In addition, current pitfalls and possibilities of practical applications for sleep enhancement are discussed, including the recent finding of impaired thermal comfort perception in insomniacs.

Finger and toe temperatures on exposure to cold water and cold air.

INTRODUCTION: Subjects with a weak cold-induced vasodilatation response (CIVD) to experimental cold-water immersion of the fingers in a laboratory setting have been shown to have a higher risk for local cold injuries when exposed to cold in real life. Most of the cold injuries in real life, however, occur in the foot in cold air rather than in the hand in cold water. Therefore, an experiment was conducted to investigate the within-subject relation between CIVD in the fingers and toes exposed to cold water and cold air. METHODS: In 4 experimental sessions, 11 healthy male subjects immersed their toes and fingers in 5 degrees C water and exposed the fingers and toes to -18 degrees C cold air for 30 min. The pad temperature of the middle three digits was measured. RESULTS: CIVD in water was more pronounced in the fingers (onset time 5.1 +/- 1.8 min; amplitude 5.0 +/- 2.1 degrees C) than in the toes (onset time 10.6 +/- 6.0 min; amplitude 3.0 +/- 1.0 degrees C). Out of 22 skin temperature responses to cold air, 13 were not identifiable as CIVD. The mean skin temperatures for fingers and toes during the last 20 min of cold exposure were 25.6 +/- 7.1 degrees C and 20.9 +/- 6.8 degrees C, respectively, for air and 9.3 +/- 1.9 degrees C and 7.1 +/- 1.3 degrees C for water immersion. There was a strong relation between the mean temperature of the fingers during cold-water immersion and toes during cold air exposure (r = 0.83, P < 0.01), showing that a weak CIVD response in the hand is related to a weak response in the foot. DISCUSSION: We conclude that the cold-water finger immersion test is related to the temperature response in the toes and may thus continue to serve as a valid indicator for the risk of local cold injuries.

Diminished capability to recognize the optimal temperature for sleep initiation may contribute to poor sleep in elderly people.

STUDY OBJECTIVES: Sleep propensity and skin temperature are functionally related. In young adults, changes of skin temperature within the comfortable thermoneutral zone affect sleep-onset latency and vigilance performance. Aging is associated with both decreased thermosensitivity and poorer sleep. Our goal was to test whether subtle manipulations of core body and skin temperature affect sleep onset in elderly people without sleep complaints and in elderly insomniacs and whether the subjective perception of these mild body temperature manipulations is preserved with aging and insomnia. DESIGN: In a 2-day semiconstant-routine protocol, 288 sleep-onset latencies were polysomnographically determined while manipulating core body and skin temperatures differentially in warm and cold directions within a comfortable thermoneutral range. SETTING: Sleep laboratory of the Netherlands Institute for Neuroscience. PATIENTS OR PARTICIPANTS: Eight elderly subjects without sleep complaints (65.8 +/- 2.8 years, mean +/- SEM) and 8 elderly insomniacs (59.1 +/- 1.9 years). MEASUREMENTS AND RESULTS: Warming the proximal skin by 0.4 degrees C facilitates sleep onset equally effective in healthy elderly (by 18% ie, by 1.84 minutes [95% confidence interval [CI], 0.76-2.92]) and elderly insomniacs (28%, 2.85 minutes [CI: 2.55-3.18]). These effects were comparable to the results in healthy young subjects, in spite of a marked decrease in the subjective perception of temperature changes in elderly subjects, especially in insomniacs. CONCLUSION: The findings show that mild changes in skin temperature have an effect on sleep propensity in elderly and indicate that elderly insomniacs may have a diminished capability to recognize that a slight increase in bed temperature facilitates the initiation or reinitiation of sleep.

Manipulation of core body and skin temperature improves vigilance and maintenance of wakefulness in narcolepsy.

CONTEXT: Impaired vigilance and sleepiness are two majordaily complaints of patients with narcolepsy. We previously showed their sleepiness to be correlated to an abnormally regulated skin temperature, i.e., increased distal skin temperature compared with proximal skin temperature. OBJECTIVE: Our goal was to investigate a possible causal contribution of skin temperature disturbances to impairments in the ability to maintain vigilance and wakefulness in narcolepsy. DESIGN: In a modified constant routine protocol, the Psychomotor Vigilance Task (PVT) and the Maintenance of Wakefulness Test (MWT) were repeatedly assessed. Meanwhile, skin and core body temperatures were mildly manipulated within the thermoneutral range of the normal diurnal rhythm using a thermosuit and hot or cold food and drinks. SETTING: Tertiary narcolepsy referral center in a university hospital PATIENTS OR OTHER PARTICIPANTS: Eight patients (5 males) diagnosed with narcolepsy with cataplexy according to the ICSD-2 criteria (mean age +/- SD: 28.6 +/- 6.4, range 18-35 years). INTERVENTION(S): None. MAIN OUTCOME MEASURE(S): MWT sleep latency and PVT response speed. RESULTS: Compared to core cooling, core warming attenuated the typical decline in PVT response speed with increasing time-on-task by 25% (P = 0.02). Compared to distal skin warming, distal skin cooling increased the time that the patients were able to maintain wakefulness by 24% (distal warming: 1.88 min. vs. distal warming: 2.34 min.; P < 0.01). CONCLUSIONS: Core body and skin temperatures causally affect vigilance and sleepiness in narcolepsy. This could lead to future practical applications.

Skin deep: enhanced sleep depth by cutaneous temperature manipulation.

With ageing, an increasingly disturbed sleep is reported as a significant complaint affecting the health and well-being of many people. The available treatments for sleep disturbance have their limitations, so we have adopted a different approach to the improvement of sleep. Since in animal and human studies skin warming has been found to increase neuronal activity in brain areas that are critically involved in sleep regulation, we investigated whether subtle skin temperature manipulations could improve human sleep. By employing a thermosuit to control skin temperature during nocturnal sleep, we demonstrate that induction of a mere 0.4 degrees C increase in skin temperature, whilst not altering core temperature, suppresses nocturnal wakefulness (P<0.001) and shifts sleep to deeper stages (P<0.001) in young and, especially, in elderly healthy and insomniac participants. Elderly subjects showed such a pronounced sensitivity, that the induced 0.4 degrees C increase in skin temperature was sufficient to almost double the proportion of nocturnal slow wave sleep and to decrease the probability of early morning awakening from 0.58 to 0.04. Therefore, skin warming strongly improved the two most typical age-related sleep problems; a decreased slow wave sleep and an increased risk of early morning awakening. EEG frequency spectra showed enhancement of low-frequency cortical oscillations. The results indicate that subtle feedback control of in-bed temperature through very mild manipulations could have strong clinical relevance in the management of disturbed sleep especially in the elderly, who have an attenuated behavioural response to suboptimal environmental temperature, which may hamper them from taking appropriate action to optimize their bed temperature.

Time-on-task impairment of psychomotor vigilance is affected by mild skin warming and changes with aging and insomnia.

STUDY OBJECTIVES: To investigate the effect of mild manipulations of core and skin temperature on psychomotor vigilance (PVT) in young adults, elderly, and elderly insomniacs. DESIGN: 432 PVTs were obtained during a 2-day semi-constant routine protocol, while differentially manipulating core and skin temperatures within a comfortable thermoneutral range. SETTING: Sleep laboratory of the Netherlands Institute for Neuroscience. PATIENTS OR PARTICIPANTS: Groups of 8 sex-matched young adults (27.0 +/- 2.4 years, mean +/- s.e.m.), elderly (65.8 +/- 2.8 years), and insomniacs (59.1 +/-1.9 years). MEASUREMENTS AND RESULTS: During the 7-minute PVTs, response speed typically declined with increasing time-on-task. Proximal skin warming by only +/- 0.6 degrees C accelerated this decline by 67% (P = 0.05) in young adults and by 50% (P < 0.05) in elderly subjects. In elderly insomniacs, proximal warming slowed down the mean response speed already from the onset of the task (3% level drop, P < 0.001). Response speed tended to decrease with age (P < 0.10), reaching significance only in elderly insomniacs (P < 0.05). Speed decrements occurred mostly towards the end of the time-on-task in young adults; earlier and more gradually in elderly without sleep complaints; and very early and in a pronounced fashion in insomniacs. Interestingly, the worsening by warming followed the time pattern already present within each group. CONCLUSIONS: The results are compatible with the hypothesis that the endogenous circadian variation of skin temperature could modulate vigilance regulating brain areas and thus contribute to the circadian rhythm in vigilance. Minute-by-minute PVT analyses revealed effects of age and insomnia not previously disclosed in studies applying time-point aggregation. Our data indicate that "age-related cognitive slowing" may result, in part, from age-related sleep problems.

Skin temperature and sleep-onset latency: changes with age and insomnia.

Throughout the 24-hour day, the occurrence of sleep and wakefulness is closely related to changes in body temperatures. Changes in skin temperature may causally affect the ability to initiate and maintain sleep. First, we briefly summarize a previously proposed neurobiological mechanism that couples skin temperature to sleep propensity. Next we review previous findings on the relation between skin temperature and sleep-onset latency, indicating that sleep propensity can be enhanced by warming the skin to the level that normally occurs prior to--and during--sleep. Finally, we present new data indicating age- and insomnia-related changes in the sleep-onset latency response to foot warming, and evaluate whether different methods of foot warming could provide an applicable strategy to address sleep complaints. Foot temperature manipulations included footbaths before sleep onset (1), and heatable bed socks applied either before (2) or after lights-off (3). In adults, sleep-onset was accelerated by warm and neutral bed socks after lights-off and correlated to the increase in foot temperature. This increase was attenuated in elderly subjects. In elderly subjects without sleep difficulties, sleep onset could be accelerated with neutral bed socks after lights-off and a warm footbath prior to lights-off. In elderly insomniacs, none of the treatments accelerated sleep onset. We illustrate that elderly subjects show an attenuated increase in foot temperature after lights-off and lose the relationship between pre-sleep heat-loss activation and sleep latency. The sensitivity of sleep propensity to foot warming changes with age and is attenuated in age-related insomnia.

Evaluation of wireless determination of skin temperature using iButtons.

Measurements of skin temperatures are often complicated because of the use of wired sensors. This is so in field studies, but also holds for many laboratory conditions. This article describes a wireless temperature system for human skin temperature measurements, i.e. the Thermochron iButton DS1291H. The study deals with validation of the iButton and its application on the human skin, and describes clinical and field measurements. The validation study shows that iButtons have a mean accuracy of -0.09 degrees C (-0.4 degrees C at most) with a precision of 0.05 degrees C (0.09 degrees C at most). These properties can be improved by using calibration. Due to the size of the device the response time is longer than that of conventional sensors, with a tau in water of 19 s. On the human skin under transient conditions the response time is significantly longer, revealing momentary deviations with a magnitude of 1 degrees C. The use of iButtons has been described in studies on circadian rhythms, sleep and cardiac surgery. With respect to circadian rhythm and sleep research, skin temperature assessment by iButtons is of significant value in laboratory, clinical and home situations. We demonstrate that differences in laboratory and field measurements add to our understanding of thermophysiology under natural living conditions. The advantage of iButtons in surgery research is that they are easy to sterilize and wireless so that they do not hinder the surgical procedure. In conclusion, the application of iButtons is advantageous for measuring skin temperatures in those situations in which wired instruments are unpractical and fast responses are not required.

Cutaneous warming promotes sleep onset.

Sleep occurs in close relation to changes in body temperature. Both the monophasic sleep period in humans and the polyphasic sleep periods in rodents tend to be initiated when core body temperature is declining. This decline is mainly due to an increase in skin blood flow and consequently skin warming and heat loss. We have proposed that these intrinsically occurring changes in core and skin temperatures could modulate neuronal activity in sleep-regulating brain areas (Van Someren EJW, Chronobiol Int 17: 313-54, 2000). We here provide results compatible with this hypothesis. We obtained 144 sleep-onset latencies while directly manipulating core and skin temperatures within the comfortable range in eight healthy subjects under controlled conditions. The induction of a proximal skin temperature difference of only 0.78 +/- 0.03 degrees C (mean +/- SE) around a mean of 35.13 +/- 0.11 degrees C changed sleep-onset latency by 26%, i.e., by 3.09 minutes [95% confidence interval (CI), 1.91 to 4.28] around a mean of 11.85 min (CI, 9.74 to 14.41), with faster sleep onsets when the proximal skin was warmed. The reduction in sleep-onset latency occurred despite a small but significant decrease in subjective comfort during proximal skin warming. The induction of changes in core temperature (delta = 0.20 +/- 0.02 degrees C) and distal skin temperature (delta = 0.74 +/- 0.05 degrees C) were ineffective. Previous studies have demonstrated correlations between skin temperature and sleep-onset latency. Also, sleep disruption by ambient temperatures that activate thermoregulatory defense mechanisms has been shown. The present study is the first to experimentally demonstrate a causal contribution to sleep-onset latency of skin temperature manipulations within the normal nocturnal fluctuation range. Circadian and sleep-appetitive behavior-induced variations in skin temperature might act as an input signal to sleep-regulating systems.

Circadian and age-related modulation of thermoreception and temperature regulation: mechanisms and functional implications.

At older ages, the circadian rhythm of body temperature shows a decreased amplitude, an advanced phase, and decreased stability. The present review evaluates to what extent these changes may result from age-related deficiencies at several levels of the thermoregulatory system, including thermoreception, thermogenesis and conservation, heat loss, and central regulation. Whereas some changes are related to the aging process per se, others appear to be secondary to other factors, for which the risk increases with aging, notably a decreased level of fitness and physical activity. Moreover, functional implications of the body temperature rhythm are discussed. For example, the relation between circadian rhythm and thermoregulation has hardly been investigated, while evidence showed that sleep quality is dependent on both aspects. It is proposed that the circadian rhythm in temperature in homeotherms should not be regarded as a leftover of ectothermy in early evolution, but appears to be of functional significance for physiology from the level of molecules to cognition. A new view on the functional significance of the circadian rhythm in peripheral vasodilation and the consequent out-of-phase rhythms in skin and core temperature is presented. It is unlikely that the strong, daily occurring, peripheral vasodilation primarily represents heat loss in response to a lowering of set point, since behavioral measures are simultaneously taken in order to prevent heat loss. Several indications rather point towards a supportive role in immunological host defense mechanisms. Given the functional significance of the temperature rhythm, research should focus on the feasibility and effectiveness of methods that can in principle be applied in order to enhance the weakened circadian temperature rhythm in the elderly.