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Milde huidverwarming verhoogt de slaperigheid en slaapdruk niet alleen bij volwassenen maar ook bij ouderen, maar ouderen met slaapproblemen kunnen deze milde veranderingen in huidtemperatuur niet of nauwelijks waarnemen, waardoor het buiten de experimentele setting/in het dagelijks leven dus mogelijk is dat ouderen met slaapproblemen wellicht in een te koud slaapomgeving proberen te slapen.

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'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.

Operations in Iraq, Afghanistan and Bosnia reveal that soldiers are exposed to extreme, complex and sustained operations, crossing the limits of human capabilities. During these operations the operational readiness or status of the soldier is estimated by the commander based on subjective observations of the physical and mental capabilities of the soldier. This commander evaluation can be biased by personal experiences and commanders own physical and mental status.

Peripheral cold injuries are often reported in mountaineers. Not only low ambient temperatures, but also the hypobaric circumstances are known to be major environmental risk factors. When the fingers are exposed to extreme cold for several minutes, cold induced vasodilation (CIVD) occurs, that is reported to have protective properties for cold injuries. Repeated immersion in cold water may lead to improved finger blood flow. In the latter study, the subjects immersed their phalanxes in ice water four times daily for one month. In this study we investigated if two weeks of repeated immersions of the hand in cold water prior to a mountain expedition to the Ama Dablam in Nepal enhanced finger blood flow response to cold.

Subtiele manipulatie van de huidtemperatuur heeft een groot effect op slaap van ouderen; met milde huidverwarming neemt de kans dat een oudere om 6.00 uur 's ochtends wakker neemt af van 58 procent tot 4 procent en verdubbelt de hoeveelheid diepe slaap gedurende de nacht.

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. Keywords: Sleep electroencephalogram; Core body temperature; Skin temperature; Thermoregulation; Sleep-onset latency; Ageing; Insomnia; Foot warming

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°C water and exposed the fingers and toes to -18°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°C) than in the toes (onset time 10.6 ± 6.0 min; amplitude 3.0 ± 1.0°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°C and 20.9 ± 6.8°C, respectively, for air and 9.3 ± 1.9°C and 7.1 ± 1.3°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.

De verstoorde nachtelijke slaap van narcolepsie kan in een experimentele setting met behulp van milde huidverwarming sterk verbeterd worden.

Lichaamtemperatuurveranderingen hebben een effect op de alertheid en slaperigheid van narcolepsiepatienten: Een lichte verhoging van de kerntemperatuur verbeterd de alertheid, terwijl een lichte afkoeling van de handen en voeten hen in staat stelt langer wakker te blijven.

The deployment of military operational personnel to hot environments has increased markedly since 1990. Several countries dispatch military personnel In-Theatre (e.g. Iraq and Afghanistan) in order to help the local population or to ensure a safe environment. In these hot climates it is hard for military personnel coming from colder environments to adapt immediately to the new environmental situation. Furthermore, military personnel have to be alert for seven days a week and 24 hours a day. Military personnel work and perform better when they are well rested1. High ambient temperatures during the night may have an influence on sleep and consequently may lead to sleep deprived military personnel. We tested whether a cooler night ambient temperature would be beneficial for the sleep of acclimated subjects as compared to a high ambient night temperature. All measurements performed in this study were specifically chosen to be also applicable for field studies in the military environment and the sleeping conditions was made comparable to the field situation by using field bed, sleeping bags and multiple sleepers in one room.

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. Keywords: Thermoregulation; Thermoreception; Vasomotor control; Aging; Alzheimer’s disease; Circadian rhythm; Sleep; Immune function