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Thermophysiological approaches to the clinical problem of difficulties initiating sleep

English title Thermophysiological approaches to the clinical problem of difficulties initiating sleep
Applicant Kräuchi Kurt
Number 102182
Funding scheme Project funding (Div. I-III)
Research institution Abteilung Chronobiologie Universitäre Psychiatrische Kliniken Basel
Institution of higher education University of Basel - BS
Main discipline Neurophysiology and Brain Research
Start/End 01.02.2004 - 31.07.2007
Approved amount 232'440.00
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Keywords (10)

vasospastic syndrome; sleep onset insomnia; cold hands and feet; chronobiology; thermoregulation; body temperatures; sleep -EEG; bathing; thermal load; phase of entrainment

Lay Summary (English)

Lay summary
BackgroundSleep habitually initiates on the declining portion of the circadian core body temperature rhythm when the rate of body heat dissipation is at its maximum. Warm hands and feet, which usually occur in the evening, promote both body heat loss and rapid sleep onset. Therefore, this thermophysiological phenomenon may have clinical relevance for insomnia, most importantly for difficulties initiating sleep (DIS). Subjects with vasospastic syndrome (VS) represent a part of the general population with a predisposition to develop cold hands and feet under normal life conditions, providing, thus, a comprehensive ‘model of nature’ to investigate the relationship between thermophysiology and DIS. AimsThe overall purpose of the project was to elucidate whether women with both VS and DIS (WVD) exhibit cold hands and feet prior the bedtime in comparison to controls (CON). Furthermore, it was tested, whether bathing at different temperatures could increase or decrease sleep onset latency (SOL) with a concomitant decrease or increase in skin temperature on hands and feet, respectively. MethodsUnder stringent controlled laboratory conditions (e.g. constant bed rest) 9 WVD were compared with 9 CON. First, the circadian system (thermophysiology, melatonin) of both subject groups were characterized together with night sleep- electroencephalogram (EEG), and second, sleep- EEG was recorded during a 2-h nap in the afternoon after cool (28°C), neutral (35°C) and warm (39°C) bathing for 30-min. ResultsIn comparison to CON, WVD exhibited a phase delay of the circadian thermophysiological system of ca. 1 hour, with no differences in sleep timing. In addition, we confirmed these results in an ambulatory study under real life conditions. This lead to the hypothesis that WVD are thermophysiologically unprepared for sleep at their habitual bedtimes, thus resulting in DIS.Analyses of night sleep-EEG recordings revealed differences both in SOL and in sleep architecture. WVD exhibited a longer SOL and less slow wave sleep (SWS, delta sleep activity) than in controls.Bathing at different temperatures altered thermophysiological state, SOL and sleep architecture of the subjects in the succeeding nap. In comparison to neutral bathing, body heat loss via hands and feet decreased after cool bathing and increased after warm bathing, respectively. The easiness to fall asleep and the sleep quality was enhanced after warm bathing and worse after cool bathing, which could be confirmed by objective sleep-EEG recordings. However, these temperature effects on SOL were less prominent in WVD than in CON. The differences between WVD and CON in slow wave sleep were strengthened by cool bathing and reduced by warm bathing.Value of the ProjectOur detailed analysis of the thermoregulatory effects on sleep initiation and the sleep-EEG provides insights to the theoretical underpinnings that account for WVD. Furthermore, it can expand the knowledge on the thermophysiological interventions for DIS, providing inexpensive and easily applicable therapies with the advantage of neither side effects nor potential for addiction of classical sleeping medications.
Direct link to Lay Summary Last update: 21.02.2013

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Associated projects

Number Title Start Funding scheme
116504 Phase of entrainment and difficulties initiating sleep in relation to thermoregulation 01.05.2007 Project funding (Div. I-III)