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Phase of entrainment and difficulties initiating sleep in relation to thermoregulation

English title Phase of entrainment and difficulties initiating sleep in relation to thermoregulation
Applicant Kräuchi Kurt
Number 116504
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 Endocrinology
Start/End 01.05.2007 - 31.10.2010
Approved amount 331'470.00
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All Disciplines (2)

Neurophysiology and Brain Research

Keywords (7)

thermoregulation; circadian rhythm; sleep-wake cyycle; difficulties initiating sleep; cold extremities; phase of entrainment; heat as zeitgeber

Lay Summary (English)

Lay summary
In study 1 (Phase delay of the sleep-wake cycle) & study 2 (circadian phase advance by morning light administration) phase of entrainment between sleep-wake cycle and circadian was changed. Both interventions (10 subjects/group having both difficulties initiating sleep and cold extremities) should have lead to increased phase angle between dim light melatonin onset time (DLMO) and time of lights off, and hence causing increased distal vasodilatation before bedtime to and decreased sleep onset latency (SOL). In study 3 heat application on the lower legs and feet should also lead to reduced SOL without changing phase of entrainment. In study 4 (Phase shifting effect of evening warm bathing) circadian phase shifting capacity of body heat loading was studied. Under unmasking CR- lab- condition study 1 & 2 revealed phase advanced DLMO, but SOL was reduced only in study 1 and not 2. However, distal vasodilatation before lights off was increased in parallel to reduced SOL, indicating that under unmasking condition distal vasodilatation before lights off goes hand in hand with a rapid onset of sleep.In all 3 ambulatory studies DLMO remained entrained to the 24h- solar cycle, leading to the expected phase advance of the circadian melatonin system in relation to the sleep-wake cycle in study 1. However, the diurnal rhythm of distal vasodilatation remained entrained to the sleep-wake cycle, underlining their close coupling. In contrast, SOL was shortened in study 1 & 3. In study 1 & 2 subjective ratings of morning alertness were increased after interventions in both ambulatory and lab -conditions. Intervention in study 3 led to less concentrativeness before lights off and to shorter SOL without changing DLMO. Thus, both phase of entrainment between circadian and sleep-wake cycle or the level of distal vasodilatation before lights off can be uncoupled by interventions under ambulatory condition, but both are capable to affect SOL independently.Sleep analyses in the study 1 & 2 revealed that interventions induced an earlier accumulation of REM sleep, whereas sleep pressure, expressed by accumulated EEG power density, did not differ. This finding is in accord with the notion that occurrence of REM sleep is mainly determined by the circadian system. In study 4 we were able to show a significant circadian zeitgeber effect of an evening heat pulse in healthy young men as indicated by phase advance of melatonin secretion, heart rate and core body temperature rhythms by ca. 2hours. Our findings give new insight into phase of entrainment between diverse physiological systems and its relevance for sleep onset disturbances.
Direct link to Lay Summary Last update: 21.02.2013

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Associated projects

Number Title Start Funding scheme
102182 Thermophysiological approaches to the clinical problem of difficulties initiating sleep 01.02.2004 Project funding (Div. I-III)