The Effect of Afternoon Body Heating on Body Temperature and Slow Wave Sleep

Abstract

Recent evidence suggests that body temperature at sleep onset affects the subsequent level of slow wave sleep. According to one hypothesis, the actual temperature is the critical factor determining the relationship. An alternative proposal is that it is the rate of fall of body temperature following sleep onset. These hypotheses were tested by measuring rectal temperature and sleep, following late afternoon passive heating in a warm bath and during a control condition. Passive heating increased rectal temperature, which then returned rapidly toward the control level. However, immediately before lights out rectal temperature was still higher in the passive heating condition, a difference that continued throughout the night. Following passive heating the amount of slow wave sleep was higher in the early part of the night. These results support the hypothesis that body temperature at sleep onset and the amount of slow wave sleep are positively related.

Effects of a Nocturnal Environment Perceived as Warm on Subsequent Daytime Sleep in Humans

“…When individuals were passively warmed before nighttime sleep, SWS increased, either over the entire night or over its first part only. 8,9,23,29,30,32,47 The difference in SWS changes observed between daytime and nighttime sleep may be due to their circadian placements, which discourage its occurrence in the former condition. The propensity of REMS to occur is high at the end of the night and in the early hours of the day.…”

“…In the case of nocturnal sleep, it was reported that REMS proportions remained unaltered by a previous passive warming. 8,9,23,29,47,32 The invariance of REMS could be related to the fact that the short-term thermal loads used induced only transient hyperthermia whose effects never reached the end of the night (the time zone favorable for REMS occurrence). Hence, it could be interesting to see whether or not human nocturnal REMS could not be altered (nay enhanced) by a diurnal thermal stress prolonging its influence until the end of the night.…”

“…INDIVIDUALS EXPOSED TO A THERMAL LOAD BEFORE 8,9,23,29,30,32,47 OR DURING 6,13,25,33,35,38,39,46 BED-TIME present alterations in their nocturnal sleep. Several adverse effects, which are known to reduce the subsequent vigilance level, have been determined, such as partial sleep deprivation and/or sleep fragmentation.…”

Heat Loss, Sleepiness, and Impaired Performance after Diazepam Administration in Humans

“…Sleep challenge tests under isolated as well as entrained conditions reveal that the occurrence and continuity of human sleep is intimately related to the circadian proximal BT rhythms (Czeisler et al, 1980;Lavie, 1986;Zulley et al, 1981), sleep propensity increases on the falling limb, and decreases on the rising limb of the proximal BT curve. In addition, many previous studies have consistently shown that various drug-based, light exposurebased, or passive body heating-based techniques produce sleep work via thermoregulatory actions (Bunnell et al, 1988;Deacon et al, 1994;Dorsey et al, 1999;Gilbert et al, 1999;Jordan et al, 1990;Krauchi et al, 1999). They have also shown an intimate temporal relation between increasing sleepiness and the degree of heat loss induced by thermoregulatory manipulations (Gilbert et al, 1999;Krauchi et al, 1999).…”

Human slow‐wave sleep and the cerebral cortex

“…The latter incorporates an energy conservation role for hSWS, where it is proposed that hSWS actively increases heat loss to reduce body temperature-the higher this temperature at sleep onset, the more the subsequent hSWS to bring the temperature down. Both hypotheses argue that hSWS is the slave of thermoregulation; however, experimental support for both of them is equivocal (Jordan et al 1990).…”