Changes in sleepiness and body temperature precede nocturnal sleep onset: Evidence from a polysomnographic study in young men

Abstract

Recent research has shown a close temporal relationship between the nocturnal decrease in rectal core temperature and the initiation of sleep. However, there is not yet a clear temporal relationship between changes in peripheral and core temperatures and nocturnal sleep onset. We recorded body temperatures in 14 adult males (age±SEM=22.1±0.6 y), who attended the sleep laboratory for an adaptation night and two counterbalanced experimental sessions. Subjects self‐selected lights‐out on one experimental night (the Habitual Sleep condition). To determine the relationship between body temperature changes and sleep onset, lights out was delayed until after 01.00 hours on the other experimental night (Delayed Sleep condition). Individual datasets in both conditions were expressed relative to the time of sleep onset in the Habitual Sleep condition only, so that they were aligned at identical clock times. Saliva samples confirmed that mean dim light melatonin onset (DLMO) occurred at 00.10±00.16 hours in the Delayed Sleep condition, which was after habitual sleep onset at 23.44±00.08 hours. Rectal core temperature (Tc) decreased significantly over time only in the Habitual Sleep condition ( P < 0.01). For the 20 min before habitual sleep onset, Delayed Sleep Tc was on average 0.1°C higher than Tc in the Habitual Sleep condition ( P < 0.01). The greater decline in Habitual Sleep Tc was associated with significantly increased peripheral hand and foot skin temperatures before sleep (both P < 0.05). Subjective sleepiness measures were higher in the Habitual Sleep onset condition from 150 min prior until sleep onset ( P < 0.01). From these results it is reasonable to infer that a sequence of thermoregulatory and sleep propensity changes occur before, but are associated with habitual sleep onset, as the changes are significantly attenuated if sleep is delayed.

Vigilance, alertness, or sustained attention: physiological basis and measurement

“…The rhythmic deeper respiration during the sleep onset period produces the expected increase in heart rate variability measures secondary to sinus arrhythmia. There is also a decline in core body temperature associated with an increase in peripheral temperature prior to sleep onset (Van Den Heuvel et al, 1998).…”

The influence of pre-sleep cognitive arousal on sleep onset processes

“…They all focus on short-term memory and working memory. Although insomnia patients tend to blame their sleep problems more on intrusive cognitivearousing thoughts than on physical arousal (Lichstein and Rosenthal, 1980), the disturbing role of changes in processes controlled by the autonomous nervous system -such as heart rate (Hall et al, 2004) and body temperature (Morris et al, 1990;van den Heuvel et al, 1998) -must be taken into account.…”

“…It is a progressive process of decline in control over mental activity and gradual changes in perceived state of consciousness (Freedman and Sattler, 1982), accompanied by gradual decrease in arousal (De Gennaro et al, 2001;Espie, 2002). This decrease is evidenced by a depression in cortical activity (Davis et al, 1938), a slowing of the heart rate (Burgess et al, 1999;Jurysta et al, 2003;Okamoto-Mizuno et al, 2008), a decline in core body temperature (Kräuchi et al, 2000;Kräuchi and Wirz-Justice, 2001;OkamotoMizuno et al, 2008;van den Heuvel et al, 1998), an increase in distal and proximal skin temperature (Kräuchi et al, 1999(Kräuchi et al, , 2000 and many more behavioural, cortical and physiological changes (Ogilvie, 2001). However, these are processes observed during sleep onset in healthy sleepers (Monroe, 1967).…”

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

“…There is growing evidence that the sleep-producing action in humans is commonly preceded by an increase in heat loss (Campbell and Broughton, 1994;Gilbert et al, 1999;Krauchi et al, 1999;Murphy and Campbell, 1997;Van den Heuvel et al, 1998). It is well established that human proximal BT declines during the night time under physiological conditions, and this is not the result of the sleep itself; it is controlled by the circadian time-keeping system (Campbell and Broughton, 1994;Gillberg and Akerstedt, 1982;Lack and Lushington, 1996;Zulley et al, 1981).…”