Effects of artificial dawn on sleep inertia, skin temperature, and the awakening cortisol response

Abstract

SUMMAR Y The effect of artificial dawn during the last 30 min of sleep on subsequent dissipation of sleep inertia was investigated, including possible involvement of cortisol and thermoregulatory processes. Sixteen healthy subjects who reported difficulty with waking up participated in random order in a control and an artificial dawn night. Sleep inertia severity was measured by subjective ratings of sleepiness and activation, and by performance on an addition and a reaction time task measured at 1, 15, 30, 45, 60, and 90 min after waking up at habitual wake up time at workdays. At all intervals, saliva samples were collected for cortisol analysis. Sleep electroencephalogram was recorded during the 30 min prior to waking up; core body temperature and skin temperatures were recorded continuously until 90 min after waking up. Subjective sleepiness was significantly decreased and subjective activation increased after waking up in the artificial dawn condition as compared with control, in which lights were turned on at waking up. These effects can be explained by effects of artificial dawn on skin temperature and amount of wakefulness during the 30 min prior to the alarm. Artificial dawn accelerated the decline in skin temperature and in the distal-to-proximal skin temperature gradient after getting up. No significant effects of artificial dawn on performance, core body temperature, and cortisol were found. These results suggest that the physiology underlying the positive effects of artificial dawn on the dissipation of sleep inertia involves light sleep and an accelerated skin temperature decline after awakening.

Dawn simulation light impacts on different cognitive domains under sleep restriction

“…One possibility is that, contrary to our design, these studies challenged sustained attention performance either during light exposure and did not specifically explore carry-over effects or after a prolonged daytime light exposure. However they are comparable to the findings from Van de Werken [44], showing that the reaction times under DsL were similar to the one under control condition. One could argue that the PVT needs a higher and, more probably, a sustained level of arousal than the SART test -which is not reached here -to get to optimal performance levels, since this task is much more monotonous with much fewer stimuli (e.g., [45]).…”

Effects of Artificial Dawn on Subjective Ratings of Sleep Inertia and Dim Light Melatonin Onset

“…In a laboratory study by our group using the same device during 1 day, similar improvements of sleepiness, but no clear effects on a simple reaction time or addition task, were found (Van de Werken et al, 2010). In future field studies, it would be interesting to test whether other measures of sleep inertia, for instance more complex reaction-time performance, grip strength, or cognitive functioning, are improved with the long-term use of the artificial dawn.…”

Sleep and school education

“…A seemingly minor modification has to do with the time of class onset. Adolescents, whose circadian rhythms are better adapted to afternoons [1,49], are handicapped for morning learning [29,101], in part due to sleep inertia [24,84] and to the substantial modifications in sleep patterns and hormonal regulation experienced by teenagers [28]. Phase delays in the circadian timing of sleep during adolescence can favor the accumulation of persisting sleep deficits if school starts too early.…”