Time course of neurobehavioral alertness during extended wakefulness in morning- and evening-type healthy sleepers.
Chronobiology International. 2011-07-01; 28(6): 520-527
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1. Chronobiol Int. 2011 Jul;28(6):520-7. doi: 10.3109/07420528.2011.590623.
Time course of neurobehavioral alertness during extended wakefulness in morning-
and evening-type healthy sleepers.
Taillard J(1), Philip P, Claustrat B, Capelli A, Coste O, Chaumet G, Sagaspe P.
(1)Sommeil, Attention et Neuropsychiatrie, Université de Bordeaux, Bordeaux,
The aim of the study was to evaluate the influence of chronotype (morning-type
versus evening-type) living in a fixed sleep-wake schedule different from one’s
preferred sleep schedules on the time course of neurobehavioral performance
during controlled extended wakefulness. The authors studied 9 morning-type and 9
evening-type healthy male subjects (21.4 ± 1.9 yrs). Before the experiment, all
participants underwent a fixed sleep-wake schedule mimicking a regular working
day (bedtime: 23:30 h; wake time: 07:30 h). Then, following two nights in the
laboratory, both chronotypes underwent a 36-h constant routine, performing a
cognitive test of sustained attention every hour. Core body temperature, salivary
melatonin secretion, objective alertness (maintenance of wakefulness test), and
subjective sleepiness (visual analog scale) were also assessed. Evening-types
expressed a higher level of subjective sleepiness than morning types, whereas
their objective levels of alertness were not different. Cognitive performance in
the lapse domain remained stable during the normal waking day and then declined
during the biological night, with a similar time course for both chronotypes.
Evening types maintained optimal alertness (i.e., 10% fastest reaction time)
throughout the night, whereas morning types did not. For both chronotypes, the
circadian performance profile was correlated with the circadian subjective
somnolence profile and was slightly phase-delayed with melatonin secretion.
Circadian performance was less correlated with circadian core body temperature.
Lapse domain was phase-delayed with body temperature (2-4 h), whereas optimal
alertness was slightly phase-delayed with body temperature (1 h). These results
indicate evening types living in a fixed sleep-wake schedule mimicking a regular
working day (different from their preferred sleep schedules) express higher
subjective sleepiness but can maintain the same level of objective alertness
during a normal waking day as morning types. Furthermore, evening types were
found to maintain optimal alertness throughout their nighttime, whereas morning
types could not. The authors suggest that evening-type subjects have a higher
voluntary engagement of wake-maintenance mechanisms during extended wakefulness
due to adaptation of their sleep-wake schedule to social constraints.
PMID: 21797780 [Indexed for MEDLINE]