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Effects of dawn simulation on markers of sleep inertia and post-waking performance in humans



To examine the effects of a simulated dawn during the last 30 min of sleep on the subsequent dissipation of sleep inertia and changes in simulated work and physical performance.


Eight participants, who reported difficulty with morning waking, were administered in a random order to a control (C) and a dawn simulation (DS) trial (starting 30 min prior to waking). Subjective ratings of sleep quality and alertness were obtained alongside measures of cognitive performance (addition and reaction time tasks measured at 5, 30 and 75 min after waking at habitual workday times). Physical performance was also measured 35 min after waking using a self-paced cycling protocol.


After waking in DS, perceived sleep quality was 1.16 ± 0.89 (p = 0.01) points higher compared with C. Ratings of alertness were significantly higher in DS than C throughout the testing period (p = 0.04). Cognitive performance improved in both trials as time awake increased (p < 0.0005). On average, participants completed a greater number of additions in DS compared with C (69.5 ± 15.3 vs 66.9 ± 16.7, p = 0.03). Reaction times were also faster in DS compared with C (0.81 ± 0.07 s vs 0.86 ± 0.06 s, p < 0.0005). The self-paced time-trial was completed 21.4 s (4.7 %) quicker in DS (p = 0.07).


These data provide the first evidence that light exposure during the last 30 min of habitual sleep can increase subjective alertness and improve both cognitive and physical performance after waking.

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Fig. 1
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Fig. 5


95 % CI:

95 % Confidence interval


Control condition


Dawn simulation condition


Enzyme-linked immunosorbent assay


Karolinska sleepiness scale


Rating of perceived exertion




Standard deviation

T c :

Intestinal temperature


Visual analogue scale


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We are grateful to Lumie for providing financial support for this study. The authors have no financial interest associated with the outcome of this study and declare that they have no conflict of interest.

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Correspondence to Andrew Thompson.

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Communicated by Dick F. Stegeman.

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Thompson, A., Jones, H., Gregson, W. et al. Effects of dawn simulation on markers of sleep inertia and post-waking performance in humans. Eur J Appl Physiol 114, 1049–1056 (2014).

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  • Artificial dawn
  • Sleep inertia
  • Performance
  • Phototherapy