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. 2013 Jan;44(1):109-11.
doi: 10.1016/j.apergo.2012.05.007. Epub 2012 Jun 12.

Can Small Shifts in Circadian Phase Affect Performance?

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Free PMC article

Can Small Shifts in Circadian Phase Affect Performance?

Helen J Burgess et al. Appl Ergon. .
Free PMC article

Abstract

Small shifts in circadian timing occur frequently as a result of daylight saving time or later weekend sleep. These subtle shifts in circadian phase have been shown to influence subjective sleepiness, but it remains unclear if they can significantly affect performance. In a retrospective analysis we examined performance on the Psychomotor Vigilance Test before bedtime and after wake time in 11 healthy adults on fixed sleep schedules based on their habitual sleep times. The dim light melatonin onset, a marker of circadian timing, was measured on two occasions. An average 1.1 h shift away from a proposed optimal circadian phase angle (6 h between melatonin onset and midpoint of sleep) significantly slowed mean, median and fastest 10% reaction times before bedtime and after wake time (p < 0.05). These results add to previous reports that suggest that humans may be sensitive to commonly occurring small shifts in circadian timing.

Figures

Figure 1
Figure 1
The individual circadian phase angles (melatonin onset to midpoint of sleep) in the sample. Two phase angles were calculated for each subject, represented by two dots connected by a horizontal line.
Figure 2
Figure 2
The individual changes in the fastest 10% reaction time from closer to a phase angle of 6 hours to further from a phase angle of 6 hours, before bed (left) and after wake (right). Each line connecting two dots represents the change in optimum 10% fastest reaction time per individual.

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