Study shows how shift workers can improve job performance and implement a realistic slee...( Westchester Ill. A study in the Dec...),Health

Westchester, Ill. A study in the Dec. 1 issue of the journal Sleep shows that the use of light exposure therapy, dark sunglasses and a strict sleep schedule can help night-shift workers create a "compromise circadian phase position," which may result in increased performance and alertness during night shifts while still allowing adequate nighttime sleep on days off.

Results show that performance was better for the experimental subjects than the controls. When the phase delays of the experimental group had likely reached the compromise circadian position, performance for this group was close to the level during day shifts, demonstrating fast reaction times with low variability and few or no lapses. In contrast, the control group continued to show longer and more variable reaction times on all night shifts.

"The major finding of this study was that complete physiological adaptation to a night shift and day sleep schedule does not appear necessary in order to improve night shift alertness and lengthen daytime sleep," said lead author Mark Smith, post-doctoral fellow in the Biological Rhythms Research Laboratory at Rush University Medical Center in Chicago. "Instead, we found that partial physiological adaptation using scheduled exposure to light and darkness is sufficient to bring night shift performance back to daytime levels. "

This study, which was number three in a series of five conducted between May and October 2007, was to establish a compromise phase position for permanent night shift work, in which the circadian clock is delayed to only partially align with the day sleep period. This partial entrainment could reduce the performance and alertness decrements during night shifts and allow a sleep schedule that is compatible with both night shifts and days off.

"Despite the effectiveness of complete adjustment to a night shift schedule for improving nighttime alertness and lengthening daytime sleep, we think th
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