A Compromise Circadian Phase Position for Permanent Night Work Improves Mood, Fatigue, and Performance

Nov 26, 2009Sleep

Adjusting body clock timing for permanent night work may improve mood, tiredness, and performance

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Abstract

After one week of intervention, 27 out of 39 subjects showed improved mood, fatigue, and performance on night shifts.

Subjects were categorized into three groups based on the degree of circadian realignment: not re-entrained, partially re-entrained, and completely re-entrained.
The partially and completely re-entrained groups exhibited significantly improved mood, reduced fatigue, and enhanced performance compared to those not re-entrained.
The performance levels of the re-entrained groups approached those typical of daytime functioning.
Interventions included bright light exposure, dark sunglasses, and scheduled sleep in darkness, which contributed to partial re-entrainment.

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STUDY OBJECTIVE: To assess night shift improvements in mood, fatigue, and performance when the misalignment between circadian rhythms and a night shift, day sleep schedule is reduced.

DESIGN: Blocks of simulated night shifts alternated with days off. Experimental subjects had interventions to delay their circadian clocks to partially align with a night shift schedule. Control subjects had no interventions. Subjects were categorized according to the degree of circadian realignment independent of whether they were in the experimental or control groups. Twelve subjects were categorized as not re-entrained, 21 as partially re-entrained, and 6 as completely re-entrained.

SETTING: Home sleep and laboratory night shifts.

PARTICIPANTS: Young healthy adults.

INTERVENTIONS: Experimental subjects had intermittent bright light pulses during night shifts, wore dark sunglasses outside, and had scheduled sleep episodes in darkness.

MEASUREMENTS AND RESULTS: A computerized test battery was administered every 2 hours during day and night shifts. After about one week on the night shift schedule, which included a weekend off, the partially and completely re-entrained groups had markedly improved mood, fatigue, and performance compared to the group that was not re-entrained. The completely and partially re-entrained groups were similar to each other and had levels of mood, fatigue, and performance that were close to daytime levels.

CONCLUSIONS: Partial re-entrainment to a permanent night shift schedule, which can be produced by feasible, inexpensive interventions, is associated with greatly reduced impairments during night shifts.

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A Compromise Circadian Phase Position for Permanent Night Work Improves Mood, Fatigue, and Performance

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