Abstract
BackgroundWe investigated circadian changes and effects on mood, sleep-related hormones and cognitive performance when nurses worked consecutive night shifts in a rapidly rotating shift system. Daytime cognitive function, sleep propensity and sleep-related hormones (growth hormone, cortisol, prolactin, thyrotropin) were compared after participants worked two and four consecutive night shifts.MethodsTwenty-three off-duty nurses, 20 nurses working two consecutive night shifts and 16 nurses working four consecutive night shifts were enrolled. All participants completed the Maintenance of Wakefulness Test, State-Trait Anxiety Inventory, Stanford Sleepiness Scale, visual attention tasks (VAT), Wisconsin Card Sorting Test, and modified Multiple Sleep Latency Test. Hormone levels were also measured four times throughout the day, at 2-h intervals.ResultsDuring the day, the participants in the night shift groups were less able to maintain wakefulness, had poor performance on VAT, and higher thyrotropin levels than did those in the off-duty group. Participants who worked two night shifts were better able to maintain wakefulness, had higher anxiety scale scores, poorer initial performance and lack of learning effect on VAT, and higher prolactin levels compared with those who worked four night shifts. There were no differences in cortisol levels between the two- and four- shift groups.ConclusionsRotating night shifts too quickly may cause anxiety and decreased attentional performance, and may impact daytime prolactin levels after night shifts. It is possible that the two-shift group had a higher cortisol level than did the four-shift group, which would be consistent with the group’s higher state anxiety scores. The negative findings may be due to the small sample size. Further studies on the effects of consecutive night shifts on mood and cortisol levels during the daytime after sleep restriction would be valuable.
Highlights
We investigated circadian changes and effects on mood, sleep-related hormones and cognitive performance when nurses worked consecutive night shifts in a rapidly rotating shift system
There were no differences in age (F(2, 56) = 1.77, p = 0.179), years of education (F(2, 56) = 2.58, p = 0.085), trait anxiety scores (43.9 ± 8.1 vs. 43.0 ± 7.6 vs. 43.8 ± 8.0; F(2, 56) = 0.08, p = 0.927), mean Total sleep time (TST) (6.9 ± 1.1 h vs. 6.7 ± 1.0 h vs. 6. 8 ± 1.2 h; F(2, 56) = 0.18, p = 0.833), mean sleep latency (MSL) of the Multiple sleep latency test (MSLT) (p = 0.314), Sleepiness Scale (SSS) scores (p = 0.451), Growth hormone (GH) (p = 0.697) or cortisol (p = 0.884) levels among the three groups (Tables 1, 2 and 3)
Significant differences did emerge in the MSL of the Maintenance of Wakefulness Test (MWT) (p < 0.001), in state anxiety levels (p = 0.009), information processing index (IPI) scores (p = 0.002), Digit Symbol Substitution Test (DSST) scores (p = 0.013), Search Test (SST) scores (p = 0.003) and levels of PRL (p = 0.003) and TSH (p = 0.003) (Tables 1, 2 and 3)
Summary
We investigated circadian changes and effects on mood, sleep-related hormones and cognitive performance when nurses worked consecutive night shifts in a rapidly rotating shift system. Sleep propensity and sleep-related hormones (growth hormone, cortisol, prolactin, thyrotropin) were compared after participants worked two and four consecutive night shifts. Sleep deprivation research [2] has shown diverse impacts on mood and cognitive performance, and many studies [3,4,5,6] have investigated the influence of night shifts on the performance of work at night. Little is known about the impact on sleep-related hormones during the daytime after working different lengths of consecutive night shifts. Research on rapidly rotating night shift systems can provide valuable information regarding circadian changes and effects on mood and cognitive performance
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