Four Night Shifts Have a Degree of Performance Adaptation

Objective: In this case control study, we investigated the process of adaptation to night shift (NS) work and recovery back to a day schedule among nurses working a fast-rotation three-shift schedule. Background: There is limited knowledge of how specific patterns of a fast-rotation shift affect nurses’ performance. Method: The cognitive performance of off-duty nurses (OD; n = 21), those working the first night of an NS (1NS; n = 21) and the last night of two (n = 21), three (n = 20), and four (4NS; n = 21) successive NSs were compared. Changes in sleep propensity, cognitive function, and anxiety were compared in the daytime after working four successive NSs followed by 24 hr off (4NS-off; n = 18) and in those off duty. Results: The visual attention task (VAT) of cognitive function was significantly worse in the 1NS group and significantly better on the last night in the 4NS group than in the other NS groups. The nurses in the 4NS-off group were less alert and had poorer VAT performance than the OD group during the daytime. Conclusion: The nurses working on NS experienced a decrease in VAT performance due to acute changes in circadian rhythm but also significant performance adaptation after four consecutive NSs. One off-duty day was insufficient to recover back to a daytime shift after four consecutive NSs. Application: In a fast-rotation three-shift schedule, performance adaptation occurred in the nurses who worked four consecutive NSs, and more than one off-duty day are needed to recover back to daytime shift after those NSs.