Comparison of sleep and attention metrics among nurses working shifts on a forward- vs backward-rotating schedule

IMPORTANCE The association of fast backward-rotating shift work (ie, anticlockwise sequence ofafternoon, morning, and night shifts) with subjective and objective measures of sleep-wake quality,daytime attention, and tiredness of health care workers has not yet been established.OBJECTIVE To investigate the association of shift rotation direction with tiredness, sleepiness, andsustained attention among nurses working forward- and backward-rotating shifts.DESIGN, SETTING, AND PARTICIPANTS Data of this cohort study were collected from nursesworking at 5 midsized Italian hospitals. The nurses had either a forward-rotating schedule (ie,morning to afternoon to night) and or a backward-rotating schedule (ie, afternoon to morning tonight). The data were collected from July 2017 to February 2020. Data analysis was performed fromMay to October 2020.EXPOSURES Participants were working either forward- or backward-rotating schedules, in whichthe sequence of 3 shifts (morning, afternoon, and night) changed in a clockwise or anticlockwisedirection.MAIN OUTCOMES AND MEASURES Sleep data were collected using the Karolinska SleepinessScale and Pittsburgh Sleep Quality Index. Sustained attention was measured using the PsychomotorVigilance Task. Tiredness was evaluated using the Tiredness Symptom Scale.RESULTS A total of 144 nurses (mean [SE] age, 41.3 [0.8] years; 92 women [63.9%]) participated inthe study; 80 nurses had forward-rotating schedules, and 64 had backward-rotating schedules.Nurses with irregular sleep-wake patterns due to night shift work had poor sleep quality (46 [57.5%]in forward-rotating schedule group; 37 [57.8%] in backward-rotating schedule group). Nursesworking backward-rotating shifts exhibited significantly greater sleepiness (F1,139 = 41.23; P < .001)and cognitive slowing (ie, longer median reaction times; F1,139 = 42.12; P < .001) than those workingforward rotations. Importantly, these differences were not affected by age, years of employment,and quality of sleep. Of nurses working on a backward-rotating schedule, 60 (93.8%) reportedelevated sleepiness (Karolinska Sleepiness Scale score7) after the night shift. The median reactiontime (F1,139 = 42.12; P < .001), 10% fastest reaction time (F1,139 = 97.07; P < .001), minor lapses(F1,139 = 46.29; P < .001), and reaction time distribution (F1,139 = 60.13; P < .001) of nurses onbackward-rotating schedules indicated a lower level of vigilance, which is negatively associated withneurobehavioral performance.CONCLUSIONS AND RELEVANCE In this study, both shift rotation models were negativelyassociated with health and cognitive performance. These findings suggest that forward shift rotationmay be more beneficial than backward rotation for several measured performance attentional