Human Systems Integration Division @ NASA Ames

Introduction: It is established that shiftwork causes sleep loss and circadian misalignment. Individuals who work non-traditional day shifts that encroach into typical sleep times, such as those in the service and transportation sectors, may also experience sleep and circadian disruption. We aimed to determine how neurobehavioral performance and sleep would be affected by work start time among individuals working a non-traditional daytime shift pattern.

Methods: We collected sleep diaries, wrist-worn actigraphy (CamNtech, Cambridge UK), and the psycho- motor vigilance task (PVT) from 44 pilots (4F) who worked a shift rotation consisting of a five-day baseline block starting in the mid-morning (baseline), five early shifts (early), five high workload midday shifts (midday), and five days of late shifts (late), each separated by 3-4 days off.
Results: Mixed-model analysis revealed that individuals obtained less sleep when working the early shifts (5.70 ± 0.73 h) relative to baseline (6.78 ± 0.86 h; P b .01). Sleep duration declined significantly from the beginning to the end of late shifts (P = .003). All shifts were associated with decreased reaction time on the PVT relative to baseline (236 ± 48; early, 257 ± 70 ms; midday 261 ± 62 ms; late 266 ± 64 ms; P b .01 for all).

Conclusions: We found that non-traditional day shifts encroach on an individual's sleep opportunity and such shifts could be a contributing factor to the high prevalence of sleep deficiency observed in modern society. Our findings suggest that it would be prudent for industries requiring such shifts to expand fatigue risk management training to individuals classified as day shift workers.