Objective In this preliminary study, using a within-subjects design, we investigated the effects of phase-advancing bedtime on sleep quality and duration among early-morning shift workers.

Methods The sleep–wake patterns of 16 healthy volunteers who work shifts with start times between 04.00–07.30 hours were recorded by wrist actigraphy and sleep diary for two weeks. In week 1, we assessed the habitual sleep–wake pattern. In week 2, participants were required to advance their bedtime to 10 hours before the start of the morning shift. Subjective sleepiness was assessed three times each day.

Results Total sleep time was longer (1.4 hours) for sleep episodes that occurred prior to days off from work compared to those prior to early-morning shifts. The intervention resulted in bedtime being advanced by 1.5 hours and total sleep time being increased by 1.0 hour, without changes to the latency, efficiency or quality of sleep, or activity level during the sleep episode. A small reduction in daytime sleepiness was found during the intervention phase for assessments taken just prior to bedtime.

Conclusions Sleep duration among early-morning shift workers is substantially truncated due to their work schedules. When participants were instructed to advance their bedtime for one week, these individuals were able to increase sleep duration without affecting sleep quality. We suggest longer term studies testing the efficacy of sleep extension as a low-cost, behavioral intervention for improving health and safety outcomes among early-morning shift workers.

Key terms actigraphy; circadian; extended sleep; phase advance; shift work; shift worker; sleep; wake maintenance zone