Morning work: effects of early rising on sleep and alertness.

The aim of the present study is to investigate how early morning work affects sleep and alertness. Twenty-two females, employed as airline cabin crew members, participated in the study. The design included two sleep conditions (work day and free day) for an early group and for a control group. The results show that early morning work reduced sleep to 5 hours and 12 minutes and that the reduction of sleep consisted of less stage 2 and rapid eye movement (REM) sleep. However, when the analysis was restricted to the first 5 hours, no differences in sleep stages, arousals, or sleep continuity were obtained between groups or conditions. Analysis of electroencephalogram (EEG) power density for the 0.5-16.5 Hz bands across nonREM periods showed no differences. With respect to the subjective ratings, early morning work was associated with more apprehension of difficulties in awakening and insufficient sleep. Daytime alertness and ease of awakening did not differ between groups, but the early group had significantly more sleepiness and complained more of unrefreshing sleep in connection with the work day compared to the free day. Ratings of insufficient sleep and high daytime sleepiness were mainly predicted (multiple regression analyses) by short total sleep time (TST), whereas apprehension of an unpleasant awakening was predicted by an early wake-up time. It was concluded that early morning work causes a reduction of sleep time and an increase in apprehension stress.