The impact of short, irregular sleep opportunities at sea on the alertness of marine pilots working extended hours.

The aim of this study was to examine the impact of brief, unscheduled naps during work periods on alertness and vigilance in coastal pilots along the Great Barrier Reef. On certain routes, the duration of the work period can extend well beyond 24 h. Seventeen coastal pilots volunteered for the study, representing almost one-third of the population. Participants collected sleep/wake and performance data for 28 days using a sleep and work diary and the palm PVT task. The average length of sleep on board was 1.4+/-1.0 h. Naps were taken regularly such that the average length of time awake between sleep periods on board a ship was 5.3+/-4.3 h. There was no change in mean reaction time across either the length of a pilotage or across the 24 h day. The results indicate that even though the naps were taken opportunistically, they tended to cluster at the high sleep propensity times. Further, frequent, opportunistic naps appeared to provide adequate recovery such that PVT performance remained stable. Pilots did report increases in subjective fatigue ratings at certain times of the 24 h day and at the end of a work period; however, these did not reach the high range. The fatigue-risk minimization strategies employed by the Australian Maritime Safety Authority and the coastal pilots appear to be effective in maintaining alertness and vigilance while at work aboard ships.