The influence of split sleep-wake schedules and daytime sleep strategies on neurobehavioural performance

Demand for 24-h access to services and goods has led to an increase in the number of employees engaged in shiftwork. However, while shiftwork has become necessary to meet community expectations, it has serious consequences for health and safety. The risk of fatigue-related accidents and injuries is a significant problem for the shift working population. This is because shiftwork places restrictions on the opportunities available for workers to obtain sleep. Shiftworkers, especially those who work night shifts, must often stay awake for long hours and sleep at times inconsistent with their body clocks, so sleep loss is common. This dissertation evaluates alternative options for arranging sleep that could potentially optimise neurobehavioural function in circumstances where long nocturnal sleep episodes are not possible. Two main approaches were used to address these aims. The first was to assess the effectiveness of split sleep-wake schedules at sustaining neurobehavioural function around the clock – with and without sleep restriction – which could have implications for work rosters in certain safety-critical industries. The second approach was to assess the effectiveness of different arrangements of daytime sleep at ameliorating the decline of night-time performance, which could have implications for the sleep strategies shiftworkers employ before and after night shifts.