Programme Contents

Impact of shift work on sleep, alertness and cognitive function– can “splitting” sleep reduce the adverse effects of night shift work?

There are currently 1.5 million shift workers in Australia, representing 16% of the workforce (Rajaratnam et al., 2013). Shift work is associated with greater levels of obesity, cardiovascular disease, type 2 diabetes and depression, and an increased risk of errors and accidents (Barger et al., 2009). A major factor contributing to these adverse health and safety effects is circadian misalignment and insufficient sleep. Night shift workers typically only obtain around 5 hours of daytime sleep before their sleep is truncated by the combination of declining homeostatic drive for sleep and increasing circadian drive for wakefulness in the early afternoon (Goel et al., 2011). The term ‘‘split sleep’’ means two or more sleep opportunities in a 24-h period, ranging from a main sleep and a supplemental nap (e.g. 6 and 2 h), through to a main sleep and several naps, to multiple naps with no clear main sleep. Spilt sleep schedules are common practice in a number of industries including healthcare, maritime and transport. There is evidence that split sleep may restore alertness and performance as effectively as consolidated sleep (Jackson et al., 2014), and that the critical factor in sustaining performance is total sleep time in 24h. In a laboratory study comparing simulated day, night and split sleep conditions, Jackson et al., (2014) found that participants on the night and split sleep schedules obtained significantly more total sleep time and less sleepiness during work hours than the day sleep condition. There is currently limited evidence of the benefits of split sleep on health outcomes. The current data suggests that a split sleep schedule may be a useful alternative to a consolidated daytime sleep schedule in industries that allow for this flexibility (Short et al., 2015). Evidence of the effectiveness of a split sleep schedule will have particular relevance for occupational environments in determining the adequate duration and effective placement of the sleep opportunities to ensure optimal productivity, health and safety outcomes for shift workers.

Barger LK, Lockley SW, Rajaratnam SM, Landrigan CP. (2009). Neurobehavioral, health, and safety consequences associated with shift work in safety-sensitive professions. Curr Neurol Neurosci Rep 9, 155-164.

Goel N, Van Dongen HPA, Dinges DF. (2011). Circadian rhythms in sleepiness, alertness, and performance. In Kryger R, Dement W, eds. Principles and practice of sleep medicine. 5th ed. St. Louis, MO: Elsevier, pp. 445–55.

Jackson ML, Banks S, Belenky G. (2014). Investigation of the effectiveness of a split sleep schedule in sustaining sleep and maintaining performance. Chronobiol Intl 31(10), 1218-1230.

Rajaratnam SM, Howard ME, Grunstein R. (2013). Sleep loss and circadian disruption in shift work: health burden and management. Med J Aus 199(8), 11-15.

Short, M. A., Agostini, A., Lushington, K., & Dorrian, J. (2015). A systematic review of the sleep, sleepiness, and performance implications of limited wake shift work schedules. Scand J Work Environ Health 41(5), 425-440.