Elsevier

Applied Ergonomics

Volume 82, January 2020, 102942
Applied Ergonomics

The impact of anticipating a stressful task on sleep inertia when on-call

https://doi.org/10.1016/j.apergo.2019.102942Get rights and content

Highlights

  • On-call workers can experience sleep inertia even after a full night's sleep.

  • Anticipating a high-stress task does not negatively impact sleep inertia severity.

  • Sleepiness is higher on waking when on-call and anticipating a low-stress task.

  • Visual search performance is better on waking when on-call than when not on-call.

Abstract

Sleep inertia, the state of reduced alertness upon waking, can negatively impact on-call workers. Anticipation of a stressful task on sleep inertia, while on-call was investigated. Young, healthy males (n = 23) spent an adaptation, control and two counterbalanced on-call nights in the laboratory. When on-call, participants were told they would be woken to a high or low stress task. Participants were not woken during the night, instead were given a 2300-0700 sleep opportunity. Participants slept ∼7.5-h in all conditions. Upon waking, sleep inertia was quantified using the Karolinska Sleepiness Scale and Psychomotor Vigilance and Spatial Configuration Tasks, administered at 15-min intervals. Compared to control, participants felt sleepier post waking when on-call and sleepiest in the low stress compared to the high stress condition (p < .001). Spatial performance was faster when on-call compared to control (p < .001). Findings suggest that anticipating a high-stress task when on-call, does not impact sleep inertia severity.

Introduction

Non-standard or irregular working arrangements, such as on-call work, are implemented to manage the 24-h demands of society and 10–25% of workers worldwide experience some sort of on-call scheduling as part of their work or volunteering role (Australian Bureau of Statistics, 2012; Cebola, 2014; Parent-Thirion et al., 2012). On-call scheduling is a resourceful way to provide around-the-clock staff coverage, particularly for unpredictable or emergency situations, such as natural disasters, fires, or for when urgent medical attention is required (Ferguson et al., 2016). During an on-call period, workers are able to continue their normal routines, but must remain available and ready to respond to a call at any time (Hall et al 2016b).

Recent research suggests that being on-call negatively impacts workers’ sleep and level of stress (Ferguson et al., 2016; Hall et al. 2016b; Nicol and Botterill, 2004). For example, studies have found that on-call workers frequently experience difficulties getting to sleep as well as reduced sleep quality and quantity, sometimes even in the absence of a call (Hall et al. 2016b; Torsvall and Åkerstedt, 1988; Wuyts et al., 2012). Workplace safety problems, such as falling asleep at work and workplace accidents and near misses, have been reported to a greater extent in workers with irregular work schedules, such as on-call, as opposed to regular working schedules (Lockley et al., 2007; Rosekind et al., 2010). This may be a particular concern for on-call workers since on-call work is frequently utilised in safety- and time-critical industries, for example, emergency services (Vincent et al., 2017; Vincent et al. 2018b). In such industries, lapses in attention or cognitive performance as a result of inadequate sleep can impact on the safety of workers as well as bystanders and the civilians they are attending to.

It has been suggested that factors such as the uncertainty and anticipation of getting a call may contribute to disrupted sleep in on-call workers (Akerstedt, 2006; Ferguson et al., 2016). In addition, the important and critical jobs that on-call workers often perform may contribute to high stress levels (Barnes, 1999). Studies outside of on-call contexts have reported that sleep is negatively impacted (leading to shortened sleep) in situations where there is anticipation of a stressful task, or event, upon waking, e.g. expecting an early morning start or anticipating high work demands (Akerstedt, 2006). As such, it is possible that the anticipation of having to perform a stressful task if called could contribute to the disrupted sleep observed in on-call workers.

In addition to disrupted sleep causing potential issues for next day performance, on-call workers can also be impacted by sleep inertia. Sleep inertia is the transitory period between sleep and alert wakefulness which is associated with subjective feelings of disorientation, reduced alertness, as well as objective reductions in cognitive performance, compared to when awake (Tassi and Muzet, 2000). A number of cognitive tasks are impaired during sleep inertia, such as reaction time (Dinges et al., 1985), logical reasoning (Naitoh et al., 1993), arithmetic and visuospatial processing (Burke et al., 2015) and decision making (Bruck and Pisani, 1999), all of which are functions required by on-call workers to effectively and safely perform their jobs. In addition, research has also found that chronic sleep restriction, as is frequently experienced by on-call workers (Torsvall and Åkerstedt, 1988), can increase the magnitude of sleep inertia, potentially as a result of an increase in slow wave sleep (deep sleep) in sleep episodes that follow sleep restriction (Balkin and Badia, 1988; McHill et al., 2017). This is concerning for on-call workers given that they can be called during their sleep and must respond immediately to a call, all while experiencing severe sleep inertia. For example, in the seconds following a call, a firefighter must fit their protective uniform and equipment and are required to move, plan, make decisions, and drive to the fire site (Paterson et al., 2016).

Since research suggests that being on-call and anticipating a stressful task may restrict sleep, on-call workers may be at risk of experiencing sleep inertia of a greater magnitude when woken to a call. This has implications for the safety and efficiency of workers as the impairments associated with sleep inertia can increase the potential for accidents and reduce work performance (Ferrara et al., 2000; Hildtich et al. 2016b). Indeed, a recent publication found that the estimated cost of injury as a result of inadequate sleep among on-call workers within Australia to be approximately $2.25 billion a year (Vincent et al. 2018a).

The impact of shift work scheduling on sleep and performance has been an area of focus in the field of ergonomics research (Ferguson et al., 2012; Paech et al., 2010; Short et al., 2016), however there has been less attention paid to the conditions of on-call work which might have a similar impact on workers. In order to develop ways to enhance the performance and safety of on-call workers, there is a need to identify where inefficiencies in performance and behaviour may originate. Therefore, the primary aim of this study was to investigate how one factor of on-call work, anticipation of a stressful task, affects sleep and then subsequently, the performance of workers upon waking during sleep inertia. It was hypothesised that anticipating a high-stress task under simulated on-call conditions would result in reduced sleep quantity, subsequently leading to more sleep inertia, that is, more severe impairments in cognitive performance and subjective sleepiness upon waking and over the 75 min post waking.

Section snippets

Methods

The current data were taken from a larger study investigating how anticipating a high-stress task impacts on performance and sleep when on-call (Sprajcer et al., 2018a). The methods and measures of this larger study have already been published elsewhere (Perrin et al., 2019; Sprajcer et al., 2018a, 2018b, 2018c), however relevant methodology for the present study is described below.

Results

Results for main effects (condition, time and the interaction) are displayed in Table 1. There was no significant main effect of order in any of the models and thus are not reported.

Discussion

The aim of the current study was to investigate how anticipation of a stressful task, when on-call, impacts on sleep quantity and then the magnitude of sleep inertia. Contrary to our hypotheses, the results found little differences between conditions for majority of the cognitive performance measures. This may have been a result of participants receiving, on average, approximately 7.5 h of sleep in all conditions. Across all conditions, impairments to cognitive performance and subjective

Conclusion

This study's results found that workers can still achieve a full night's sleep when anticipating a call to perform a stressful task. Despite this, sleep inertia is still present upon waking and workers' ability to efficiently and safely perform tasks, including driving to a worksite, may be compromised. Interestingly, our findings suggest that when anticipating a high-stress task (e.g. fighting a house fire), workers may feel less sleepy upon waking than when anticipating a low-stress task

Contributors

Conceived and designed the experiments: SAF LL SMJ GEV. Performed the experiments: KK MS GEV SMJ. Analyzed the data: KK. Wrote the paper: KK SMJ GEV MS LL BA SAF.

Funding

This study was funded by an Australian Research Council Discovery grant (DP 150104497). Dr Grace Vincent is supported by an Early Career Fellowship at Central Queensland University.

Conflicts of interest

None.

Ethics approval

This study was approved by the Central Queensland University Human Research Ethics committee (H1507-158).

Acknowledgements

We would like to thank the project staff and the participants for volunteering their time. Part of this study has been presented and published as a conference abstract at Sleep Down Under 2017 and The 14th Annual Scientific Meeting of the Australasian Chronobiology Society.

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