Adult life consists of work, non-work, and sleep. All individuals experience a relationship between how well and how much they sleep and subsequent functioning the next day, and the amount and quality of sleep is determined by external and internal factors. Internal factors include personality, individual sleep patterns, and physiological systems, and external factors include the time available to sleep and the sleep environment. For some individuals, the lines between sleep, non-work, and work are more blurred then others, and external factors shape sleep patterns to a greater extent. This is especially the case for military and naval personnel during combat operations and exercises. The primary aim of this thesis is to provide a framework for understanding how sleep quality and sleep duration affect job performance. The research within is based on four key assumptions. Firstly, that lack of sleep and low quality sleep in general decreases cognitive, emotional, and social functioning, which subsequently negatively influences job performance. Secondly, individuals are affected differently by disturbed sleep quality. Thirdly, that group processes, such as leadership, can moderate the negative impact of disturbed sleep on performance. Lastly, the link between sleep and one’s own and others’ perceived job performance is not uniform for different work-sleep schedules. The thesis investigates these hypotheses in three samples of naval personnel of the Royal Norwegian Navy during active combat operations and during naval training exercises. The first paper tracks sleep quality, as measured by symptoms of insomnia, during a four-month counterpiracy mission in the Gulf of Aden, including measurements before the mission, at the halfway point, and towards the end. It separates the crew of 281 naval personnel into high and low hardiness groups based on the mean hardiness level as measured by the DRS-15-R (Dispositional Resilience Scale 15 Revised). Repeated-measures ANOVA showed that the overall sleep quality and insomnia symptoms among the personnel were highest at the midway point and that the high hardiness group showed a trend of overall better sleep quality. The results also showed a significant interaction of hardiness and time, where the lower hardiness group experienced a stable trend of worse sleep quality, while the high hardiness group showed an increase in sleep problems in the middle of the mission, but fewer problems before and towards the end of the mission. The paper concludes that having a hardy disposition is associated with better sleep quality during a naval mission and that external factors such as operational tempo, stress, and fatigue might remove differences between resilient and less resilient sailors at the midway point of the mission. The second paper aims to elaborate on the hardy advantage identified in paper 1. Insomnia is a multi-faceted construct, and it confounds sleep quality and the next day’s performance. In the second paper, we investigate if the results of paper 1 are due to hardy sailors having better sleep quality and subsequent increased performance (mediation) or if hardy sailors are less affected by disturbed sleep quality as measured by next day performance (moderation). The two hypotheses were tested in a sample of 65 naval cadets during a challenging training exercise using a diary study format. Hardiness was measured with the DRS- 15-R before the mission, daily sleep quality and duration were measured with single sleep diary items, and daily naval work performance was measured by peer ratings of performance. The results were also controlled for individual differences in neuroticism and were obtained using multi-level analysis. The results did not support a hardy advantage due to better sleep quality, but rather that hardy sailors do not show the same deterioration of performance when faced with worsening sleep quality. Highhardiness naval personnel have an overall performance advantage, which increases as the crew experiences a drop in sleep quality. Overall, paper 1 and paper 2 indicate that resilient and hardy naval personnel have a different response to disturbed sleep. This effect might be due to differences in susceptibility to mood and cognitive impairment, but also to increased willfulness and increased engagement of high-performance individuals as the whole crew experiences cumulative fatigue at sea.
The thesis’s third paper explores the role of sleep duration in addition to sleep quality in a sample of 78 naval cadets during a similar type of demanding training exercise as the sample in paper 2. The overall research focus of paper 3 was to uncover the isolated effects of sleep duration and sleep quality on two self-rated performance measures – task performance and contextual work performance – as well as to uncover the possible role of high-quality leadership as a buffer against the effects of disturbed sleep quality on work performance. The possibility of paradoxical negative performance outcomes due to increased sleep is rarely discussed in organizational and military/operational sleep research. However, during extraordinarily demanding 24- hour continuous operations with severe limitations on sleep, increasing sleep might come at the cost of non-task-related work activities. We hypothesized that sleep quality is positively related to both measures of performance, while sleep duration is positively associated with task performance but negatively associated with contextual performance (e.g. helping others or volunteering for extra work). We also hypothesized that perceived high quality transformational leadership negatively moderates both links between sleep quality and performance. The results showed that sleep quality was positively related to both performance measures. Sleep duration was, however, negatively related to contextual work performance but showed no directional relationship with self-rated task performance. In addition, perceived transformational leadership moderated the link between sleep quality and task performance, but not the link between sleep quality and contextual work performance. The results of the study suggest that during challenging work conditions with extraordinary 24-hour shift work, increasing sleep duration is associated with a drop in contextual performance, an effect that leaders and managers should take into account when planning. The results also show how leaders can partially mitigate the negative effects of worsening sleep quality.
In conclusion, the results from paper 1 and paper 2 both suggest that disturbed sleep might cause a drop in work performance and that this drop is partially dependent on the individual’s resiliency to the worsening sleep quality associated with a naval mission. This could inform personnel selection and might provide a framework for increasing sailors’ work capacity when facing high-paced 24-hour operational activity. The results from paper 1 and paper 3 collectively show that sleep quality and duration have different effects in the context of 24-hour operations, and increasing the demands on the crew without any considerations for time available to sleep can decrease work performance because the crew has to prioritize between sleep and work. Additionally, all three papers point to two possible solutions to the inevitability of disturbed sleep during a naval mission – selecting the most resilient crew based on dispositional hardiness and using transformational leadership as a tool to buffer its negative effects.