Sleep inertia refers to the temporary transitional state from sleep to wake, marked by lowered arousal and impaired cognitive-behavioural performance. This period of impairment is of particularly concern to people on call, such as first responders. However, the research is inconclusive on how well sleep inertia can be measured with the various subjective and performance measures that are currently used to assess impairment from sleep inertia.
Research Questions / Hypotheses
The aim of this study is to investigate how subjective insights reflect the effect of sleep inertia and how they associate with cognitive performance. First, it is hypothesised that over the course of experiment, 1) Subjective sleepiness, physiological symptoms and cognitive symptoms will decrease over time, reflecting the effect of sleep inertia, and 2) performance in serial addition task and visual selection task will improve over time, reflecting the recovery of sleep inertia. Second, we will take exploratory analyses to investigate how subjective sleepiness, physiological symptoms and cognitive symptoms associate with performance during sleep inertia.
A total of 113 REP participants signed up for the study. 74 participants completed the consent forms, and 40 participants attempted the experiment in the morning.
Participants completed the experiment on their personal computer. The experiment involved repeating the same block of tasks (total of ten blocks) for 60 minutes (figure 1). Within each block, the participants rated their sleepiness, physiological symptoms and cognitive performance and then completed a sequential addition task. After the addition task, the same set of subjective questions were presented again, and the participants then completed a visual selection task (end of a block).
Each of the subjective and performance measures were submitted to repeated measures ANOVA, to understand how the measures changed over the course of the experiment.Repeated measure correlations were used to measure the association between the subjective measures and cognitive performance. First, contrary to our predictions, we did not observe any change in subjective sleepiness and cognitive insights over the course of the experiment. Regarding the associations between subjective insights and cognitive performance, all three subjective measures selectively associated with some, but not all performance measures within individuals over time. However, these associations were low, suggesting that subjective insights are unreliable predictors for performance.
The present study suggests that sleep inertia only has an effect on subjective physiological symptoms, but not on sleepiness and cognitive insights. In the existing literature, however, sleepiness has often been used as the only subjective measure in the context of sleep inertia, despite its inconsistency in reflecting the sleep inertia effect. The present study implies that the current focus on subjective sleepiness during sleep inertia may lack reliability and validity. Therefore, it is important that when using subjective measures to investigate sleep inertia, that different dimensions are employed to ensure a more consistent understanding of the phenomenon. The results were communicated as honour's thesis and conference presentation.