The Effect of Sleep Quality on Sleepiness, Cognition and Mood

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The Effect of Sleep Quality on Sleepiness, Cognition and Mood

Sally Robinson


This study examined the effect of sleep quality on sleepiness, cognition and mood using 100 university students using convenience sampling. Participants tested themselves in two testing sessions: one after awakening from a night of self-reported “good sleep” and the other after “poor sleep”. Participants tested their sleepiness using the Karolinska Sleepiness Scale (KSS), their cognitive performance with a Trail Making Task (TMT) and a Digit Symbol Substitution Task (DSST), and their mood using the Positive and Negative Affect Scale (PANAS). The results supported the hypotheses that sleepiness would be lower, cognitive functioning would be higher, and mood would be more positive and less negative following a good night’s sleep than a poor night’s sleep. This study highlights the importance of a good night’s sleep to maintain good mood and cognitive functioning.


Reduction in sleep quality is a widespread problem in modern society. A major component of poor sleep quality is sleep deprivation, which is an inadequate quantity of sleep, especially the deeper stages of sleep (stages 3 and 4) and REM sleep. Many studies have concentrated on relating sleep deprivation to psychological measures, because sleep deprivation is easily measurable. Sleep deprivation is widely due to increased work-pressure and busy lifestyles (Bonnet & Arand, 1995; Rajaratnam & Arendt, 2001). Reduced sleep quality, whether a result of sleep deprivation or other problems, also has a major impact on cognitive functioning and mood, causing financial and social cost.

Research relating sleep quality and sleepiness has produced unclear findings. About 10-25% of people report sleepiness – a feeling of tiredness when an individual physiologically needs sleep (Roehrs, Carskadon, Dement, & Roth, 2005). Akerstedt and Gillberg (1990) compared self-reported sleepiness to EEG results. They found that moderate to high levels of self-reported sleepiness were linked to increased energy levels in the alpha and theta bands (which are associated with sleep). Horne’s review (2010) highlights that self-reported sleepiness and ‘need for sleep’ are not synonymous. Anderson, Plannen and Horne (2009) found no link between self-reported sleep deficit and sleepiness scores as measured by the KSS.

Research has consistently found the sleep loss depresses cognitive functioning and mood. A comprehensive review suggests this is due to sleep loss affecting hippocampal areas (Meerlo, Mistlberge, Jacobs, Heller, & McGinty, 2009). Dinges et al. (1997) subjected 16 participants to seven consecutive nights of 33% reduction in normal sleep time, and found that mood and cognitive performance progressively declined. Mood was measured using the Profile of Mood States (POMS), while cognition was measured using a psychomotor vigiliance task (PVT), a probed recall memory (PRM) task, and a serial-addition (SAD) task, all of which are commonly used tests. Blagrove and Akehurst (2001) found similar results. Pilcher and Huffcutt’s meta-analysis (1996) concluded that a median sleep-deprived individual performs at approximately the same standard as a 9th percentile non-deprived individual, when performance is considered as an average of mood state, motor functioning and cognitive performance.

In a review on the relationship between sleep and stress, studies on humans and rodents have dfound that sleep deprivation can affect mood by causing temporary increases in activity of neuroendocrine stress systems, such as the hypothalamic-pituitaryadrenal axis and the autonomic sympatho-adrenal system (Meerlo, Sgoifo, & Suchecki, 2008). Animal studies found changes to neuroendocrine systems similar to those seen in stress-related disorders (such as depression) in humans, and therefore suggest that insufficient sleep might predispose people to stress-related disorders (Meerlo et al., 2008). The negative effects of sleep deprivation on mood have also been shown with house officers following night duty (Orton & Gruzeller, 1989), train drivers (Torsvall & Akerstedt, 1987) and doctors doing residency training (Bartle, Sun, & Thompson, 1988).

There is more to sleep quality than measuring sleep deprivation. Van Dongen, Maislin and Dinges (2003) and Drake et al. (2001) found that the detrimental effects of sleep loss vary as a function of rate of sleep loss.   Van Dongen et al. (2003) found that participants restricted to six hours of sleep for 14 days had working memory performance (as measured by a digit symbol substitution task performance like the current study) similar to participants deprived completely of one night’s sleep. Restriction of sleep to 4 hours reduced working memory performance  to levels similar to those after 2 nights of complete sleep deprivation. Van Dongen et al. (2003) suggested that reduction in performance is due to time spent awake in excess of a usual wakefulness period.

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Knowledge concerning consequences of chronic partial sleep deprivation, as it occurs in real life, is incomplete (Meerlo et al., 2008; Pilcher & Huffcutt, 1996). The aim of the present study is to investigate the impact of reduced quality of sleep on sleepiness, cognitive performance and mood. This study extends sleep deprivation studies by focusing on sleep quality as the independent variable, which is affected by factors other than restricted sleep. The study endeavors to increase awareness of the importance of sleep, in particular by highlighting how detrimental poor quality sleep can be, by demonstrating the negative impacts of reduced sleep ...

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