What Effect Does Sleep Have on Physiological and Cognitive Performance

Abstract

The National Sleep Foundation’s Annual Sleep in America poll of 2018 showed that only ten percent of Americans rates sleep as a top priority. With all the literature that is taught about how vital sleep is to one’s health, these results were shocking. Sleep is an essential physiological need for survival. To be deprived of sleep has many unwanted effects on the body. Total sleep deprivation has been shown to negatively affect many physiological, cognitive, and behavioral measures within the body (Miro et. al. 2002). Studies have shown that sleep deprivation can cause damage to brain cells, impair immune response, affect short term and long-term memory, restrict learning, and most of all decrease cognitive performance. In research a distinction between total and partial sleep deprivation is important to adequately consider the effects of sleep loss. Sleep deprivation is a study design to assess the effects of sleep loss. Total sleep deprivation is more thoroughly examined even though partial sleep deprivation is more commonly experienced. Although there are vast studies and a profound amount of research on the effects of sleep deprivation, there are still many unanswered questions. The discrepancies in the studies account for age, gender, the type of sleep deprivation that is being tested, the allotted time of sleep, and the individual. Despite the discrepancies shown in various research, it is known knowledge that sleep deprivation has several effects on physiological and cognitive performance.

Introduction​

A person’s daily performance can be heavily influenced by the lack of sleep. Sleep is becoming more of a cliché in today’s society. A new saying has been adopted that states I’ll sleep when I die. Sleep loss is one of the most important yet underestimated causes of disruption in a person’s quality of life. Sleep is essential to the body and brain. It was proposed that sleep detoxifies the brain, controls thermoregulation, and conserves energy (Maquet 2001). When being researched it is common to find sleep deprivation broken into two separate categories. Total sleep deprivation refers to the avoidance of sleep for a period of at least twenty-four hours or greater. Then you have partial sleep deprivation in which the usual number of hours one sleeps is reduced within the twenty-four-hour period. Sleep from a physiological perspective was first examined by a French Scientist name Henri Pieron. Then in the 1920’s, Dr. Nathaniel Klietman began questioning the regulation of sleep, wakefulness, and circadian rhythms. The main symptoms of sleep loss are excessive daytime sleepiness, depressed mood, poor memory, and/or concentration (Dinges et al., 2005). Major research has been explored for decades on the cognitive effects of sleep deprivation (Maquet 2002; Stickgold 2005) and the importance of sleep to body restitution (Maquet 2001). Although many variables and more accurate research methods are being used to see just how sleep really affects physiological health, there are still many unanswered questions regarding the exact amount one needs to sleep and the type of sleep that is needed to remain healthy. Each of these studies are contributing greatly to catch the world’s view on just how vital sleep is. This paper will address the literature as such from various studies showing how sleep loss negatively impacts the physiological, cognitive, and behavioral measures within the body.

Sleep and Sleep Deprivation

​Several studies suggest that the average amount of hours needed are between seven and eight a day (Kripke et al 2002; Kronholm et al 2006). However, the need for sleep varies depending on the individual. Homeostatic process S and circadian process C are the two processes that regulates sleep. The circadian process C affects the thresholds for the onset and offset of a sleep episode. The homeostatic process S revolves around the sleep and wakefulness. The two processes determine the sleep/wake cycle and can be used to describe the fluctuations in alertness and vigilance (eg, Achermann 2004). The process has now been revised and is used as the principal study in sleep deprivation. This sums up the background and characteristics of sleep and sleep loss.

The effects of sleep deprivation are innumerable. For this reason, focus will be given to the effects on the immune system, the Prefrontal Cortex of the brain, short term memory, long term memory, and brain cells. As the body rest, it replenishes itself and fights off any threats. They fighting system is referred to as the immune system response. The immune system response is regulated by three physiological events. The three events are wakefulness, non-rapid eye movement, and rapid eye movement (Nayyab et.al. 2017). The association between the immune system and sleep came about in the 1970’s. Immunoregulatory cytokine is a key player in sleep regulation and has levels associated with sleep propensity in the brain (Krueger 2008). This showed that sleep regulated cytokines effect the immune system. The body has to rest in order to remain healthy to perform physically and mentally.

Brains that are sleep deprived have to work harder to perform which affects the PFC of the brain. Brain imaging studies show this to be true by showing the brains of the sleep deprived hysterically pumping energy into the prefrontal cortex to overcome the lack of sleep. In addition, neuroimaging studies have found that after one night of sleep deprivation the blood flow to the prefrontal cortex is profoundly affected (Drummond 1999). The prefrontal cortex is responsible for executive functions of the brain which include: decision-making skills, self-observation, prioritizing, and planning. The prefrontal cortex leads us into short term and long-term memory. As the tasks performed intertwine as basic cognitive capacities.

People who experience sleep loss usually experience a decline in cognitive performance and changes in mood (Philibert 2005). The most thoroughly evaluated cognitive performance measured in sleep deprivations include attentional functions, working memory, and long-term memory. Sleep deprivation impairs visual short-term memory and limits its capacity. A fMRI study done showed declines in behavioral performance and reductions in parietal and extrastriatal activation after sleep loss (Chee 2007). Moreover, according to (Chee 2008) attention lapse following sleep loss showed reduced activation in the visual sensory cortex and thalamus.

Sleep deprivation limits the capacity to retain new experiences to memory. Research showed that a lack of sleep compromises the neural and behavioral capacity for retaining new experiences to long-term memory (Yoo,Gujar, Hu, Jolesz, & Walker 2007). These same findings support the hypothesis that lower brain areas involved in arousal, attentional functions, and sensory/perceptual gating contribute to impairments in memory following sleep deprivation. Sustained attention is referred to as vigilance throughout this paper. As stated before, although many studies show the negative effects of sleep deprivation there are still many unanswered questions about sleep.

Discrepancies and Common bias

Most hypothesis of these studies have received major support. Sleep deprivations usually focus on proving one of two hypotheses. According to (Alhola et al 2005) these two hypotheses are: general effects on alertness and attention, and/or selective effects on certain brain structures and functions. The hypothesis was supported but there was limitations and some studies that showed no effects of sleep deviations within a twenty-four-hour period. The differences in age and gender of participants, as well as the duration of sleep duration, complicated the comparison of the results. Studies show that older participants functioned better than younger participants. In aging the accumulation of sleep pressure seems to be reduced during wakefulness (Murillo-Rodriguez et al 2004), which could account for older adults performing better despite lack of sleep. Some Sleep deprivations studies have found impairment only in performance speed, whereas accuracy has remained intact (De Gennaro et al 200; Chee and Choo 2004). In others, the results are the opposite (Kim et al 2001; Gosselin et al 2005). In addition, comparing the effects of partial sleep deprivation and total sleep deprivation based on existing literature has proven difficult. For this reason, only one study used a control to show a decline in cognitive performance using both types of sleep deviations (Van Dongen et al 2003). According to (Alhola and Paivi 2007), methodological shortcomings are to blame for the common biases such as inadequate descriptions of protocols, failure to control the practice effect, individual sleep history or napping during the studies, and insensitive cognitive measures. All in all, most studies evaluated proved the hypothesis to be true that sleep deprivation does have an effect on physiological and cognitive performance.

Conclusion

​In conclusion, the reviewed literature showed that there is so much to learn and become acquainted with about sleep. While some studies may not have shown any deviation within a twenty-four-hour period, others showed that over time the lack of sleeping hours in a day adds up over a brief time to cause an adverse effect. These sleep studies are shedding light on just how important sleep is to performance and health. More studies are needed and needs to be mainstream. There are so many important people working in a field that requires some type of sleep deprivation. Sleep studies also need to find some type of control in the homes or spaces in which one can truly show just how they sleep. While the literature showed the many effects of the brain and body, it also shed light on just how much research is needed to be readily present for the world.

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