Literature Review

Lydia Sedy

English 102 - T/TH 1:00pm

Prof. Sonia Apgar Begert

29 May 15

Literature Review

Many college students are known for procrastination, all nighter study sessions before exams, and similar activities that seriously affect sleep schedules. This project will look at how poor quality sleep has a number of negative consequences, encouraging students and teachers alike to consider their sleep schedules an important aspect of their life. Sources used for this project fall into five general categories: the first defines negative sleep habits and the next four explore sleep’s effects on learning/memory, academic performance, behavioral functioning, and overall body health.

A number of excellent studies expose negative sleep habits in the United States. The National Sleep Foundation published an article on their website in 2008 titled “Longer Work Days Leave Americans Nodding Off On the Job,” summarizing the 2008 Sleep in America poll. They observe that 65% of Americans report having sleep problems. These include fragmented sleep, defined as repeatedly interrupted sleep, difficulty falling asleep, or not feeling refreshed upon awakening. More than half of the responders also built up a sleep debt during the weekend. This is defined as not sleeping enough during the week and then “catching up” on lost hours during the weekend. This behavior was studied by Jaques Taillard, Pierre Philip, and Bernard Bioulac in their article "Morningness/Eveningness and the Need for Sleep” which was published in the Journal of Sleep Research in 1999. This study examines the effects of morning/eveningness on daytime sleepiness. One particular characteristic of Eveningness is building up a sleep debt, as well as going to bed and waking at later times of day. 617 participants completed a variety of questionnaires, out of which the authors found a clear link between daytime sleepiness and sleep debt.

Has our society been sleeping less over the years? Yu Sun Bin, Nathaniel Marshall, and Nick Glozier sought to answer this question in their study "Sleeping at the Limits: The Changing Prevalence of Short and Long Sleep Durations in 10 Countries” published in 2013 in the American Journal of Epidemiology. The authors analyzed cross-sectional surveys for 10 countries conducted in the past three decades. The differences in survey methods do not enable you to compare countries, but for our purposes we will isolate the United States. The authors found that in 1985, of 3,000 survey participants, 11.7% reported regularly sleeping less than 6 hours. By 2007, this number dropped to 9.2% in the over 11,000 survey participants that responded. The authors describe this idea that we are sleeping less might be derived from the fact that people generally sleep less as they get older, skewing our perceptions of actual change. This does seem to contradict what some studies report, as the 2001-2002 Sleep in America poll conducted by the National Sleep Foundation found that from 1960-2002, self reported sleep duration had decreased, the average respondents sleeping around 8.5 hours in 1960 to 7 hours in 2002.

A significant trend in the research of sleep concerns sleep’s effect on memory and learning. Dang-Vu and colleagues determine many aspects of this in their article “A role for sleep in brain plasticity” published in 2006 in Pediatric Rehabilitation. Their extensive, scientific study refers to over 200 references to support their arguments. A number of specific processes and how sleep affects them are carefully studied, including neural development, consolidation of memories, reactivations of neurons during sleep, neurotransmitter levels, gene transcription, and protein synthesis. Many of these processes are associated with both learning and memory. Particularly of note was that the authors found extensive evidence for role of sleep in brain development. They also found that during sleep, neurons “repeat” activations to incorporate experiences into long term memory. Pierre Maquet conducted a similar study in his article, “The Role of Sleep in Learning and Memory” published in the 2001 New Series issue of Science. Marquet carefully tracked brain activities during sleep, and found distinctive patterns that matched the activity recorded while awake. This suggests memories are repossessed or “consolidated” during sleep. Marquet also found that subjects who were allowed to sleep after training performed significantly better on later tests. Although both of these studies are preliminary, they speak to the significant role of sleep in memory.

One way to study the importance of sleep is to observe what goes wrong without it. Tina Saey reports about a study on fragmented sleep and memory in her article, “Sleep Interruptions Erode Memory” which appeared in the 2011 edition of Science News. This study particularly examined the need for continuous sleep in mice. The mice were introduced to new objects, and then expected to sleep. Their sleep was interrupted once every minute for an extended period of time. In previous studies, waking mice can cause stress and add other factors to the study that affect the results. In this version, a light-sensing protein was introduced into the brain, so that by stimulating the cells, you can “wake” the mice without adding stress. This more accurate experiment found that mice who got interrupted sleep could not remember the objects they had seen before, and treated them just like new objects. Although the study is on mice and not humans, it expresses a strong relationship between sleep and memory. M. Gradisar and colleagues narrow their study to working memory, as seen in their article "Adolescent Sleep and Working Memory Performance," published in Sleep and Biological Rhythms in 2008. The authors examined the correlation between insufficient sleep in adolescents and working memory performance. Working memory is defined as “the ability to temporarily store and manipulate information while performing complex cognitive tasks.” One task required students to remember a sequence of numbers and then later “operate” on the numbers, for example, by changing the order in which they appeared. The authors found that students who had slept less did not perform as well on the tests, specifically the more complex tasks that involved manipulating the information. Students who got the optimal eight to nine hours of sleep took less time to fall asleep and had less daytime sleepiness, which also contributed to better results on the tasks. Again, another study which shows the role of sleep in memory.

If sleep has such a significant effect on memory, does it affect academic performance? I found several studies attempting to answer this question, among them the notable Mickey Trockel, Michael Barnes, and Dennis Egget and their article “Health-Related Variables and Academic Performance Among First-Year College Students: Implications for Sleep and Other Behaviors.” Published in 2000 in Journal of American College Health. The authors explore the effects of many health-related variables on the GPAs of random students. Variables included sleep habits, work hours, exercise, spiritual health, nutrition, and social support. Of the 31 variables surveyed, sleep habits, such as wake time, bedtime, and total sleep time, showed the most significant correlation with higher GPAs. Jane Gaultney specifically examines sleep and GPAs in her study “The Prevalence of Sleep Disorders in College Students: Impact on Academic Performance.” which appeared in the same journal, Journal of American College Health, in 2010. 1,845 students took part in her survey, and their GPAs were obtained from the registrar’s office to prevent any bias. Gaultney did find that GPAs were significantly correlated with the amount of sleep the students received, however while they were evident, those correlations were “weak.” Gaultney warns readers the relationship between sleep and GPAs has not been proven to be cause-and-effect. However, the evidence of sleep having some play in academic performance is being explored more and more. Yu-Chih Chiang and colleagues’ recent 2014 study, “The Effects of Sleep on Academic Performance and Job Performance.” appeared in College Student Journal. This study examines the effects of poor sleep on academic performance and also included job performance. The authors formed an online questionnaire, and student GPAs were obtained from the registrar’s office to prevent bias. It was found that students who had trouble falling asleep had lower GPAs. William Kelly, Kathryn Kelly, and Robert Clanton completed yet another study on the correlation titled, "The Relationship Between Sleep Length and Grade-Point Average Among College Students." which appeared in an earlier edition of College Student Journal in 2001. The study did find that students who slept nine or more hours every 24 had a higher GPA on average. However, students who slept the average amount (7-8 hours) did not have significantly different GPAs from short sleepers (6 hours or less).

Amy Wolfson and Mary Carskadon also explored academic success as well as a variety of other things in their study “Sleep Schedules and Daytime Functioning in Adolescents.” published in Child Development in 1998. A survey was given to 3,120 students from four schools in Rhode Island. The survey considered sleep time, bedtime, and risetime during school-nights and weekends, as well as academic performance, daytime sleepiness, sleep/wake problems, and depressive mood. The authors found that students reporting B’s or better had more total sleep time and generally earlier bedtimes. Student’s reporting C’s or worse reportedly slept less and went to bed later.

Although each study I have cited warns that it is difficult to prove a cause and effect relationship between sleep and academic performance, the correlation has been repeatedly observed, and sleep should be considered an important asset for academic success.

Another trend in the sources I have reviewed involves sleep’s effect on behavioral functions. Wolfson’s and Carskadon’s study, mentioned above, also examines on sleep’s effect on behaviors. They found that students who slept less than an adequate amount had more sleep/wake issues, “such as [arriving] late to class because of oversleeping, [being] tired or dragged out nearly every day, or [needing] more than one reminder to get up.” They also reported more daytime sleepiness and depressive moods. Avi Sadeh, Reut Gruber, and Amiram Raviv’s more recent study, “Sleep, Neurobehavioral Functioning, and Behavior Problems in School-Age Children.” published in 2002 in Child Development, had similar results. The authors explored how sleep affects neurobehavioral functioning (NBF) in school-aged children. The children’s sleep habits were assessed by wearing a small actigraph on their wrist while they slept. This device records sleep activities throughout the night. A series of six tests, measuring motor speed, reaction time, omission/commission errors, and digit learning was then conducted twice each day. Correlations between sleep quality and test performance suggest that children who got poor quality sleep had greater problems with attention, reaction, and behavior regulation. The following year, Sadeh and his team conducted a more narrowed study, “The Effects of Sleep Restriction and Extension on School-Age Children: What a Difference an Hour Makes” which appeared in the 2003 edition of Child Development. Their aim was to look particularly on the effects of a minimal difference in sleep time on NBF, ranging from 30 minutes to one hour. This was done to reflect the regular changes that may result in a child's day to day life. They found that extension of sleep led to improved memory function and improved performance on a complex reaction test, behaviors they report have been correlated with classroom behaviors in the past.

Sadeh and his team are not the only ones investigating sleep’s effect on behaviors. Richard Millman’s study, published in 2005 in Pediatrics, titled “Excessive Sleepiness in Adolescents and Young Adults: Causes, Consequences, and Treatment Strategies”, also supports their work. Millman reviewed 150 other studies, articles, and publications to explore changes in adolescents sleep patterns, define factors of chronic insufficient sleep, explain the effect of insufficient sleep on a number of functions, and report common sleep disorders and solutions. Millman found extensive support that daytime sleepiness (caused by less total sleep time or fragmented sleep) has negative effects on performance and cognitive abilities, such as decision making and judgement, lack of attention, and the tendency to fall asleep in class. Also, sleep fragmentation has been found to cause irritability and depressive moods. Carlos Schenck reported similar findings in his book Sleep: A Groundbreaking Guide to the Mysteries, the Problems, and the Solutions published by the Penguin Group in 2007. He gives a broad scope of information on sleep, mostly discussing sleep disorders, such as insomnia, sleep apnea, and more serious issues such as sleepwalking and other parasomnias. However, Schenck lists many consequences of inadequate sleep, including decreased concentration and decision-making abilities, irritability, and frustration.

One of the most interesting studies I found on sleep and behavior was by Samantha Clickinbeard and colleagues, titled "Sleep and Delinquency: Does the Amount of Sleep Matter?" published in the Journal of Youth & Adolescence in 2011. This study examines delinquent behavior in adolescents and the amount of hours they slept.  The authors state that their findings should be repeated before considered absolute, but they did find that children who slept less were involved in more property delinquency. The authors also acknowledge that the correlation between sleep and delinquency might not be causational, and that the sleep problems themselves may be a cause of other issues with self-control. However, the evident link between sleep loss and more delinquency is very interesting.

A trend that cannot be ignored in this field is sleep’s effect on physical health. Shih-Yu Lee and colleagues explore this in their article, “Stress and Sleep Disturbances in Female College Students” published in the American Journal of Health Behavior in 2013. The authors aim to define the relationships between sleep, stress, and wellbeing, particularly looking at depressive and physical symptoms. They had 103 female students record their sleep habits for 7 days, and take a standardized questionnaire. Lee and colleagues found that women who had poor quality sleep had more daytime fatigue and worse depressive and physical symptoms. Participants who experienced less sleep time overall also expressed the same problems. Mary Wells and Bradley V. Vaughn found similar results in their study "Poor Sleep Challenging the Health of a Nation." Published in 2012 in the  Neurodiagnostic Journal. The authors reviewed over 80 credible sources, from scientific studies to government agencies, aiming to give a comprehensive report on the negative effects of poor sleep. Throughout their research, they found poor sleep contributing to major disasters, such as the Challenger Space Shuttle explosion or the Three Mile Island nuclear accident. Other themes included sleep’s impact on performance and productivity, stress, and health and mortality. They found that insufficient sleep was correlated with many chronic issues such as heart disease, stroke, depression, and diabetes.