Do you know about sleep? Do you know about the critical role it plays in your life? Do you know about the hazards of not getting enough sleep? You may think that not sleeping enough may make you tired, but there is much more to it. Insufficient sleep and poor sleep quality have negative effects on health, including weight gain, obesity, diabetes, hypertension and cardiovascular disease, as well as decline in cognitive abilities such as memory and thinking skills. Indeed, insufficient sleep is a public health problem. Sleep deprivation is also bad for your immune system.
A 2012 study carried out in humans found that sleep deprivation results in lower antibody responses to the hepatitis B virus vaccine and predicted a decreased likelihood of being clinically protected from hepatitis B infection. Thus, the study provided a possible explanation for the already known association of poor sleep with increased susceptibility to infectious diseases.
Now, results from a study (Transcriptional Signatures of Sleep Duration Discordance in Monozygotic Twins) recently published in the scientific journal Sleep (January 25, 2017) show that sleep deprivation leads to a dysregulated immune response. For the study, researchers obtained blood samples from 11 pairs of identical twins—within a pair, the two twins had a different sleep patterns. Why did the researchers use identical twins? Environmental and genetic factors could influence the study results, and using identical twins—which are exposed to similar environmental conditions and are genetically similar—allowed to minimize the influence of these factors.
The researchers used the blood samples to purify peripheral blood leukocytes. Then they identified the leukocytes’ gene expression profiles. They discovered that the twin with shorter sleep duration had a depressed immune system, compared with his or her sibling.
Nathaniel Watson, senior author of the study, said in a press release: “The results are consistent with studies that show when sleep deprived people are given a vaccine, there is a lower antibody response and if you expose sleep deprived people to a rhinovirus they are more likely to get the virus. This study provides further evidence of sleep to overall health and well-being particularly to immune health.”
Watson added: “What we show is that the immune system functions best when it gets enough sleep. Seven or more hours of sleep is recommended for optimal health.”
In the same press release, Sina Gharib, senior author of the study, explained that a lot of existing data shows that curtailing sleep—for a limited time in the laboratory setting—can increase inflammatory markers and activate immune cells. Little is known, though, about the effects of longstanding short sleep duration under natural conditions. This study employed “real world” conditions, he said, and showed for the first time that chronic short sleep shuts down programs involved in immune response of circulating white blood cells.
Not only sleep deprivation, but anything that gives stress to the body can potentially weaken immune response. In another study, it was found that moderate psychological stress can significantly temper immune response to influenza vaccine in healthy young adults (Link 1). The recommended amount of sleep for a young adult is 7-9 hours (Link2), and from personal experience as a working student, I know that 9 hours of sleep is a rare luxury. Sleeping length differs from person to person, and some people can make a do with 6 hours of sleep and not show any symptoms of sleep deprivation or feel tired, while other may need 10 hours of sleep. One important issue with this article is that it does not define what qualifies as sleep deprivation. It would be useful to know how much deviation from ‘normal sleeping hours’ (hours of sleep require not to feel tired) is considered sleep deprivation.
1) https://www.ncbi.nlm.nih.gov/pubmed/15039506
2)https://sleepfoundation.org/excessivesleepiness/content/how-much-sleep-do-we-really-need-0
In addition to all the problems mentioned in the article, short sleep duration correlates with poor academic performance. According to a study done in 2012, students who sleep 8-9 hours/day tend to have a higher GPA than those who sleep less1. The study revealed that the less you sleep, the worse the GPA will be. This relates to me and may relate to many students as well. I usually do better in an exam when I sleep well the night prior to it. Another study that was done in China suggested that delaying the starting time for schools should help in increasing the school performance in Chinese children2. These two studies and many more show the correlation between insufficient sleep and poor school performance. This article and all the conducted studies about sleep indicate that sleeping well helps in improving your academic performance and your body’s health as well.
1- https://www.ncbi.nlm.nih.gov/pubmed/26825591
2- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3707878/
It is without doubt that sleeping is a behavior that is part of a human’s daily routine, however knowing the fact that it is detrimental to the function of the immune system is mind blowing. Over the past decade, many researches have been conducted to identify the role of sleep in correlation to human’s health while showing that a lack of sleep such as insomnia and many other increase the risk of infectious disease and contribute to all-cause mortality such as cardiovascular disease, cancer and major depression. sleep disturbance has also been found to be associated with a reduced magnitude of immune response to several types of vaccines. Initial studies focused on the link between psychological stress and vaccine response and revealed that sleep amounts partially explained the impaired vaccine responses. (Miller et al.(2004). In another study, it was found that natural sleep disturbance, in contrast to experimental sleep loss, is associated with alterations in the relative distribution of immune cells; marked decreases in the numbers of CD3+, CD4+, and CD8+ T cells have been reported in patients with chronic insomnia (Savard et al. 2003). Sleep disturbance also induces a relative shift toward a type 2 response as evidenced by a lower ratio of stimulated production of IFN-γ/IL-10 as compared to responses in those without a sleep disturbance (Redwine et al. 2003), which provides insight into the immune processes that might contribute to impaired vaccine responses or susceptibility to infections in persons who are experiencing acute or chronic sleep disturbances.
Citation: https://www.ncbi.nlm.nih.gov/pubmed/25061767
It appears that chronic sleep deprivation can cause more than just increased inflammatory markers and decrease immune responses to infections. Sleep plays a significant role in our body’s ability to maintain homeostasis(1). Chronic sleep deprivation has been correlated with the onset of autoimmune diseases such as systemic lupus erythematosus, scleroderma, and rheumatoid arthritis. The start of these conditions could be due to continuous activation of immune cells. If these cells are continuously activated there is an increased chance of these cells going rogue which could lead to an autoimmune disease(2). For example, imaging a person was constantly getting a sunburn on their face. By repeatedly damaging the tissues on their face, their endothelial cells would continuously be dividing to repair the damage. The more a cell divides and makes more of itself, the more likely that the cell will divide incorrectly turning into a cancerous cell. This idea holds true for immune cells. If they are continuously activated there is a chance that an immune cell that attacks self-tissues was not destroyed during the sorting process of the immune system which would lead to a destruction of healthy cells and tissues.
(1)Sleep: a health imperative. https://www.ncbi.nlm.nih.gov/pubmed/22654183
(2)Autoimmune rheumatic disease and sleep: a review. https://www.ncbi.nlm.nih.gov/pubmed/26402614
Connections between the immune system and sleep are investigated by many studies. While the study mentioned in the article reveals the reducing sleep time affects the immune system, one recent study shows that the quality of sleep also influences the immune system. In this study, Huang et al. discover that levels of circulating inflammatory factors IP10, IL6 and hs-CRP increased in healthy menopausal women who had a poorer sleep quality according to their self-evaluations. The increase of these inflammatory factors relates to the low-grade systemic inflammation. Although the immune system and sleep, which includes the duration and quality of sleep, clearly relate to each other, the causal relationship between the changes in immune systems and sleep is not absolute. Instead, an interactional relationship between the immune system and sleep should be emphasized. Studies have shown that the immune system, on the other hand, participates in sleep regulation as well. In the article, “Moderate exercise training modulates cytokine profile and sleep in elderly people” published in 2012, the researchers found that six months of training improves sleep in the elderly and is related to changes in cytokine profiles which lead to the anti-inflammatory effect. By understanding the interaction between immune system and sleep, efforts can be made to improve human health and life quality.
Chronic sleep deprivation is a condition that many people posses. The article states that humans function best when adequate sleep is obtained. Not getting enough sleep leads to adverse side effects. Sleep deprivation can lead to increased fatigue and drowsiness. (1) The adverse side effects also translate to the immune system as stated in the article. In a study done in 2016, chronic sleep deprivation lead to decreased CD4+ and CD8+ T cell sub-populations in the lymph organs. (2) As stated, the loss of sleep correlates with a decreased amount of immune cell response capability. The reduced immune cell response can also lead to higher rates of infection, which will lead to adverse side effects in the body. An example is when a double shift worker sleeps 4-5 hours a day, while working a full day. (1) Over time, there will be a correlation in decreased work performance and weakened immune response. Overall, this article gives evidence to the relation of sleep and immune cell response.
(1) : https://www.ncbi.nlm.nih.gov/pubmed/28123655
(2) : https://www.ncbi.nlm.nih.gov/pubmed/28069386
Sleep and the immune system have been known to have a relationship that correlates to one another. In a study done by Connor Ames, Erin Bolan, and Eva Szentirmai macrophages were proven to be a cellular component that plays a major role between the reciprocal relationship of sleep and the immune system. Liposomes that contained clodronate (CCL) were injected into mice in order to induce apoptosis of macrophages. These injections reduced the amount of both the M1 and M2 macrophage populations.Those mice with acute CCL injections showed a short term increase in non-rapid-eye movement sleep (NREMS) and body temperature. Which lead to a weak recovery sleep response after sleep deprivation, along with a sensitivity too cold. The evidence found indicated that macrophages must function properly in order to maintain a normal sleep after sleep deprivation and through cold environments.
Reference: https://www-ncbi-nlm-nih-gov.ezproxy.gsu.edu/pmc/articles/PMC4956207/
Having enough sleep is important because it helps the body recover from stressful events that have occurred through the day. That could be anything from studying all day to running a marathon. At the end of the day, your body needs to regain energy by sleeping. It has always been recommended to get at least 7-8 hours of sleep. In addition, in another study, researchers revealed that even partial sleep deprivation could have an effect on performance. The study was done on cyclists who had enough sleep and those who were partially sleep deprived after a training session and found that those that were sleep deprived were less motivated to train (1). Not only does sleep deprivation impair performance, it can also affect body mass. Another study that was done comparing the number of hours people slept to their body mass found that those who slept less had an increase in fat mass (2). This therefore implies that obesity is closely correlated with sleep deprivation. All the studies that have been done, including the ones in this article, show how significantly harmful sleep deprivation is to the overall body performance and health.
https://www-ncbi-nlm-nih-gov.ezproxy.gsu.edu/pubmed/28247026
https://www-ncbi-nlm-nih-gov.ezproxy.gsu.edu/pubmed/28220551
When relating sleep deprivation and the effect on our immune system response, many studies have seen a decrease population of two important innate immune cells: neutrophils and natural killer cells. In a recent study, healthy young adult men with sleep deprivation were tested and blood samples were collected. The same men could get the recommended amount of sleep and blood samples were collected again. Researchers discovered that the population of circulating neutrophils decreased significantly compared to the population of circulating neutrophils after the men had rest. It was also discovered that sleep deprivation affected the diversity of neutrophil subset as well. There were more immature neutrophils present in the blood than any other subset during chronic sleep deprivation (1). This could possibly explain why people with sleep deprivation have weaker immune responses when an infection is present. In a similar study, sleep deprived male mice were tested and spleen tissue samples were collected. The results showed that the NK count dramatically decreased as well as the activity of these cells became weaker (2). The decreased cytoxicity activity of NK cells against melanoma cells was a major discovery in this study and could serve as a possible linkage between sleep deprivation and cancer in future research studies.
(1) https://www-ncbi-nlm-nih-gov.ezproxy.gsu.edu/pubmed/24878171
(2) https://www-ncbi-nlm-nih-gov.ezproxy.gsu.edu/pubmed/25929826
Sleep deprivation can effect your mind in a drastic manner. I have a friend who thought she saw millions of spiders drop from the sky onto her bed while she was trying to study because she only had two hours of sleep that night. I personally have also though I have seen or heard things that were not there because I had not gotten an adequate amount of sleep. There was a recent study conducted on shift workers to see what the effects of sleep deprivation had on the immune system. They have found that those with acute deprivation had a beneficial increase in Natural Killer cells, CD4+ lymphocytes, CD8+, monocytes, and granulocytes. Those with chronic deprivation had an opposite effect.
Sleep, immunity and shift workers: A review.:https://www.ncbi.nlm.nih.gov/pubmed/28123655
Sleep deprivation and sleeping disorders are one of the most prevalent ailments affecting millennials, especially college students. Because of rapid developments in technology, the quality and duration of sleep is deteriorating due to young adults spending countless hours on a computer or smart phone. As a young college student majoring in a STEM field, I have experienced the detrimental effects of sleep deprivation personally. Sleep deprivation can lead to sleeping disorders and more debilitating conditions such as depression. In a study conducted in 2015, poor sleep quality was correlated to increased risk factors for major depression. For the study, researchers analyzed the quality of sleep and depressive symptoms observed in many same-sex identical twin pairs. This experiment found that processing of emotions significantly decreased in subjects who were sleep deprived which can lead to depressive symptoms in these subjects as well. Another group of researchers view this relationship between sleep deprivation and the onset of depression as a behavioral defense against infection. This study attempts to prove the protective function of depression as a way for the adaptive immune system in humans to fight off pathogens. However, I disagree with this study because it implies that the few positive effects of depression, isolation from the public which can reduce contact with pathogens, outweigh the severely detrimental effects it can have on a person, debilitating mental/physical state and even suicidal actions. Sleep deprivation promotes the onset of depression which can lead to detrimental physical, mental, and emotional consequences. College students rarely sleep because of the responsibilities and rigorous classes they must take and are especially susceptible to sleep deprivation and depression.
-“Depression as an evolutionary strategy for defense against infection”: http://www.sciencedirect.com/science/article/pii/S0889159112005326
-“ Poor sleep predicts symptoms of depression and disability retirement due to depression”: http://www.sciencedirect.com/science/article/pii/S0165032714006247
Sleep is a key recovery process for our bodies. Long term deprivation of sleep can put a person at a higher risk of developing many major long standing illnesses such as heart disease and hypertension. A lack of sleep has also been linked to the inflammatory cytokines (1). Many pathogens that cause infections in humans enter through your gastrointestinal tract. If these tissues are highly inflamed and distressed they cannot adequately protect you from these pathogens allowing them to enter and cause clinical infection. The paper looks at the correlation between sleep deprivation and the occurrence of inflammatory bowel disease and other inflammatory diseases related to an increased cytokine production. With an increased pathogen uptake in the gut, an autoimmune disorder can be triggered called Chron’s disease. With patients suffering from Chron’s disease, pathogens can enter the body more freely in the GI system and when the body sends the immune response sometimes it picks up on the “self” cells that are a part of the GI system, creating the autoimmunity. Sleep deprivation only exacerbates this cycle as well as what you consume daily (2).
1. https://www.ncbi.nlm.nih.gov/pubmed/27134599
2. Mother-in-law personal experience
While the effect sleep deprivation has on the immune system hasn’t been established, there have been many studies that indicate a relationship between the two. The relationship has been investigated for nearly 2000 years now, for example, Hippocrates highlighted the presence of sleepiness during acute infections. A related 2016 research article focused on shift workers, who tend to suffer from chronic sleep deprivation. The study was a literature review of previous studies conducted on the matter and analyzed the various conclusions made. One of the studies has shown that there are differences between acute and chronic sleep deprivation. During acute deprivation, there is a temporary increase in the activity of natural killer cells, while chronic deprivation has shown a decrease in NK cells. The immunological changes caused by both types of sleep deprivation have proved to cause an increase in susceptibility to viral infections because of the impact the change has on the innate immune system. The effect sleep deprivation has on the circadian rhythm has also been identified as having the potential to affect the immune system. Cells of the innate and adaptive immune system exhibit circadian expression as variation in the blood count. The effect was illustrated in a 2012 study that discovered there was a reduction of vaccine protection from the Hepatitis B virus in patients that received fewer than six hours of sleep.
Citations:
1. https://www.ncbi.nlm.nih.gov/pubmed/28123655
2. https://www.ncbi.nlm.nih.gov/pubmed/22851802
This was an interesting read. Sleep deprivation indeed causes a myriad of issues from simply feeling tired to health issues such as weight gain and obesity. As an individual who used up late into the night to do work, I feel that I was once a direct sufferer of the effects of inadequate sleep. However, over the years, I committed myself to planning better and thus received better sleep and I feel that I have benefitted as a result. The fact that the immune system and antibody responses are linked with sleep deprivation is quite interesting to me. In fact, other researchers have claimed that immune responses also have an effect on sleep quality just as a lack of sleep effects the immune system (1). However, I believe more research needs to be conducted to see if sleeping more can reverse poor antibody responses and more about why a lack of sleep is linked with decreased immune system functioning (is there a causal link?)
Source:
1. https://www.ncbi.nlm.nih.gov/pubmed/28069386
I found this article to be insight based on my own personal experience with the topic. I realized that most of the time I get sick, it is right after an exam week where I got less than five hours of sleep per day. I always knew my immune system would be weakened from this, but the data in this article showed exactly why this is happening. Chronic sleep deprivation lowers antibody production to certain pathogens and leukocyte gene expression, making you more susceptible to common infectious agents like Rhinovirus. Like the article suggested, carrying out the study with identical twins was a good way to insure accuracy of reported results. A point I would like to point out is how sleep deprivation can lower antibody production when given a vaccine. This is a fact I feel nurses and doctors should mention and run by patients before administering vaccinations.
In our society, acute sleep deprivation is one of the most common diseases found in most adults. The effects of such sleep deprivation have been known to cause anxiety and, as previously stated, immunosuppression. However, little is known beyond forcing bed rest as a way to help alleviate these symptoms and their last effects. A recent study found a potential therapeutic way to help lower anxiety and inflammation by giving lab rats an extract made from the leaves of Withania somnifera. This could help be used as a dietary supplement instead of simply having the people ‘wait it out’.
https://www.ncbi.nlm.nih.gov/pubmed/28004351
This post talk about how sleep deprivation have negative impact on our immune system. Several researches show that sleep deprivation has close association with some chronic inflammation disease such as type II diabetes and inflammation bowel disease (IBD). The reason is that sleep deprivation tends to increase the level of some proinflammatory cytokines such as Interlukin-1 (IL-1) and Interlukin-6 (IL-6), and some tumor necrosis factors(TNF). Fluctuation of those cytokines also detected in some gastrointestinal disease such as IBD and liver disorder. Moreover, those cytokines also play an important role in regulate sleep-wake cycle. According to Santos study, “Changes in serum cytokine levels with these underlying diseases will affect sleep, as cytokines are major modulators of the sleep-wake cycle.” Which shows that those cytokines promote sleep while sleep deprivation will activate IL-1 and TNF. Experiment shows that IBD patients who sleep less than 6 hours per day are tend to have higher level of proinflammatory cytokines and more easy to trigger a flare. The relationship between IBD and sleep deprivation creating a negative feedback loop which sleep deprivation increase the level of proinflammatory cytokines and therefore worsening the disease condition and then the cycle continue. Since sleep is close associated with IBD, some of the medications that associated with sleep disturbances are assigned to patient for disease management. For example, melatonin, which associated with sleep promotion, has been used as a treatment for IBD because of its ability to reduce the inflammation in the intestinal mucosa. Moreover, sleep deprivation can also trigger inflammation by increasing depression and stress level. The gut-brain axis is the bidirectional communication between the central neuron system (CNS) and the gastrointestinal tract. Under the stress condition, corticotrophin-releasing hormone is produced by the paraventricular nucleus of the hypothalamus. This hormone then triggers the release of the cortisol from the adrenal gland. Cortisol plays an important role in the modulation of gut permeability by changing the composition and function of the intestinal mucosal barrier. The intestinal mucosal barrier is selectively permeable under normal condition which limiting the passage of the harmful compounds. The releasing of the cytokines will affect this protection ability and allowing the passage of the unwanted compound such as dietary antigen and gut microbiotas which then causing the dysfunction of immune reaction. Therefore, increasing sleep duration and quality has been used as the treatment for autoimmune disease management.
Cited:
1. https://www.ncbi.nlm.nih.gov/pubmed/23376797
2. https://www.ncbi.nlm.nih.gov/pubmed/27134599
3. https://www.ncbi.nlm.nih.gov/pubmed/25830558
4.https://www.ncbi.nlm.nih.gov/pubmed/17517356
Sleep deprivation is a serious problem in our country full of stressed-out, working class families in our capitalist-run society. Since it has become such a problem, scientists continued to try and understand patterns of the sleep deprived and how it relates to memory loss. To the naked-untrained eye, it only makes sense that cognitive skills may not be are sharp for people living with serious sleeping problems. Many studies have already shown strong correlations with memory loss and sleep deprived individuals. However, the rest of the story to how memory loss even begins in the brain has not be exposed. This study selected demonstrates that there are factors of how sleep deprivation has an effect on memory consolidation by synaptic consolidation and system consolidation which is how the brains stores memory in the hippocampus. Their experiment was used to backtrack and find out what led to problem. The study shows that sleep deprivation led to a negative impact of the hippocampcal cAMP and mTORC1 signaling. The goal was try to restore the hippocampus cAMP levels and restore hippocampal mTORC1 signaling along with other similar factors that underlined the reasoning for memory loss. Restoring the hippocampal cAMP and the experimental restoration of hippocampal mTORC1 signaling both led to a decreased memory-loss correlated to memory defects. Though having a good night sleep is still vital, as for the topic of memory loss, scientists can reach higher heights with trying to decrease that negative effect it causes on the human brain.
Sleep is a vital aspect of our mental and physical health. While some people fulfill the required range of sleep (7-8 hours), others face difficulty in falling asleep. Sleep is mediated by neurotransmitters in the brain that communicate between the brain and spinal cord, and regulate hormone release. Melatonin is a hormone released that causes the onset of sleep. Exposure to blue light, emitted by cell phone and television, inhibits melatonin release and thus cause latency in the onset of sleep. Other factors include eating a large portion of meal within 3 hours before bedtime. This correlates to longer sleep time and intervals of wake. Therefore, to have good sleeping patterns one should practice healthy diet and avoid factors that can affect falling asleep, such as exposure to blue light before bedtime.
1. https://www-ncbi-nlm-nih-gov.ezproxy.gsu.edu/pubmed/28271579
I could definitely relate to this article. This is coming from a person who suffers from sleep deprivation, this article was eye-opening for me and sends a warning call. Even though I’m very well aware of the critical of sleep in the human body, my daily attempt in juggling school work and working almost 3o hours every week is no doubt catching up to me. Although I have not experienced any new onset of sickness, reading this article prove that it is bound to occur if I keep going with my habits. The immune system is no doubt, the most significant aspect of keeping the human body free of pathogens, and this article just fuels my desire to get more than enough sleep per day. Apart from my personal experiences, This article was an overall good read, the research on using the twins was a very good idea as it showed just how sleep could play a significant role in people’s immune system who are exposed to the same environments and similar circumstances. A research conducted at the UCLA Semel Institute for Neuroscience showed that there is a correlation between sleep deprivation and the onset of depression and inflammatory disorders. This raises the question of why sleep is related to so many abnormalities in the human body. It would be interesting to conduct more research on other aspects of the human body that a decrease in sleep could potentially have an effect on as well.
Source:
1. https://www.ncbi.nlm.nih.gov/pubmed/27510422
2. https://www.ncbi.nlm.nih.gov/pubmed/28142285
Sleep deprivation is not only linked to a weak immune system, but it is also linked to poor eyesight and trouble retaining memory. As we sleep, some of the short term memory gets stored in long-term memory. If we don’t sleep and rest our brain the short term memories, we make throughout the day will never be saved ad we forget most of the things we did in the previous day. A study done by Alzoubi and colleagues tested a methanolic extract of the fruits of Arbutus andrachne on sleep-deprived mice. The study showed that A. andrachne reduced the hippocampus GSH/GSSg ratio and activity of GPX, which prevented short and long term impairment. It is also proven that light receptors in your eye die and repair while you sleep. As a student, it is important to get some rest because it improves your memory and repair eyesight for efficient studying
Arbutus andrachne L. Reverses Sleep Deprivation-Induced Memory Impairments in Rats https://www.ncbi.nlm.nih.gov/pubmed/28101814
Sleep is definitely an important component of our everyday lives. It helps us to restore our energy so we can get back to our busy routine. When we don’t get adequate sleep our immunity and mental health takes a toll such as unregulated immune responses, memory and critical thinking skills. Sleep deprivation affects our daily lives in the working environment as well. In a recent review, 15% to 25% that make up the workforce are shift workers. The shift workers that were followed and studied had to find a balance between productivity and sleep time. As a result, the shift workers experienced chronic sleep deprivation with increased fatigue and drowsiness (1). According to the International Classification of Sleep Disorders (ICSD-3), shift work disorder is prevalent in about 2–5% of the US working population (2). Shift worker disorder is diagnosed by meeting four criteria: 1. There is a report of insomnia and/or excessive sleepiness 2. Symptoms have been present and associated with the shift work schedule for at least three months. 3. A sleep log demonstrating 14 days (work and free days) disturbed sleep and wake patterns. 4. No other sleep disorder can classify these symptoms (3).
Sources
(1) https://www.ncbi.nlm.nih.gov/pubmed/28123655
(2) http://www.sciencedirect.com/science/article/pii/S1984006316300815
(3) American Academy of Sleep Medicine (AASM)
IL Darien (Ed.), International classification of sleep disorders (3rd ed.n), American Academy of Sleep Medicine (2014)
http://www.sciencedirect.com/science/article/pii/S1984006316300815