Somnology

Summary

Somnology is the scientific and clinical study of sleep, sleep disorders, and sleep-associated issues. Somnologists are interested in diverse physical and psychological processes of sleep and their correlations with wakefulness, lifestyle, and environment. Humans spend, on average, spend one-third of their lifetime sleeping. According to the United States (US) Centers for Disease Control and Prevention (CDC), between fifty and seventy million Americans suffered from chronic sleep problems in 2024. The study of sleep is an important issue because many accidents involve a lack of sleep. There is both high clinical and medical interest and a huge potential for services and products, ranging from medication to meditation, which will improve the quantity or quality of sleep.

Definition and Basic Principles

Somnology is the scientific and clinical study of sleep. The term is derived from the Latin somnus, “sleep,” and the Greek logos, “word” or “reason.” Somnologists study the processes, both physical and psychological, that constitute sleep and examine how these processes relate to wakefulness, lifestyle, and environment. They conduct research on diverse scientific and medical problems such as insomnia or parasomnias.

Somnology is the science behind much of sleep medicine. Sleep medicine involves the diagnosis and treatment of sleeping disorders, disturbances, and problems. In sleep laboratories, neurological and biophysical data are recorded, collected, assessed, and interpreted with the help of polysomnography.

Somnology does not include oneirology, the scientific study of dreams, which includes cultural, arts-related, anthropological, psychoanalytical, psychological, and neurological approaches.

Background and History

In Greek mythology, sleep is viewed as having a close relationship with death—Hypnos, the god of sleep, is the brother of Thanatos, the god of death—and as being a negation of wakefulness. The Greek philosopher Aristotle believed that sleep was an active, integrated aspect of the process of life, with the function of recreation and life maintenance.

In 1924, German psychiatrist Hans Berger recorded the first human electroencephalogram (EEG). In 1937, American physicist Alfred Lee Loomis and his colleagues used data from EEGs to first describe different stages of sleep. Nathaniel Kleitman, a professor of physiology at the University of Chicago, and Eugene Aserinsky, one of his graduate students, identified rapid eye movement (REM) sleep in 1952 and defined it in 1953. In the 1960s, German biologist Jürgen Aschoff, one of the founders of chronobiology, first used the term “zeitgeber” to refer to an external cue that sets or resets an organism's biological clock in the scientific literature on sleep. William C. Dement, another of Kleitman's graduate students, was an important figure in the early study of REM sleep. Dement initiated a narcolepsy clinic in 1964 and founded the world's first sleep laboratory, the Sleep Research Center, at Stanford University in 1970.

In 1968, Allan Rechtschaffen and Anthony Kales standardized the criteria for the different stages of sleep in their Rechtschaffen and Kales (R&K) system. In 1975, Dement founded the Association of Sleep Disorders Centers, which later became the American Academy of Sleep Medicine. The association developed a diagnostic nomenclature of sleep disorders in 1979, which was revised in 1990. In 2007, the association published The AASM Manual for the Scoring of Sleep and Associated Events: Rules, Terminology, and Technical Specifications, a revision of the R&K system; this resource was then consistently revised and updated over subsequent years.

How It Works

Somnologists have divided sleep into non-REM and REM phases or stages. Three stages of non-REM sleep have been identified: N1, N2, and N3. Sleep normally consists of four to six cycles of non-REM and REM sleep. Each cycle usually follows the order of N1, N2, N3, N2, and REM and lasts between 90 and 120 minutes. In the N1 stage, also called drowsy sleep or somnolence, a person's conscious awareness of the environment and the tone of their muscles, diminishes. In the N2 stage, conscious awareness of the environment disappears, and muscular activity diminishes. Adults spend around one-half of their sleeping time in phase N2. In N3, known as deep sleep, delta sleep, or slow-wave sleep, parasomnias may occur. Usually, N3 phases are longer earlier in the night, and the length of REM phases increases late at night and early in the morning. All four to six REM sleep phases added together amount to around 90 to 120 minutes (about one-quarter) of total sleeping time. During REM, heart and breathing rates are irregular, and normally, clitoral or penile tumescence occurs. Although brain activity has been recorded in areas associated with sense perception, balance, and body movement during REM, in a healthy person, muscular activity is suspended, a phenomenon known as atonia. People who wake up during a REM phase can more easily remember their dreams; therefore, it is thought that most dreaming occurs during this stage of sleep and that little (or less) dreaming occurs in non-REM sleep. If REM sleep is repeatedly interrupted, the sleeper will compensate with longer REM phases at a later stage (rebound sleep).

Functions of Sleep. Sleep has diverse functions related to developmental, restorative, and memory processes. A certain quality and quantity of sleep (especially in the REM phase) is vital for humans, mammals, and certain other animals. The total sleeping time in adults ranges from six to nine hours per night; an average of seven hours is optimal for health. Newborn babies sleep up to eighteen hours per day, but as children grow older, they sleep fewer hours. Sleep (particularly REM) is important for brain development, especially in infants. Sleep deprivation (especially of slow-wave and REM sleep) negatively affects cognitive functions, complex processing capability, and memory. Sleep deprivation hampers the restorative processes of the organism and its immune system, which manifests, for example, as a lower white blood cell count and impeded wound healing. Anabolic hormones, which build tissues and organs, are secreted during sleep.

Applications and Products

A polysomnogram can help physicians assess sleeping patterns and diagnose sleeping abnormalities. Many tools and products can improve the quality or quantity of sleep, ranging from simple behavioral and sleeping environment adjustments to significant medical interventions. If a sleep-related problem such as insomnia is not the symptom of a medical condition, often a patient's sleep can be improved through simple behavioral or sleep environment adjustments.

Polysomnography. Polysomnography is used to monitor and record biophysical and neurological data during sleep. It is used both in the scientific study of sleep and in diagnosing (or ruling out) parasomnias, insomnias, and other sleep-related problems. The test is usually performed during the night and monitored by a technician; the result is a polysomnogram. The test measures, records, and assesses brain waves by electroencephalography (EEG), eye movements by electrooculography (EOG), heart rhythm by electrocardiography (EKG), and skeletal muscle activity by electromyography (EMG). Additionally, depending on the purpose of the test, several other tests can be performed. Nasal and oral airflow can be measured to detect sleep apnea, a disorder in which a person stops breathing momentarily numerous times during sleep. Pulse oximetry can measure the oxygen saturation of the blood, which will drop in the case of sleep apnea. Microphones can pick up sounds, such as snoring or speaking during sleep. The sleeper is often videotaped during the test, partly to monitor the individual and partly to determine if parasomnias are present.

Behavioral Adjustments. Simple behavioral adjustments for those with sleep disorders include getting out of bed if the person is unable to get back to sleep after fifteen to twenty minutes and avoiding stimulants such as coffee, nicotine, chocolate, and sugary foods in the afternoon. Those with sleep disorders are also told to avoid alcohol, which initially might help induce sleep, because it can cause them to wake up more easily during the night. Sleep medicine professionals recommend that people eat a light meal two hours before going to bed or drink a glass of milk just before sleeping. Activities that encourage sound sleep are light exercise, sexual intercourse, walking, and taking a warm bath or shower. Sleeping in loose clothes made from natural materials, using guided imagery, and establishing sleeping rituals such as reading, listening to music, or meditating can improve sleep. Leaving electronics out of the bedroom and avoiding light from electronics before bedtime can enhance sleep. Other suggestions include developing a positive attitude toward going to bed, limiting daytime naps, losing weight if overweight, and undergoing psychotherapy or counseling to address the root of the problem that keeps the person awake.

Environmental Adjustments. The environment can be modified so that it is conducive to falling and staying asleep. For example, the room can be darkened and made quieter through curtains and window shutters or special soundproof windows. The temperature and humidity of the sleeping environment can be adjusted with the help of air-conditioning, heating, fans, or air humidifiers. Other recommendations include removing all unnecessary items from the sleeping environment, using natural materials for bedding and bedroom furnishings, and limiting electronic sources of disturbance (such as televisions, computers, and cell phones).

Special Sleeping Devices. Many sleep products are available, although some of them are of questionable benefit. Products range from nightly use products such as custom-made or weight-adjusted beds, weighted blankets, contoured pillows, special bed or pillow covers, sleeping bags, and pajamas to less common items such as dawn-simulating devices for shift workers, blackout curtains, snoring aids, music to sleep by, white-noise machines, and bed-wetting alarms.

Sleeping Medications and Clinical Sleeping Aids. Sleep medications range from herbal, ayurvedic, homeopathic, and allopathic to placebo treatments. Some plants, such as lavender and hops, have a calming effect and are used in alternative treatments for sleeping problems. Most clinically prescribed allopathic treatments (sleeping pills) contain benzodiazepines or nonbenzodiazepines, which are sedative-hypnotic drugs. The side effects, which are various and can be severe, include a reduction in the length of REM sleep, dizziness, confusion, anxiety, depression, drug dependency, cancer, and increased mortality. Circadian rhythm sleep disorders related to jet lag, shift work, and delayed sleep phases can sometimes be treated successfully with melatonin. Melatonin has only a few short-term side effects, but its long-term effects have not been thoroughly studied. Circadian rhythm sleep disorders can also be treated with bright light therapy, which exposes a person to light of a specific bandwidth between 3,000 and 10,000 lux for a few minutes or up to several hours, depending on the specific disorder. If sleep apnea is diagnosed, the use of a continuous positive airway pressure (CPAP) device might be prescribed. This device keeps the airway open during sleep so that breathing is not interrupted. Although, in the past, CPAP machines were bulky and hard to sleep with, innovations in CPAP masks have made them more comfortable and easier to use with the aim that more patients will use them. In certain cases of obstructive sleep apnea, the surgical removal of throat tissue may be necessary. In many cases, weight loss can eliminate sleep apnea.

Careers and Course Work

The two most important professions related to sleep medicine are the sleep physician and the sleep technologist/polysomnographic technologist. Students who are interested in a career as a sleep technologist should study a program accredited by the Commission on Accreditation of Allied Health Education Programs. At least thirty-five educational institutions offer accredited programs for polysomnographic technologists. In Canada, the Canadian Sleep Society is the accrediting body for educational programs for polysomnographic technologists. Sleep physicians are clinical specialists who diagnose and treat sleep disorders. They must graduate from medical school and should pursue a specialty in neurology, psychiatry, internal medicine, or pulmonology. Then, they can further specialize in sleep medicine and become board-certified in the field of sleep medicine.

Social Context and Future Prospects

Sleep patterns vary and depend on a person's culture. In areas with little or no artificial light, people have sleep patterns interrupted by wakefulness. In hunter-gatherer and nomadic cultures, people sleep for shorter periods but more often and also during the day. In such cultures, boundaries between wakefulness and sleep are sometimes less clear than in Western cultures. Cultural research suggests that sleeping for seven to eight hours at a stretch, regarded as customary in developed societies, is an ideal rather than a natural sleeping pattern. This research also sheds light on the definition of sleep abnormalities, as from this perspective, not all sleep abnormalities or disorders are necessarily unnatural. This is an area in which additional scientific study is needed.

Research, services, and products promising to improve the quality and quantity of sleep have to take a holistic approach to the individual sleeper and their environment. Highly industrialized societies have more sleep-disturbing factors, such as air and noise pollution, artificial light, and electronic appliances. Stress levels are also higher in highly industrialized societies, interfering with sleep. Because prescription sleep medicines have side effects, including dependency, alternative methods of treating sleep disorders are in high demand. Those with sleep disorders are also ready consumers of information and products that they believe will help them sleep better. In the mid-2020s, people hoping to improve their sleeping habits had increasingly turned to wearable devices that could digitally track and provide information about sleeping patterns. However, such data was treated with professional caution at that point as the technology was still considered inferior to polysomnography and inconsistent for validation through research. Regardless, treatment of sleep disorders may improve people's health and produce significant profits for healthcare professionals and industries involved in healthcare.

Bibliography

“About Sleep.” CDC, 15 Mar. 2024, www.cdc.gov/sleep/about/?CDC‗AAref‗Val=https://www.cdc.gov/sleep/about‗us.html. Accessed 30 May 2024.

Chervin, Ronald D., ed. Common Pitfalls in Sleep Medicine: Case-Based Learning. New York: Cambridge UP, 2014.

Chokroverty, Sudhansu, and Michel Billiard, eds. Sleep Medicine: A Comprehensive Guide to Its Development, Clinical Milestones, and Advances in Treatment. New York: Springer, 2015.

Kryger, Meir H., ed. Atlas of Clinical Sleep Medicine. Philadelphia: Saunders, 2010.

Noyed, Daniel. “Best CPAP Machines of 2024: Our Expert Picks.” Sleep Foundation, 15 Feb. 2024, www.sleepfoundation.org/best-cpap-machines. Accessed 30 May 2024.

Otman, Haley. "A Consumer Sleep Tracker Researchers Can Actually Use." M Health Lab, University of Michigan, 31 Oct. 2019, labblog.uofmhealth.org/body-work/a-consumer-sleep-tracker-researchers-can-actually-use. Accessed 1 Dec. 2020.

Ramos, Alberto R. “Sleep Deprivation, Sleep Disorders, and Chronic Disease.” CDC, 31 Aug. 2023, www.cdc.gov/pcd/issues/2023/23‗0197.htm. Accessed 30 May 2024.

Smith, Harold R., Cynthia L. Comella, and Birgit Högl, eds. Sleep Medicine. New York: Cambridge UP, 2008.

Summers-Bremner, Eluned. Insomnia: A Cultural History. London: Reaction, 2010.