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Sleep is a sedentary state of mind and body. It is characterized by altered consciousness, relatively inhibited sensory activity, reduced muscle activity and reduced interactions with surroundings. It is distinguished from wakefulness by a decreased ability to react to stimuli, but more reactive than a coma or disorders of consciousness, with sleep displaying different, active brain patterns.
Jet lag is a physiological condition that results from alterations to the body's circadian rhythms caused by rapid long-distance trans-meridian travel. For example, someone flying from New York to London, i.e. from west to east, feels as if the time were five hours earlier than local time, and someone travelling from London to New York, i.e. from east to west, feels as if the time were five hours later than local time. The phase shift when traveling from east to west is referred to as phase-delay of the circadian circle, whereas going west to east is phase-advance of the circadian circle. Most travelers find that it is harder to timezone adjust when traveling to the east. Jet lag was previously classified as one of the circadian rhythm sleep disorders.
A circadian rhythm, or circadian cycle, is a natural, internal process that regulates the sleep–wake cycle and repeats roughly every 24 hours. It can refer to any process that originates within an organism and responds to the environment. These 24-hour rhythms are driven by a circadian clock, and they have been widely observed in animals, plants, fungi and cyanobacteria.
Chronobiology is a field of biology that examines timing processes, including periodic (cyclic) phenomena in living organisms, such as their adaptation to solar- and lunar-related rhythms. These cycles are known as biological rhythms. Chronobiology comes from the ancient Greek χρόνος, and biology, which pertains to the study, or science, of life. The related terms chronomics and chronome have been used in some cases to describe either the molecular mechanisms involved in chronobiological phenomena or the more quantitative aspects of chronobiology, particularly where comparison of cycles between organisms is required.
Delayed sleep phase disorder (DSPD), more often known as delayed sleep phase syndrome and also as delayed sleep–wake phase disorder, is a delaying of a person's circadian rhythm compared to those of societal norms. The disorder affects the timing of biological rhythms including sleep, peak period of alertness, core body temperature, and hormonal cycles.
Non-24-hour sleep–wake disorder is one of several chronic circadian rhythm sleep disorders (CRSDs). It is defined as a "chronic steady pattern comprising [...] daily delays in sleep onset and wake times in an individual living in a society". Symptoms result when the non-entrained (free-running) endogenous circadian rhythm drifts out of alignment with the light–dark cycle in nature. Although this sleep disorder is more common in blind people, affecting up to 70% of the totally blind, it can also affect sighted people. Non-24 may also be comorbid with bipolar disorder, depression, and traumatic brain injury. The American Academy of Sleep Medicine (AASM) has provided CRSD guidelines since 2007 with the latest update released in 2015.
A phase response curve (PRC) illustrates the transient change in the cycle period of an oscillation induced by a perturbation as a function of the phase at which it is received. PRCs are used in various fields; examples of biological oscillations are the heartbeat, circadian rhythms, and the regular, repetitive firing observed in some neurons in the absence of noise.
A zeitgeber is any external or environmental cue that entrains or synchronizes an organism's biological rhythms, usually naturally occurring and serving to entrain to the Earth's 24-hour light/dark and 12-month cycles.
Circadian rhythm sleep disorders (CRSD), also known as circadian rhythm sleep-wake disorders (CRSWD), are a family of sleep disorders which affect the timing of sleep. CRSDs arise from a persistent pattern of sleep/wake disturbances that can be caused either by dysfunction in one's biological clock system, or by misalignment between one's endogenous oscillator and externally imposed cues. As a result of this mismatch, those affected by circadian rhythm sleep disorders have a tendency to fall asleep at unconventional time points in the day. These occurrences often lead to recurring instances of disturbed rest, where individuals affected by the disorder are unable to go to sleep and awaken at "normal" times for work, school, and other social obligations. Delayed sleep phase disorder, advanced sleep phase disorder, non-24-hour sleep–wake disorder and irregular sleep–wake rhythm disorder represents the four main types of CRSD.
Shift work sleep disorder (SWSD) is a circadian rhythm sleep disorder characterized by insomnia, excessive sleepiness, or both affecting people whose work hours overlap with the typical sleep period. Insomnia can be the difficulty to fall asleep or to wake up before the individual has slept enough. About 20% of the working population participates in shift work. SWSD commonly goes undiagnosed, so it's estimated that 10–40% of shift workers have SWSD. The excessive sleepiness appears when the individual has to be productive, awake and alert. Both symptoms are predominant in SWSD. There are numerous shift work schedules, and they may be permanent, intermittent, or rotating; consequently, the manifestations of SWSD are quite variable. Most people with different schedules than the ordinary one might have these symptoms but the difference is that SWSD is continual, long-term, and starts to interfere with the individual's life.
A chronotype is the behavioral manifestation of underlying circadian rhythm's myriad of physical processes. A person's chronotype is the propensity for the individual to sleep at a particular time during a 24-hour period. Eveningness and morningness are the two extremes with most individuals having some flexibility in the timing of their sleep period. However, across development there are changes in the propensity of the sleep period with pre-pubescent children preferring an advanced sleep period, adolescents preferring a delayed sleep period and many elderly preferring an advanced sleep period.
Light effects on circadian rhythm are the effects that light has on circadian rhythm.
David F. Dinges is an American sleep researcher and teacher.
Fatigue is a major safety concern in many fields, but especially in transportation, because fatigue can result in disastrous accidents. Fatigue is considered an internal precondition for unsafe acts because it negatively affects the human operator's internal state. Research has generally focused on pilots, truck drivers, and shift workers.
Charles A. Czeisler is an American physician and sleep researcher. He is a researcher and author in the fields of both circadian rhythms and sleep medicine.
Second wind, a colloquial name for the scientific term wake maintenance zone, is a sleep phenomenon in which a person, after a prolonged period of staying awake, temporarily ceases to feel drowsy, often making it difficult to fall asleep when exhausted. They are the result of circadian rhythms cycling into a phase of wakefulness. For example, many people experience the effects of a second wind in the early morning even after an entire night without sleep because it is the time when they would normally wake up.
The morningness–eveningness questionnaire (MEQ) is a self-assessment questionnaire developed by researchers James A. Horne and Olov Östberg in 1976. Its main purpose is to measure whether a person's circadian rhythm produces peak alertness in the morning, in the evening, or in between. The original study showed that the subjective time of peak alertness correlates with the time of peak body temperature; morning types have an earlier temperature peak than evening types, with intermediate types having temperature peaks between the morning and evening chronotype groups. The MEQ is widely used in psychological and medical research and has been professionally cited more than 4,000 times.
Studies, which include laboratory investigations and field evaluations of population groups that are analogous to astronauts, provide compelling evidence that working long shifts for extended periods of time contributes to sleep deprivation and can cause performance decrements, health problems, and other detrimental consequences, including accidents, that can affect both the worker and others.
A constant routine protocol is a common method used in human circadian rhythm research to study internally generated, or endogenous, circadian rhythms without the effect of external, or exogenous, influences. In the method, subjects are kept in constant conditions for at least 24 hours. These include constant light and temperature, as well as constant semi-recumbent posture. In addition, subjects' food intake is evenly distributed throughout the protocol, and subjects are typically not allowed to sleep for the duration. While in these conditions, subjects are often assessed for a number of variables of interest. Two of the most common and best understood of these variables are core body temperature and melatonin.
Charmane Eastman is an American academic research scientist whose career has focused on studying circadian rhythms and their relationships to sleep, jet lag, and shift work. She has also studied winter depression, more properly known as seasonal affective disorder (SAD). Of special focus are the effects of bright light and melatonin on circadian rhythms.
References
- ↑ Mitler MM, Carskadon MA, Czeisler CA, Dement WC, Dinges DF, Graeber RC. "Catastrophes, sleep, and public policy: consensus report". Sleep11:100-109, 1988.
- Eastman C. "Are separate temperature and activity oscillators necessary to explain the phenomena of human circadian rhythms?" In: Moore-Ede MC, Czeisler CA, editors. Mathematical Models of the Circadian Sleep-Wake Cycle. New York, Raven, 1984. pp. 81–103.
- US Congress Office of Technology Assessment. Biological Rhythms: Implications for the Worker. Washington DC, US Government Printing Office, 1991. - ↑ Miller, J. C. (2006). In Search of Circasemidian Rhythms . Report no. 2006-0074. Brooks City-Base TX: Air Force Research Laboratory.
- ↑ Broughton RJ. "SCN controlled circadian arousal and the afternoon "nap zone"." Sleep Res Online1(4):166-178, 1998,
- Broughton RJ. "Biorhythmic variations in consciousness and psychological functions". Canadian Psychological Reviews16:217-230, 1975.
- Broughton RJ. "Chronobiological aspects and models of sleep and napping". In: Dinges DF, Broughton RJ (eds.), Sleep and Alertness: Chronobiological, Behavioral and Medical Aspects of Napping. New York, Raven Press, 71-98, 1989. - ↑ Bjerner B, Holm A, Swennson A. "Diurnal variation in mental performance: A study of three-shift workers". Br J Ind Med12:103-110, 1955.
- Browne RC. "The day and night performance of teleprinter switchboard operators". Occupational Psychology23:1-6, 1949.
- Folkard S, Lombardi DA, Tucker PT. "Shiftwork: safety, sleepiness and sleep". Industrial Health43:20–23, 2005.
- Harris W. "Fatigue, circadian rhythm, and truck accidents". Chapter 8 in Mackie RR (ed.), Vigilance: Operational Performance, and Physiological Correlates. New York, Plenum Press, 1977.
- Harris W. "Relationships between length of time driving, time of day, and certains kinds of accidents". Pages 51-64 in Mackie RR, Miller JC, Effects of Hours of Service, Regularity of Schedules, and Cargo Loading on Truck and Bus Driver Fatigue (NTIS PB290957). Goleta CA, Human Factors Research, Inc., 1978.
- Hildebrandt G, Rohmert W, Rutenfranz J "12 and 24 h rhythms in error frequency of locomotive drivers and the influence of tiredness". Int J Chronobiology2:175-180, 1974.
- Kogi K, Ohta T. "Incidence of near accidental drowsing in locomotive driving during a period of rotation". J Human Ergology4:65-76, 1975.
- Langlois PH, Smolensky MH, His BP, Weir FW. "Temporal patterns of reported single-vehicle car and truck accidents in Texas, USA, during 1980-1983". Chronobiologia2:131-140, 1985.
- Lavie P, Wollma M, Pollack I. "Frequency of sleep–related traffic accidents and hour of the day". Sleep Research15:275, 1986.
- Mitler MM. "Two-peak patterns in sleep, mortality and error". Proc Intl Sympos on Sleep and Health Risk, Springer Verlag, 1989.
- Prokop O, Prokop L. "Ermuding und einschlafen am steuer". Dtsch Z Gerichtl Med44:343-355, 1955. - ↑ Rutenfranz J, Colquhoun P. "Circadian rhythms in human performance". Scand J Work Environ & Health5:167-177, 1979.
- ↑ Colquhoun WP, Blake MJF, Edwards RS. "Experimental studies of shift-work I: A comparison of 'rotating' and 'stabilized' 4-hours shift systems". Ergonomics11:437-453, 1968.
- Colquhoun WP, Paine MWPH, Fort A. "Circadian rhythm of body temperature during prolonged undersea voyages". Aviat Space Environ Med49(5):671-678, 1978.
- Colquhoun WP, Paine MWPH, Fort A. "Changes in the temperature rhythm of submariners following a rapidly rotating watchkeeping system for a prolonged period". Int. Arch. Occup. Environ. Health42:185-190, 1979.
- Martineaud JP, Cisse F, Samb A. "Circadian variability of temperature in fasting subjects". Scripta Medica (Brno)73(1):15–24, 2000. - ↑ Maggioni C, Cornelissen G, Antinozzi R, Ferrario M, Grafe A, Halberg F. "A half-yearly aspect of circulating melatonin in pregnancies complicated by intrauterine growth retardation". Neuroendicrinology Letters20:55-68, 1999.
- ↑ Hayashi M, Morikawa T, Hori T. "Circasemidian 12 h cycle of slow wave sleep under constant darkness". Clin Neurophysiol113(9):1505-16, 2002.