“polyphasic sleep”
(coined by early 20th century psychologist “J.S. Szymanski”)
(a ‘pollack’)
(refers to the practice of sleeping multiple times in a 24-hour period—usually, more than 2, in contrast to ‘biphasic sleep’ —and does not imply any particular schedule)
(the term polyphasic sleep is also used by an online community which experiments with ultra-short napping to achieve more time awake each day)
An example of polyphasic sleep is found in patients with irregular sleep-wake pattern, a circadian rhythm sleep disorder which usually is caused by head injury or dementia.
Much more common examples are the sleep of human infants and of many animals.
Elderly humans often have disturbed sleep, including polyphasic sleep
In their 2006 paper “The Nature of Spontaneous Sleep Across Adulthood”, Campbell and Murphy studied sleep timing and quality in young, middle-aged and older adults.
They found that, in free-running conditions, the average duration of major nighttime sleep was significantly longer in young adults than in the other groups.
The paper states further:
“Whether such patterns are simply a response to the relatively static experimental conditions, or whether they more accurately reflect the natural organization of the human sleep/wake system, compared with that which is exhibited in daily life, is open to debate.
However, the comparative literature strongly suggests that shorter, polyphasically-placed sleep is the rule, rather than the exception, across the entire animal kingdom (Campbell and Tobler, 1984; Tobler, 1989).
There is little reason to believe that the human sleep/wake system would evolve in a fundamentally different manner.
That people often do not exhibit such sleep organization in daily life merely suggests that humans have the capacity (often with the aid of stimulants such as caffeine or increased physical activity) to overcome the propensity for sleep when it is desirable, or is required, to do so”
.
In crisis and other extreme conditions, people may not be able to achieve the recommended eight hours of sleep per day.
Systematic napping may be considered necessary in such situations.
Dr. Claudio Stampi, as a result of his interest in long-distance solo boat racing, has studied the systematic timing of short naps as a means of ensuring optimal performance in situations where extreme sleep deprivation is inevitable, but he does not advocate ultrashort napping as a lifestyle.
Scientific American Frontiers (PBS) has reported on Stampi’s 49-day experiment where a young man napped for a total of three hours per day.
It purportedly shows that all stages of sleep were included.
Stampi has written about his research in his book “Why We Nap: Evolution, Chronobiology, and Functions of Polyphasic and Ultrashort Sleep” (1992)
In 1989 he published results of a field study in the journal Work & Stress, concluding that “polyphasic sleep strategies improve prolonged sustained performance” under continuous work situations
The U.S. Military
The US military has studied fatigue countermeasures.
An Air Force report states:
“Each individual nap should be long enough to provide at least 45 continuous minutes of sleep, although longer naps (2 hours) are better.
In general, the shorter each individual nap is, the more frequent the naps should be (the objective remains to acquire a daily total of 8 hours of sleep).”
The Canadian Marine Pilots
Similarly, the Canadian Marine Pilots in their trainer’s handbook report that:
“[u]nder extreme circumstances where sleep cannot be achieved continuously, research on napping shows that 10- to 20-minute naps at regular intervals during the day can help relieve some of the sleep deprivation and thus maintain minimum levels of performance for several days. However, researchers caution that levels of performance achieved using ultrashort sleep (short naps) to temporarily replace normal sleep, are always well below that achieved when fully rested.”
NASA
HYPERLINK “http://en.wikipedia.org/wiki/NASA” \o “NASA” NASA, in cooperation with the National Space Biomedical Research Institute, has funded research on napping. Despite NASA recommendations that HYPERLINK “http://en.wikipedia.org/wiki/Astronaut” \o “Astronaut” astronauts sleep 8 hours a day when in space, they usually have trouble sleeping 8 hours at a stretch, so the agency needs to know about the optimal length, timing and effect of naps. Professor HYPERLINK “http://en.wikipedia.org/wiki/David_F._Dinges” \o “David F. Dinges” David Dinges of the HYPERLINK “http://en.wikipedia.org/wiki/University_of_Pennsylvania_School_of_Medicine” \o “University of Pennsylvania School of Medicine” University of Pennsylvania School of Medicine led research in a laboratory setting on sleep schedules which combined various amounts of “anchor sleep,” ranging from about 4 to 8 hours in length, with no nap or daily naps of up to 2.5 hours. Longer naps were found to be better, with some cognitive functions benefiting more from napping than others. Vigilance and basic alertness benefited the least while HYPERLINK “http://en.wikipedia.org/wiki/Working_memory” \o “Working memory” working memory benefited greatly. Naps in the individual subjects’ biological daytime worked well, but naps in their nighttime were followed by much greater HYPERLINK “http://en.wikipedia.org/wiki/Sleep_inertia” \o “Sleep inertia” sleep inertia lasting up to an hour. HYPERLINK “http://en.wikipedia.org/wiki/Polyphasic_sleep” \l “cite_note-9” [10]
[ HYPERLINK “http://en.wikipedia.org/w/index.php?title=Polyphasic_sleep&action=edit§ion=6” \o “Edit section: The Italian Air Force” edit]The Italian Air Force
The Italian Air Force (Aeronautica Militare Italiana) also conducted experiments for their pilots. In schedules involving night shifts and fragmentation of duty periods through the entire day, a sort of polyphasic sleeping schedule was studied. Subjects were to perform two hours of activity followed by four hours of rest (sleep allowed), this was repeated four times throughout the 24-hour day. Although sleep was allowed, subjects adopted a schedule of not sleeping at all during the first rest period of the day. The AMI published findings that “total sleep time was substantially reduced as compared to the usual 7-8 hour monophasic nocturnal sleep” while “maintaining good levels of vigilance as shown by the virtual absence of EEG microsleeps.” EEG HYPERLINK “http://en.wikipedia.org/wiki/Microsleep” \o “Microsleep” microsleeps are measurable and usually unnoticeable bursts of sleep in the brain while a subject appears to be awake. Nocturnal sleepers who sleep poorly may be heavily bombarded with microsleeps during waking hours, limiting focus and attention. HYPERLINK “http://en.wikipedia.org/wiki/Polyphasic_sleep” \l “cite_note-10” [11]
[ HYPERLINK “http://en.wikipedia.org/w/index.php?title=Polyphasic_sleep&action=edit§ion=7” \o “Edit section: Scheduled napping to achieve more ‘wake-time'” edit] Scheduled napping to achieve more ‘wake-time’
People have tried to adopt a polyphasic schedule of naps totalling about two to six hours per day, in order to gain more time awake in their day.
In an early mention of systematic napping as a lifestyle, HYPERLINK “http://en.wikipedia.org/wiki/Buckminster_Fuller” \o “Buckminster Fuller” Buckminster Fuller advocated a regimen consisting of 30 minute naps every six hours, which he reportedly followed for two years. The short article about Fuller’s sleep in HYPERLINK “http://en.wikipedia.org/wiki/Time_%28magazine%29” \o “Time (magazine)” TIME in 1943 also refers to such a schedule as “intermittent sleeping”, and it notes:
“Eventually he had to quit because his schedule conflicted with that of his business associates, who insisted on sleeping like other men.“ HYPERLINK “http://en.wikipedia.org/wiki/Polyphasic_sleep” \l “cite_note-11” [12]
However, it is not clear when Fuller practiced any such sleep pattern, and whether it was really as strictly periodic as claimed in that article; it has also been said that he ended this experiment because of his wife’s objections. HYPERLINK “http://en.wikipedia.org/wiki/Polyphasic_sleep” \l “cite_note-12” [13]
Critics consider the theory behind severe reduction of total sleep time by way of short naps unsound, claiming that there is no brain control mechanism that would make it possible to adapt to the “multiple naps” system. They say that the body will always tend to consolidate sleep into at least one solid block, and express concern that the ways in which the ultrashort nappers attempt to limit total sleep time, restrict time spent in the various stages of the sleep cycle, and disrupt the circadian rhythm of the body, will eventually cause them to suffer the same negative effects as those with other forms of HYPERLINK “http://en.wikipedia.org/wiki/Sleep_deprivation” \o “Sleep deprivation” sleep deprivation and HYPERLINK “http://en.wikipedia.org/wiki/Circadian_rhythm_sleep_disorder” \o “Circadian rhythm sleep disorder” circadian rhythm sleep disorders, such as decreased mental and physical ability, increased stress and anxiety, and a weakened immune system. HYPERLINK “http://en.wikipedia.org/wiki/Polyphasic_sleep” \l “cite_note-13” [14]
HYPERLINK “http://en.wikipedia.org/wiki/Sara_Mednick” \o “Sara Mednick” Sara Mednick, Ph.D., whose sleep research investigates napping, included a chapter, Extreme Napping, in her book Take a Nap! Change Your Life. HYPERLINK “http://en.wikipedia.org/wiki/Polyphasic_sleep” \l “cite_note-14” [15] In response to questions from readers about the “uberman” schedule, she wrote in May 2007:
“This practice rests upon one important hypothesis that our biological rhythms are adaptable. This means that we can train our internal mechanisms not only when to sleep and wake, but also when to get hungry, have energy for exercise, perform mental activities. Inferred in this hypothesis is that we have the power to regulate our mood, metabolism, core body temperature, endocrine and stress response, basically everything inside this container of flesh we call home. Truly an Uberman feat!“ HYPERLINK “http://en.wikipedia.org/wiki/Polyphasic_sleep” \l “cite_note-15” [16]
[ HYPERLINK “http://en.wikipedia.org/w/index.php?title=Polyphasic_sleep&action=edit§ion=8” \o “Edit section: Comparison of sleep patterns” edit] Comparison of sleep patterns
HYPERLINK “http://en.wikipedia.org/wiki/File:Monophasic.png” \o “Image:Monophasic.png” INCLUDEPICTURE “http://upload.wikimedia.org/wikipedia/commons/8/8e/Monophasic.png” \* MERGEFORMATINET HYPERLINK “http://en.wikipedia.org/wiki/File:Biphasic.png” \o “Image:Biphasic.png” INCLUDEPICTURE “http://upload.wikimedia.org/wikipedia/commons/c/c3/Biphasic.png” \* MERGEFORMATINET
HYPERLINK “http://en.wikipedia.org/wiki/File:Everyman.png” \o “Image:Everyman.png” INCLUDEPICTURE “http://upload.wikimedia.org/wikipedia/commons/d/d5/Everyman.png” \* MERGEFORMATINET HYPERLINK “http://en.wikipedia.org/wiki/File:Uberman.png” \o “Image:Uberman.png” INCLUDEPICTURE “http://upload.wikimedia.org/wikipedia/commons/6/61/Uberman.png” \* MERGEFORMATINET HYPERLINK “http://en.wikipedia.org/wiki/File:Dymaxion.png” \o “Image:Dymaxion.png” INCLUDEPICTURE “http://upload.wikimedia.org/wikipedia/commons/2/20/Dymaxion.png” \* MERGEFORMATINET
[ HYPERLINK “http://en.wikipedia.org/w/index.php?title=Polyphasic_sleep&action=edit§ion=9” \o “Edit section: Bloggers” edit] Bloggers
Starting in 1999, several people have experimented with alternative sleep patterns intended to reduce HYPERLINK “http://en.wikipedia.org/wiki/Sleep” \o “Sleep” sleep time to 2–6 hours daily in order to have more time awake, and some of them have blogged their experiences. This is purportedly achieved by spreading out sleep into short naps of around 15–45 minutes throughout the day, and in some variants, a core sleep period of a few hours at night. The systematic napping patterns are, by the online proponents, called polyphasic sleep, and napping schedules include the Everyman sleep schedule and the Uberman sleep schedule. HYPERLINK “http://en.wikipedia.org/wiki/Polyphasic_sleep” \l “cite_note-16” [17]
The blogger PureDoxyk, who coined the Uberman and Everyman names, wrote about her initial experimentation, HYPERLINK “http://en.wikipedia.org/wiki/Polyphasic_sleep” \l “cite_note-17” [18] and then went on to write extensively about the Everyman sleep schedule and polyphasic sleep in general on her blog. HYPERLINK “http://en.wikipedia.org/wiki/Polyphasic_sleep” \l “cite_note-18” [19] These efforts culminated in the 80-page monograph Ubersleep. HYPERLINK “http://en.wikipedia.org/wiki/Polyphasic_sleep” \l “cite_note-19” [20]
According to reports by PureDoxyk and others, it takes roughly 7-14 days to convert to a polyphasic napping schedule. During the first few days, they claim, the body will experience controlled sleep deprivation and can be expected to enter HYPERLINK “http://en.wikipedia.org/wiki/Rapid_eye_movement_%28sleep%29” \o “Rapid eye movement (sleep)” REM and deep sleep stages more quickly during each nap. After the first week, some bloggers mention vivid dreams occurring during each[ HYPERLINK “http://en.wikipedia.org/wiki/Wikipedia:Citation_needed” \o “Wikipedia:Citation needed” citation needed] nap and a refreshed feeling of wakefulness shortly after each nap.
Different sleep patterns may give individually varied results; the blogger HYPERLINK “http://en.wikipedia.org/wiki/Steve_Pavlina” \o “Steve Pavlina” Steve Pavlina reported difficulty switching from Uberman’s sleep schedule, after five months, to Fuller’s Dymaxion sleep schedule and gave up the attempt. WebMD’s Dr. Breus ended his short series on Sleep Hackers by reporting Pavlina’s return to monophasic sleep in 2006, HYPERLINK “http://en.wikipedia.org/wiki/Polyphasic_sleep” \l “cite_note-20” [21] due to social problems caused by the unusual sleep schedule. HYPERLINK “http://en.wikipedia.org/wiki/Polyphasic_sleep” \l “cite_note-21” [22]
Polyphasic sleeping blogs have become quite common and one can find blogs offering general information on polyphasic sleeping HYPERLINK “http://en.wikipedia.org/wiki/Polyphasic_sleep” \l “cite_note-22” [23] HYPERLINK “http://en.wikipedia.org/wiki/Polyphasic_sleep” \l “cite_note-23” [24] as well as many offering personal accounts of their experiences. HYPERLINK “http://en.wikipedia.org/wiki/Polyphasic_sleep” \l “cite_note-24” [25] HYPERLINK “http://en.wikipedia.org/wiki/Polyphasic_sleep” \l “cite_note-25” [26] HYPERLINK “http://en.wikipedia.org/wiki/Polyphasic_sleep” \l “cite_note-26” [27] HYPERLINK “http://en.wikipedia.org/wiki/Polyphasic_sleep” \l “cite_note-27” [28] HYPERLINK “http://en.wikipedia.org/wiki/Polyphasic_sleep” \l “cite_note-28” [29] HYPERLINK “http://en.wikipedia.org/wiki/Polyphasic_sleep” \l “cite_note-29” [30] HYPERLINK “http://en.wikipedia.org/wiki/Polyphasic_sleep” \l “cite_note-30” [31] HYPERLINK “http://en.wikipedia.org/wiki/Polyphasic_sleep” \l “cite_note-31” [32]
Segmented sleep, divided sleep, bimodal sleep pattern and interrupted sleep are modern Western terms for a HYPERLINK “http://en.wikipedia.org/wiki/Polyphasic_sleep” \o “Polyphasic sleep” polyphasic or biphasic sleep pattern found in HYPERLINK “http://en.wikipedia.org/wiki/Medieval_Europe” \o “Medieval Europe” medieval and HYPERLINK “http://en.wikipedia.org/wiki/Early_modern_Europe” \o “Early modern Europe” early modern HYPERLINK “http://en.wikipedia.org/wiki/Europe” \o “Europe” Europe and many non-industrialised societies today, where the night’s sleep is divided by one or more periods of wakefulness. This is particularly common in the winter. HYPERLINK “http://en.wikipedia.org/wiki/Segmented_sleep” \l “cite_note-0” [1]
The human HYPERLINK “http://en.wikipedia.org/wiki/Circadian_rhythm” \o “Circadian rhythm” circadian rhythm controls a sleep-wake cycle of wakefulness during the day and sleep at night. Superimposed on this basic rhythm is a secondary one of light sleep in the early afternoon (see HYPERLINK “http://en.wikipedia.org/wiki/Siesta” \o “Siesta” siesta) and quiet wakefulness in the early morning.
The two periods of night sleep were called first sleep (occasionally dead sleep) and second sleep (or morning sleep) in medieval HYPERLINK “http://en.wikipedia.org/wiki/England” \o “England” England. First and second sleep are also the terms in the HYPERLINK “http://en.wikipedia.org/wiki/Romance_languages” \o “Romance languages” Romance languages, as well as the HYPERLINK “http://en.wikipedia.org/wiki/Tiv” \o “Tiv” Tiv of HYPERLINK “http://en.wikipedia.org/wiki/Nigeria” \o “Nigeria” Nigeria: In French, the common term was premier sommeil or premier somme; in Italian, primo sonno; in Latin, primo somno or comcubia nocte. HYPERLINK “http://en.wikipedia.org/wiki/Segmented_sleep” \l “cite_note-1” [2] There is no common word in English for the period of wakefulness between, apart from paraphrases such as first waking or when one wakes from his first sleep and the generic watch (in its old meaning of being awake). In HYPERLINK “http://en.wikipedia.org/wiki/French_language” \o “French language” French an equivalent generic term is dorveille (“twixt sleep and wake”).
this period of wakefulness was often only semi-conscious, as the French term implies. It was highly valued in medieval Europe as a time of quiet and relaxation. Peasant couples were often too tired after a long day’s work to do much more than eat and go to sleep, but they would wake later on to talk and make love. People would also use this time to pray and reflect,and to interpret dreams, which were more vivid at that hour than upon waking in the morning and even to visit. This was also a favorite time for scholars and poets to write uninterrupted.
There is evidence from sleep research that this period of nighttime wakefulness, combined with a midday nap, results in greater alertness than a monophasic sleep-wake cycle. The brain exhibits high levels of the pituitary hormone prolactin during the period of nighttime wakefulness, which may contribute to the feeling of peace that many people associate with it. It is in many ways similar to the hypnogogic and hypnopompic states which occur just before falling asleep and upon waking, respectively.
Because members of modern industrialised societies, with late hours facilitated by electric lighting, no longer have this sleep pattern, they may misinterpret and mistranslate references to it in literature. Common interpretations of the term ‘first sleep’ are ‘beauty sleep’ and ‘early slumber’. A reference to first sleep in the Odyssey was translated as such in the 17th century, but universally mistranslated in the 20th
The modern assumption that consolidated sleep with no awakenings is the normal and correct way for human adults to sleep leads many to approach their doctors with complaints of maintenance insomnia or other sleep disorders. Their concerns might best be addressed by assurance that their sleep conforms to historically natural sleep patterns
The optimal amount of sleep is not a meaningful concept unless the timing of that sleep is seen in relation to an individual’s circadian rhythms. A person’s major sleep episode is relatively inefficient and inadequate when it occurs at the “wrong” time of day; one should be asleep at least six hours before the lowest body temperature. The timing is correct when the following two circadian markers occur after the middle of the sleep episode and before awakening:
maximum concentration of the hormone melatonin, and
minimum core body temperature.
The National Sleep Foundation in the United States maintains that seven to nine hours of sleep for adult humans is optimal and that sufficient sleep benefits alertness, memory, problem solving, and overall health, as well as reducing the risk of accidents. A widely publicized 2003 studyperformed at the University of Pennsylvania School of Medicine demonstrated that cognitive performance declines with six or fewer hours of sleep.
A University of California, San Diego, psychiatry study of more than one million adults found that people who live the longest self-report sleeping for six to seven hours each night. Another study of sleep duration and mortality risk in women showed similar results. Other studies show that “sleeping more than 7 to 8 hours per day has been consistently associated with increased mortality”, though this study suggests the cause is probably other factors such as depression and socioeconomic status, which would correlate statistically. It has been suggested that the correlation between lower sleep hours and reduced morbidity only occurs with those who wake after less sleep naturally, rather than those who use an alarm.
Researchers at the University of Warwick and University College London have found that lack of sleep can more than double the risk of death from cardiovascular disease, but that too much sleep can also double the risk of death. Professor Francesco Cappuccio said, “Short sleep has been shown to be a risk factor for weight gain, hypertension, and Type 2 diabetes, sometimes leading to mortality; but in contrast to the short sleep-mortality association, it appears that no potential mechanisms by which long sleep could be associated with increased mortality have yet been investigated. Some candidate causes for this include depression, low socioeconomic status, and cancer-related fatigue. …In terms of prevention, our findings indicate that consistently sleeping around seven hours per night is optimal for health, and a sustained reduction may predispose to ill health.”
Furthermore, sleep difficulties are closely associated with psychiatric disorders such as depression, alcoholism, and bipolar disorder. Up to 90% of adults with depression are found to have sleep difficulties. Dysregulation found on EEG includes disturbances in sleep continuity, decreased delta sleep and altered REM patterns with regard to latency, distribution across the night and density of eye movements
A circadian rhythm is a roughly-24-hour cycle in the biochemical, physiological or behavioral processes of living entities, including plants, animals, fungi and cyanobacteria (see bacterial circadian rhythms). The term “circadian”, coined by Franz Halberg, comes from the Latin circa, “around,” and diem or dies, “day”, meaning literally “approximately one day.” The formal study of biological temporal rhythms such as daily, tidal, weekly, seasonal, and annual rhythms, is called chronobiology.
Circadian rhythms are endogenously generated, and can be entrained by external cues, called Zeitgebers, the primary one of which is daylight. These rhythms allow organisms to anticipate and prepare for precise and regular environmental changes.
HYPERLINK “http://en.wikipedia.org/wiki/File:Biological_clock_human.PNG” \o “Overview of human circadian biological clock with some physiological parameters.” INCLUDEPICTURE “http://upload.wikimedia.org/wikipedia/commons/thumb/5/5f/Biological_clock_human.PNG/400px-Biological_clock_human.PNG” \* MERGEFORMATINET
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Overview of human circadian biological clock with some physiological parameters.
The earliest known account of a circadian rhythm dates from the 4th century BC, when Androsthenes, a ship captain serving under Alexander the Great, described diurnal leaf movements of the tamarind tree. The first modern observation of endogenous circadian oscillation was by the French scientist Jean-Jacques d’Ortous de Mairan in the 1700s; he noted that 24-hour patterns in the movement of the leaves of the plant Mimosa pudica continued even when the plants were isolated from external stimuli.
In 1918 J. S. Szymanski showed that animals are capable of maintaining 24-hour activity patterns in the absence of external cues such as light and changes in temperature. Joseph Takahashi discovered the genetic basis for the mammalian circadian rhythm in 1994
To differentiate genuinely endogenous circadian rhythms from coincidental or apparent ones, three general criteria must be met: 1) the rhythms persist in the absence of cues, 2) they persist equally precisely over a range of temperatures, and 3) the rhythms can be adjusted to match the local time.
The rhythm persists in constant conditions (for example, constant dark) with a period of about 24 hours. The rationale for this criterion is to distinguish circadian rhythms from those “apparent” rhythms which merely are responses to external periodic cues. A rhythm cannot be declared to be endogenous unless it has been tested in conditions without external periodic input.
The rhythm is temperature-compensated, i.e. it maintains the same period over a range of temperatures. The rationale for this criterion is to distinguish circadian rhythms from other biological rhythms arising due to the circular nature of a reaction pathway. At a low enough or high enough temperature, the period of a circular reaction may reach 24 hours, but it will be merely coincidental.
The rhythm can be reset by exposure to an external stimulus. The rationale for this criterion is to distinguish circadian rhythms from other imaginable endogenous 24-hour rhythms that are immune to resetting by external cues and hence do not serve the purpose of estimating the local time. Travel across time zones illustrates the necessity of the ability to adjust the biological clock so that it can reflect the local time and anticipate what will happen next. Until rhythms are reset, a person usually experiences jet lag.
[ HYPERLINK “http://en.wikipedia.org/w/index.php?title=Circadian_rhythm&action=edit§ion=3” \o “Edit section: Origin” edit] Origin
| HYPERLINK “http://en.wikipedia.org/wiki/File:Question_book-new.svg” \o “Question book-new.svg” INCLUDEPICTURE “http://upload.wikimedia.org/wikipedia/en/thumb/9/99/Question_book-new.svg/50px-Question_book-new.svg.png” \* MERGEFORMATINET This section needs additional HYPERLINK “http://en.wikipedia.org/wiki/Wikipedia:Citing_sources” \l “Inline_citations” \o “Wikipedia:Citing sources” citations for HYPERLINK “http://en.wikipedia.org/wiki/Wikipedia:Verifiability” \o “Wikipedia:Verifiability” verification. Please help HYPERLINK “http://en.wikipedia.org/w/index.php?title=Circadian_rhythm&action=edit” \o “http://en.wikipedia.org/w/index.php?title=Circadian_rhythm&action=edit” improve this article by adding HYPERLINK “http://en.wikipedia.org/wiki/Wikipedia:Reliable_sources” \o “Wikipedia:Reliable sources” reliable references. Unsourced material may be HYPERLINK “http://en.wikipedia.org/wiki/Template:Fact” \o “Template:Fact” challenged and HYPERLINK “http://en.wikipedia.org/wiki/Wikipedia:Verifiability” \l “Burden_of_evidence” \o “Wikipedia:Verifiability” removed. (October 2007) |
Photosensitive proteins and circadian rhythms are believed to have originated in the earliest cells, with the purpose of protecting the replicating of DNA from high HYPERLINK “http://en.wikipedia.org/wiki/Ultraviolet” \o “Ultraviolet” ultraviolet radiation during the daytime. As a result, replication was relegated to the dark. The fungus HYPERLINK “http://en.wikipedia.org/wiki/Neurospora” \o “Neurospora” Neurospora, which exists today, retains this clock-regulated mechanism. Rhythmicity appears to be as important in regulating cyclic biochemical processes within an individual, as in coordinating with the environment. This is suggested by the maintenance (heritability) of circadian rhythms in fruit flies after several hundred generations in constant laboratory conditions (Sheeba et al. 1999), as well as the experimental elimination of behavioral but not physiological circadian rhythms in quail (Guyomarc’h et al. 1998, Zivkovic et al. 1999).
The simplest known circadian clock is that of the prokaryotic HYPERLINK “http://en.wikipedia.org/wiki/Cyanobacteria” \o “Cyanobacteria” cyanobacteria. Recent research has demonstrated that the circadian clock of Synechococcus elongatus can be reconstituted in vitro with just the three proteins of their central oscillator. This clock has been shown to sustain a 22-hour rhythm over several days upon the addition of HYPERLINK “http://en.wikipedia.org/wiki/Adenosine_triphosphate” \o “Adenosine triphosphate” ATP. Previous explanations of the HYPERLINK “http://en.wikipedia.org/wiki/Prokaryotic” \o “Prokaryotic” prokaryotic circadian timekeeper were dependent upon a DNA transcription / translation feedback mechanism.
It is an unanswered question whether circadian clocks in eukaryotic organisms require translation/transcription-derived oscillations. For although the circadian systems of eukaryotes and prokaryotes have the same basic architecture: input – central oscillator – output, they do not share any homology. This implies probable independent origins.
In 1971, Ronald J. Konopka and HYPERLINK “http://en.wikipedia.org/wiki/Seymour_Benzer” \o “Seymour Benzer” Seymour Benzer first identified a genetic component of the biological clock using the fruit fly as a model system. Three mutant lines of flies displayed aberrant behavior – one had a shorter period, another had a longer one and the third had none. All three mutations mapped to the same gene, which was named HYPERLINK “http://en.wikipedia.org/wiki/Period_%28gene%29” \o “Period (gene)” period. HYPERLINK “http://en.wikipedia.org/wiki/Circadian_rhythm” \l “cite_note-5” [6] The same gene was identified to be defective in the sleep disorder FASPS ( HYPERLINK “http://en.wikipedia.org/wiki/Familial_advanced_sleep_phase_syndrome” \o “Familial advanced sleep phase syndrome” Familial advanced sleep phase syndrome) in human beings thirty years later – underscoring the conserved nature of the molecular circadian clock through evolution. We now know many more genetic components of the biological clock. Their interactions result in an interlocked feedback loop of gene products resulting in periodic fluctuations that the cells of the body interpret as a specific time of the day.
A great deal of research on biological clocks was done in the latter half of the 20th century. It is now known that the molecular circadian clock can function within a single cell; i.e., it is cell-autonomous. HYPERLINK “http://en.wikipedia.org/wiki/Circadian_rhythm” \l “cite_note-6” [7] At the same time, different cells may communicate with each other resulting in a synchronized output of electrical signaling. These may interface with endocrine glands of the brain to result in periodic release of hormones. The receptors for these hormones may be located far across the body and synchronize the peripheral clocks of various organs. Thus, the information of the time of the day as relayed by the HYPERLINK “http://en.wikipedia.org/wiki/Eye” \o “Eye” eyes travels to the clock in the brain, and, through that, clocks in the rest of the body may be synchronized. This is how the timing of, for example, sleep/wake, body temperature, thirst, and appetite are coordinately controlled by the biological clock.
[ HYPERLINK “http://en.wikipedia.org/w/index.php?title=Circadian_rhythm&action=edit§ion=4” \o “Edit section: Importance in animals” edit] Importance in animals
Circadian rhythmicity is present in the HYPERLINK “http://en.wikipedia.org/wiki/Sleep” \o “Sleep” sleeping and feeding patterns of animals, including human beings. There are also clear patterns of core body temperature, HYPERLINK “http://en.wikipedia.org/wiki/Brain_wave” \o “Brain wave” brain wave activity, HYPERLINK “http://en.wikipedia.org/wiki/Hormone” \o “Hormone” hormone production, cell regeneration and other biological activities. In addition, HYPERLINK “http://en.wikipedia.org/wiki/Photoperiodism” \o “Photoperiodism” photoperiodism, the physiological reaction of organisms to the length of day or night, is vital to both plants and animals, and the circadian system plays a role in the measurement and interpretation of day length.
Timely prediction of seasonal periods of weather conditions, food availability or predator activity is crucial for survival of many species. Although not the only parameter, the changing length of the photoperiod (‘daylength’) is the most predictive environmental cue for the seasonal timing of physiology and behavior, most notably for timing of migration, hibernation and reproduction. HYPERLINK “http://en.wikipedia.org/wiki/Circadian_rhythm” \l “cite_note-7” [8]
[ HYPERLINK “http://en.wikipedia.org/w/index.php?title=Circadian_rhythm&action=edit§ion=5” \o “Edit section: Impact of light-dark cycle” edit] Impact of light-dark cycle
The rhythm is linked to the light-dark cycle. Animals, including humans, kept in total darkness for extended periods eventually function with a HYPERLINK “http://en.wikipedia.org/wiki/Free-running_sleep” \o “Free-running sleep” freerunning rhythm. Each “day,” their sleep cycle is pushed back or forward, depending on whether their HYPERLINK “http://en.wikipedia.org/wiki/Endogenous” \o “Endogenous” endogenous period is shorter or longer than 24 hours. The environmental cues that each day reset the rhythms are called HYPERLINK “http://en.wikipedia.org/wiki/Zeitgeber” \o “Zeitgeber” Zeitgebers (from the German, Time Givers). HYPERLINK “http://en.wikipedia.org/wiki/Circadian_rhythm” \l “cite_note-health.am-8” [9] It is interesting to note that totally-blind subterranean mammals (e.g., HYPERLINK “http://en.wikipedia.org/wiki/Blind_mole_rat” \o “Blind mole rat” blind mole rat Spalax sp.) are able to maintain their endogenous clocks in the apparent absence of external stimuli.
Freerunning organisms that normally have one consolidated sleep episode will still have it when in an environment shielded from external cues, but the rhythm is, of course, not entrained to the 24-hour light/dark cycle in nature. The sleep/wake rhythm may, in these circumstances, become out of phase with other circadian or HYPERLINK “http://en.wikipedia.org/wiki/Ultradian” \o “Ultradian” ultradian rhythms such as HYPERLINK “http://en.wikipedia.org/wiki/Temperature” \o “Temperature” temperature and HYPERLINK “http://en.wikipedia.org/wiki/Digestion” \o “Digestion” digestion.[ HYPERLINK “http://en.wikipedia.org/wiki/Wikipedia:Citation_needed” \o “Wikipedia:Citation needed” citation needed]
Recent research has influenced the design of HYPERLINK “http://en.wikipedia.org/wiki/Human_spaceflight” \o “Human spaceflight” spacecraft environments, as systems that mimic the light/dark cycle have been found to be highly beneficial to astronauts.[ HYPERLINK “http://en.wikipedia.org/wiki/Wikipedia:Citation_needed” \o “Wikipedia:Citation needed” citation needed]
[ HYPERLINK “http://en.wikipedia.org/w/index.php?title=Circadian_rhythm&action=edit§ion=6” \o “Edit section: Arctic animals” edit] Arctic animals
Norwegian researchers at the HYPERLINK “http://en.wikipedia.org/wiki/University_of_Troms%C3%B8” \o “University of Tromsø” University of Tromsø have shown that some Arctic animals ( HYPERLINK “http://en.wikipedia.org/wiki/Ptarmigan” \o “Ptarmigan” ptarmigan, HYPERLINK “http://en.wikipedia.org/wiki/Reindeer” \o “Reindeer” reindeer) show circadian rhythms only in the parts of the year that have daily sunrises and sunsets. In one study of reindeer, animals at HYPERLINK “http://en.wikipedia.org/wiki/70th_parallel_north” \o “70th parallel north” 70 degrees North showed circadian rhythms in the autumn, winter, and spring, but not in the summer. Reindeer at HYPERLINK “http://en.wikipedia.org/wiki/78th_parallel_north” \o “78th parallel north” 78 degrees North showed such rhythms only autumn and spring. The researchers suspect that other Arctic animals as well may not show circadian rhythms in the constant light of summer and the constant dark of winter. HYPERLINK “http://en.wikipedia.org/wiki/Circadian_rhythm” \l “cite_note-9” [10] HYPERLINK “http://en.wikipedia.org/wiki/Circadian_rhythm” \l “cite_note-10” [11]
However, another study in northern Alaska found that HYPERLINK “http://en.wikipedia.org/wiki/Ground_squirrel” \o “Ground squirrel” ground squirrels and HYPERLINK “http://en.wikipedia.org/wiki/Porcupine” \o “Porcupine” porcupines strictly maintained their circadian rhythms through 82 days and nights of sunshine. The researchers speculate that these two small mammals see that the apparent distance between the sun and the horizon is shortest once a day, and, thus, a sufficient signal to adjust by. HYPERLINK “http://en.wikipedia.org/wiki/Circadian_rhythm” \l “cite_note-11” [12]
[ HYPERLINK “http://en.wikipedia.org/w/index.php?title=Circadian_rhythm&action=edit§ion=7” \o “Edit section: Biological clock in mammals” edit] Biological clock in mammals
HYPERLINK “http://en.wikipedia.org/wiki/File:Circadian_rhythm_labeled.jpg” \o “Diagram illustrating the influence of light and darkness on circadian rhythms and related physiology and behavior through the suprachiasmatic nucleus in humans.” INCLUDEPICTURE “http://upload.wikimedia.org/wikipedia/commons/5/55/Circadian_rhythm_labeled.jpg” \* MERGEFORMATINET
HYPERLINK “http://en.wikipedia.org/wiki/File:Circadian_rhythm_labeled.jpg” \o “Enlarge” INCLUDEPICTURE “http://en.wikipedia.org/skins-1.5/common/images/magnify-clip.png” \* MERGEFORMATINET
Diagram illustrating the influence of light and darkness on circadian rhythms and related HYPERLINK “http://en.wikipedia.org/wiki/Physiology” \o “Physiology” physiology and behavior through the HYPERLINK “http://en.wikipedia.org/wiki/Suprachiasmatic_nucleus” \o “Suprachiasmatic nucleus” suprachiasmatic nucleus in humans.
The primary circadian “clock” in HYPERLINK “http://en.wikipedia.org/wiki/Mammal” \o “Mammal” mammals is located in the HYPERLINK “http://en.wikipedia.org/wiki/Suprachiasmatic_nucleus” \o “Suprachiasmatic nucleus” suprachiasmatic nucleus (or nuclei) ( HYPERLINK “http://en.wikipedia.org/wiki/SCN” \o “SCN” SCN), a pair of distinct groups of HYPERLINK “http://en.wikipedia.org/wiki/Cell_%28biology%29” \o “Cell (biology)” cells located in the HYPERLINK “http://en.wikipedia.org/wiki/Hypothalamus” \o “Hypothalamus” hypothalamus. Destruction of the SCN results in the complete absence of a regular sleep/wake rhythm. The SCN receives information about illumination through the eyes. The HYPERLINK “http://en.wikipedia.org/wiki/Retina” \o “Retina” retina of the eyes contains not only “classical” HYPERLINK “http://en.wikipedia.org/wiki/Photoreceptor” \o “Photoreceptor” photoreceptors but also photoresponsive retinal HYPERLINK “http://en.wikipedia.org/wiki/Ganglion_cells” \o “Ganglion cells” ganglion cells. These cells, which contain a photo pigment called HYPERLINK “http://en.wikipedia.org/wiki/Melanopsin” \o “Melanopsin” melanopsin, follow a pathway called the HYPERLINK “http://en.wikipedia.org/wiki/Retinohypothalamic_tract” \o “Retinohypothalamic tract” retinohypothalamic tract, leading to the SCN. If cells from the SCN are removed and cultured, they maintain their own rhythm in the absence of external cues.
It appears that the SCN takes the information on the lengths of the day and night from the retina, interprets it, and passes it on to the HYPERLINK “http://en.wikipedia.org/wiki/Pineal_gland” \o “Pineal gland” pineal gland, a tiny structure shaped like a HYPERLINK “http://en.wikipedia.org/wiki/Pine_cone” \o “Pine cone” pine cone and located on the HYPERLINK “http://en.wikipedia.org/wiki/Epithalamus” \o “Epithalamus” epithalamus. In response the pineal secretes the hormone HYPERLINK “http://en.wikipedia.org/wiki/Melatonin” \o “Melatonin” melatonin. Secretion of melatonin peaks at night and ebbs during the day and its presence provides information about night-length.
The circadian rhythms of humans can be entrained to slightly shorter and longer periods than the Earth’s 24 hours. Researchers at Harvard have recently shown that human subjects can at least be entrained to a 23.5-hour cycle and a 24.65-hour cycle (the latter being the natural solar day-night cycle on the planet HYPERLINK “http://en.wikipedia.org/wiki/Mars” \o “Mars” Mars). HYPERLINK “http://en.wikipedia.org/wiki/Circadian_rhythm” \l “cite_note-12” [13]
[ HYPERLINK “http://en.wikipedia.org/w/index.php?title=Circadian_rhythm&action=edit§ion=8” \o “Edit section: Determining the human circadian rhythm” edit] Determining the human circadian rhythm
The classic phase markers for measuring the timing of a mammal’s circadian rhythm are
melatonin secretion by the pineal gland and
core body temperature.
For temperature studies, people must remain awake but calm and semi-reclined in near darkness while their rectal temperatures are taken continuously. The average human adult’s temperature reaches its minimum at about 05:00 (5 a.m.), about two hours before habitual wake time, though variation is great among normal HYPERLINK “http://en.wikipedia.org/wiki/Chronotype” \o “Chronotype” chronotypes.
Melatonin is absent from the system or undetectably low during daytime. Its onset in dim light, dim-light melatonin onset (DLMO), at about 21:00 (9 p.m.) can be measured in the blood or the saliva. Its major HYPERLINK “http://en.wikipedia.org/wiki/Metabolite” \o “Metabolite” metabolite can also be measured in morning urine. Both DLMO and the midpoint (in time) of the presence of the hormone in the blood or saliva have been used as circadian markers.
However, newer research indicates that the melatonin offset may be the most reliable marker. Benloucif et al. in Chicago in 2005 found that melatonin phase markers were more stable and more highly correlated with the timing of sleep than the core temperature minimum. They found that both sleep offset and melatonin offset were more strongly correlated with the various phase markers than sleep onset. In addition, the declining phase of the melatonin levels was more reliable and stable than the termination of melatonin synthesis. HYPERLINK “http://en.wikipedia.org/wiki/Circadian_rhythm” \l “cite_note-13” [14]
One method used for measuring melatonin offset is to analyze a sequence of urine samples throughout the morning for the presence of the melatonin HYPERLINK “http://en.wikipedia.org/wiki/Metabolite” \o “Metabolite” metabolite 6-sulphatoxymelatonin (aMT6s). Laberge et al. in Quebec in 1997 used this method in a study which confirmed the frequently found delayed circadian phase in healthy adolescents. HYPERLINK “http://en.wikipedia.org/wiki/Circadian_rhythm” \l “cite_note-14” [15]
[ HYPERLINK “http://en.wikipedia.org/w/index.php?title=Circadian_rhythm&action=edit§ion=9” \o “Edit section: Outside the \”master clock\”” edit] Outside the “master clock”
More-or-less independent circadian rhythms are found in many organs and cells in the body outside the suprachiasmatic nuclei (SCN), the “master clock.” These clocks, called peripheral oscillators, are found in the esophagus, lung, liver, pancreas, spleen, thymus and the skin. HYPERLINK “http://en.wikipedia.org/wiki/Circadian_rhythm” \l “cite_note-15” [16] Though oscillators in the skin respond to light, a systemic influence has not been proven so far. HYPERLINK “http://en.wikipedia.org/wiki/Circadian_rhythm” \l “cite_note-16” [17] HYPERLINK “http://en.wikipedia.org/wiki/Circadian_rhythm” \l “cite_note-17” [18] There is some evidence that also the olfactory bulb and prostate may experience oscillations when cultured, suggesting that also these structures may be weak oscillators.
Furthermore, HYPERLINK “http://en.wikipedia.org/wiki/Liver” \o “Liver” liver cells, for example, appear to respond to feeding rather than to HYPERLINK “http://en.wikipedia.org/wiki/Light” \o “Light” light. Cells from many parts of the body appear to have freerunning rhythms.
[ HYPERLINK “http://en.wikipedia.org/w/index.php?title=Circadian_rhythm&action=edit§ion=10” \o “Edit section: Light and the biological clock” edit] Light and the biological clock
Light resets the biological clock in accordance with the HYPERLINK “http://en.wikipedia.org/wiki/Phase_response_curve” \o “Phase response curve” phase response curve (PRC). Depending on the timing, light can advance or delay the circadian rhythm. Both the PRC and the required HYPERLINK “http://en.wikipedia.org/wiki/Illuminance” \o “Illuminance” illuminance vary from species to species and lower light levels are required to reset the clocks in nocturnal rodents than in humans.
Lighting levels that affect circadian rhythm in humans are higher than the levels usually used in artificial lighting in homes. According to some researchers HYPERLINK “http://en.wikipedia.org/wiki/Circadian_rhythm” \l “cite_note-semj-18” [19] the illumination intensity that excites the circadian system has to reach up to 1000 HYPERLINK “http://en.wikipedia.org/wiki/Lux” \o “Lux” lux striking the retina. In addition to light intensity, wavelength (or color) of light is a factor in the entrainment of the body clock. HYPERLINK “http://en.wikipedia.org/wiki/Melanopsin” \o “Melanopsin” Melanopsin is most efficiently excited by blue light, 420-440 nm HYPERLINK “http://en.wikipedia.org/wiki/Circadian_rhythm” \l “cite_note-19” [20] according to some researchers while others have reported 470-485 nm.
It is thought that the direction of the light may have an effect on entraining the circadian rhythm; HYPERLINK “http://en.wikipedia.org/wiki/Circadian_rhythm” \l “cite_note-semj-18” [19] light coming from above, resembling an image of a bright sky, has greater effect than light entering our eyes from below.
[ HYPERLINK “http://en.wikipedia.org/w/index.php?title=Circadian_rhythm&action=edit§ion=11” \o “Edit section: The myth of the 25-hour day” edit]The myth of the 25-hour day
Early investigators determined the human circadian period to be 25 hours or more.
They went to great lengths to shield subjects from time cues and daylight, but they were not aware of the effects of indoor electric lights. The subjects were allowed to turn on light when they were awake and to turn it off when they wanted to sleep. Electric light in the evening delayed their circadian phase. These results became well known. HYPERLINK “http://en.wikipedia.org/wiki/Circadian_rhythm” \l “cite_note-hno-20” [21]
[ HYPERLINK “http://en.wikipedia.org/w/index.php?title=Circadian_rhythm&action=edit§ion=12” \o “Edit section: The human circadian period” edit]The human circadian period
Modern research under very controlled conditions has shown the human period for adults to be just slightly longer than 24 hours on average. Czeisler et al at Harvard found the range for normal, healthy adults of all ages to be quite narrow: 24 hours and 11 minutes ± 16 minutes. The “clock” resets itself daily to the 24-hour cycle of the earth’s rotation. HYPERLINK “http://en.wikipedia.org/wiki/Circadian_rhythm” \l “cite_note-hno-20” [21]
[ HYPERLINK “http://en.wikipedia.org/w/index.php?title=Circadian_rhythm&action=edit§ion=13” \o “Edit section: Human health” edit] Human health
Timing of medical treatment in coordination with the body clock may significantly increase efficacy and reduce drug toxicity or adverse reactions. For example, appropriately timed treatment with HYPERLINK “http://en.wikipedia.org/wiki/Angiotensin_converting_enzyme_inhibitors” \o “Angiotensin converting enzyme inhibitors” angiotensin converting enzyme inhibitors (ACEi) may reduce nocturnal blood pressure and also benefit HYPERLINK “http://en.wikipedia.org/wiki/Left_ventricular” \o “Left ventricular” left ventricular (reverse) remodeling.
A short nap during the day does not affect circadian rhythms.
A number of studies have concluded that a short period of sleep during the day, a power-nap, does not have any effect on normal circadian rhythm, but can decrease stress and improve productivity
There are many health problems associated with disturbances of the human circadian rhythm, such as seasonal affective disorder (SAD), delayed sleep phase syndrome (DSPS) and other circadian rhythm disorders. Circadian rhythms also play a part in the reticular activating system which is crucial for maintaining a state of consciousness. In addition, a reversal in the sleep-wake cycle may be a sign or complication of uremia, azotemia or acute renal failure.
Disruption to rhythms usually has a negative effect. Many travelers have experienced the condition known as jet lag, with its associated symptoms of fatigue, disorientation and insomnia.
A number of other disorders, for example bipolar disorder and some sleep disorders, are associated with irregular or pathological functioning of circadian rhythms. Recent research suggests that circadian rhythm disturbances found in bipolar disorder are positively influenced by lithium’s effect on clock genes
Disruption to rhythms in the longer term is believed to have significant adverse health consequences on peripheral organs outside the brain, particularly in the development or exacerbation of cardiovascular disease. The suppression of melatonin production associated with the disruption of the circadian rhythm may increase the risk of developing cancer
Circadian rhythms and clock genes expressed in brain regions outside the SCN may significantly influence the effects produced by drugs such as cocaine. Moreover, genetic manipulations of clock genes profoundly affect cocaine’s actions.
Jet lag, also jetlag or jet-lag, medically referred to as “desynchronosis” is a physiological condition which is a consequence of alterations to circadian rhythms; it is classified as one of the circadian rhythm sleep disorders. Jet lag results from rapid long-distance transmeridian (east-west or west-east) travel, as on a jet plane
The condition of jet lag may last many days, and recovery rates of 1 day per eastward time zone or 1 day per 1.5 westward time zones are mentioned as fair guidelines
When traveling across a number of time zones, the body clock will be out of synchronisation with the destination time, as it experiences daylight and darkness contrary to the rhythms to which it has grown accustomed: the body’s natural pattern is upset, as the rhythms that dictate times for eating, sleeping, hormone regulation and body temperature variations no longer correspond to the environment nor to each other in some cases. To the degree that the body cannot immediately realign these rhythms, it is jet lagged.
The speed at which the body adjusts to the new schedule depends on the individual; some people may require several days to adjust to a new time zone, while others experience little disruption. Crossing one or two time zones does not typically cause jet lag.
The condition is not linked to the length of flight, but to the transmeridian (east-west) distance traveled. A ten-hour flight from Europe to southern Africa does not cause jet lag, as travel is primarily north-south. A five hour flight from the west to the east coast of the United States may well result in jet lag.
Crossing the International Date Line does not contribute to jet lag, as the guide for calculating jet lag is the number of time zones crossed, and the maximum possible disruption is plus or minus 12 hours. If the time difference between two locations is greater than 12 hours, subtract that number from 24. Note, for example, that the time zone GMT+14 will be at the same time of day as GMT-10, though the former is one day ahead of the latter.
The symptoms of jet lag can be quite varied, depending on the amount of time zone alteration. They may include the following:
Digestive problems
Headache
Fatigue, irregular sleep patterns, temporary insomnia
Disorientation, grogginess, irritability
Mild depression
Other symptoms which some may attribute to jet lag, such as nausea, ear aches and swollen feet, may be caused by the mode of travel rather than the time zone change
There seems to be some evidence that for most people, traveling west to east is more disruptive. This may be because most people have a circadian period which is a bit longer than 24 hours, making it easier to stay up later than to get up earlier
It may also be that flights to the east are more likely to require people to stay awake more than one full night in order to adjust to the local time zone. For example, comparing a typical schedule for a traveler flying to the East vs a traveler flying to the West:
Westbound from London to Los Angeles, VIA BA0279, Jan 29, 2008. Time zone difference 8 hours.
| Westbound | Biological clock | Los Angeles local time |
| Departure | JAN 29 – 10:05 | JAN 29 – 02:05 |
| Arrival | JAN 29 – 21:10 | JAN 29 – 13:10 |
| Bedtime | JAN 30 – 06:00 | JAN 29 – 22:00 |
Eastbound from Los Angeles to London, VIA BA0278, Jan 29, 2008.
| Eastbound | Biological clock | London local time |
| Departure | JAN 29 – 10:05 | JAN 29 – 18:05 |
| Arrival | JAN 29 – 18:11 | JAN 30 – 02:11 |
| Bedtime | JAN 30 – 14:00 | JAN 30 – 22:00 |
The first scenario is equivalent to staying up all night and going to bed at 6am the next day — 8 hours later than usual. But the second scenario (eastward) is equivalent to staying up all night and going to bed at 2pm the next day — 14 hours after the time one would otherwise have gone to bed. Some sleep onboard will help the situation somewhat.
Since the experience of jet lag varies among individuals, it is difficult to assess the efficacy of any single remedy. Gradual adjustment over the course of several days of the onset of sleep while maintaining its regular length of 7–8 hours can reduce fatigue and prevent depression. When the goal is to catch-up with local time (vs. fallback to), this can be aided by avoiding afternoon naps and eating an early and carbohydrates-rich, low-protein dinner
Most chemical and herbal remedies, including the hormone melatonin, have not been tested nor approved by official agencies such as the United States Food and Drug Administration.
Few studies have tested the use of melatonin for jet lag and have given mixed results, likely because the timing of administration needs to be precise and individualized
a recent study in hamsters showed that sildenafil (known commercially as viagra) aided in a 50% faster recovery from shifts comparable to eastward travel experienced by humans and was effective starting at low doses.
however, this use has not been tested in humans and is considered an off-label use by the drug’s manufacturers.
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(the presence of ‘low-level light’ at night also accelerates recovery rate in both east- and west-travelling hamsters of all ages by 50%; this is thought to be related to simulation of ‘moonlight’)
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