Shiftwork adaptation technique: reset your circadian rhythm by fasting

Researchers in the Division of Sleep Medicine at Harvard Medical School and Beth Israel Deaconness Medical Center in Boston published a paper in this week's journal Science in which they cite the discovery of a second circadian clock in humans which appears to be triggered by fasting. The authors note that this discover could be used to reduce the effects of jet lag and could also help shiftworkers adapt to night work.

Human's primary internal clock is triggered by light. This is the clock we hear about most often -- getting exposure to bright light to increase alertness and avoiding light when trying to sleep. This second clock is triggered by food. The evolutionary underpinnings of the clock seem to be that for early humans not to have food available was a life-threatening situation. If they could not obtain food, their bodies kicked into an extra level of alertness to enable them to continue to search out food. Dr. Clifford Saper, one of the authors of the paper, noted it takes about 16 hours of fasting for this second clock to kick in and override the light-based clock.

This will be particularly important for shiftworkers on a rotating schedule as they prepare for the night shift, or a fixed schedule night shift worker returning to work after days off. A shiftworker might be able to reset his or her circadian rhythms faster by avoiding eating anything during the day prior to the night shift. This would raise alertness levels and the shiftworker would be able to then eat during the overnight shift. The same could also be used by air travelers to avoid jet lag. If the air traveler avoid eating ANYTHING on the flight on a flight from New York to Australia, he or she would better adapt upon arrival.

This will undoubtedly be studied further, so it's subject to modification, but the researchers are credible, and the work being published in the journal Science lends even more credibility. I think there's enough at this point that you might consider using this technique if you're having trouble adapting to night shifts.

Reference:
"Differential Rescue of Light- and Food-Entrainable Circadian Rhythms."
Patrick M. Fuller, Jun Lu, and Clifford B. Saper.
Science Vol. 320. no. 5879, pp. 1074 - 1077.
Published online on 23 May 2008.

Circadian rhythms drive your healthcare

If you've looked into it at all, you know that circadian rhythms drive your sleep. But did you also know that time of day is a factor in the effectiveness of some medicines. That's been known for sometime -- there's actually a term for this, "chronopharmacology", which is a very cool word to have in your vocabulary -- but researchers from many universities and institutions have found 60 pharmaceuticals whose effectiveness varies by time of day. For more on this, read When is the right time to take your pills.

Circadian rhythm "peaks and valleys" and drowsy driving

There are two circadian functions that we can observe on our own without complex measurements: changes in temperature and changes in drowsiness. These two are usually closely related and are most significant from 3:00 to 5:00 AM and PM (Figure). As core body temperature decreases, drowsiness increases.

Melatonin levels are substantially increased (a strong contributor to drowsiness). At the same time there is an increase firing of the brain’s sleep-inducing organs.

These inhibit the neural system/structures that keep our brain in the active waking state. This is the same system that acts on the brain of the baby rocked to sleep by its parent. Before sleep (bedtime), the brain begins a firing pattern that is characteristic to initial stages of sleep. With the depression in the activity of the neural system, we quickly lose interest in demanding intellectual activities. Soon the only thing we can think of is sleep. Once we rest in an undisturbed place, we drift into “dreamland”.

The risk of danger increases when sleepy people have a critical task to perform, like driving. In a National Sleep Foundation poll, half of Americans (51%) reported driving while drowsy during the past year and nearly one out of five (17%) say they have actually dozed off behind the wheel. According to the National Highway Traffic Safety Administration, 100,000 auto accidents occur each year because of “fall-asleep” crashes.

A AAA Foundation for Traffic Safety study identified lifestyle factors that contribute to sleepy driving. People who hold more than one job, who get six hours or less of sleep, or who drive between midnight and 6 a.m. are at significantly higher risk of a drowsy driving crash. Other studies show that sleep-deprived drivers have reactions like those of people who have been drinking alcohol. Your performance, particularly of critical tasks, is equally impaired by 17 hours of continuous wakefulness or a .05 BAC. Something to think about if you’re planning a trip.

Source: http://www.lakehurst.navy.mil/nlweb/safety/documents/traffic-safety/Shiftwork-Pamphlet.pdf.

Related Posts:

* Worker who falls asleep at wheel after 27 hours on the job denied workers comp

* Drowsy driving quiz -- for shiftworkers, and everyone else

* Tips to help you avoid drowsy driving

Railroad engineer files suit over work-induced circadian rhythm disorder

Steve Rennels, a former Norfolk-Southern engineer, has sued his employer claiming the irregular work shifts he was required to work caused a disruption to his circadian rhythms, negatively affecting his health and quality of life.

There's a brief article about this in The Madison St. Clair Record (Madision, Wisconsin, USA) -- Railroad engineer claims sleep disorder in $50K suit.

Importance of the Circadian Clock for Human Health and Well-Being

Nearly all physiological and behavioral functions in humans occur on a rhythmic basis, which in turn leads to dramatic diurnal rhythms in human performance capabilities. Regardless of whether it results from voluntary (e.g., shift work or rapid travel across time zones) or involuntary (e.g., illness or advanced age) circumstances, a disturbed circadian rhythmicity in humans has been associated with a variety of mental and physical disorders and may negatively impact safety, performance, and productivity.

Many adverse effects of disrupted circadian rhythmicity may, in fact, be linked to disturbances in the sleep-wake cycle. Some rhythmic processes are more affected by the circadian clock than by the sleep-wake state, whereas other rhythms are more dependent on the sleep-wake state.
For most animals, the timing of sleep and wakefulness under natural conditions is in synchrony with the circadian control of the sleep cycle and all other circadian-controlled rhythms. Humans, however, have the unique ability to cognitively override their internal biological clock and its rhythmic outputs. When the sleep-wake cycle is out of phase with the rhythms that are con-trolled by the circadian clock (e.g., during shift work or rapid travel across time zones), adverse effects may ensue.

In addition to the sleep disturbances associated with jet lag or shift work, sleep disorders can occur for many other known and unknown reasons. And although disturbed sleep is a hallmark of many human mental and physiological disorders, notably affective disorders, it is often unclear whether the sleep disturbances contribute to or result from the illness. Other circadian rhythm abnormalities also are often associated with various disease states, although again the importance of these rhythm abnormalities in the development (i.e., etiology) of the disease remains unknown (Brunello et al. 2000).

One important factor contributing to researchers’ inability to precisely define the role of circadian abnormalities in various disease states may be the lack of knowledge of how circadian signals from the SCN are relayed to target tissues. To further elucidate the regulation of circadian rhythms, researchers need a better understanding of the nature of circadian signal output from the SCN and of how these output signals may be modified once they reach their target systems. Such an enhanced understanding also would allow for a better delineation of the importance of normal temporal organization for human health and disease.

The finding that two major causes of death-heart attacks and strokes- show time-of-day variation in their occurrence is a case in point. If scientists knew more about the mechanisms responsible for the rhythmicity of these disorders, they might be able to identify more rational therapeutic strategies to influence these events. Finally, given that dramatic changes occur in the circadian clock system with advanced age, these changes may underlie, or at least exacerbate, the age-related deterioration in the physical and mental capabilities of older adults.

Conclusions
Although researchers in just the past few years have made great advances in understanding the molecular basis of circadian rhythmicity, this progress builds on extensive research carried out in many laboratories during the past 50 years. Within the same period, other researchers in numerous laboratories have elucidated the critical role played by the SCN in the regulation of circadian rhythmicity in mammals and per-haps other vertebrates.

***

By Martha Hotz Vitaterna, Ph.D., Joseph S. Takahashi, Ph.D., and Fred W. Turek, Ph.D.

MARTHA HOTZ VITATERNA, PH.D., is a senior research associate in the Center for Functional Genomics, Northwestern University, Evanston, Illinois. JOSEPH S. TAKAHASHI, PH.D., is the director of the Center for Functional Genomics, the Walter and Mary E. Glass Professor in the Department of Neurobiology and Physiology, and an investigator at the Howard Hughes Medical Institute, Northwestern University, Evanston, Illinois. FRED W. TUREK, PH.D., is the director of the Center for Sleep and Circadian Biology and is the Charles T. and Emma H. Morrison Professor in the Department of Neurobiology and Physiology, Northwestern University, Evanston, Illinois.

Source: http://www.niaaa.nih.gov/publications/arh25-2/85-93.htm

Related Posts:
* Overview of circadian rhythms
* Your internal body clock: the suprachiasmatic nucleus (SCN)
* The study of circadian rhythms
* Glossary of shiftwork terms: shiftwork, sleep, circadian rhythms, and more

Study finds chronic disruption can cause heart and kidney disease

University Health News today posted an article Chronic Sleep Disruption Can Cause Heart And Kidney Disease. The subject of the article is pretty self-explanatory, based on the title, and it discusses research conducted at the Peter Munk Cardiac Centre of the Toronto General Hospital (Toronto, Ontario, Canada).

Dr. Michael Sole, Cardiologist and founding director of the Peter Munk Cardiac Centre and Professor of Medicine and Physiology at the University of Toronto suggests that shiftworkers working on a rotating schedule should try to maintain the same shift for a month at a time to reduce the circadian disruption.

Shiftwork in music -- Kenny Chesney, George Strait, REM, and more

If Shiftwork had an anthem, right now it would certainly be Kenny Chesney's duet with George Strait, the song, "Shiftwork" from his "Just Who I Am" CD. With a chorus of ...

Talking about a bunch of shift work
A big ol' pile of shift work
Work seven to three
Three to eleven
Eleven to seven

Other honorable mentions would be REM's "Day Sleeper" from their Up CD, a song that actually uses the phrase "circadian rhythm."

Receiving department, 3 a.m.
Staff cuts have socked up the overage
Directives are posted
No callbacks, complaints
Everywhere is calm

Of course, a few years back, Tina Turner put out a CD entitled "24/7" although it was really just the name of the album.

Time to set your clocks ahead (and lose an hour of sleep)

It's time once again, albeit earlier than usual, to set your clocks forward an hour. Yes, this Sunday night, March 9 in the wee hours of the morning, we'll be losing an hour -- even the folks in Indiana. While this seems like a minor inconvenience, there are actually real safety issues as our already sleep-deprived society loses another hour of sleep (because, let's face it, most people don't modify their schedule to lose a waking hour).

Studies have found accidents rates increase in the week immediately after the shift to standard time as we reset our circadian clocks. And, not coincidentally, accident rates decrease in the fall immediately after we when we gain an extra hour.

[As an aside, studies have found that the energy savings often touted as the
reason for shifting to daylight savings time, are nonexistent. In fact,
energy usage appears to have increased by roughly 4% this year in Indiana which
shifted to daylight savings for the first time. Maybe we can finally get
rid of this annoying and unsafe practice, although as I understand it, retailers
feel the extra daylight hours at the end of the day increase people's spending.]

Yesterday, USA Today ran an article on this very issue, Bodies don't 'spring ahead', that is worth taking a look at. Today's Wall Street Journal also ran a helpful article Learning to Live Like an Early Bird by Melinda Beck.

So remember to reset your clocks, and please be careful next week. Even if you plan appropriately for the lost sleep, the other folks on the road may not.

Your internal body clock: the suprachiasmatic nucleus (SCN)

Although studies of unicellular organisms point to the cellular nature of the system generating circadian rhythms, the circadian pacemaker in higher organisms is located in cells of specific structures of the organism. These structures include certain regions of the brain (i.e., the optic and cerebral lobes) in insects; the eyes in certain invertebrates and vertebrates; and the pineal gland, which is located within the brain, in nonmammalian vertebrates.

In mammals, the circadian clock resides in two clusters of nerve cells called the suprachiasmatic nuclei (SCN), which are located in a region at the base of the brain called the anterior hypothalamus.

The role of the SCN was demonstrated by the landmark discovery in the early 1970s that by damaging (i.e., lesioning) the SCN in rats, researchers could disrupt and abolish endocrine and behavioral circadian rhythms (Klein et al. 1991). Furthermore, by transplanting the SCN from other animals into the animals with the lesioned SCN, investigators could restore some of the circadian rhythms.

Finally, the SCN’s role as a master pacemaker regulating other rhythmic systems was confirmed by similar studies in hamsters, which demonstrated that the restored rhythms exhibited the clock properties (i.e., the period, or phase, of the rhythm) of the donor rather than of the host (Ralph et al. 1990). The discovery that the SCN is the site of primary regulation of circadian rhythmicity in mammals gave researchers a focal point for their research: if one wanted to understand 24-hour timekeeping, one needed to study the clock in the SCN.

Recently, however, researchers have been surprised to find that circadian rhythms could persist in isolated lungs, livers, and other tissues grown in a culture dish (i.e., in vitro) that were not under the control of the SCN (Yamazaki et al. 2000). These observations indicate that most cells and tissues of the body may be capable of modulating their activity on a circadian basis.
Such findings do not, however, diminish the central role played by the SCN as the master circadian pacemaker that some-how coordinates the entire 24-hour temporal organization of cells, tissues, and the whole organism.

The physiological mechanisms underlying this coordination include signals emitted by the SCN that act on other nerve cells (i.e., neural signals) or which are also distributed through the blood to other organs (i.e., neurohormonal signals). To date, however, the characteristics of the circadian signal itself-that is, the specific manner in which the SCN “talks” to the rest of the body-remain unknown (see Stokkan et al. 2001).

Although the effects of SCN lesions on numerous rhythms have been elucidated, their effects on sleep are less clear. Thus, SCN lesions clearly disrupt the consolidation and pattern of sleep in rats but have only minimal effects on the animals’ amount of sleep or sleep need (Mistlberger et al. 1987). For this and other reasons, researchers have postulated that sleep is subject to two essentially independent control mechanisms: (1) the circadian clock that modulates the propensity for sleep and (2) a homeostatic control that reflects the duration of prior waking (i.e., “sleep debt”).

Recently, however, studies in squirrel monkeys found that SCN lesions can affect the amount of sleep. Moreover, sleep studies in mice carrying changes (i.e., mutations) in two of the genes influencing circadian cycles (i.e., the DBP and Clock genes) indicated that these mutations resulted in changes in sleep regulation (Naylor et al. 2000; Franken et al. 2000).

Both of these observations raise the intriguing possibility that the homeostatic and circadian controls may be more interrelated than researchers previously thought.

By Martha Hotz Vitaterna, Ph.D., Joseph S. Takahashi, Ph.D., and Fred W. Turek, Ph.D.
MARTHA HOTZ VITATERNA, PH.D., is a senior research associate in the Center for Functional Genomics, Northwestern University, Evanston, Illinois. JOSEPH S. TAKAHASHI, PH.D., is the director of the Center for Functional Genomics, the Walter and Mary E. Glass Professor in the Department of Neurobiology and Physiology, and an investigator at the Howard Hughes Medical Institute, Northwestern University, Evanston, Illinois. FRED W. TUREK, PH.D., is the director of the Center for Sleep and Circadian Biology and is the Charles T. and Emma H. Morrison Professor in the Department of Neurobiology and Physiology, Northwestern University, Evanston, Illinois.

Source: http://www.niaaa.nih.gov/publications/arh25-2/85-93.htm

The study of circadian rhythms

The roots of the study of biological rhythms reach back to the 1700s and the work of the French scientist de Mairan, who published a monograph describing the daily leaf movements of a plant. De Mairan observed that the daily raising and lowering of the leaves continued even when the plant was placed in an interior room and thus was not exposed to sunlight. This finding suggested that the movements represented something more than a simple response to the sun and were controlled by an internal clock.

De Mairan’s apt observations illustrate one critical feature of circadian rhythms- their self-sustained nature. Thus, almost all diurnal rhythms that occur under natural conditions continue to cycle under laboratory conditions devoid of any external time-giving cues from the physical environment (e.g., under constant light or constant darkness). Circadian rhythms that are expressed in the absence of any 24-hour signals from the external environment are called free running.

The persistence of rhythms in the absence of a dark-light cycle or other exogenous time signal (i.e., a Zeitgeber) seems to indicate the existence of some kind of internal timekeeping mechanism, or biological clock. However, some investigators have pointed out that the persistence of rhythmicity does not necessarily exclude the possibility that other, uncontrolled cycles generated by the Earth’s revolution on its axis might be driving the rhythm (see Aschoff 1960).

The hypothesis that such uncontrolled geomagnetic cues might play a role in the persistence of rhythmicity can be refuted by a second characteristic feature of circadian rhythms: These cycles persist with a period of close to, but not exactly, 24 hours. If the rhythms were exogenously driven, they should persist with a period of exactly 24 hours. The seeming imprecision is an important feature of rhythmicity, however.

As Pittendrigh (1960) demonstrated, the deviation from a 24-hour cycle actually provides a means for the internal time-keeping system to be continuously aligned by and aligned to the light-dark environment. This continuous adjustment results in greater precision in controlling the timing, or phase, of the expressed rhythms, because little drift is allowed to occur before the rhythm is “reset” to the correct phase.

A third characteristic property of circadian rhythms is their ability to be synchronized, or entrained, by external time cues, such as the light-dark cycle. Thus, although circadian rhythms can persist in the absence of external time cues (meaning that they are not driven by the environment), normally such cues are present and the rhythms are aligned to them. Accordingly, if a shift in external cues occurs (e.g., following travel across time zones), the rhythms will be aligned to the new cues. This alignment is called entrainment.
Initially, it was unclear whether entrainment was achieved by modulating the rate of cycling (i.e., whether the cycle was shortened or lengthened until it was aligned to the new cues and then reverted to its original length) or whether entrainment was achieved by discrete “resetting” events.

Experiments resulting from this debate led to fundamental discoveries. For example, researchers discovered that the organism’s response to light (i.e., whether a cycle advances, is delayed, or remains unchanged) differs depending on the phase in the cycle at which it is presented (Pittendrigh 1960). Thus, exposure to light during the early part of the individual’s “normal” dark period generally results in a phase delay, whereas exposure to light during the late part of the individual’s normal dark period generally results in a phase advance.

In addition to the timing of the light exposure, the light intensity can modulate cycling periods when organisms are left in constant light. Thus, exposure to brighter light intensities can lengthen the period in some species and shorten it in other species. This phenomenon has been dubbed “Aschoff’s rule”(Aschoff 1960). Ultimately, both mechanisms of entrainment appear to be aspects of the same thing, because the consequences of Aschoff’s rule can be predicted or explained by the phase-response curves to light.

Although the light-dark cycle clearly is the major Zeitgeber for all organisms, other factors-such as social interactions, activity or exercise, and even temperature-also can modulate a cycle’s phase. The influence of temperature on circadian rhythms is particularly interesting in that a change in temperature can affect the phase of a cycle without substantially altering the rate of cycling.
This means that the cycle may start at an earlier or later-than-normal time but still have the same length. On the one hand, this ability of the internal clock’s pacemaker to compensate for changes in temperature is critical to its ability to predict and adapt to environmental changes, because a clock that speeds up and slows down as the temperature changes would not be useful.
On the other hand, temperature compensation also is rather puzzling, because most kinds of biological processes (e.g., biochemical reactions in the body) are accelerated or slowed by temperature changes.

Ultimately, this riddle has provided a clue to the nature of the internal clock- that is, the fact that circadian rhythms have a genetic basis. Such a program of gene expression would be more resistant to temperature alteration than, for example, a simple biochemical reaction. Two final properties of circadian rhythms also provide important hints of the rhythms’ makeup. One of these properties is the rhythms’ ubiquity in nature: Circadian rhythms exist in a broad array of biological processes and organisms, with similar properties and even similar phase-response curves to light.

The other property is that circadian rhythms appear to be generated at the cellular level, because the rhythms of unicellular organisms (e.g., algae or the dinoflagellate Gonyaulax) are much the same as rhythms of highly complex mammals. Both of these observations suggest that a cycle in the activation (i.e., expression) of certain genes might underlie the timekeeping mechanism.

By Martha Hotz Vitaterna, Ph.D., Joseph S. Takahashi, Ph.D., and Fred W. Turek, Ph.D.
MARTHA HOTZ VITATERNA, PH.D., is a senior research associate in the Center for Functional Genomics, Northwestern University, Evanston, Illinois. JOSEPH S. TAKAHASHI, PH.D., is the director of the Center for Functional Genomics, the Walter and Mary E. Glass Professor in the Department of Neurobiology and Physiology, and an investigator at the Howard Hughes Medical Institute, Northwestern University, Evanston, Illinois. FRED W. TUREK, PH.D., is the director of the Center for Sleep and Circadian Biology and is the Charles T. and Emma H. Morrison Professor in the Department of Neurobiology and Physiology, Northwestern University, Evanston, Illinois.

Source: http://www.niaaa.nih.gov/publications/arh25-2/85-93.htm

Related posts:
* Overview of circadian rhythms
* Glossary of shiftwork terms: shiftwork, sleep, circadian rhythms, and more
* The drivers of human alertness and sleep

Glossary of shiftwork terms: shiftwork, sleep, circadian rhythms, and more

Chronobiology: A subdiscipline of biology concerned with the timing of biological events, especially repetitive or cyclical phenomena, in individual organisms.

Circadian: A term derived from the Latin phrase “circa diem,” meaning “about a day”; refers to biological variations or rhythms with a cycle of approximately 24 hours. Circadian rhythms are self-sustaining (i.e., free running), meaning that they will persist when the organism is placed in an environment devoid of time cues, such as constant light or constant darkness. For comparison, see diurnal, infradian, and ultradian.

Day shift: In an 8-hour shift operation, the day shift may also be called the first shift and typically begins between 6 am and 8 am. In a 12-hour shift operation, this shift typically also begins between 6 am and 8 am.

Diurnal: Varying with time of day. Diurnal rhythms may persist when the organism is placed in an environment devoid of time cues, such as constant light or constant darkness. Therefore, diurnal variations can be either light driven or clock driven. For comparison, see circadian.

Entrainment: The process of synchronization of a timekeeping mechanism to the environment, such as to a light-dark cycle. For comparison, see free running.

Evening shift: This most commonly refers to the second shift in an 8-hour operation and typically begins between 2 pm and 4 pm. Also often referred to as the swing shift.

Fatigue countermeasures: Any of an array of steps taken to help people maintain alertness, specifically to help shiftworkers maintain health and safety. These may include such things as napping and sleep strategies, managing the use of caffeine and other substances to promote alertness or sleep, lighting and temperature of the work environment, and many other areas.

Fixed schedule: A shift schedule in which workers are permanently assigned to a specific shift -- day, evening, or night. This contrasts with a rotating schedule.

Free running: The state of an organism (or rhythm) in the absence of any entraining stimuli. Typically, subjects are kept in constant dim light or constant darkness to assess their free-running rhythms. For comparison, see entrainment.

Graveyard shift: See night shift.

Infradian: A term derived from the Latin phrase “infra diem,” meaning “less than a day”; refers to biological cycles that last more than 1 day and, therefore, have a frequency of less than one per day. For comparison, see circadian and ultradian.

Masking: The obscuring of the “true” state of a rhythm by conditions that prevent its usual expression. Usually, the phase of an entrained rhythm or the absence of entrainment (e.g., in an animal that is unable to entrain because of some defect) is said to be masked by a light cycle. For example, the aversion of a nocturnal rodent to bright light results in its activity onset appearing to coincide with the absence of light, or “lights off,” when the animal actually has been awake for hours. For comparison, see entrainment.

Night shift: In an 8-hour shift operation, the night shift may also be called the third shift and typically begins between 10 pm and midnight. In a 12-hour shift operation, this shift typically begins between 6 pm and 8 pm. Also sometimes referred to as the graveyard shift.

Nonrapid eye movement (NREM) sleep: Sleep stages that include the “deeper” stages of sleep in which dreaming typically does not occur. Also referred to as slow-wave sleep. There are four non-rapid eye movement (NREM) sleeps stages. Stage 1 is a transitional phase, with brain activity slowing. This is the drowsy state when sudden movements and hallucinations may occur. In stage 2 sleep, muscular activity decreases and humans lose awareness of their environment. We stay in stage 2 sleep for approximately half of a typical session of sleep.
Stage 3 is a deep phase of sleep, characterized by slow-wave wave activity. This is the stage in which people experience sleep walking, sleep talking, and bed wetting. Stage 4 sleep is a deeper stage of sleep but similar to stage 3. For comparison, see rapid eye movement sleep.

Phase shift: A change in the phase of a rhythm. This change can be measured by observing a change in the timing of a phase reference point (e.g., activity onset or the nocturnal rise in the release of the hormone melatonin) from the timing expected based on previous, free-running cycles. Phase shifts may be either advances (i.e., the phase reference point occurs earlier than normal) or delays (i.e., the phase reference point occurs later than normal).

Phase-response curve (PRC): A graphical summary of the phase shifts produced by a particular manipulation, such as a light pulse or a pharmacological treatment, as a function of the phase (i.e., circadian time) at which the manipulation occurs. Defining the PRC to light has enabled researchers to understand and predict how entrainment to light cycles is accomplished.

Rapid eye movement (REM) sleep: A stage of light sleep characterized by rapid eye movements and associated with dreaming. REM sleep is the stage when humans dream most and muscle activity falls. Also called paradoxical sleep. For comparison, see nonrapid eye movement sleep.

Rota: See shift schedule.

Rotating schedule: A shiftwork schedule in which workers rotate between day and night shifts on a 12-hour shift schedule, or between day, evening, and night shifts on an 8-hour shift schedule. There are many factors to consider when setting the speed and direction of the rotation. This contrasts with a fixed schedule.

Shift schedule: The schedule of shifts to be worked. Also referred to as a rota, particularly in European countries. See also rotating schedule and fixed schedule.

Sleep stages: Human sleep consists of 5 stages, each with its own unique characteristics, through which humans cycle while they sleep. See rapid eye movement sleep and non-rapid eye movement sleep.

Suprachiasmatic nucleus or nuclei (SCN): A cluster of nerve cells located in the brain region called the hypothalamus that is responsible for generating and coordinating circadian rhythmicity in mammals.

Swing shift: See evening shift.

Ultradian: A term derived from the Latin phrase “ultra diem,” meaning “more than a day”; refers to biological cycles that last less than 1 day and, therefore, have a frequency of more than one per day. For comparison, see circadian and infradian.

Zeitgeber: A German word literally meaning “time-giver.” A time cue capable of entraining circadian rhythms. Light represents the most important Zeitgeber.

Sources: National Shiftwork Information Center research staff, http://www.niaaa.nih.gov/publications/arh25-2/85-93.htm

Have terms you'd like to see defined?
Post a comment. We'll add them to the list. This glossary is an ongoing project.

Overview of circadian rhythms

You certainly don't need to be an expert on human physiology to work shiftwork, but understanding a bit of the science can be both interesting and helpful if you're a shiftworker. So with this and future posts we'll be bringing you information to help you do just that.

The daily light-dark cycle governs rhythmic changes in the behavior and/or physiology of most species. Studies have found that these changes are governed by a biological clock, which in mammals is located in two brain areas called the suprachiasmatic nuclei. The circadian cycles established by this clock occur throughout nature and have a period of approximately 24 hours.

In addition, these circadian cycles can be synchronized to external time signals but also can persist in the absence of such signals. Studies have found that the internal clock consists of an array of genes and the protein products they encode, which regulate various physiological processes throughout the body. Disruptions of the biological rhythms can impair the health and well-being of the organism.

One of the most dramatic features of the world in which we live is the cycle of day and night. Correspondingly, almost all species exhibit daily changes in their behavior and/or physiology. These daily rhythms are not simply a response to the 24-hour changes in the physical environment imposed by the earth turning on its axis but, instead, arise from a timekeeping system within the organism.

This timekeeping system, or biological “clock,” allows the organism to anticipate and prepare for the changes in the physical environment that are associated with day and night, thereby ensuring that the organism will “do the right thing” at the right time of the day. The biological clock also provides internal temporal organization and ensures that internal changes take place in coordination with one another.

The synchrony of an organism with both its external and internal environments is critical to the organism’s well-being and survival; a lack of synchrony between the organism and the external environment may lead to the individual’s immediate demise. For example, if a nocturnal rodent were to venture from its burrow during broad daylight, the rodent would be exceptionally easy prey for other animals. Similarly, a lack of synchrony within the internal environment might lead to health problems in the individual, such as those associated with jet lag, shift work, and the accompanying sleep loss (e.g., impaired cognitive function, altered hormonal function, and gastrointestinal complaints).

The mechanisms underlying the biological timekeeping systems and the potential consequences of their failure are among the issues addressed by researchers in the field of chronobiology.
In its broadest sense, chronobiology encompasses all research areas focusing on biological timing, including high-frequency cycles (e.g., hormone secretion occurring in distinct pulses throughout the day), daily cycles (e.g., activity and rest cycles), and monthly or annual cycles (e.g., reproductive cycles in some species).

Among these interrelated areas of chronobiology, we'll focus on one frequency domain-the daily cycles known as circadian rhythms.

The term “circadian” derives from the Latin phrase “circa diem,” which means
“about a day.”

Although virtually all life forms- including bacteria, fungi, plants, fruit flies, fish, mice, and humans-exhibit circadian rhythms, this review is primarily limited to the mammalian system. Other animals are discussed only in cases in which they have contributed to the understanding of the mammalian system, particularly in studies of the molecular genetic makeup of the time-keeping system.

* * * * * *
By Martha Hotz Vitaterna, Ph.D., Joseph S. Takahashi, Ph.D., and Fred W. Turek, Ph.D.

MARTHA HOTZ VITATERNA, PH.D., is a senior research associate in the Center for Functional Genomics, Northwestern University, Evanston, Illinois. JOSEPH S. TAKAHASHI, PH.D., is the director of the Center for Functional Genomics, the Walter and Mary E. Glass Professor in the Department of Neurobiology and Physiology, and an investigator at the Howard Hughes Medical Institute, Northwestern University, Evanston, Illinois. FRED W. TUREK, PH.D., is the director of the Center for Sleep and Circadian Biology and is the Charles T. and Emma H. Morrison Professor in the Department of Neurobiology and Physiology, Northwestern University, Evanston, Illinois.

Source: http://www.niaaa.nih.gov/publications/arh25-2/85-93.htm

The health effects of light at night

On February 22, US News and World Report posted an article discussing the effect of light exposure at night on health. In the article, Light at Night: How to Counter the Health Effects, reporter Debra Kotz speaks with neurology and lighting experts about the effects of lighting on circadian rhythms, sleep, and health.

Prepare for daylight savings time

Sleep. Most people need every minute they can get. So, every year articles remind us that daylight savings time is coming and provide tips to minimize the disruption. This year with the extended daylight savings time schedule, we'll need those reminders earlier.

Many may think, "what's the big deal, it's only an hour?" but research has shown accident rates go up in the week following the start of daylight savings. It appears losing an hour of sleep does really matter and resetting your circadian clock by even just an hour is worth your attention. Of course, as we always say, if it has to do with sleep and is important to the general public, it's even more important for shiftworkers.

The main points is to prepare early over a few days to try to shift your bedtime earlier by an hour or at least part of it. To accomplish that, use all of the Tips for getting better sleep we've posted previously. These include making the sleeping room dark, quiet, comfortable temperature, etc.

Here's another brief article that provides some additional tips from a hospital press release -- Don't Lose Sleep Over Daylight Saving Time.

The drivers of human alertness and sleep

Your alertness is the result of nine elements, what Dr. Martin Moore-Ede in his book The Twenty-Four-Hour Society termed the nine switches of alertness. Knowing these elements can help you better manage your environemtn and behavior to improve your alertness or help you sleep. The nine elements are:

1. Interest, opportunity, or sense of danger -- when you are mentally engaged or threatened in some way, your body rises to the challenge by increasing alertness.
2. Physical activity -- when you are physically active, you increase your alertness. This effect can last for a while, making sleep difficult after intense exercise.
3. Time of day on your circadian clock -- if your body is telling you it's night time, your alertness will drop. You can reset your circadian clock (as evidenced when you travel across time zones) but it takes time and careful attention if you're a shiftworker.
4. Your sleep "bank balance" -- if you have gotten inadequate sleep over the past few days, your alertness will suffer.
5. Ingested nutrients and chemicals -- caffeine and other substances have a stimulating effect while tryptophan and sleeping pills will encourage sleep.
6. Environmental light -- bright lighting wakes you up and dim lighting tends to make you sleepy.
7. Temperature -- warm and stuffy rooms make you sleepy while cold, bracing increases alertness.
8. Sound -- loud, erratic noises increase alertness while soft sounds and white noise reduce it.
9. Aroma -- This last one, aroma, has somewhat less research to support it, but there is at least some evidence that certain aromas have a stimulating effect while others have just the opposite. Scents like lemon and peppermint have been found to increase alertness.

Keep these factors in mind and use them to your advantage.

Adapting to night shifts -- helping shiftworkers adapt and avoid shiftworker maladaptation

Adapting to nighttime or daytime work requires synchronization of your biological clock (which controls your circadian rhythms) to the work schedule. Maladaptation results if your biological clock is not adjusted to the work schedule. To adapt the biological clock, shiftworkers must be exposed to daylight (or bright artificial light of 1,000 lux or more) both upon awakening and
throughout their active periods (for example, during work hours).

Also, shiftworkers must avoid bright light from approximately three hours prior to the end of their long sleep period.

The only way to fully adapt to nightshift schedules is to reset the biological clock so that energy peaks during nighttime. Work must take place under artificial light (of at least 1000 lux) that mimics daylight. Although this is a far lower level than actual daylight, it will seem far brighter than normal indoor lighting which is typically in the 300-400 lux range. Sleep must take place in a dark and noise-free environment for approximately seven to eight hours. Failure to control daylight and/or light exposure is a significant contributor to fatigue and shiftwork maladaptation.

Maladaptation to shiftwork schedules and lack of energy-restoration sleep can result in persistent sleepiness, low energy, lack of motivation, and depression; in performance degradation during duty hours; and in increased safety risk.

Other health effects such as increased incidence of cardiovascular disease, gastrointestinal disorders, and sleep disorders have been historically documented in populations subjected to shiftwork maladaptation. The combined effects of disrupted sleep and biological clock disorganization can lead to endurance degradation, jet-lag-like symptoms, irritability, depression, and, in extreme cases, psychosis.

Optimizing Adaptation to Shiftwork
Optimizing shiftworker rest, while preventing shift lag (inadequate adjustment to shiftwork schedules), can contribute significantly to shiftworker adaptation to work and life aboard a maritime vessel.

Listed below are some recommendations that can prevent shift schedules from inducing short and disrupted sleep periods and shift lag.

Avoid allowing staff to work more than 12 hours in a 24-hour period. Count
these 24 hours from the time shiftworkers wake up from their longest daily sleep
period (not naps).

Total Adaptation to Night Work

• Provide bright-light exposure (e.g., fluorescent bulbs of at least 1000 lux) during the work period. Note: This artificial-light exposure can only be implemented in environments where night vision is not required for performing normal duties (so, for instance, ambulance drivers who will need to be able to drive in the dark at night should not be exposed to bright artificial lighting between calls).
• Provide nightshift staff with small-size meals that promote energy and alertness (high protein, low fat, low sugar, low starch, no dairy products or turkey).
• Adjust meal times so nightshift personnel can eat a brunch on waking (at approximately 1:00 pm), including brewed coffee and breakfast foods, if desired.
• Adapt the cafeteria services to accommodate crewmember needs. This accommodation supports both safety and crew morale.

Partial Adaptation to Night Watch or Work Schedules
When bright lights cannot be used in the work environment, stick to the following recommendations:

• Reduce the duration of the shift in order to minimize the impact of endurance degradation on safety. Promote exercise in the evening hours.
• Allow shiftworkers from any shift ending in the morning hours to retire prior to sunrise, and to sleep at least seven to eight hours free of noise and with absolutely no interruptions.
• Overtime should be scheduled to occur after wake-up time (e.g., from 2:00 pm to 6:00 pm), whereas leisure activities should be scheduled for the evening hours.

Source: http://www.uscg.mil/hq/g-m/cems/PDF/light_management.pdf.

Circadian rhythms and seasonal affective disorder (SAD)

I'm always surprised at how much attention the press gives to sleep and circadian rhythms. While this is of general interest to the general public, these topics should be of great interest to the shiftworking world. Here are a few items we've come across today:

Winter Blues May Be Treatable Depression
The NBC affiliate in Orlando, Florida, USA (WESH) discusses seasonal affective disorder (SAD), light treatment and other issues pertaining to winter-time depression. Shiftworkers can also be susceptible to this sort of disorder.

Gray skies bring winter blues
The Orion Online (Chico, California, USA) also discusses seasonal affective disorder, with a particular slant on college students, 25% of whom are affected by winter blues.

Human skin cells hide circadian clock -- are you a Lark or an Owl?
An article in NewScientist discusses a National Academy of Sciences journal article showing that genes as well as environmental factors such as day length have a major influence on the circadian clock. WebMD also published an article based on the same study -- "Morning Lark or Night Owl? Genes Know Skin Cells May Reflect Whether Someone Is a Morning Person or a Night Person."

Ed

Suggested reading on circadian rhythms and light exposure

A couple of articles I've been reading that I wanted to let you know about.

An article on SeparationsNow.com called "Clocking On" discusses circadian rhythms and how they work.

Seasonal affective disorder (or SAD) is a mental health issue that has some similarities with shiftwork since light exposure is a critical element to good health and mood. An article in today's issue of The Gazette (Colorado Springs, Colorado, USA) Wintertime depression: a sad state provides a nice overview.

Ed

Shiftwork schedule factors: speed and direction of rotation

Adapting to rotating shifts can be affected by the speed of rotation and the direction of rotation. Speed of rotation means the number of consecutive day, evening, or night shifts before a shift change occurs. Direction of rotation means the order of shift change:

• A forward rotation is in the clockwise direction, from day to evening to night shift.
• A backward rotation is in the counterclockwise direction, from day to night to evening shift.

Different rotation speeds also affect a worker's ability to get used to change of shift times. We have already talked about the same situation under permanent versus rotating shifts. Longer rotations (for example, three to four weeks of working the same hours) are sup-posed to allow workers more time to get used to night shifts.

However, workers usually return to a day schedule on their days off. A fast rotation (every two days, for example) allows no time to get used to night work. Some researchers prefer the fast rotation, because the worker quickly gets through the tough shifts and then has a couple of days off. Very fast rotations are used in Europe more than in America.

Direction of rotation can affect the ability of circadian (daily body) rhythms to adapt to the change in work times. Sleep, for example, is a circadian rhythm because each person sleeps for part of every day. Some researchers suggest that a forward, or clockwise, rotation is better for helping a worker adjust to new sleep times.

This suggestion was made because it is easier to go to bed later and wake up later than earlier. Our body rhythms make us feel more awake and alert in the early evening. This makes it harder to fall asleep earlier. Backward rotations work against the body rhythm by forcing the worker to go to sleep earlier and earlier.

Although we don't have hard and fast numbers, it seems that back-ward rotation schedules are used frequently in the United States. It is not completely clear why. It is partly because of custom (We always did it this way) and partly because workers like the “long change.”

In the long change, workers pick up an extra day off when going to evening shifts after night shifts. This happens because evening shift starts late in the day, which leaves most of that day free for non-work activities.

We'll continue this discussion of shiftwork schedule factors.

Other recent posts on shiftwork scheduling include:

• Shiftwork schedules: fixed or rotating
• Best practices for managing a shiftwork operation

Ed

Source: Plain Language About Shiftwork (NIOSH)

Shiftworker lifestyle training: fatigue countermeasures, sleep strategies, and more

From time to time articles appear in the general press about the dangers of shiftwork. It's important to understand the risks, but it's equally important to focus on practical steps to improve the health, safety and work performance of shiftworkers in 24/7 operations. One relatively easy, and relatively inexpensive step 24/7 business operators can take is to provide their employees with shiftworker lifestyle training.

Shiftworkers' alertness, hence their ability to perform effectively, is dependent on many factors. Some of those factors are beyond their control, such as their work schedule, but others are directly affected by the individual's actions. Lifestyle training means giving workers the knowledge they need to make appropriate adjustments to their lives in order to ensure health and safety.

As the name suggests, successful lifestyle training affects a worker's entire life, not merely his or her time at work. Adjustments on the part of shiftworkers will therefore be contingent upon acceptance by spouses and family members who also will be affected. For this reason, we recommend including spouses in lifestyle training whenever possible.

Lifestyle training should start with a non-technical discussion of circadian rhythms and how they effect human alertness. Shiftworkers, whether nurses, police officers, pilots, factory workers, or whomever, must understand there is a fundamental difference between day shift work and night shift work. Humans have evolved over millions of years to be awake during the day and asleep at night. Unless shiftworkers acknowledge this basic fact, the rest of the training process is meaningless.

After this first step, lifestyle training should address the following areas and provide specific details on fatigue countermeasures:

Sleep
Seven or eight hours of uninterrupted sleep are important to everyone's health and well-being. Our bodies are not programmed to sleep during the day. As a result, daytime sleep typically reduces both the quantity and quality of sleep. Making sure the sleeping room is dark, quiet, well-ventilated, and not too warm is an important step. A high-quality mattress also improves sleep.

Nutrition
People who work the night shift need to know about general nutrition, but that alone is not enough. Our bodies simply were not designed to eat at night. Your stomach won't digest full meals, so you should eat in smaller portions. Spicy, rich, and fatty foods are particularly hard to handle at night. Careless eating habits can cause indigestion, discomfort, drowsiness, and weight gain.

Family and social life
All shiftworkers have to think about many things differently than 9-to-5 workers. This is particularly true if you are trying to maintain a family and social life. Celebrating holidays a week early, videotaping children's birthday parties, and breakfast dates are just some of the accommodations you can make to keep connected to the rest of your life. People who emphasize communication and plan effectively have shown that work and family can mix and that single people can have a social life.

Job performance and safety
You need to emphasize safety because accidents are more likely to occur at night than on other shifts. One study found the number of accidents is 23 percent higher on the night shift. With knowledge of the factors that affect alertness, you can avoid safety lapses, improve work performance, and prevent falling asleep at the wheel.

Lifestyle training improves job performance, as well as employees' health, safety, and quality of life. This has been most thoroughly documented in a report on CANALERT '95, an alertness assurance program funded by Canada's three largest railroads, which took before-and-after measurements of a broad range of criteria. [More about CANALERT '95 at the Brotherhood of Locomotive Engineers website or at Railway Age.]

The improved health and quality of life, in turn, improve morale and tend to lower absenteeism and turnover rates. Absenteeism and turnover are particularly problematic in round-the-clock operations because of the difficulty of getting substitute workers on short notice and training new workers in a continuous operation environment.

Shiftworkers: have you received some sort of lifestyle training? Was it helpful? Did it include your spouse?

24/7 Managers: does your company provide shiftworker lifestyle training? What are the costs and benefits?

Share your opinions and experiences. Post a comment now.