Jet Lag

Physiology

Eddie sez:

When I was 23 I flew from the northern tip of Maine to California, to Hawaii, to Guam, to the island of Diego Garcia, a distance of nearly 15,000 nautical miles in just a week. Piece of cake.

These days if I fly an out-and-back to Teterboro, crossing no time zones, but I don't get home until 2 a.m., I am messed up for the next three days. What gives?

In my nearly forty years of traversing time zones against the will of my internal chronometer I've adopted four distinctly different philosophies to combat jet lag but in the end, I think I will settle on a completely different approach altogether.

Everything here is from the references shown below, with a few comments in an alternate color.

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Photo: The big trip, 1980, from Eddie's logbook.

Coming to Grips with Jet Lag:

Four Strategies:

Okay, a Fifth:

Last revision:

20140201

Understanding Jet Lag

Ignore it (mind over matter)

When I was young and indestructable, jet lag didn't seem to be much of a factor. That wasn't true of everyone that age. But the effects are definitely less pronounced. You think you can just ignore the problem, hence the mindset that you simply reset the clock on your wrist and everything else takes care of itself. A normal trip for our Hawaii Boeing 707 squadron was from Hawaii to Japan, Korea, or the Phillippines. I used to hit the ground running, wondering why I was often solo the first day. Ah, youth . . .

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Photo: The EC-135J (Boeing 707), from Eddie's logbook, circa 1982.

You might say that dealing with fatigue is a personal matter and so long as you show up ready to fly, there is nothing more to be said on the subject:

[ICAO Annex 6 Part II, ¶2.2.5.2] The pilot-in-command shall be responsible for ensuring that a flight: will not be commenced if any flight crew member is incapacitated from performing duties by any cause such as injury, sickness, fatigue, the effects of any psychoactive substance;

You do have to do something about it, however:

[ICAO Annex 6 Part II, ¶3.4.2.8] The operator shall establish and implement a fatigue management programme that ensures that all operator personnel involved in the operation and maintenance of aircraft do not carry out their duties when fatigued. The programme shall address flight and duty times and be included in the operations manual.

Besides, ignoring it ignores your basic physiology.

[Burdick pp. 65-69]

  • Begin with the physics: you are several miles in the air, moving quickly and, bound by gravity, essentially falling. One of the peculiar consequences of Einstein's theory of special relativity is that time moves more slowly aboard a very swiftly moving object compared to the time of an observer who's standing still. Experiments have verified it: atomic clocks placed aboard jet planes have been found to tick more slowly by a matter of nanoseconds over several hours than a stationary clock on the ground. (In the plane itself, one second is still exactly one second long, identical in duration to the previous second; only observers in a nonmoving frame measure it as slower.) The effect is small but real. In March 2016, astronaut Mike Kelly returned to earth after spending five hundred and twenty days in orbit, circling the planet at nearly eighteen thousand miles an hour. In that time his earthbound twin brother, Mark, who was born first by six minutes, had aged by an additional five milliseconds.
  • Then there are the time zones: twenty-four in total, each an hour wide and spaced more or less evenly along Earth's lines of longitude, every fifteen degrees apart. Time zero is Greenwich, England, where the Royal Observatory is located. Because Earth is a rotating sphere, the sun can't illuminate all of it at once, so the daylight hours can't occur everywhere simultaneously; time zones are what make it possible for "twelve noon" to mean the same thing — the middle of the day, when the sun is about at its zenith-most everywhere in the world, even though it occurs in only one time zone at a time. Time zones came into use, piecemeal, in the nineteenth century, as a way to help railroads coordinate the schedules of their expanding rail networks. By 1929 most of the world had signed on to the hourly time-zone scheme, although some countries today have their time zones set on the half-hour and even, in Nepal, at the forty-five-minute mark. In 1949 the geographically sprawling China adopted the opposite strategy and reduced its five time zones to a single large one.
  • Nowadays, with air travel, we cross time zones regularly. In the seven hours it takes to fly from Paris to New York, one can erase the six-hour difference between the cities. Clocks are ultimately local; what time it is depends on where you are. If you're on a plane-moving at some fast speed, staring down at an unending canvas of ocean-your where and when are changing with every moment. My watch may still be set to Paris time, some hours behind me, while the informational map on the headrest in front of me reports the time in New York, which is still hours away. I'm in between for an indefinite-seemingly eternal period of time.
  • There is a central time on our flight, up in the cockpit with the suprachiasmatic captain. The universally coordinated time of the world's many atomic clocks, sifted and weighted according to the advisory algorithms of the B.I.P.M. in Paris, is continuously transmitted via satellite into the guidance systems of moving cargo ships, rental cars, and planes. Out in the main cabin, however, it's every clock for itself. Some passengers doze, others eat. Some aim themselves toward the late afternoon meeting that awaits them; others are recovering from their early morning effort to catch the flight. And others still are lost in onboard-movie time, far away and ending happily. Traveling west, bathed in constant daylight, devoid of meaningful time cues, we follow our own decentralized hours.
  • Suprachiasmatic: of the hypothalamus. I guess the author is saying we pilots are smart. B.I.P.M. is the International Bureau of Weights and Measures.

  • How the brain's suprachiasmatic nucleus disseminates its time throughout the human body is still poorly understood. But the process takes time: hours to days. If you're subjected to a sudden shift in your light regime and are forced to adjust to a new schedule — the sort of thing that happens when you cross a few time zones, or even for the day or two following the switch to or from daylight saving time — your peripheral clocks don't fall back in line all at once or at the same rate. Your body ceases to be a synchronized confederacy of clocks and instead becomes, temporarily, a conflagration of temporally autonomous states. That's the essence of jet lag. When my suprachiasmatic nucleus lands in New York, my liver may still be on Nova Scotia time and my pancreas may be somewhere over Iceland. For a few days, my digestive system will be out of whack, as my brain directs me to eat food at hours when my organs aren't fully aligned to metabolize it. (The body recovers at a rate of about one time zone per day.) The result is gastroenteritis, a common complaint of long-distance travelers and airline pilots. Jet lag is not in your head; it's an ailment of your entire, desynchronized body.

So can you ignore jet lag?

[]Fatigue Management Guide, ¶2.1] There is a widespread belief that sleep time can be traded off to increase the amount of time available for waking activities in a busy lifestyle. However, sleep science makes it very clear that sleep cannot be sacrificed without consequences.

Perhaps a primer on sleep itself is in order.

[]Fatigue Management Guide, ¶2.1.1]

  • A complex series of processes is taking place in the brain during sleep. Various methods have been used to look at these processes, from reflecting on dreams to using advanced medical imaging techniques. Sleep scientists have traditionally looked at sleep by monitoring electrical patterns in brain wave activity, eye movements, and muscle tone. These measures indicate that there are two very different types of sleep:
    • Non-rapid eye movement (Non-REM) sleep; and
    • Rapid eye movement (REM) sleep.
  • During non-rapid eye movement sleep (non-REM sleep), brainwave activity gradually slows compared to waking brainwave activity. The body is being restored through muscle growth and repair of tissue damage. Non-REM sleep is sometimes described as “a quiet brain and quiet body.” Across a normal night of sleep, most adults normally spend about three quarters of their sleep time in non-REM sleep.
  • Non-REM sleep is divided into three stages, based on the characteristics of the brainwaves. Stages 1 and 2 represent lighter sleep (it is not very difficult to wake someone up). It is usual to enter sleep through Stage 1 and then Stage 2 non-REM.
  • Stage 3 non-REM sleep is also known as slow-wave sleep (SWS) or deep sleep. Basically, in SWS the brain stops processing information from the outside world and huge numbers of brain cells (neurons) start firing in synchrony, generating big, slow electrical waves. More stimulation is needed to wake someone up than from non-REM Stages 1 and 2. During SWS, consolidation of certain types of memory is occurring, so SWS is necessary for learning. Waking up from SWS, various parts of the brain have to reactivate in sequence.
  • The longer you are awake and the more physically active you are, the more slow-wave activity your brain will show in your next sleep period. Thus SWS fits the traditional idea that sleep somehow restores you from the demands of waking activities. This is sometimes described as the ‘sleep homeostatic process’.
  • During non-rapid eye movement sleep (non-REM sleep) brainwave activity looks similar to waking brainwave activity. However in REM sleep, from time to time the eyes move around under the closed eyelids — the so-called “rapid eye movements” — and this is often accompanied by muscle twitches and irregular heart rate and breathing. Most adults normally spend about a quarter of their sleep time in REM sleep.
  • During REM sleep, the brain is repairing itself and information from the previous day is being sorted and related to stored memories. People awakened from REM can typically recall vivid dreaming. During REM sleep, the body cannot move in response to signals from the brain, so dreams cannot be acted out. (The signals effectively get blocked in the brain stem and cannot get through to the spinal cord.) People sometimes experience brief paralysis when they wake up out of a dream, when reversal of this “REM block” is slightly delayed. Because of these features, REM sleep is sometimes described as a “busy brain and paralyzed body”.
  • Across a normal night of sleep, non-REM sleep and REM sleep alternate in a cycle that lasts roughly 90 minutes (but is very variable in length, depending on a number of factors). Figure 2-2 is a diagram summarizing the non-REM/REM cycle across the night in a healthy young adult who goes to bed at 11:00 pm and wakes around 07:30am. Real sleep is not as tidy as this — it includes more arousals (transitions to lighter sleep) and brief awakenings. Sleep stages are indicated on the vertical axis and time is represented across the horizontal axis.
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    Figure: The non-REM/REM cycle across the night, from Fatigue Guide, Figure 2-2.

  • In each non-REM/REM cycle across a normal night of sleep:
    • the amount of slow-wave sleep decreases (there may be none at all in later cycles); and
    • in contrast, the amount of REM sleep increases.
  • People sometimes experience grogginess or disorientation when they first wake from sleep. This is known as sleep inertia. It can occur when waking from any stage of sleep but may be worse after longer periods of sleep.

Beat it (cold turkey)

Our 89th Airlift Wing Gulfstreams at Andrews Air Force Base tended to split their time evenly between domestic and international trips. My longest duty day was from Washington, D.C. to the depths of the old Soviet Union. We took off about 7 p.m. and didn't make it to our destination until 20 hours and eight time zones later. A favorite technique of ours was to simply arrive when you arrive, and stay up until bedtime in the new location. That first day was painful, but, in theory, you are all set starting the next day. Everyone believed this, but tended to ignore the evidence to the contrary.

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Photo: The C-20B (Gulfstream III), from Bill Shull and Eddie's logbook, circa 1992.

Strategic naps

[]Fatigue Management Guide, ¶2.1.3]

  • Uninterrupted non-REM/REM cycles are the key to good quality sleep, so operators should develop procedures that minimize interruptions to crewmembers’ sleep.
  • Rest periods (in flight or on layovers) should include protected blocks of time (sleep opportunities) during which crewmembers are not contacted except in emergencies. These protected sleep opportunities need to be known to crewmembers and all other relevant personnel. For example, calls from crew scheduling should not occur during a rest period as they can be extremely disruptive.
  • Operators should also develop procedures to protect crewmember sleep at layover and napping facilities. For example, if a rest period occurs during the day at a layover hotel, the operator should make arrangements with the hotel to restrict access to the section of the hotel where crewmembers are trying to sleep (such as no children, crewmembers only) and instruct their staff to honor the necessary quiet periods (for example, no maintenance work or routine cleaning).

Staying awake until Local bedtime

Sleeping immediately and staying in bed until local morning

Going Chemical

[]Fatigue Management Guide, ¶2.1.3] Caffeine (in coffee, tea, energy drinks, colas and chocolate) stimulates the brain, making it harder to fall asleep and disrupting the quality of sleep. Some people are more sensitive to effects of caffeine than others, but even heavy coffee drinkers will have lighter and more disturbed sleep if they drink coffee close to bedtime (although they may not even notice this). Nicotine in cigarettes is also a stimulant and affects sleep in a similar way. Alcohol on the other hand makes us feel sleepy but it also disturbs sleep. While the body is processing alcohol (at the rate of about one standard drink per hour), the brain cannot obtain REM sleep. Pressure for REM sleep builds up, and sleep later in the night often contains more intense REM periods and is more disturbed as a consequence.

Give in to it (surrender)

By the time I became a civilian, everything had changed. By then I had already seen much of the world and the threat of missing something that first day in the new location was no longer compelling enough to play the "hit the ground running" routine. We tended to arrive and head for bed. One of our normal trips when I flew for Compaq Computer was to fly from Houston, Texas, to Munich Germany. We would arrive about noon, go to bed, somehow get up for dinner and go right back to bed. We would stay messed up for three days, fly home, and spend another three days messed up.

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Photo: The Challenger 604, from Eddie's logbook, circa 2002.

Understanding Jet Lag

[]Fatigue Management Guide, ¶2.3.5]

  • Flying across time zones exposes the circadian body clock to sudden shifts in the day/night cycle. Because of its sensitivity to light and (to a lesser extent) social time cues, the circadian body clock will eventually adapt to a new time zone. During the period of adaptation, common symptoms include wanting to eat and sleep at times that are out of step with the local routine, problems with digestion, degraded performance on mental and physical tasks, and mood changes.
  • Studies with participants flown as passengers have identified the following factors that affect the rate of adaptation to a new time zone.
    • Adaptation generally takes longer when more time zones are crossed.
    • Adaptation is usually faster after westward travel (phase delay) than after eastward travel (phase advance) across the same number of time zones. The fact that the innate cycle of the circadian body clock is slightly longer than 24 hours (for most people) probably contributes to this. It is easier to lengthen the cycle to adapt to a westward shift.
    • After eastward flights across 6 or more time zones, the circadian body clock may adapt by shifting in the opposite direction, for example shifting 18 time zones west rather than 6 time zones east. When this happens, some rhythms shift eastward and others westward (known as resynchronization by partition) and adaptation can be particularly slow.
    • Rhythms in different functions can adapt at different rates, depending on how strongly they are influenced by the circadian body clock. Thus, during adaptation, rhythms in different body functions can be out of step with each other, as well as out of step with the day/night cycle.
    • Adaptation is faster when the circadian body clock is more exposed to local time cues, including outdoor light, and exercising and eating on local time.
    • Beginning a trip with a sleep debt seems to increase the duration and severity of jet lag symptoms.
  • Crewmembers who operate transmeridian flights rarely have enough time in a destination to adapt fully to local time, with 1-2 day layovers being typical. However, different patterns of transmeridian flights can have different effects. For example, there appears to be very little circadian adaptation across flights leaving and returning to a crewmember’s domicile time zone, with a 1-2 day layover in the destination city. On the other hand, longer sequences of back-to-back transmeridian flights can lead to the circadian body clock adopting a non-24-hour period that may be close to its innate period 22. This presumably happens when repeated time zone crossings are combined with a non-24-hour sleep/wake pattern, so that there are no longer any 24-hour day/night cues to synchronize the circadian body clock.
  • It appears that if you are flying "out and back" with just 1 - 2 days for the "out," you may be better off keeping yourself on your home's time zone.

"Split sleep"

[]Fatigue Management Guide, ¶2.2.3]

  • The laboratory studies referenced earlier allowed participants a single sleep opportunity at night. However, split sleep is common during different types of flight operations. For example, in-flight sleep on long flights results in split sleep (either by the use of controlled rest or where augmented crews enable scheduled in-flight rest breaks). Layovers after transmeridian flights also commonly include split sleep, as do daytime layovers between night duty periods without transmeridian flights.
  • Laboratory studies suggest that having a restricted sleep period at night plus a daytime nap has equivalent recovery value to an identical total amount of sleep taken in one consolidated block at night.17 However, these are short-term studies that take place in dark, quiet laboratory environments with no distractions, and participants are fully adapted to the local time zone. These conditions do not always apply in 24/7 flight operations, so careful consideration is needed before applying the findings to crewmembers.
  • An important advantage of split sleep is that it reduces the length of time that a crewmember is continuously awake.

Fight it (scientifically)

My third decade of international flying included charter operations in the Gulfstream V where we often started on the East Coast of the United States and would end up halfway around the world. My longest nonstop trips in a single duty day took me as far as Beijing, China, or Jeda, Jordan. (Both of these just under 14 hours.)

Clearly I needed something better than what I had done in the past. It was time to turn to science.

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Photo: The Gulfstream G450, from Eddie's logbook, circa 2012.

Strategically scheduling meals

[Burdick pp. 65-69]

The scientific literature sometimes refers to your body's peripheral clocks as "slave" clocks beholden to the suprachiasmatic nucleus. But they can behave autonomously, and under the right circumstances they're capable of synchronizing their circadian rhythms not to the master clock and the natural cycle of daylight but to orders received from elsewhere. It turns out that food sends a particularly strong message to certain components of the body's clock. Several studies in the past decade have demonstrated that eating meals on a regular timetable can shift the phase of the liver's circadian clock, causing it to ignore the light-based timetable relayed from the brain and to perhaps even send a message of its own back upstream. Mealtime, not solar time, comes to define the liver's day. "If you feed a lab mouse in the middle of its sleep cycle, it will soon learn to wake up shortly beforehand," Chris Colwell, a leading circadian researcher at U.C.L.A., told me. "I tell my students, If the pizza guy starts delivering to your house every day at four a.m., I guarantee you'll start waking up at three-thirty."

One way to minimize jet lag, then, especially after a long flight, is to avoid eating the airline meals as they're handed out by the flight attendant. Their protocol requires that they feed you every couple of hours, typically on a schedule defined by the clock of the city you departed from. In transit, absent the normal light cues, the liver will drive the circadian clock, cementing you further to the time zone you're trying to leave behind. Better to set your watch immediately to the time zone of your destination and schedule your meals as if you'd already arrived. "The standard advice we give to people who are traveling," Colwell says, "is to expose yourself to light and mealtimes, as well as social interactions, as soon as you can." He also advocates eating breakfast. "If humans work in any way like lab mice do," he said, "breakfast is important to keeping those signals, so you don't go all haywire when those light signals aren't present."

Colwell's research suggests that regular exercise may also help drive the circadian system. In his lab he found that the suprachiasmatic nucleus generates stronger signals in mice that are allowed to exercise on a running wheel than it does in less-active mice; the effect was greatest in mice that were allowed to run only early in their waking day. The biggest beneficiaries were mice that lacked a particular clock protein — when they exercised late in their day, the suprachiasmatic nucleus showed an improved ability to send its organizing signals to the heart, liver, and other organs. Running more made their clocks run better. It's too early to know if scheduled exercise might help humans to the same extent. But the idea is tantalizing, Colwell said, because the quality of our master clock declines with age. "'"I'm barely fifty and I'm having trouble sleeping through the night," he said. "And I'm getting more tired during the day." Even timekeepers get old.

Jet lag, at least, is temporary. But humans are finding other, more lasting ways to defy the standard division of daylight and darkness, and the effects are worrisome. Millions of Americans do shift work: they drive through the night, work the late shift at the shipping center, or keep a crazy schedule at the hospital. Many suffer from what circadian biologists call social jet lag, with consequences that are more than merely inconvenient or uncomfortable. One of the key functions of the circadian clock is to supervise the body's metabolism-to ensure that we eat when we're hungry and that our cells receive the nutrients they need at the right time. But many researchers are finding that people who habitually work off-hour shifts are more likely to be obese, be diabetic, or suffer from heart disease. Mounting evidence suggests that there's a strong link between circadian misalignment-a sleep-wake cycle that's out of step with one's circadian clock-and metabolic disorder, a suite of conditions, including diabetes, that result when the body's system for digesting food falls out of step with the process of producing and storing energy.

Millions of dollars are spent studying what we should eat, but when we eat may be equally important. Mice that eat when they should be sleeping — that is, at the wrong time in their circadian cycle — gain more weight than mice that eat at normal hours, one recent study found. Although most studies on circadian misalignment have looked at rodents and nonhuman primates, medical researchers increasingly are turning their attention to human subjects. In one Harvard study, ten human volunteers were trained to live on a twenty-eight-hour day. By the fourth day their schedules had inverted: they were awake, and eating, in the middle of the night. Four days later their schedule had inverted back to normal. Within ten days-the length of the study-the subjects' blood pressures had skyrocketed, their blood sugar levels were above normal, and three volunteers were classified as prediabetic. The confirmed cause wasn't lack of sleep; rather it was the fact that the subjects were consistently eating at times of day when their organs and adipose cells weren't primed to metabolize the food. "Even after just a few days, they showed striking changes in glucose metabolism," one of the study's authors noted. "The rapid onset within just a few days shows that such changes may even temporarily affect the millions of people experiencing jet lag every year."

The current obesity epidemic has many causes, including our sedentary lifestyle and less-than-exemplary diet. But the circadian research suggests another, less visible culprit: increasingly we are trying to colonize the wrong part of the day. "We have a perfectly good endogenous timing system that works based on the old rules," Colwell said. "It's crazy to think that just because we've invented electric lights we can ignore it."

Stragetic use of caffeine

[]Fatigue Management Guide, ¶2.1.3] Caffeine can be useful to temporarily reduce sleepiness on duty because it blocks a chemical in the brain (adenosine) that increases sleepiness. It can also be used in advance of a period that is likely to be associated with higher fatigue (e.g. the early hours of the morning). Caffeine takes approximately 30 minutes to have an effect and can last for up to 5 hours, (but people differ widely in how sensitive they are to caffeine and how long the effects last). It is important to remember that caffeine does not remove the need for sleep and it should only be used as a short term strategy. For maximum benefit, caffeine should be avoided when alertness is high, such as at the beginning of a duty period, and instead used at times when sleepiness is expected to be high, e.g. towards the end of a long duty period or at the times in the circadian body clock cycle when sleepiness is greater.

[]Fatigue Management Guide, ¶4.1.10]

  • Caffeine is a widely consumed substance that has been shown to increase alertness and improve motivation and concentration30 . Therefore, it is frequently used as a fatigue countermeasure. Although it can be used to improve alertness in the short term, it does not address the brain’s underlying need for sleep
  • So why does caffeine make you feel good? A chemical called adenosine builds up in the brain when you have been awake for a long period of time, making you feel sleepy. Caffeine blocks the action of adenosine. Preventing the action of adenosine also results in other chemicals in the brain being released. The consequence is that you feel more alert and energetic. About 15 minutes after consuming caffeine the effects can be felt and these effects can last for between 2.5 to 4.5 hours and even longer in some individuals.
  • If caffeine is to be used as a fatigue countermeasure, then it should be consumed strategically (i.e., not used when already alert). Caffeine use can be considered after long periods of wakefulness and at times in the circadian cycle when alertness decreases (i.e., approximately 1500-1700 hours and 0300-0500 hours). Caffeine, in combination with a short nap, has been shown to be an effective fatigue countermeasure, and may also minimize the effects of sleep inertia when waking31. Since it takes at least 15 minutes for caffeine to enter the bloodstream, an individual can fall asleep before the alerting effects of caffeine occur.
  • Caffeine consumption should be limited near bedtime, as it can interfere with and disrupt sleep. For some individuals, even small amounts can cause problems sleeping. Care should be taken when caffeine is consumed regularly (i.e. daily) because mild dependence can occur. It is also possible to experience side effects such as stomach problems, dizziness, rapid heartbeat, irritability, anxiety, tremors, dehydration, high blood pressure and insomnia. To prevent more severe health risks associated with high levels of caffeine use it is recommended that healthy adults should not consume more than 500-600mg per day. Table 4-6 provides a list of caffeine amounts in common foods and beverages.

Strategic use of lights, noise, and temperature

[]Fatigue Management Guide, ¶2.1.3] Environmental factors can also disturb sleep. Bright light increases alertness (and can be a short-term countermeasure to temporarily relieve fatigue in the work environment). It is much easier to sleep in a dark room. Heavy curtains or a mask can be used to block out light. Sudden sounds also disturb sleep. Masking them using white noise can help, for example tuning the radio in the hotel room between stations. Falling asleep requires being able to lower core body temperature (by losing heat through the extremities), so it is easier to fall asleep if the room is cooler rather than hotter. For most people (18-20 °C/ 64-68 °F) is an ideal room temperature for sleep. A comfortable sleep surface is also important.

Strategic use of naps

[]Fatigue Management Guide, ¶2.1.3] Studies using polysomnography show that crewmembers’ sleep in onboard crew rest facilities is lighter and more fragmented than their sleep on the ground4. Sleep during flight deck naps is also lighter and more fragmented than would be predicted from laboratory studies5. Nevertheless, there is good evidence that in-flight sleep improves subsequent alertness and reaction speed and is a valuable mitigation strategy in fatigue management. Interestingly, the fragmented quality of in-flight sleep is not seen in studies in hypobaric chambers at cabin pressures (6,000-8,000 feet), so it cannot be due to altitude6. The factors most commonly identified by crewmembers as disturbing their in-flight sleep are random noise, thoughts, not feeling tired, turbulence, ambient aircraft noise, inadequate bedding, low humidity, and going to the toilet.

Polysonogram: a record of a person's sleep pattern, breathing, heart activity, and limb movements during sleep.

[]Fatigue Management Guide, ¶2.1.4]

  • Scientific evidence shows that the longer a crewmember remains awake, the worse their alertness and performance become. This is due to an increasing homeostatic pressure for sleep associated with the longer period of wakefulness. . Sleep is the only way to reverse this.
  • The US National Transportation Safety Board has examined the relationship between time since awakening (TSA) and errors in 37 aircraft accidents (1978-1990) in which flight crew actions or inactions were causal or contributing factors9. The median TSA at the time of the accident was 12 hours for captains and 11 hours for first officers. Six crews were classified as low TSA (both the captain and the first officer were below the median) and six crews were classified as high TSA (both the captain and the first officer were above the median). For low TSA crews, the median time awake was 5.3 hours for captains and 5.2 hours for first officers. For high TSA crews the median time awake was 13.8 hours for captains and 13.4 hours for first officers. Overall, high TSA crews made about 40% more errors than low TSA crews (12.2 versus 8.7 errors), primarily due to making more errors of omission (5.5 versus 2.0 errors). In terms of error types, high TSA crews made significantly more procedural errors and tactical decision errors than low TSA crews.
  • Research supports the benefits of napping as a mitigation in flight operations. For two-pilot crews on long range flights, planned 40-minute nap opportunities on the flight deck seat have been shown to provide an average of 23 minutes of sleep and to improve alertness and performance at top of descent, with no apparent effect on subsequent layover sleep10. Note that not all regulators permit flight deck napping.

    Avoid It

    Does Age Matter?

    []Fatigue Management Guide, ¶2.1.3] Across adulthood, the proportion of sleep time spent in slow-wave sleep declines, particularly among men. In addition sleep generally becomes more fragmented after about age 50-60 years. These age-related trends are seen in the sleep of flight crewmembers, both on the ground and in the air. A study of in-flight sleep on delivery flights of B-777 aircraft (from Seattle to Singapore or Kuala Lumpur) found that older pilots took longer to fall asleep, obtained less sleep overall, and had more fragmented sleep than their younger colleagues.


    Burdick, Alan, Why Time Flies: A Mostly Scientific Investigation, Simon & Schuster, New York, NY, 2017

    Duty Rest Guidelines for Business Aviation,, Flight Safety Foundation, April 2014

    Fatigue Management Guide for General Aviation Operators of Large and Turbojet Aeroplanes, Flight Safety Foundation, First Edition, 2016

    ICAO Annex 6 - Operation of Aircraft - Part 2 General Aviation, International Standards and Recommended Practices, Annex 6 to the Convention on International Civil Aviation, Part II, 9th edition, July 2016