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.
Photo: The big trip, 1980, from Eddie's logbook.
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 . . .
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, ¶184.108.40.206] 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, ¶220.127.116.11] 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]
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.
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]
Figure: The non-REM/REM cycle across the night, from Fatigue Guide, Figure 2-2.
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.
Photo: The C-20B (Gulfstream III), from Bill Shull and Eddie's logbook, circa 1992.
Fatigue Management Guide, ¶2.1.3]
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.
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.
Photo: The Challenger 604, from Eddie's logbook, circa 2002.
Fatigue Management Guide, ¶2.3.5]
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.
Fatigue Management Guide, ¶2.2.3]
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.
Photo: The Gulfstream G450, from Eddie's logbook, circa 2012.
[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."
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]
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.
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]
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
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