Internal Time: Chronotypes, Social Jet Lag, and Why You’re So Tired

by Roenneberg, Till

  15

  When Will My Organs Arrive?

  It was 7 P.M. when Oscar, a middle-aged and slightly rotund surgeon, handed his new acquaintance two glasses: one with gin, tonic, lime, and ice; the other with plain tonic water. “I didn’t know how strong you want your G&T, so I brought some extra tonic,” he said. “I’m Oscar, by the way.”

  “Thanks for the drink, Oscar. My name is Jerry.”

  When Oscar had settled in one of the comfortable, overstuffed leather armchairs, he raised his glass, which appeared to contain a Bloody Mary. “Cheers.” After taking a sip, he put the glass down on the stylish glass table in front of him and took a single peanut out of a small bowl. “Have you reached your wife?” he asked, continuing the conversation.

  “She won’t pick up the phone—we had a fight, and I told her to go to the dinner party on her own,” answered Jerry, the younger and definitely fitter one of the pair. His face expressed both disappointment and anger.

  Oscar looked at him with understanding. “I couldn’t help overhearing that you were having a difficult time on the phone,” said Oscar. “I’m sorry,” he added after a little pause. “When I was still married, I found myself a victim of many similar quarrels. They just don’t know what we go through in our jobs.”

  Jerry nodded slowly. He looked like he was about to fall asleep, and his gaze was turned inward. With a jerk of his head he forced himself back to reality. “Sorry, what did you just say?”

  Oscar slightly rephrased his last statement. “Our spouses, they don’t appreciate the constant stress we are under.” This time Jerry’s acknowledging nod was more engaging.

  “What do you do for a living?” he asked. “Or are you already retired?”

  “No, not yet,” said Oscar. “I am a surgeon specializing in organ transplants.” Unexpectedly the younger man broke into an almost hysterical laughter. A group of people sitting nearby turned to look at him. Oscar also looked at him in surprise. “What’s so funny about that?”

  “Oh, I’m sorry,” murmured Jerry, still fighting his giggling fit. “It’s just that I’m also an organ specialist.”

  “How nice, we’re colleagues! Where are you based? Let me guess—Cincinnati? They are building up a new unit for organ transplantations there, and I had heard that some colleagues were also in town. We must have met before, perhaps at a conference. I’m so sorry—I have a bad memory for faces—it’s names for me. What is your last name?”

  Jerry’s laughter became louder again. “I don’t think that we have any reason to have met before—my organ is bigger than yours.” Oscar thought that he had definitely given him too much gin. He didn’t like where this was going—he loathed men’s jokes. When Jerry saw the expression on Oscar’s face he stopped laughing immediately. “I am sorry, that wasn’t at all meant the way it must have sounded. I’m not a doctor, although my ‘patients’ also desperately need my expertise. My specialty is antique pipe organs—I service and repair them.”

  Oscar’s irritated look softened and now he, too, laughed and raised his glass. “Here’s to the different organs in our lives!” he said cheerfully and took another sip.

  Only now did Jerry realize how open to misinterpretation and potentially tasteless his remark must have seemed. He wanted to change the subject. “Can I get you another Bloody Mary?”

  “No, thank you; anyhow, this is only tomato juice. I couldn’t tolerate alcohol at this time of day. I would immediately fall asleep, and my liver would throw a temper tantrum.” For some minutes, the two men sat in silence before Oscar picked up the conversation. “How long have you been here?”

  “I arrived just over two days ago and went directly to the museum, which has a beautiful but sick old pipe organ. I worked on my ‘patient’ for almost twenty-four hours. Luckily, some organ parts didn’t arrive until yesterday, so I got some sleep while waiting for them. But all in all I can’t have slept for more than four hours over the past couple of days—never can in these situations.”

  Now Oscar was the one to react surprisingly. He violently shook his head while grinning widely. “These coincidences are becoming ridiculous. I also arrived just over two days ago. A rather complicated transplantation was scheduled for yesterday morning, but the donor liver arrived more than twelve hours late. So I was on call and on the phone all that time, and after that I had to perform a long and complicated operation. I hardly got any sleep either.”

  Jerry looked at the empty glass in his hand and felt the gin rushing to his head. He wanted to put the glass down on the table in front of him but missed its edge by half an inch. The glass fell on the floor but, thanks to the carpet, didn’t break. He picked up two slices of lime and the remnant of an ice cube, put them back into the empty glass, and placed it on the table. But while pulling back his hand, he knocked over the bowl of peanuts, which neither of them had touched since Oscar had had his one and only. Jerry’s apparent good mood had totally vanished. He now looked deeply depressed. “Maybe she was in such a foul mood because I got her out of bed when I called. I should be at home more, then things might possibly improve between us.”

  Jerry reached for his mobile and punched in their home number. He never stored the important numbers because he was convinced that his brain would gradually lose its memory capacity if he were to completely rely on speed-dial buttons. But now he had to key in the number several times, and eventually had to look it up. When he finally got through, no one answered. His depression seemed to be getting worse by the minute. “Our lifestyle is definitely not good for the family—that’s for sure,” said Oscar. He had the feeling Jerry needed to be cheered up a bit. “I always try to look on the bright side. The short sleep I got this morning, for example, was one of the first in weeks that wasn’t interrupted by an asthma attack. I had a hefty one this afternoon, though.”

  Jerry decided that the G&T had been a lousy idea. He still wasn’t hungry, but he had to give his stomach something to work on besides alcohol, and he definitely needed some caffeine. “I see that they have croissants over there. I’ll get myself a cup of coffee to go with it,” he said. “I’ll also try to find out whether there are any new developments. What about you? Can I get you something?”

  “I don’t think I’ve eaten for twelve hours or more. So, yes, that’s an excellent idea. Let’s have breakfast and get ready to go home!” exclaimed Oscar.

  What does the two men’s conversation tell us about the body clock? Where are they, and how can we make sense of the clues they provide? Let’s review the evidence—you may want to do so on your own before continuing.

  The story begins with a statement about time of day—it is seven o’clock in the evening—and ends with Oscar’s exclamation, “Let’s have breakfast!” This blatant discrepancy may have put you on the trail. What scenario reconciles this apparent contradiction? You already know that the distribution of chronotypes in a population can be so wide that the extreme larks and the extreme owls are up to twelve hours apart. Could that be an explanation for having breakfast twelve hours out of synch with local time? Probably not; although the most extreme chronotypes are twelve hours apart, they are generally only six hours out of synch with the rest of the world—six hours too early or six hours too late. So the issue of chronotypes is most likely not the basis for the two men’s desynchrony with their local time (just for the record, Oscar is a definite early type and Jerry is more of an owl).

  Based on what you have read in the previous chapter you might speculate that the two gentlemen are having their conversation on another planet, possibly on Neptune with its eighteen-hour day. A short day like that would make their chronotypes so late that the gentlemen’s craving for breakfast at seven in the evening would be conceivable. But then you know that in that story WASPS never sent humans to Neptune. You would also correctly discard the possibility that the two are on Mars because you know that in that situation they would have breakfast at some ungodly early hour. Perhaps the two are subjects who have just finished a long
experiment in the Andechs bunker, putting them completely out of touch with local time. Yet both state they have recently finished critical tasks in their profession—one in a museum, the other in a transplant center.

  It seems quite apparent that Oscar’s and Jerry’s internal time is completely out of synch with their external, local time. The simplest explanation, and one familiar to many of us, is that they have just travelled halfway around the globe, so that their biological clocks haven’t had a chance to catch up yet. In support of that supposition, they both mention that they arrived only a couple of days ago. But where are they, and to what time zone are their biological clocks still set? From their conversation, we can conclude that their home base is the United States. So the question becomes: what country is about twelve time zones away from the United States?

  Oscar and Jerry are sitting in the business-class lounge at Narita Airport in Tokyo and have just learned that their flight to Boston will be delayed by an as-yet-unforeseeable time. People strike up conversations for the oddest reasons, but fellow travelers, stranded and headed to the same destination, have so much in common that it would seem almost impolite not to communicate. They had overheard each other’s telephone conversations, and Oscar was not able to avoid hearing Jerry’s big row with his wife. The delay would not get Jerry back in time for the dinner party, and his wife didn’t hold back her frustration. It wasn’t the first time his work schedule had conflicted with their social engagements. She completely ignored the fact that her husband was suffering the worst possible kind of jet lag—a complete half-day out of synch (the reason why Jerry got hold of his wife just before she was about to wake up).

  In our modern mobile world, millions of people have suffered from jet lag at least once when visiting friends or taking vacations in distant countries. People whose jobs take them to many different parts of the world find themselves in this rotten state with sad regularity. But what symptoms characterize jet lag a bit more accurately than just feeling lousy? The most conspicuous symptom is tiredness. However, that state is not necessarily specific to jet lag. If someone travelled from Helsinki to Cape Town, he or she might also feel severely tired without ever having left the time zone, merely due to the length of the exhausting trip (not to mention that this traveler would also journey from winter to summer, or from autumn to spring, or vice versa). The major difference between travelling long distances within time zones as opposed to across time zones is that the passenger from Helsinki would have no problem sleeping at the right time of night in Cape Town and would thus recover quite readily from the exhausting voyage. But just travelling long distances across time zones does not necessarily throw the traveler into the state of jet lag.

  Long ago, before airplanes carried travelers across the Atlantic, they may have suffered from seasickness but certainly not from jet lag. As the word says, it takes a jet to elicit this state because the main cause for this syndrome is the speed at which we travel from one time zone to another, from one time of dawn to another, from one time of dusk to another, and from one different social timing to another. Our body clocks can cope with the slow changes of dawn and dusk that we experience when travelling by ship. If we were to take a boat from Europe to America, it would be a bit like living on Mars: every evening the sun would set and every morning it would rise a bit later, making the days longer than twenty-four hours. Of course, we would much more easily synchronize to these longer days if we spent some time on deck—especially in the evenings—thereby exposing ourselves to bright light at a time of our body clock when light expands the internal day. If we were to take a boat in the other direction, from America to Europe, we would live on yet another planet with days shorter than twenty-four hours by travelling against the rotation of our globe. If the boat didn’t cruise too fast across the Atlantic, these shorter days would still be within the range of entrainment of our body clock, so that our internal time would arrive in synchrony with the external time. According to the principles of entrainment, we would become slightly earlier chronotypes when travelling west and slightly later chronotypes when travelling east.

  However, when it takes us less than a day to travel across half of the globe, our body clock is left behind. The shortest flight from Boston to Tokyo takes fifteen hours and twenty-five minutes. If Oscar and Jerry had left Boston’s Logan Airport at 8 A.M., it would already be 9 P.M. in Tokyo, and they would arrive at Narita Airport half an hour after noon local time (it would actually be a whole date-day later since they would have crossed the date line). Their internal time would, however, be set to thirty minutes before midnight—approximately half a day out of synch.1

  Another symptom of jet lag is nighttime insomnia despite utter exhaustion. Based on the calculations above, this is not surprising. Unless we have travelled to a holiday destination, we are expected to be active when our body clock is on its way to bed, and we have to try and catch up on sleep when our internal alarm clock “announces” that it is time to get up. As a rule of thumb, it takes the body clock approximately one day per travelled time zone to adjust to the new cycle of light and darkness, so that Bostonians travelling to Japan would need approximately twelve days until they functioned normally again. The difficulty of not being able to sleep adds to the exhaustion of the trip itself. Since this state may continue for many days after arrival at the destination, the traveler cannot compensate for the exhaustion experienced during the long flight.

  Holidaymakers are often advised to live as much as possible according to the normal day at their destination if they want to get rid of their jet lag as quickly as possible. This includes being active and seeking daylight when the sun is up, and resting in darkness at the usual times of the host country, even if normal sleep is impossible during the first few days after arrival. It also means avoiding taking too long a siesta in the afternoon. Siestas roughly correspond to bedtime at home, making it even less possible to sleep through the new local night. The stronger you can make the new zeitgeber, the faster your body clock will arrive at the new destination. The rule of thumb about our body clock needing one day for each shifted time-zone hour is an approximation. Most people can adjust more easily when flying to the west. Going west, their clock adapts by expanding their internal days, which are already longer than twenty-four hours. Accordingly, adjustments after travelling in the opposite direction are more difficult, especially for late chronotypes. Only extreme early types report adjusting faster and more easily when travelling from west to east.

  Other symptoms of jet lag are reduced alertness, poor motor coordination and reduced cognitive skills.2 You might think that these symptoms go with the territory when we suffer from exhaustion and profound sleep deprivation. But again the combination of being active at the wrong internal time and being exhausted and sleep-deprived exaggerates our impairment. Cognitive states (like vigilance, alertness, and attention) and skills (like motor coordination, performing simple calculations, or memory tasks) are as much under the control of the body clock as sleep and wakefulness, body temperature, or circulating hormones.3 The Constant Routine experiments, during which subjects are tested around the clock without sleeping or moving around much, have shown that subjects perform worst at many skills sometime during the second half of the internal night and improve thereafter, despite having been awake for an even longer time.4

  Not being able to properly catch up on our sleep and our exhaustion is not the only problem we face during jet lag—sudden mood changes and even depression are sometimes also symptoms.5 Another important issue during jet lag concerns our appetite and our digestion. Both are controlled by the body clock, so that during jet lag we get hungry at times when we should try to find sleep, and we have no desire to eat when the locals normally do. If we force ourselves to eat, we confront our stomach with food when it cannot produce enough of the juices necessary for normal and efficient digestion. At the other end of the day, we might lie in bed trying to sleep but feeling hungry. Our stomach anticipates food and produces digestiv
e juices that can then act only on its empty self—an ideal condition to support the development of ulcers.

  Our brain and our digestive tract seem to suffer most. Or perhaps they are those parts of our body that give us the most obvious problems during jet lag. Scientists at the University of Virginia submitted rats to conditions that simulated jet lag and found that the SCN, the master clock in the brain, apparently adjusts much faster to a new light–dark cycle than peripheral tissues like muscles, lung, or liver, shown in the rhythm of wheel-running activity.6 In a similar series of experiments, the Virginia researchers investigated what happens if they put animals on restricted feeding programs.7 In the control conditions, they gave animals access to food during the night, corresponding to the normal activity time of the nocturnal rat. After a week, they shifted the feeding times by several hours without changing the times of the light–dark cycle. The results of these experiments suggest that the clock in the liver can be entrained by food, while the master clock in the brain, the SCN, continues to entrain exclusively to the light–dark cycle. Under these conditions, the normal circadian harmony of the different body clocks is pulled apart.

  The temporal disharmony of different body parts may be an important cause of our lousy feeling in the state of jet lag. The Virginia experiments also indicate that it may take different organs a longer or shorter time to adjust to the new time regime at the destination. Jet lag sufferers can therefore justifiably ask the question, “When will my organs arrive?” Most chronotypes adjust more easily after a westward flight, although some rare early types adjust better in the other direction. Imagine that the different organs of our body showed similar differences in adjustment, some by expanding and others by compressing their internal days. In that case, it would even be conceivable that while Oscar and Jerry flew from Boston to Tokyo on a westward flight via California, some of their organs virtually had to fly the other way around the globe, via Paris and Moscow. Until all the different organs “arrived” at their final destination, it would not be surprising to feel lousy.