Sleep + Extra Darkness = Math Prof’s Formula for Combating Jet Lag

Submitted on Tuesday, 12/20/2011, at 4:35 PM

December 19, 2011

Travelers who have taken long flights eastward know it all too well: The sluggish, altogether unpleasant feeling one experiences waking up the first day in a new time zone. For some, that condition of desynchronosis, or jet lag, can be a mere annoyance. For others, it can be a real vacation headache, disrupting sleep patterns and digestion for days.

Amherst College math professor Tanya Leise, however, wants travelers during this holiday season to know that there are ways to manage jet lag. Leise has long worked with collaborators from several institutions across the country studying the “body clock” that governs the biological processes of humans, and she is an expert in modeling the circadian system in mammals. She spoke with the Office of Public Affairs recently about her research on jet lag and some time-tested strategies for avoiding the condition.

What is jet lag?

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It’s the disruption of the internal body clock that people experience when traveling across time zones. In the hypothalamus in the brain, there’s a small region of around 20,000 neurons that are dedicated to keeping track of time of day—the body’s internal clock. When we travel long distances and change time zones in a very short period of time, we need to help that internal clock shift to the new time zone. If we do things that make it switch the wrong way, we can exacerbate jet lag.

What are the symptoms of jet lag?

The most common one, of course, is fatigue, but there are others, such as stomach problems and dehydration. Some symptoms are actually a result of travel; when you’re on a plane, for example, you may forget to drink water and keep yourself hydrated. Your digestive system is also preparing for meals at the completely wrong times. So when you fill your stomach with the rich foods we eat while on vacation or at the holidays—and at a time when it isn’t expecting food—your stomach isn’t going to feel very nice; you might have a lot of indigestion.

Some people also have problems falling asleep at the right time or trouble getting up in the morning. That’s because that “master clock” of neurons in the brain is controlling other internal clocks throughout your body. Those clocks can be in your liver, your stomach—even in your bones, skin and muscles. The hypothalamus sends messages to them telling them what they are supposed to be doing at specific times of the day, and, if your schedule is off because of being in a different time zone, the whole system can be in real upheaval.

Will people switching time zones always experience jet lag?

Well, there are two directions you can fly to change time zones—east or west. If you fly west, you just have to stay up a little later and stay in bed a little later than normal to adjust. People usually don’t have as hard a time adapting to that; our internal clocks are a little longer than 24 hours and it’s easier to adjust to time change in that direction.

Flying east, though, can be really hard. Someone traveling, for example, from Boston to London or Paris, where you’re switching five or six time zones—you have to get up five or six hours earlier than you normally would and that’s really hard. The question is how can you help yourself adapt to make that process easier.

What has your research shown to work the best?

People typically follow one of three strategies, and my colleagues and I took a look at each approach. The first and probably most common strategy is to do a really short night by forcing yourself to get up at a normal time of morning in the new time zone, and then following your new schedule right off the bat. That tends to not work so well. We have what’s called a phase-response curve where, if you see bright light early in the morning, the waking phase of your day is advanced—you’re adjusting to a more eastern time zone. But if you see bright light in your internal evening phase, it causes your internal clock to delay and makes you feel as if you’re in a more western time zone. So if you try to do a short night to adjust to flying to London or Paris, you’ll actually get light at the wrong time of day. It will shift you in the wrong direction and make things worse. It’s not a good strategy.

Some people say that if you wake up an hour earlier each day several days before you fly, you’ll get yourself pre-adjusted to a new time zone before you travel. We also took a look at that approach. In practice, that means going to bed and waking up an hour earlier the first day, then going to bed and waking up an hour earlier than that the second day, and so on. That strategy can work fairly well, but it can be very hard to do—you’ll be a couple of hours off of your normal routine. It’s often not compatible with your schedule and it’s hard to force your body to do. You just may not be tired enough to go to sleep when you’re getting in bed. It may not help as much as you hoped.

What does work—because it coordinates with this whole internal phase-response we have to light—is instead of doing a single short night, have a slightly shorter night but sleep in a couple of hours later in the time zone than you might normally get up according to the clock. Do that for two days and avoid light in the morning in the new time zone. If you usually wake up at home at 8 a.m., for example, try getting out of bed at more like 10 a.m. in the morning of your new time zone and make a point not to expose yourself to light at those earlier times in the morning. Or, if you do have to get up, at least put on sunglasses, wear a hat or do something to avoid light stimulation. That will help everything change in the correct direction very rapidly. The conventional wisdom out there already said this approach was a good idea and my modeling confirmed this. It disrupts the traveler’s schedule minimally and it’s also something people find easy to do. It’s much easier to sleep in than get up early.

It sounds like light is the key element here.

It is. The rule is that you want exposure to bright light—outside light—no more than two hours earlier than you would’ve gotten up in your original time zone. It’s a little complicated to calculate, but you want to make sure you’re not getting exposed to bright light too early when it could hit the wrong part of your phase-response curve. You want to delay exposure to light until late morning when you travel eastward.

Does that hold for artificial light as well as sunlight?

If you’re exposing yourself only to indoor light and not outdoor light, it’s not so bad, as long as you make sure later in the morning to go out and expose yourself to the more intense sunlight. It’s that contrast of light that’s important—your internal clock needs to get blasted with the outdoor light so it can say, “Ah, I’m going to respond to that.”

I’ve heard that melatonin, the hormone related to circadian rhythms, helps with sleep and, by extension, jet lag, too. Would you recommend travelers take a melatonin supplement?

Melatonin can be helpful, but only in small doses. A large dose can actually be counterproductive because it keeps your body flooded with melatonin for too long. You want to take half a milligram an hour or two before you’re going to fall asleep. It has to be the right time and the right dose to be effective. Large doses can be counterproductive, causing grogginess and other side effects the following morning.

What is your approach to avoiding jet lag?

I try to stay hydrated and to follow that third strategy where I adjust my schedule so I’m getting light at the right times. I’ve found it really works. Our internal clock is very sensitive to outdoor light, so getting outside at the right time can make a huge difference in terms of perking you up and putting things in the right place. It’s also why some people get seasonal affective disorder. When we’re not getting any natural light, we can get depressed because our internal clocks aren’t getting that bright light to regulate our systems—bright light is really essential for good health. You need to be outside during the day getting some of that to feel optimal.

To sum up, what’s the main advice you’d give people traveling eastward?

Make sure you’re sipping water all of the time—that will make a huge difference. Make sure you have small, light meals for a couple of days until you feel adjusted; that will prevent a lot of symptoms. Make sure that you are on a regular schedule: Get to bed at a normal time and, delay exposing yourself to light until later in the morning. It’s also important to avoid alcohol if you’re experiencing symptoms of jet lag. Finally, just take care of yourself—don’t overdo it.