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| Jet lag can make a bench in a foreign country look like a nice place to sleep ... for several hours. |
Jet Lag
How Jet Lag Works
BY PATRICK J. KIGER
If you have plans to
take a long trip that involves flying across several time zones, you already
may be dreading that exhausted, sleepless, irritable feeling that results when
your body is forced to reset its internal rhythms.
Jet
lag, also known as desynchronosis, can cause insomnia, daytime sleepiness, loss
of concentration and alertness, fatigue, irritability, disorientation, depression
and gastrointestinal ills [source: Eastman and
Burgess].
Unfortunately,
it afflicts almost everybody. A 1998 study found that 94 percent of Americans
who fly long distances suffered from jet lag, and 45 percent considered their
symptoms severe [source: James].
Jet
lag makes many of us miserable, but it's more than just unpleasant.
The
Pentagon worries that jet lag will impair pilots' performance and endanger
soldiers on missions, and companies worry that jet-lagged executives may not
bring their "A" game to meetings and make bad deals as a result [source: Eastman and
Burgess].
Those
worries are justified. According to a 2010 study by University of California
researchers, the brains of hamsters subjected to chronic jet lag created
new neurons at about half the rate of normal stay-at-home members of their
species, and showed memory and learning deficits as a result [source: Sanders].
There's
growing evidence that jet lag may even harm your health, particularly as you
age.
2006
University of Virginia study, for example, found that while younger mice were
able to rebound from the effects of air travel, being subjected to the
equivalent of a Washington-to-Paris flight each week increased the death rate
among older rodents [source: Wilber].
Other
research indicates that jet lag can aggravate menstrual discomfort and even
contribute to the development of heart disease and diabetes by altering eating
patterns [source: Eastman and
Burgess].
So
what's a weary traveler to do? Over the years, people have experimented with
all sorts of remedies, from jogging to trying to fight off sleepiness with
frequent doses of caffeine, to various herbal and food-supplement remedies.
While
the magic bullet that would totally eliminate jet lag remains elusive, health
experts say there's a lot you can do to help your body adjust to travel between
time zones and to feel your best, no matter where you land.
But
first, here's some information on what causes jet lag, and why it makes us so
miserable.
What Causes Jet Lag?
We
have groupings of interacting molecules in cells throughout our body that act
as biological clocks, telling our glands when to release hormones and adjusting
our body temperature and other variables.
Just
as the world's watches and bell towers all rely upon the Royal Observatory in
Greenwich, UK, the body's tiny biological clocks follow a master timepiece --
20,000 nerve cells called the suprachiasmatic nucleus, or SCN, located in
the brain's hypothalamus region [source: NIH].
The
SCN keeps your body operating on a regular pattern of sleep-wake cycles and
body functions known as a circadian rhythm.
When
it's time to get some sleep, for example, the natural time-keeping system
releases a hormone called melatonin, which makes us go beddy bye.
The
SCN knows when it's a good time to do this because it's located conveniently
close to the optic nerves, which relay the perception of light from the eyes to
the brain.
Basically,
when there's less light, the SCN tells you to release more melatonin, and you
nod off. But the body also likes regularity, so this natural clock gets
accustomed to going off at the same time every night [source: NIH].
But
your body's timekeeping system has trouble drastically resetting itself that
quickly, and when you cross multiple time zones, you get all messed up as a
result.
The
problem is at its worst when you fly eastward, say from Chicago, in the United
States, to Paris, France. When it's nighttime at your destination, your body
still thinks it's late afternoon. You may wind up lying sleepless in your hotel
bed all night, and finally doze off just when it's time to get up for lattes
and croissants [source: Eastman and
Burgess].
You feel rotten
because sleeplessness disrupts just about every biological function in the
body.
It
causes the release of stress hormones, which make you feel anxious and grumpy.
It drives up your blood pressure, and sends inflammation-stimulating chemical
markers flooding through your arteries.
The
shift also disrupts the release of appetite-regulating hormones, so that you
get a craving to scarf down a lot of food at a time when you normally don't eat
at all.
And
finally, it disrupts your body's regular release of melatonin, which in
addition to inducing sleep helps regulate other hormones and protects you
against diseases such as cancer [source: Stein].
Why Jet Lag is So Difficult to Overcome
Resetting
the body's natural clockwork is a lot tougher than remembering which buttons to
press down on your Timex Ironman.
The
average free-running period of the human circadian clock actually is slightly
longer than 24 hours, so most of us have a natural tendency to drift slightly
later each day.
That
may be why the body adjusts better to phase delay (flying east to west) mode
than it does to phase advance (west to east) mode, which necessitates going to
bed earlier.
In
one study, it took subjects four days to adjust to a 12-hour phase delay, while
a comparison group undergoing a 12-hour phase advance still couldn't get to
sleep normally eight days later [source: Eastman and
Burgess].
Another
complication is that light isn't the only thing that influences sleep. Your
body's temperature also fluctuates during sleep, reaching its minimum
temperature ("Tmin," in sleep-scientist lingo) about three hours
before you normally rise.
Jet
lag symptoms tend to be the worst when you are forced to awaken while you are
still at your normal Tmin. That's why you may feel out of sorts and mentally
dull, even after what seems like a full night's sleep [source: Eastman and
Burgess].
Over
the years, travelers have experimented with numerous remedies for jet lag.
Some
people just try to gut it out, even though staying up all night and all through
the next day until bedtime isn't exactly a good thing for your body or your
mental health.
Others
swear by herbal remedies, or by taking additional melatonin, which is sold as a
supplement.
Still
others try to circumvent jet lag by taking overnight flights and trying to
snooze in their seats, with the help of a sleeping medication.
Doctors,
however, advise strongly against this last solution.
The
human body, as it turns out, is not designed for deep sleep while sitting, and
immobilizing a person for long periods in that position escalates the risk of
thrombosis, the formation of blood clots.
The
New England Journal of Medicine recently documented the case of an otherwise
healthy 36-year-old woman who, after sleeping in an airliner seat for seven
hours, suffered what turned out to be a fatal stroke [source: Schneider].
But
don't fret. In the next section, we'll give you some advice from medical and
travel experts on safer, more effective ways to cope with jet lag.
What the Experts Recommend
If
you're expecting a simple, just-pop-a-pill solution for jet lag, we hope you're
not too disappointed to discover that it doesn't yet exist.
But
if you're determined to beat the travel blues, try a regimen advocated in a
2009 article by biological rhythms researchers Charmane I. Eastman and Helen J.
Burgess of Chicago's Rush University Medical Center.
They
suggest gradually readjusting your rhythms prior to a trip, using a light box,
a device that exposes you to simulated sunlight.
To
phase-advance on a west-to-east trip, go to bed an hour earlier for several
nights before the flight. Awaken earlier, and use the light box to get a dose
of brightness.
Conversely,
to handle an east-to-west journey, stay up a couple of hours later for several
nights before the trip, using the light box at your normal bedtime to stimulate
you. Upon awakening, avoid bright light for several hours. If you have to go
outside, wear dark glasses [source: Eastman and
Burgess].
Eastman
and Burgess also suggest using melatonin, a supplement that's not FDA approved
but which has been shown in studies to help alter circadian rhythms.
To
aid in west-to-east phase advance, take 0.5 mg. about four and a half hours
before bedtime, and progressively move the doses earlier in the day as you
start going to bed earlier. For an east-to-west trip, reverse the process [source: Eastman and
Burgess].
If
that sounds too complicated, you may prefer the U.S. Centers for Disease
Control and Prevention's tips for minimizing circadian woes.
The
CDC suggests that you keep up on your exercise regimen, eat a balanced diet and
get enough rest in the weeks before a trip, apparently in the belief that a
healthy lifestyle will help you to rebound quicker from the rigors of travel.
While
you're in the air, the CDC recommends avoiding alcohol and caffeine, both of
which can have disruptive effects upon sleep, and drinking plenty of water.
The
CDC also advises you to wear loose, comfortable clothing and to move around in
the cabin when you have the opportunity.
Finally,
CDC suggests not stressing out about jet lag. Instead, if possible, simply
adjust your schedule so that you don't to have any crucial meetings or big
decisions to make until you've had a couple of days to regain your mental
acuity [source: Yanni].
Patrick Kiger
Patrick J. Kiger
has written for HowStuffWorks since 2008 covering a wide array of topics, from
history and politics to pop culture and technology. He worked as a newspaper
reporter for the Pittsburgh Press, and the Orange County Register in
California, where he covered one of the biggest serial murder cases in U.S.
history, and also as a staff writer at Baltimore Magazine. As a freelancer,
Patrick has written for print publications such as GQ, Mother Jones and the Los
Angeles Times, and on the web for National Geographic Channel, Discovery News,
Science Channel and Fast Company, among others. In recent years, he's become
increasingly interested in how technological advances are altering urban life
and the design of cities, and has written extensively on that subject for Urban
Land magazine. In his spare time, Patrick is a longtime martial arts student
and a fan of crime fiction, punk rock and classic Hollywood films.
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