When travelling across multiple time zones, the rhythm of day and night changes, which confuses our bodies. — BORIS ROESSLER/dpa
When you fly across multiple time zones, an unwelcome greeter may be waiting for you at the airport that can rob you of sleep, upset your stomach and generally make you feel out of sorts: jet lag.
Dorothee Steven, a psychologist in the Institute of Aerospace Medicine’s Department of Sleep and Human Factors Research at the German Aerospace Centre (DLR) in Cologne, Germany explains what causes jet lag, what the symptoms are, and what, if anything, you can do to prevent or alleviate it.
What causes jet lag?
It has to do with your body’s circadian rhythm, or “internal clock”, Steven says. Based in the brain’s hypothalamus, it helps regulate, in roughly 24-hour cycles, many biological processes, most notably the sleep-wake cycle.
“Light is the strongest synchroniser for your internal clock,” Steven says. If the time of daylight and darkness abruptly shifts, as it does when you cross several time zones in an air plane, the rhythm can be discombobulated and need time to adjust.
Flying eastward often causes more severe jet lag symptoms than flying westward because your internal clock has to reset itself forward, not backward, and waking up earlier is typically harder to get used to than going to bed later.
If you leave London at 4pm on a Tuesday and arrive in Beijing at 9am on Wednesday, your internal clock says it’s 2am and probably well past your bedtime as the Chinese capital is just starting its day.
In the reverse direction at the same departure time, you arrive in London at 7pm.
Can jet lag be prevented?
You can try to adjust your sleep schedule starting several days before your trip, primarily with strategically timed light exposure, Steven says. When it’s still dark outside, daylight lamps can simulate daylight. When it’s still light outside, you can darken your bedroom. Your sleep time should shift.
“This is all rather onerous and often not socially compatible though,” she concedes. And it can’t wholly prevent jet lag, but at best only moderate it. What’s more, a possible side effect is experiencing a mini jet lag before you even step into the plane.
What are the symptoms of jet lag?
Sleep problems first and foremost, since you can’t sleep at your accustomed time. You may find you experience a disrupted sleep-wake cycle, mentally and physically.
“Your mind isn’t as sharp. You feel a little like you’re packed in cotton wool,” says Steven.
Your reactions aren’t as quick, and you can’t do things such as mental arithmetic as well. You may also be more sensitive and irritable than usual due to a lack of sleep.
There are numerous physical symptoms too, including gastrointestinal problems such as stomach ache and indigestion.
What to do to ease jet lag?
You should get on the normal sleep-wake cycle where you are. “A guideline: When it’s light outside, you should be awake, and when it’s dark, you should rest,” Steven says.
If you arrive in the US at 6pm on a flight from Central Europe, for instance, it’s the middle of the night back at your point of departure. Nevertheless, Steven says, you should resist your internal clock’s urge to go to bed and, if possible, do something outside before it gets dark.
What if you’re so sleepy you’ve just got to sleep?
A daytime nap is fine if the urge to sleep is overpowering. However, sleep medicine specialists recommend that it not exceed 20 to 30 minutes. So set an alarm.
What if you should sleep but can’t?
Let’s say it’s late in the evening at your destination but you can’t fall asleep because it’s midday at your point of departure and your internal clock has you wide awake.
In that case, your social or business commitments permitting, you should lie down to signal to your body that it’s bedtime, Steven says.
You could also take the hormone melatonin, which she describes as “a kind of synchronisation medication”. Made naturally by the body, melatonin regulates the sleep-wake cycle and helps induce sleep by having the opposite effect of bright light.
It’s also available as an over-the-counter supplement.
Steven advises against taking prescription sleeping pills such as benzodiazepines, as “their sedative effects can make jet lag worse”.
Another tip is in the days before your trip, try to gradually adjust your mealtimes to match those at your destination, and time your meals to local mealtimes once you’re there. It’s best to eat light meals at first to help avoid digestive troubles.
Unfortunately, there’s no silver bullet for jet lag, “simply because your internal clock is so sluggish,” Steven says.
How long does jet lag last?
As a rule of thumb, about a day for each time zone crossed, she says. The biggest adjustments, and therefore strongest symptoms, are in the beginning. “By the second, third or fourth day you usually feel that the worst is over.”
If you’ve crossed many time zones though, you may well have problems falling or staying asleep for a week or longer. – TOM NEBE/dpa
