Ah, jet lag - that dreadful feeling that descends when you arrive in Paris keen to tour the Louvre and your body aches to be back home nestled in your bed.
Sadly, the joys of long-distance travel are often dampened by the body's inability to rapidly acclimatize to a new location three or more time zones from your own.
To be sure, not everyone reacts the same way to long-distance jet travel. Some bounce back relatively quickly. Others are plagued by sleepy days and sleepless nights for more of their trip than they would like.
In general, experts say, travelling across three time zones or more triggers jet lag. And for the first eight time zones at least, the problem is definitely worse when travelling from west to east than from east to west.
So if you are departing from Halifax, you will suffer more jet lag travelling to Rome (five hours ahead) than to Vancouver (four hours behind).
"Advancing the clock is more difficult than delaying the clock," explains Dr. Robert Auger, an assistant professor of psychiatry and medicine at the Mayo Clinic college of medicine and a consultant at the Mayo Center for Sleep Medicine in Rochester, Minn.
"The problem is that for most of us, our internal circadian clocks are slightly longer than 24 hours. And so we're much more able to delay our clock, which is what needs to occur when you travel westward."
What that means is that for most people, pushing yourself to stay awake a few hours later than normal in a westward destination is much easier than trying to force yourself to fall asleep at 6 p.m. in an eastward destination.
That problem is exacerbated by the fact that the scheduling for the majority of Europe-bound (and Africa via Europe-bound) flights deprives North American passengers of a night's sleep, arriving in what is the early morning, local time, but the middle of the night, body time.
"It actually makes the least sense from the standpoint of adapting your circadian rhythms, for the traveller, anyway," Auger says of overnight eastward flights across time zones.
That's because exposure to light first thing in the morning at your destination after you've jumped four to nine time zones eastward actually impedes the ability of your circadian rhythms to adapt to local time.
The term circadian rhythm refers to the body's internal clock, set primarily by exposure to light and dark. Recalibrating your internal clock isn't as simple as trying to immediately match your waking and sleeping hours to the time at your destination. It's estimated that it takes about a day per time zone jumped to acclimatize.
That process can be sped up following a schedule of light avoidance and light exposure, experts say. But the schedule is not intuitive. Auger says people who really need or want to minimize the impact of jet lag may have to go to lengths that are "fairly heroic."
A schedule mapped out in a March 2007 article on jet lag in the medical journal The Lancet suggests that if your travels jump you six time zones ahead (eastward travel) you need to avoid light at your destination between 3 a.m. and 9 a.m. and actively seek light from 11 a.m. to 5 p.m.
That means avoiding light on your arrival after an overnight flight to Europe. Emulate the celebs and don dark glasses - Auger says they will help.
When it is time to expose yourself to light, natural is probably best but light boxes such as those used for seasonal affective disorder should also work, he says.
But if you've travelled overnight, try not to combine light avoidance with napping - that may actually slow your adaptation to local time. Your nap could eat into your light exposure time and could keep you up well into the wee hours of the night local time.
For a trip that takes you five time zones backwards (westward), you should avoid light at your destination between midnight and 6 a.m., and seek light between 4 p.m. and 10 p.m., according to the Lancet article, which was written by researchers from Liverpool John Moores University in Liverpool, England.
If your trip is a quickie - three days or less - studies suggest your best bet is to ignore trying to adapt to local time.
"You will definitely have less jet lag symptoms if you remain on your home schedule in that setting," Auger says. "Because the prospect of adjusting within several days is impossible."
Those who aren't averse to a little assistance could consider using melatonin to help reset their clocks. Auger says two milligrams to eight milligrams of melatonin at the sleep time of your travel location should help alleviate jet lag symptoms. Melatonin is sold as a natural health product in pharmacies and stores that sell supplements.
Prescription sleeping pills can also come in handy for travel-induced insomnia, though they may not help with the daytime symptoms of jet lag, Auger says. The authors of The Lancet article warn against using a prescription sleep aid for the first time while travelling, noting some people have reactions to some of the available medications.
Some tips for minimizing jet lag from Dr. Robert Auger, from the Mayo Clinic's Center for Sleep Medicine:
-Try to maximize sleep before and during your travels. Sleep deprivation prior to your trip could make jet lag worse.
-Do some research. Find out the recommended times to avoid and receive light at your destination, based on the number of time zones you jump.
-Consider taking melatonin at bed time in your travel location. Two-to-eight milligrams should suffice.
