Jet lag, also called jet lag disorder, is a temporary sleep problem that can affect anyone who quickly travels across multiple time zones.
Your body has its own internal clock (circadian rhythms) that signals your body when to stay awake and when to sleep. Jet lag occurs because your body's clock is still synced to your original time zone, instead of to the time zone where you've traveled. The more time zones crossed, the more likely you are to experience jet lag.
Jet lag can cause daytime fatigue, an unwell feeling, difficulty staying alert and gastrointestinal problems. Jet lag is temporary, but it can significantly reduce your vacation or business travel comfort. Fortunately, there are steps you can take to help prevent or minimize jet lag.
Symptoms of jet lag can vary. You may experience only one symptom or you may have many. Jet lag symptoms may include:
- Disturbed sleep — such as insomnia, early waking or excessive sleepiness
- Daytime fatigue
- Difficulty concentrating or functioning at your usual level
- Stomach problems, constipation or diarrhea
- A general feeling of not being well
- Mood changes
A disruption to your circadian rhythms
Jet lag can occur anytime you cross two or more time zones. Jet lag occurs because crossing multiple time zones puts your internal clock (circadian rhythms), which regulates your sleep-wake cycle, out of sync with the time in your new locale.
For example, if you leave New York on a flight at 4 p.m. on Tuesday and arrive in Paris at 7 a.m. Wednesday, your internal clock still thinks it's 1 a.m. That means you're ready for bed just as Parisians are waking up.
And because it takes a few days for your body to adjust, your sleep-wake cycle, along with most other body functions, such as hunger and bowel habits, remains out of step with the rest of Paris.
Factors that increase the likelihood you'll experience jet lag include:
- Number of time zones crossed. The more time zones you cross, the more likely you are to be jet-lagged.
- Flying east. You may find it harder to fly east, when you "lose" time, than to fly west, when you gain time.
- Being a frequent flyer. Pilots, flight attendants and business travelers are most likely to experience jet lag.
- Being an older adult. Older adults may need more time to recover from jet lag than do younger adults.
Motor vehicle accidents caused by drowsy driving may be more likely in people who are jet-lagged.
A few basic steps may help prevent jet lag or reduce its effects:
- Arrive early. If you have an important meeting or other event that requires you to be in top form, try to arrive a few days early to give your body a chance to adjust.
- Get plenty of rest before your trip. Starting out sleep-deprived makes jet lag worse.
- Gradually adjust your schedule before you leave. If you're traveling east, try going to bed one hour earlier each night for a few days before your departure. Go to bed one hour later for several nights if you're flying west. If possible, eat meals closer to the time you'll be eating them at your destination.
Regulate bright light exposure. Because light exposure is one of the prime influences on your body's circadian rhythm, regulating light exposure may help you adjust to your new location.
In general, exposure to light in the evening helps you adjust to a later than usual time zone (traveling westward), while exposure to morning light can help you adapt to an earlier time zone faster (traveling eastward).
The one exception is if you have traveled more than eight time zones from your original time zone, because your body might mistake early morning light for evening dusk. Your body might also mistake evening light for early morning light.
So, if you've traveled more than eight time zones to the east, wear sunglasses and avoid bright light in the morning, and then allow as much sunlight as possible in the late afternoon for the first few days in your new location.
If you have traveled west by more than eight time zones, avoid sunlight a few hours before dark for the first few days to adjust to the local time.
- Stay on your new schedule. Set your watch to the new time before you leave. Once you reach your destination, try not to sleep until the local nighttime, no matter how tired you are. Try to time your meals with local mealtimes, too.
- Stay hydrated. Drink plenty of water before, during and after your flight to counteract the dehydrating effects of dry cabin air. Dehydration can make jet lag symptoms worse. Avoid alcohol and caffeine, as these can dehydrate you and affect your sleep.
- Try to sleep on the plane if it's nighttime at your destination. Earplugs, headphones and eye masks can help block out noise and light. If it's daytime where you're going, resist the urge to sleep.
Jet lag is generally temporary and usually doesn't need treatment. Symptoms often improve within a few days, though they sometimes last longer.
However, if you're a frequent traveler continually bothered by jet lag, your doctor may prescribe light therapy or medications.
Lifestyle and home remedies
Use sunlight to reset your internal clock. It's the most powerful natural tool for regulating the sleep-wake cycle.
Morning light exposure can usually help you adjust to an earlier time zone (traveling eastward), while evening light helps you adapt to a later time zone (traveling westward). Plan ahead to determine the best times for light exposure based on your departure and destination points and overall sleep habits:
- Before your trip. You can start light therapy up to three days before travel to help you adjust to your new time zone before you arrive at your destination. If you're traveling east, try waking about one hour earlier than your usual wake time and get at least one hour of light exposure. Do this daily until you leave for your trip, waking one hour earlier each day. You should also adjust your bedtime to one hour earlier each night if possible. For westward travel, delay your wake and bedtimes.
- At your destination. If you've traveled eastward and crossed three to five time zones, try avoiding bright daylight first thing in the morning. Try to get several hours of bright light exposure in mid- to late morning. If you're crossing more time zones or traveling west, avoid bright light the morning of arrival, but seek sunshine in the early afternoon. During the day, dark glasses can help block out light when you need to avoid exposure. At night, draw the window blinds or drapes or use a sleep mask. For each day on your trip, gradually shift your light exposure earlier.
Combining light exposure with exercise such as walking or jogging may help you adapt to the new time even faster.
As a jet lag remedy and sleep aid, melatonin has been widely studied, and it's now a commonly accepted part of effective jet lag treatment. The latest research seems to show that melatonin aids sleep during times when you wouldn't normally be resting, making it beneficial for people with jet lag.
Your body treats melatonin as a darkness signal, so melatonin generally has the opposite effect of bright light.
The time at which you take melatonin is important. If you're trying to reset your body clock to an earlier time, such as after flying east, you should take melatonin at local bedtime nightly until you have become adapted to local time. If you're trying to reset your body clock to a later time, such as after flying west, melatonin should be taken in the morning.
Doses as small as 0.5 milligram seem just as effective as doses of 5 milligrams or higher, although higher doses have been shown by some studies to be more sleep promoting. If you use melatonin, take it 30 minutes before you plan to sleep or ask your doctor about the proper timing.
Avoid alcohol when taking melatonin. Side effects are uncommon but may include dizziness, headaches, daytime sleepiness, loss of appetite, and possibly nausea and disorientation.