Symptoms of jet lag can vary. You may experience only one symptom or multiple symptoms. 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
- Muscle soreness
- Menstrual symptoms in women
Symptoms worse the farther you travel
Jet lag symptoms usually occur within a day or two of travel if you've traveled across at least two time zones. Symptoms are likely to be worse or last longer the more time zones that you've crossed, especially if you travel in an easterly direction. It's estimated to take about a day to recover for each time zone crossed.
When to see a doctor
Jet lag is temporary. But if you are a frequent traveler and continually struggle with jet lag, you may benefit from seeing a sleep specialist.
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 or circadian rhythms, which regulate your sleep-wake cycle, out of sync with the time in your new locale.
For example, you lose six hours on a usual New York to Paris flight. That means that if you leave New York at 4:00 p.m. on Tuesday, you arrive in Paris at 7:00 a.m. Wednesday. According to your internal clock, it's 1:00 a.m., and 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.
The influence of sunlight
A key influence on your internal clock is sunlight. That's because light influences the regulation of melatonin, which in turn is a synchronizing signal to cells throughout the body.
Certain cells in the tissue at the back of your eye (retina) transmit the signal of light to an area of your brain called the hypothalamus. At night, when this signal is low, the hypothalamus tells the pineal gland, a small organ situated in the brain, to release the hormone melatonin. During the day, the light signals to the hypothalamus result in the opposite, such that the pineal gland produces very little melatonin.
You may be able to ease your adjustment to your new time zone by exposing yourself to daylight in the new time zone so long as the timing of light is done properly.
Airline cabin pressure and atmosphere
Some research shows that changes in cabin pressure and high altitudes associated with air travel may contribute to some symptoms of jet lag, regardless of travel across time zones.
Not drinking enough water during your flight can dehydrate you. In addition, drinking too many beverages with caffeine or alcohol during your flight can affect your sleep and cause some symptoms of jet lag.
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 it back.
- 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.
Extreme variations in circadian rhythms have been reported in some instances of heart attacks and strokes, but this is rare.
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.
If you have traveled 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, 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.
- 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 planeif 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.