Jet lag, also called desynchronosis, is a temporary disorder that causes fatigue, insomnia, and other symptoms as a result of air travel across time zones.
A tiny part of the brain called the hypothalamus acts like an alarm clock to activate various body functions such as hunger, thirst, and sleep. It also regulates body temperature, blood pressure, and the level of hormones and glucose in the bloodstream. To help the body tell the time of day, fibers in the optic nerve of the eye transmit perceptions of light and darkness to a timekeeping center within the hypothalamus.
Thus, when the eye of an air traveler perceives dawn or dusk many hours earlier or later than usual, the hypothalamus may trigger activities that the rest of the body is not ready for, and jet lag occurs.
Symptoms include fatigue and general tiredness, inability to sleep at night, loss of concentration, loss of drive, headaches and general malaise. Jet-lag occurs when biological rhythms are disrupted as a result of rapid transitions across multiple time-zones. Such desynchronization of rhythms also occurs in nocturnal shift work employees who transfer to night shifts.
A classical rhythm is represented by a sine wave, fluctuations occurring cyclically about a mean value rising to a peak and half a cycle later dropping to a trough. Twenty-four hour rhythms are known as circadian (about a day). An example of a biological rhythm is core temperature. We can find the characteristics of rhythms using the mathematical technique of cosinor analysis to determine the mean, the peak, the amplitude, and the time the peak occurs (the acrophase).
The symptoms of jet lag can be quite varied, depending on the amount of time zone alteration, time of day and individual differences.
They may include the following:
- Fatigue, irregular sleep patterns, insomnia.
- Disorientation, grogginess, irritability.
- Mild depression.
- Constipation or diarrhea.
Jet lag is a chronobiological-related problem, similar to issues often induced by shift work. When traveling across a number of time zones, the body clock will be out of synchronization with the destination time, as it experiences daylight and darkness contrary to the rhythms to which it has grown accustomed: the body's natural pattern is upset, as the rhythms that dictate times for eating, sleeping, hormone regulation and body temperature variations no longer correspond to the environment nor to each other in some cases. To the degree that the body cannot immediately realign these rhythms, it is jet lagged.
The speed at which the body adjusts to the new schedule depends on the individual; some people may require several days to adjust to a new time zone, while others experience little disruption. Crossing one or two time zones does not typically cause jet lag.
The condition is not linked to the length of flight, but to the transmeridian (west–east) distance traveled. A ten-hour flight from Europe to southern Africa does not cause jet lag, as travel is primarily north–south. A five-hour flight from the east to the west coast of the United States may well result in jet lag.
Crossing the International Date Line does not contribute to jet lag, as the guide for calculating jet lag is the number of time zones crossed, and the maximum possible disruption is plus or minus 12 hours. If the time difference between two locations is greater than 12 hours, subtract that number from 24. Note, for example, that the time zone GMT+14 will be at the same time of day as GMT−10, though the former is one day ahead of the latter.
The following are 12 tips to help travelers minimize the effects of jet lag.
Tip 1: Stay in shape
If you are in good physical condition, stay that way. In other words, long before you embark, continue to exercise, eat right, and get plenty of rest. Your physical stamina and conditioning will enable you to cope better after you land. If you are not physically fit, or have a poor diet, begin shaping up and eating right several weeks before your trip.
Tip 2: Get medical advice
If you have a medical condition that requires monitoring (such as diabetes or heart disease), consult your physician well in advance of your departure to plan a coping strategy that includes medication schedules and doctor's appointments, if necessary, in the destination time zone.
Tip 3: Change your schedule
If your stay in the destination time zone will last more than a few days, begin adjusting your body to the new time zone before you leave. For example, if you are traveling from the U.S. to Europe for a one-month vacation, set your daily routine back an hour or more three to four weeks before departure. Then, set it back another hour the following week and the week after that. Easing into the new schedule gradually in familiar surroundings will save your body the shock of adjusting all at once.
Tip 4: Avoid alcohol
Do not drink alcoholic beverages the day before your flight, during your flight, or the day after your flight. These beverages can cause dehydration, disrupt sleeping schedules, and trigger nausea and general discomfort.
Tip 5: Avoid caffeine
Likewise, do not drink caffeinated beverages before, during, or just after the flight. Caffeine can also cause dehydration and disrupt sleeping schedules. What's more, caffeine can jangle your nerves and intensify any travel anxiety you may already be feeling.
Tip 6: Drink water
Drink plenty of water, especially during the flight, to counteract the effects of the dry atmosphere inside the plane. Consider taking your own water aboard the airplane if allowed.
Tip 7: Move around on the plane
While seated during your flight, exercise your legs from time to time. Move them up and down and back and forth. Bend your knees. Stand up and sit down. Every hour or two, get up and walk around. Do not take sleeping pills, and do not nap for more than an hour at a time.
These measures have a twofold purpose. First, they reduce your risk of developing a blood clot in the legs. Research shows that long periods of sitting can slow blood movement in and to the legs, thereby increasing the risk of a clot. The seat is partly to blame. It presses against the veins in the leg, restricting blood flow. Inactivity also plays a role. It decelerates the movement of blood through veins.
If a clot forms, it sometimes breaks loose and travels to the lungs, lodges in an artery, and inhibits blood flow. The victim may experience pain and breathing problems and cough up blood. If the clot is large, the victim could die. Second, remaining active, even in a small way, revitalizes and refreshes your body, wards off stiffness, and promotes mental and physical acuity which can ease the symptoms of jet lag.
Tip 8: Break up your trip
On long flights traveling across eight, 10, or even 12 time zones, break up your trip, if feasible, with a stay in a city about halfway to your destination. For example, if you are traveling from New York to Bombay, India, schedule a stopover of a few days in Dublin or Paris. (At noon in New York, it is 5 p.m. in Dublin, 6 p.m. in Paris, and 10:30 p.m. in Bombay.)
Tip 9: Wear comfortable shoes and clothes
On a long trip, how you feel is more important than how you look. So, wear comfortable clothes and shoes. Avoid items that pinch, restrict, or chafe. When selecting your trip outfit, keep in mind the climate in your destination time zone. Dress for your destination.
Tip 10: Check your accommodations
Upon arrival, if you are staying at a hotel, check to see that beds and bathroom facilities are satisfactory and that cooling and heating systems are in good working order. If the room is unsuitable, ask for another.
Tip 11: Adapt to the local schedule
The sooner you adapt to the local schedule, the quicker your body will adjust. Therefore, if you arrive at noon local time (but 6 a.m. your time), eat lunch, not breakfast. During the day, expose your body to sunlight by taking walks or sitting in outdoor cafes. The sunlight will cue your hypothalamus to reduce the production of sleep-inducing melatonin during the day, thereby initiating the process of resetting your internal clock.
Tip 12: Use sleeping medications wisely—or not at all
Try to establish sleeping patterns without resorting to pills. However, if you have difficulty sleeping on the first two or three nights, it's okay to take a mild sedative if your physician has prescribed one. But wean yourself off the sedative as soon as possible. Otherwise, it could become habit-forming.