Jet lag is a condition in which a person's normal sleep cycle is disturbed by travel across time zones.
Because a person's brain chemistry cycles on approximately a 24-hour clock roughly corresponding to nights and days, a person who travels between different time zones needs time for his or her internal body clock to reset itself and adjust to the new time zone.
The body usually develops a set pattern of times when it is used to eating, sleeping, working, and performing other activities. Jet lag occurs because the brain chemistry is reacting to a change in the schedule of normal activities, particularly sleeping and waking.
The common symptoms of jet lag include: fatigue and drowsinessfeeling worn outdifficulty sleepinga temporary loss of appetitefeeling disorientedfeeling lightheadedfeeling irritabledifficulty concentratingtemporary coordination problems
The primary cause of jet lag is crossing time zones and then trying to get the body to react and adjust right away. Flying north or south does not cause jet lag. The more time zones crossed, the more difficult it is for the body to adjust to the new time zone. The body can generally adjust to a time change of about 1 or 2 hours per day. After travel across three time zones, which often occurs in a trip from the west to the east coast, the body may need up to 3 days to adjust to the new time.
Some measures may help prevent or lessen the severity of jet lag. These include: adjusting the body's internal clock in advance. For instance, people can start adjusting their daily schedules to match the time zones they will travel to before travel takes place. People can set their watches to the new times a day before travel, and begin eating, sleeping, and working as if they were already there.eating light and drinking plenty of fluids. Before the flight, a high-protein, low-calorie meal is advised. The amount of salty and fatty foods eaten should be limited. Dry air during the flight can cause dehydration, so people are advised to drink plenty of non-alcoholic fluids. Water is best, and many experienced travelers bring their own bottles of water with them.exercising frequently. Even getting up periodically and walking up and down the aisles of the plane can help, which may be the only exercise possible. Sitting in a cramped airplane seat for an extended time is uncomfortable for everyone. During a stopover, people may want to take a few minutes and leave the plane to go for a brisk walk around the terminal, if possible.getting enough sleep. People may want to try sleeping on the plane or plan to arrive at their destinations in time to catch a nap before starting activities. Mild sedatives or melatonin may help some people get sleep during travel.Upon arrival, the most important cue to adjusting the body clock and turn on the body's own melatonin secretion at the right time is lightafter a westward flight, to stay awake while it is daylight at the destination and to try to sleep when it gets dark; after an eastward flight, to be awake but avoid bright light in the morning, and to be outdoors as much as possible in the afternoon. Another option is to use either melatonin or a short acting sleep medication such as zolpidem (i.e., Ambien, Ambien CR), temazepam (i.e., Restoril), or triazolam (i.e., Halcion). Melatonin taken at bedtime works both by shifting the body clock and by causing a hypnotic effect. A hypnotic medication treats one symptom by providing sleep, but it does not shift the circadian body clock.
Multiple randomized controlled trials comparing melatonin with placebo in long distance travelers (crossing five or more time zones) have found a clear reduction in jet lag when melatonin had been taken. One review concluded that 2-5 mg melatonin taken at bedtime after arrival is effective and may be worth repeating for the next two to four days, together with the non-drug measures already mentioned. But people who have not had jet lag on a previous trip may well never need it.
In one study, when compared to melatonin, zolpidem (i.e., Ambien, Ambien CR) had the best effect on jet lag symptoms but had a higher rate of side effects than melatonin. Melatonin alone used for several days after arrival was the second choice followed by a combination of melatonin and zolpidem.
Most people will recognize when they have jet lag. The fatigue, drowsiness, irritability, and other symptoms will be clear to someone who has just traveled between different time zones.
There are no long term effects.
The only risk to others is when a person who is suffering from jet lag becomes unpleasant and uncomfortable to be around. Jet lag is not contagious.
There are no medical treatments for jet lag. Time will make jet lag disappear. When multiple time zones are crossed, such as in overseas travel, some people may want to use a mild sedative, sleeping pill, or melatonin to help "reset" their internal body clocks and get enough sleep.
Sedatives, such as diazepam (i.e., Valium), and sleeping pills, such as diphenhydramine (i.e., Benadryl), may cause prolonged sleepiness and may impair coordination. Melatonin may not work in some people and has caused sexual dysfunction in animals.
People gradually adjust to the new time zones and need no further treatment.
People can monitor their own symptoms of jet lag.
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Mayo Clinic Family Health Book, Second Edition, 1996, Published by William Morrow and Company, 1350 Ave. of the Americas, New York, NY 10019