Jet lag

Jet lag (aka "jetlag" or "jet-lag"), is a physiological condition which is a consequence of alterations to the circadian rhythm. Such alterations result from shift work, transmeridian travel, or altered day length. They are known as desynchronosis, dysrhythmia, dyschrony, jet lag, or jet syndrome. The condition is generally believed to be the result of disruption of the "light/dark" cycle that entrains the body's circadian rhythm. It can be exacerbated by environmental factors.

Characteristic symptoms of jet lag include:
 * Dehydration and loss of appetite
 * Headaches and/or sinus irritation
 * Fatigue
 * Disorientation and/or grogginess
 * Nausea and/or upset stomach
 * Insomnia and/or highly irregular sleep patterns
 * Irritability, Irrationality

The maximum jet lag a person can experience is 12 hours. If the difference in time between two places is greater than 12 hours, subtract that number from 24. For example, there is a 16 hour time difference between Los Angeles (standard time) and Hong Kong. Thus, 24 &#x2212; 16 = 8 hours of jet lag. The person will incur the same amount of jet lag as someone traveling between London and Los Angeles, where the actual time difference is 8 hours. Disregard the difference in date if flying across the International Date Line.

The condition is not linked to the length of flight, but to the transmeridian (ie, East-West) distance traveled. Hence a ten hour flight between Oslo and Johannesburg is less inducive of jet lag than a five hour flight between New York and Los Angeles. There is no firm agreement as to which direction of travel is worse. Some believe that travelling east is worse as it "accelerates" the passage through various time zones (a night might only last 3 hours when flying east), and because the symptoms of travelling west, such as waking earlier in the morning, can be easier to integrate with ordinary life. Others counter that the impact is worse when one travels away from one's "habitual" time zone, and is minimised when returning to it.

Prevention and recovery
Simple prevention can be good sleep aboard and lots to drink (but not coffee or alcohol) to reduce the effects of dehydration on the body, caused by the dry air at altitude and the interruption of regular eating/drinking patterns. Seasoned travelers set their clock to the destination time zone as soon as practical and join the new rhythm. Exposure to sunlight may be a factor to reset the body's clock. For people who don't fly multiple times per week, it can be an effective non-drug remedy to skip sleep entirely for one night and one day and then go to bed at a normal destination-area bedtime on the next day.

Recent research shows that the pineal hormone melatonin may reduce the effects of jet lag. Studies have not identified side effects from such short-term use. Many products on the market claim to treat the effects of jet lag. Since the experience of jet lag varies among different individuals, it is difficult to assess the efficacy of any single remedy. In addition, most chemical and herbal remedies are not tested or approved by the Food and Drug Administration, so their safety has not been scientifically established.

Acupuncture or acupressure is also a common treatment for jet lag. Whereas various parts of the body work optimally at different periods throughout the day, pressure points are used to stimulate the nerves corresponding to each period at the new location's corresponding time. For example, if a certain organ "turns on" when you wake up, an acupuncturist/acupressurist would advocate stimulating that organ at 7 a.m. each morning once you arrive at the new location. Normally there is a whole series of these points, to be tapped with the patient's finger, at different times throughout the day in order to "trick" the body into thinking it's that time of day.

The condition of jet lag generally lasts a few days or more, and medical experts have deemed that a recovery rate of "one day per time zone" is a fair guideline. Sleep, relaxation, moderate exercise and sensible diet seem to be the simplest recovery agents.

Good sleep hygiene promotes rapid recovery from jet lag.

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