Jet lag

Jet lag (or "jetlag"), also jet syndrome, is a physical condition caused by crossing time zones during flight. The condition is generally believed to be the result of disruption to the circadian rhythms (i.e. the "light/dark" cycle) of the body. It can also be exacerbated by experiencing sudden changes in climate or seasonal conditions, as well as the reduced oxygen, partial pressure, excess noise and low humidity commonly experienced in the cabin of an aircraft.

Related Topics:
Time zone - Flight - Circadian rhythms - Climate - Oxygen - Partial pressure - Humidity

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Characteristic symptoms of jet lag include:

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• Fatigue
• Disorientation and/or grogginess
• Nausea and/or upset stomach
• Headaches and/or sinus irritation
• Insomnia and/or highly irregular sleeping patterns
• Dehydration and loss of appetite
• 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 − 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 time difference really is eight.

Related Topics:
Los Angeles - Hong Kong - London

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The condition is not linked to the length of flight, but to the east-west distance traveled. Hence a ten hour flight between Oslo and Johannesburg will probably be less inducive of jet lag than a four 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). Others counter that the impact is worse when one travels away from one's "habitual" time zone, and is minimised when returning to it.

Related Topics:
Oslo - Johannesburg - New York

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