Definition: Circadian dysrhythmia, or jet lag, is due to biologic and psychological stress after rapid air travel across multiple time zones. The condition is generally believed to be the result of disruption to the circadian rhythms 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, excessive noise and low humidity commonly experienced in the cabin of an aircraft.

Aetiology/Risk Factors that can contribute to the incidence of jet lag include the following:
Crossing time zones
Poor pre-flight condition: over-tired, excited, stressed, nervous or hung-over
Consumption of coffee, tea, alcohol and fruit juices in flight
Lack of exercise
Lack of exposure to sunlight

Common signs and symptoms of jet lag include:
Fatigue for days after the flight
Disorientation, difficulty concentrating, irritability
Broken sleep
Dehydration
Peripheral oedema