Fatigue and interruption of the sleep–wake cycle caused by disturbance of normal body biorhythms as a result of flying across different time zones. Jet-lag provokes daytime sleepiness and insomnia at night. Other symptoms include reduced physical and mental activity, and poor memory. Jet-lag tends to be worse after an eastward flight (which shortens the traveller’s day) than after a westward one. Treatment with the pituitary hormone melatonin is claimed by some to reduce the severity of jet-lag.


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