Jet Lag

What is jet lag?

Jet lag refers to the group of physical and physiological symptoms associated with rapid crossing of multiple time zones (meridians). These symptoms are due mainly to the disturbance of the body' s natural rhythm and sleep-wake cycle. The time for re-establishment of body' s natural rhythm equilibrium is generally greater with eastward than westward flights.

How do you recognize jet lag?

Symptoms of jet lag include difficulty in sleeping, tiredness, mood disturbance, tummy upset (e.g. loss of appetite). Jet lag can adversely affect performance, such as manual and cognitive skills.

Prevention of jet lag

  • Travellers should rest fully and not be sleep-deprived at the start of a trans-meridian journey.

  • If the trip lasts less than 3 days, attempt to keep to the Hong Kong time schedule of sleep and activity instead of that of the destination.

  • If the trip lasts more than 3 days, one should immediately adopt the sleep/meal times of the destination and synchronise with destination's time as quickly as possible. If necessary, take a short nap during the day for the first few days to help your adaptation.

  • Outdoor light exposure at destination can reduce symptoms of jet lag.

  • Avoid too much alcohol and coffee during flight.

  • Take plenty of fluid. Limited alcohol intake can also help.

  • Refrain from taking sleeping pills unless necessary. Discuss the use with your doctor.

  • Melatonin is a hormone that has been widely publicized to alleviate jet lag. However, there are uncertainties about its safety, and inappropriate timing of dosages may worsen jet lag. You should consult your doctor for further information.

  • Avoid making important decisions or driving immediately on arrival after crossing many time zones.


Last revision date: 10 October 2012