Definition

Jet lag is part of a syndrome under the concept of fatigue, which occurs in connection with rapid travel through more than 2-3 time zones.

The symptoms are:

• Disturbance of sleep patterns

• Fatigue, difficulties concentrating, and annoyance

• Reduced performance, mentally and physically

• Indigestion

The symptoms are due to a discrepancy between the biological body clock and the actual time pertaining to the locality (astronomical local time). Upon arrival, the individual’s “body clock” will remain set to the departure locality’s time, and this will create confusion relative to the external influences and the rhythm of life at the destination locality.

Many physiological functions vary with the time of day, for example, body temperature, blood pressure, pulse, urine production, hormone production, sleep periods, and level of activity. Mental and physical performance varies correspondingly. This biological body clock adapts only slowly to the new local time.

The severity of jet lag symptoms depends partly on the number of time zones passed and partly on whether one is travelling towards the east or the west. Normally, symptoms are worst when travelling east as one needs to shorten the day, whereas the human circadian rhythm finds it easier to adapt to the prolonging of the day. Moreover, the severity of jet lag varies greatly from person to person. The symptoms often increase with age. 

Melatonin, which is a naturally occurring hormone that has an influence on sleep regulation, has for a couple of years now been recommended as a treatment for adjusting the circadian rhythm faster. However, the latest research does not support this indication. If required, short-acting hypnotic drugs with a short half-life (e.g. temazepam, zolpidem) can be used.

Although no real treatment for jet lag is available, taking certain precautions can ameliorate the worst effects of it. In the following, a distinction is drawn between shorter and longer stays in a different time zone:

Short stopovers in a different time zone:

• It is beneficial to keep to the local time at home as closely as possible in order to preserve the

   individual’s body clock (“anchor time”).

Longer stays in a different time zone:

• Make an attempt to achieve a certain degree of acclimatisation to local time at the destination

   before setting off. When travelling west, get up later and go to bed later. When travelling east,       get up earlier and go to bed earlier.

• A daytime flight is to be preferred. Try to arrange arrival at bedtime in the country of arrival.

• Limit alcohol intake during the journey.

• Immediately after arrival, adopt local time with regard to sleeping and meal times.

• During the first few days, attempt to spend as much time as possible outside in the daylight.

• Try to sleep more than usual the first few days – if necessary with the help of a mild sleeping pill.

• Avoid isolation, as social influences promote re-synchronisation of the body clock.

• Relax for the first few days (24 hours for each five time zones).

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