Dr's Casebook: Causes of jet lag and how to minimise effects

Dr Keith Souter writes: Travel fatigue is a cluster of symptoms that arise simply from the tiring effect of travelling. Long flights are often uncomfortable, monotonous and subject to a dehydrating effect. Dry cabin air contributes, but alcohol, tea or coffee will all tend to dehydrate you. It is best to take your fluids as water or fruit juices and resist the alcohol temptation. It is also worth knowing that cabin air pressure is not set at the equivalent of ground pressure, but at the altitude of a small mountain. This increases the effect of alcohol.

Studies have been done to distinguish between travel fatigue and jet lag, by comparing long haul flights in which one travels North or South within the same time zone, with flights which cross several time zones. In the former you get travel fatigue only. In the latter you get jet lag. You recover from travel fatigue swiftly, within 24 hours, but jet lag can take several days, depending upon how many time zones are crossed.

Jet lag is due to imbalance between the various body rhythms and the environmental rhythms. The most obvious rhythm is the sleep and activity rhythm, which results in alteration in physical and mental functioning. Effectively, the body clock controls the secretion of a chemical called melatonin from the pineal gland in the brain. Light turns the mechanism off. Unfortunately, once it has been switched off for a while it can take days to regain balance – hence jet lag.

If you are travelling westwards, aim to stay awake while it is daylight, and upon arriving at the destination try to sleep when darkness falls. If you are travelling eastwards, try to stay awake but avoid bright morning light and try to go out in the afternoon. If you do this you will more readily adjust the body clock to turn on the melatonin secretion according to your new time zone.