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Jet lagThis factsheet is for people who travel on long-distance flights and wish to learn about jet lag. It is now possible to fly to far-reaching parts of the globe in a matter of hours. If you travel on a long-haul flight, your body's circadian rhythms (also known as your body clock), which control the timing of routine functions such as eating and sleeping, can be disrupted. Your body clock can take a number of days to adjust to the new rhythm of daylight and darkness and this is called jet lag. Time zonesThe world is divided into 24 time zones. The Greenwich meridian in London, UK, is the base. The time changes by one hour for every 15 degrees travelled in either direction from the Greenwich meridian. If you travel over three time zones you are at risk of jet lag. This means that if you fly from the UK to Europe, Africa and the Middle East you will not be affected by jet lag. However, if you are travelling from the UK or Europe to the following countries you may be affected:
SymptomsThe symptoms of jet lag are different for different people. It depends on how far you have flown and how many time zones you have crossed. Most people with jet lag feel tired but can't drop off to sleep at the 'right' times. You might find that you are awake and alert late at night and very tired in the day time. Other symptoms of jet lag include:
What causes jet lag?Jet lag is caused by a disruption to your body clock. Your body clock gets used to a regular rhythm of daylight and darkness, so when you travel to a new time zone it disrupts this normal rhythm. With modern long range aircraft, the need for 'stop overs' has been reduced. You can therefore cross a number of time zones in a matter of hours and your body finds it difficult to catch up. Your body needs time to adjust to new times of light, darkness and meals. It may also need to adjust to differences in temperature. People who have a strict routine tend to suffer most from jet lag. However, children and babies, who can sleep almost any time, rarely show symptoms of jet lag. There are a number of things that can make jet lag worse including:
The level of oxygen in the aeroplane cabin can also be a factor. Cabin air contains ample oxygen for healthy passengers but because cabin air pressure is relatively low, the amount of oxygen carried in the blood is reduced compared to sea level. Passengers with certain medical conditions, such as heart and lung disease and anaemia, may not tolerate this very well. If you have such a medical condition you should speak to your airline. How long will jet lag last for?Jet lag tends to be more of a problem if you're flying east because your body finds it harder to adjust to a slightly shorter day than a slightly longer one. You can calculate roughly how many days you are likely to be affected by jet lag using the formula below.
For example, an eastbound flight from Cape Town to Perth crosses six time zones: 6 divided by 1.5 = approximately four days of jet lag. Managing jet lagThere are a number of measures you can take to try and prevent jet lag. Before you travel you can try:
Whilst in the air you can try:
When you arrive:
MelatoninMelatonin is a hormone that is produced from a small gland under the brain. It is released in the evening and tells the brain it is time to sleep - this is part of your body clock. There have been a number of studies to see if taking melatonin supplements can prevent jet lag, but results have been mixed. Melatonin is not licensed to prevent jet lag in the UK and little is known of its long-term effects.If you want to take melatonin for jet lag, you should get advice from your doctor. Short stay tripsIf you only plan to stay in a distant country for a short amount of time (one or two days) then there is a limited amount you can do about jet lag. It is unlikely that you will be able to adjust in that time. If travelling on business, it may be helpful to arrange important meetings to coincide with daytime in your home country. Taking medicationIf you have to take medication at certain times of the day (such as insulin if you are diabetic or the contraceptive pill) you should seek medical advice before you travel. Further information
References
Reviewed by Dr James Quekett, Bsc.MB Ch.B MRCGP DRCOG DFFP. partner/principal general practitioner at Rowcroft Medical Centre and Dr Paul Stoddart, MBChB DipObs DOccMed, senior regional physician, London BUPA Wellness. Published by BUPA's health information team, healthinfo@bupa.com, February 2006.
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Help recover from jet lag with a bodyclock or SAD lamp
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