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Jet lag

Published by Bupa's health information team, July 2008.

This factsheet is for people who have jet lag, or who would like information about it.

Jet lag is a temporary condition that causes a number of symptoms including disturbed sleep patterns, digestion problems and a lack of energy (fatigue) following air travel across a number of time zones.

• About jet lag
• Symptoms of jet lag
• Causes of jet lag
• Diagnosis of jet lag
• Prevention and treatment of jet lag
• Special considerations
• Further information
• Questions and answers
• Sources

About jet lag

It's now possible to fly to countries around the world in a matter of hours. If you fly across several different time zones, your body's normal circadian rhythms (also known as your body clock) can be disrupted. Your circadian rhythms control the timing of routine functions, such as eating and sleeping. When you arrive at your destination after a long flight, 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.

Symptoms of jet lag

The symptoms of jet lag are different for everyone. It also depends on how far you have flown, how many time zones you have crossed and in which direction you have travelled.

Most people with jet lag feel tired but can't drop off to sleep at the right times. You might find that you're awake and alert late at night and feel very tired during the day time.

Other symptoms of jet lag include:

• indigestion
• disturbed digestion and bowel habits
• loss of appetite
• difficulty concentrating
• memory problems
• clumsiness
• feeling generally unwell
• lack of energy (fatigue)
• increased frequency of headaches
• irritability

Causes of 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 and travelling to a different time zone disrupts this.

The world is divided into 24 time zones based around Greenwich meridian in London, UK. The time changes by one hour for every 15 degrees travelled in either direction from here.

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 or the Middle East you probably won't be affected by jet lag. However, you may have symptoms if you're travelling from the UK to the following regions:

• Asia
• Australasia
• the Pacific islands
• the US and Canada
• Central and South America

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.

If you're an older traveller or you have a strict routine, you may suffer more from jet lag. Children and babies are less likely to show symptoms of jet lag because they can usually sleep at any time.

There are a number of things that can make jet lag worse, including:

• dehydration
• tiredness
• lack of sleep
• alcohol
• stress

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 compared to what your body is used to, the amount of oxygen carried in the blood is reduced. Passengers with certain medical conditions, such as heart and lung disease and anaemia, may find this uncomfortable. If you have such a medical condition, you should speak to your GP and the airline before travelling.

Diagnosis of jet lag

The diagnosis of jet lag will be based on your symptoms and how many time zones you have crossed.

You can calculate roughly how many days you're likely to be affected by jet lag using the formula below.

• Approximately half the number of time zones crossed after a flight to the west.
• Approximately two-thirds the number of time zones crossed after a flight to the east.

For example, an eastbound flight from Cape Town to Perth crosses six time zones: two-thirds of six is approximately four days of jet lag.

Prevention and treatment of jet lag

There are a number of measures you can take to try and prevent jet lag.

Self-help

Before you travel you can try:

• getting up and going to bed earlier if you're flying east
• getting up and going to bed later if you're flying west

While in the air:

• adjust your watch to the destination time as soon as you get on the plane
• make sure you drink enough fluids (not alcohol or caffeinated drinks)
• move about as often as you can

When you arrive:

• try to get into a routine immediately - caffeine is a stimulant that is frequently used to maintain daytime alertness
• spend the daytime outdoors, as natural light can help your body clock adjust
• take some exercise every day

If you only plan to stay in a distant country for a short length of time (one or two days) then there is a limited amount you can do about jet lag. It's unlikely that your body will be able to adjust in that time.

If you're travelling on business, it may be helpful to arrange important meetings to coincide with daytime in your home country.

Medicines

Melatonin is a hormone that is produced by a small gland under your brain. It's released in the evening and tells your brain it's 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 isn't licensed as a medicine in the UK and little is known of its long-term effects, therefore it's not recommended for use. Be careful if you're considering buying medicines on the internet, particularly prescription-only medicines. If you buy medicines over the internet, there is a risk that they are from unregulated or illegal websites. If they are, there will be no guarantee of safety, quality or effectiveness of the medicines provided. It's illegal to sell medicines on the internet in the UK. To protect patient safety, the law states they must be prescribed by a doctor, and dispensed by a pharmacist.

Other treatments

When done at the appropriate time, exposure to bright sunlight or light from a special bulb may reduce your symptoms of jet lag. The best time to do this depends upon the direction you're travelling and the number of time zones you have crossed. For more information seek advice from your GP or a travel clinic.

Special considerations

Taking medicines when travelling

If you have to take medication at set times of the day (such as insulin if you are diabetic or the contraceptive pill) you should seek medical advice from your GP before you travel. He or she will advise you when to take your medicines if you are crossing different time zones.

Further information

• National Travel Health Network and Centre
  www.nathnac.org

Sources

• International travel and health. World Health Organization, 2007. www.who.int
• The impact of flying on travellers health: a guide for healthcare professionals. British Medical Association, 2004. www.bma.org.uk
• Waterhouse J, Reilly T, Atkinson G, et al. Jet lag: trends and coping strategies. Lancet 2007;369:1117-1129. www.lancet.com
• Melatonin for jet lag? Bandolier. www.jr2.ox.ac.uk/bandolier, accessed 6 February 2008

This information was published by Bupa's health information team and is based on reputable sources of medical evidence. It has been peer reviewed by Dr W H Simpson, MBBS, General Practitioner, and by Bupa doctors. The content is intended for general information only and does not replace the need for personal advice from a qualified health professional.

Publication date: July 2008.