Before the advent of fast air travel, journeys were slow enough for us to adjust gradually to different time zones. The main symptoms of jet lag are due to our sleep schedule being disrupted.
What causes jet lag?
Many of the systems in our bodies are controlled by our internal clock. The normal cycle of sleeping at night and being awake in the daytime is called a circadian rhythm. All living beings, even plants, function with this rhythm controlling an internal clock. The rhythm is created by the cycle of daylight and darkness. When travelling, it takes some time for your internal clock to adjust to the new time zone and to the different hours of daylight. This adjustment time causes the syndrome known as jet lag.
Normally, feeling sleepy at bedtime is partly due to a hormone called melatonin. Melatonin is made by a part of our brain called the pineal gland. Most melatonin is produced when it is dark. Light blocks production of melatonin. When travelling, it takes a few days for the correct cycle of melatonin increases and decreases to be re-established.
If you are travelling over three time zones or fewer, jet lag is not usually a problem. It usually affects people travelling across more than three time zones. So if the time at your destination is three or more hours different to that at the start of your journey, you are likely to experience jet lag. The more the time difference, the greater the problem jet lag is likely to be.
If you are travelling west to east, you are more likely to have problems with jet lag. In this direction, you have to advance your time clock, which is more difficult than delaying it. In this direction, you have to try to go to sleep when you are not tired.
If you are travelling more slowly, by boat or car, your body clock will be able to adjust gradually. Jet lag only affects people travelling quickly across several time zones.
People who travel frequently, particularly airline pilots and crew, are most likely to have problems with jet lag. Others may need to fly frequently as part of their job. It can be a problem for athletes competing in different parts of the world. Performance in sport or other jobs may be less good due to jet lag symptoms.
Symptoms of jet lag
The most common symptoms of jet lag are related to sleep. You may have difficulty getting to sleep at bedtime and struggle to wake up in the morning. Or you may be tired long before bedtime and wake up while it is still night and too early to get up. This will depend on whether your destination time is ahead or behind the time at the start of your journey. This in turn depends if you are travelling west to east, or east to west.
The effect of this difficulty with sleeping is feeling tired and not being able to function as well as usual. Both physically and mentally, you may not be able to function as normal. Specifically this might result in:
- Feeling tired or exhausted.
- Having difficulty staying awake.
- Disturbed nights and not being able to sleep well.
- Feeling giddy or light-headed.
- Not being able to concentrate well or remember things as well as usual.
- Being less co-ordinated than usual.
- Feeling jittery and anxious.
- Being more irritable than usual.
- Feeling low in mood.
- Not wanting to join in normal activities.
- Poorer performance in sports than usual (particularly a problem for athletes).
Appetite is also affected by jet lag, as you may not be hungry at the normal mealtimes at your destination. This in turn may affect your bowel habits and function. You may become constipated, or have looser stools than normal, feel sick or have indigestion. Other aspects of travel, such as cabin pressure, can also have an effect on your bowel. Changes in cabin pressure can cause bloating, for example, which may contribute to your symptoms.
How to recover from jet lag
Jet lag gradually subsides on its own after a few days, as your body clock adapts to the new time zone. There are a number of strategies which may help you get over it more quickly. Some of these strategies are:
- After arrival at your destination, try to change your schedule to the new time zone as quickly as possible. Avoid going to sleep until it is a reasonable bedtime for the new time zone. Set alarms to stop you oversleeping in the morning.
- Caffeine-containing drinks such as coffee or cola may help keep you awake until it is a reasonable time to go to sleep. However, avoid these in the six hours before you plan to go to sleep, or they may interfere with sleep.
- Prior to going to bed, try to relax. Avoid large meals, heavy exercise and exciting books or films before sleeping. Avoid caffeine and alcohol before bedtime, as these may interfere with sleep. Try to keep the room in which you are sleeping dark and quiet.
- On the plane, only try to sleep if it is a normal sleep time for your destination. Eye shades or ear plugs may help if you are trying to get to sleep.
- Limit alcohol on the plane.
- Consider gradually adapting your sleep schedule slightly towards the destination times in the few days before departure. For example, start going to bed and getting up an hour or two earlier or later than usual, so the difference is not so big when you arrive.
- In the daytime at your destination, expose yourself to outside natural light as much as possible. This will help your internal clock adjust.
- If you are only in the new time zone for two to three days it may be easier to stay on your original timings. Eat and go to sleep at times that would be normal for you, even if they aren't the right times for the place you are now in. This may not be practical for everybody, as it depends on what you want or need to do while you are away.
Other strategies to try to change exposure to light are sometimes used. There is not yet much evidence to assess how well these work. Outdoor natural light is the best but some people use light boxes inside to try to increase the amount of light. The idea is that this cuts down the amount of natural melatonin released by the brain. This will then delay the time when you start to feel sleepy. However, more studies need to be done to find out what would be the best time to use light therapy and how long for. This would vary depending on which direction you have travelled and the time difference between the start and finish.
Another technique used by some people is blocking out certain types of light. Shortwave or 'blue' light is thought to be most important in stopping melatonin being released. Therefore, glasses which block blue light, worn at certain times, can help you release melatonin earlier than usual. This would be helpful if you are trying to bring forward the time you go to sleep - for example, after travelling west to east.
Are there any medicines to help with jet lag?
Most people do not need medicines to help with jet lag and there are no treatments specifically licensed for this. Occasionally it may be necessary to take sleeping tablets to help you get back into a sleeping pattern. Sleeping tablets are addictive, so they are only for occasional use and for people who are severely affected by jet lag.
Another tablet sometimes used is melatonin. This is a tablet form of the natural melatonin hormone which your brain produces. There have been studies which show melatonin helps the symptoms of jet lag, particularly for people travelling east. However, in the UK melatonin is not licensed for jet lag. This is because there is not yet enough evidence about any side-effects, particularly if it has to be taken regularly. It is also not yet known what dose should be used or the time at which it should be taken.
Further reading and references
Foreign Travel Advice by Country; GOV.UK
The World Factbook; Central Intelligence Agency
NHS Fit For Travel: Travel health information for people travelling abroad from the UK; Health Protection Scotland
information on carrying medication overseas; International Narcotics Control Board
Sleep disorders - shift work and jet lag; NICE CKS, Aug 2013 (UK access only)
Lackner JR; Motion sickness: more than nausea and vomiting. Exp Brain Res. 2014 Aug232(8):2493-510. doi: 10.1007/s00221-014-4008-8. Epub 2014 Jun 25.
Wright T; Middle-ear pain and trauma during air travel. BMJ Clin Evid. 2015 Jan 192015. pii: 0501.
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