We all have an internal body clock (sometimes referred to as our circadian rhythm), which controls when we feel sleepy and when we feel active. This clock is governed by daylight – so we get used to a regular rhythm of daylight and darkness. If you travel to a different time zone, your body clock will be out of sync with local time. This can leave you feeling sleepy during the day and wide-awake at night.
The world is divided into 24 time zones, with each one an hour different from the next. All the time zones are measured from the Greenwich Meridian reference point in London, UK. The time changes by one hour for every 15 degrees travelled in either direction from the Meridian.
You can get symptoms of jet lag if you cross three or more time zones. So if you fly from the UK to Europe, Africa or the Middle East, you probably won’t be much affected. But if you travel from the UK to Asia, Australasia, America or Canada, chances are that you will.Key fact: Jet lag tends to be more of a problem if you’re flying east. This is because your body will find it harder to adjust to a shorter day than a longer one.
Jet lag can zap your energy during the day and leave you feeling tired. It can disturb your sleep too – you might have trouble getting off to sleep, or wake up during the night or early in the morning. You might also find it difficult to concentrate, and be a bit clumsy or irritable because you’re so tired.
Jet lag can cause other problems too because other parts of your body, such as your digestive system, also have internal clocks. You might get indigestion, find it difficult to go to the toilet and have no appetite. Jet lag can make you feel generally out of sorts.
How long your symptoms will last and how severe they are depends on the number of time zones you cross during your flight. You might start to feel better in just a couple of days. But if you’ve travelled a long distance, it can take as long as a couple of weeks to feel better.
Here are some examples of how your flight time and direction can affect jet lag.
There are a few things that can make jet lag worse, which include the following.
- Tiredness. Get plenty of rest before your flight and during your flight too. See ‘Help your body clock adjust’ below for more information.
- Dehydration. Drink plenty of water before and on the flight to keep hydrated.
- Alcohol. Although it may help you to nod off, alcohol impairs the quality of sleep. If you drink to the point that you get a hangover, it can make jet lag feel a whole lot worse. If you do drink before or during your flight, make sure it’s no more than a couple.
- Caffeine. This can disrupt sleep like alcohol. Don’t drink any more caffeine than you normally would and hold off within six hours of going to bed.
Dr Paula Franklin, Medical Director, Bupa UK, says:
"My secret weapon when I’m travelling and know that jet lag is lurking on the horizon is to drink lots of water. I do this as soon as I get to the airport and keep drinking throughout my journey and beyond. Dehydration can increase the effects of jet lag so I know it’s important to do what I can to minimise it. I’d recommend you always have a bottle of water with you when you board the plane and keep topping up throughout the flight. Continue to drink plenty of water for the duration of your trip. This really works for me."
Top tip: Make sure you take everything you’ll need to help you sleep on the plane in your carry-on bag. This might include noise-cancelling headphones or foam earplugs, a sleep mask and a neck pillow – whatever you need to get some z’s.
Shift your internal body clock
If your business trip is for more than two or three days, it’s worth trying to help your body adjust to the new time zone. You can start this process of shifting your internal clock before you leave.
- If you’re flying east, try getting up and going to bed an hour or two earlier.
- If you’re flying west, get up and go to bed an hour or two later.
It’s a good idea to shift your mealtimes to this schedule too.
As soon as you board your flight, adjust your watch to the destination time. Make the most of the opportunity to get some rest during your flight. Try to get as much sleep as possible – even short naps can help.
When you arrive, try to get into the local routine immediately and if work allows, get some time outdoors. Natural light can help your body clock adjust. Exposure to bright light in the morning will bring you closer to sleeping earlier, while exposure to light in the evening will delay sleep.
- If you travelled east, try to get more morning light after you arrive and keep out of the sun in the afternoon. Wear sunglasses or pull the blinds down at work to help keep light out.
- If you went west, try and get some afternoon light and keep out of the light in the morning. Light boxes
If you can’t get out in natural light, artificial light, from a light box or goggles for example, may help to combat jet lag.
Another area of emerging science is blue light therapy. As well as changes in light intensity that happen as the Sun rises and sets, the colour of light is thought to change too. Light may be bluer around dawn and dusk and yellower when the sun is higher in the sky. And early research suggests this may have an impact on how our body clock measures the time of day.
- To delay your body clock, seek out blue light at dusk to keep you awake for longer.
- To turn your clock forward, get up earlier and go out at dawn, or use a blue light box. Combine that with avoiding blue light exposure at dusk.
More work needs to be done to fully understand this but in the interim you might like to give it a try.
There is a range of smartphone apps that can help you tackle jet lag. They can help with everything from planning your sleeping schedule before your trip to when to seek out light to help your body adjust. Check what’s out there – many are free.
If you hit the gym before heading to the office, it might help you feel better because exercise can help you to get over jet lag. But make sure you do it during the day and not within four hours of going to bed because it can keep you awake.
If you regularly travel for work, it’s another reason to get fit. If you’re not in great shape, you will probably take longer to recover from jet lag.
Time your meetings well
You might find it helps to arrange important meetings to coincide with daytime in your home country so you feel more on the ball. Or at least wait until you’re a day in to have critical meetings.
Keep a diary
We all react in different ways to crossing time zones. If you often travel for work, it’s a good idea to keep a diary of your symptoms of jet lag. This can help you learn how your body responds and also if any measures you take help. You will then be better prepared and can adapt accordingly to cope with jet lag. And better still, rather than not being at your best, you will be more productive to get the most out of your trip.
Short business trips
If you’re only staying a couple of days, your body is unlikely to have time to adjust to local time. It’s probably best to just to stick to your usual (home) timings. Although this sounds tough, there’s a silver lining – if you wake up ridiculously early it’s a great time to get some extra work done undisturbed.
There aren’t any specific medicines for jet lag. However, there’s evidence to suggest that the hormone melatonin can help improve your sleep, mood and memory. Melatonin hasn’t been licensed for jet lag yet but a specialist travel doctor may prescribe it to you off-licence. Book an appointment at a travel clinic if you want to give this a try.
If you’re tired when you need to be alert, for example you’re stacked with meetings from the get-go, caffeine can help as a temporary pick-up. But don’t drink lots of coffee after midday because it will compound any problems you’re having sleeping.
If you’ve had trouble sleeping because of jet lag before, talk to a specialist doctor at a travel clinic before you go on your trip. They might suggest you take sleeping tablets for a few days after you arrive until your body clock adjusts. But don’t take them for any longer than this.
Also, it’s important not to take sleeping tablets on your flight. This is because if you sit still for too long, it can increase your risk of deep vein thrombosis (DVT).
- National Travel Health Network and Centre
- TP 14573: Fatigue risk management system for the Canadian aviation industry – fatigue management strategies for employees. Chapter 16 – jet lag. Transport Canada. www.tc.gc.ca, published 20 May 2011
- Greenwich mean time (GMT). Royal Museums Greenwich. www.portcities.org.uk, accessed 20 July 2015
- Yellow book. Chapter 2: the pre-travel consultation. Centers for Disease Control and Prevention. www.cdc.gov, published 10 July 2015
- Jet lag and sleep phase disorders. BMJ Best Practice. www.bestpractice.bmj.com, published 7 May 2015
- Jet lag. World Health Organization. www.who.int, accessed 20 July 2015
- Sleep disorders – shift work and jet lag. NICE Clinical Knowledge Summaries. cks.nice.org.uk, published August 2013
- van Diepen HC, Foster RG, Meijer JH. A colourful clock. PLos 2015; 13(5):e1002160. doi:10.1371/journal.pbio.1002160
- Weir RE, Hagen CC. Jet lag and shift work. Sleep Med Clin 2014; 9:561–70. www.sleep.theclinics.com
- National Travel Health Network and Centre
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Reviewed by Rachael Mayfield-Blake, Bupa Health Content Team, September 2015.
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