Posted by Dr Sophie Bostock - Sleep Expert on 1st Aug 2023
Jet Lag: What is it, and What Can You Do About it?
If you are jetting off to cheer on the Lionesses this summer, you may be wondering how your body clock will cope..
The 2023 Women's World Cup will be played across 10 different stadiums, nine host cities and four different time zones. Four of the host cities are in New Zealand, which is 11 hours ahead of UK time. In Australia, Brisbane, Melbourne, and Sydney are 9 hours ahead, Adelaide is 8.5 hours ahead, and Perth is 7 hours ahead of UK time.
The Lionesses flew into Sydney, Australia on 7th July, 11 days before their first game with Haiti. Their coaching team allowed 4 days post arrival before scheduling a full training session. So why does recovery from overseas flights take so long? And what can you do to speed it up?
What is jet lag?
Jet lag is a mismatch or misalignment of our internal body clocks - or circadian rhythms - with our environment, which can make us feel disorientated and unwell. Most people experience the symptoms of jet lag when they fly across more than 3 time zones, but a transition of just 1 hour can still impact on physical, emotional and cognitive performance.
We are programmed to wake and sleep according to a 24 hour, or ‘circadian’ rhythm rhythm. Every cell in our bodies carries an internal clock, with instructions to follow a regular pattern of activity and recovery. Under usual circumstances, this clock is aligned with the light-dark cycle of the sun so that we feel active during daylight hours and sleep during the night.
When you fly across multiple time zones, your internal rhythms don’t have time to adjust their timing to fit the new environment. This might mean that you try to eat when your body clocks are anticipating sleep, or get into bed at a time when your internal clocks are telling you to be wide awake, for example.
When we try to behave at odds with our internal rhythms, our internal processes work less efficiently, putting the brain and body under strain, and negatively impacting performance.
What are the symptoms of jet lag?
When most people think of jet lag they think about feeling sleepy during the day, or not being able to sleep at night. Sleepless nights are the most obvious effect of being out of sync with local time, but jet lag can also mean that some of our internal clocks adapt faster than others, so they fall out of sync with each other. Every system in the body can be affected by jet lag.
The symptoms may include:
- Difficulty falling asleep, or staying asleep
- Lack of energy
- Feeling generally unwell, headaches, dizziness
- Irritability, and a worsening of existing mood problems
- Stomach and GI upsets, changes in appetite, nausea, constipation, irritable bowel symptoms
- Cognitive problems, including poor concentration and memory lapses
- Parasomnias, such as sleep walking, sleep talking and sleep paralysis
- In rare cases, severe jet lag has also been linked to seizures
How does jet lag impact on sports performance?
The Lionesses were wise to fly with plenty of time to adjust to their new time zone. As outlined above, jet lag can impact on fatigue, alertness and motor performance. Analyses of results for baseball and basketball teams in the US has shown that teams which fly east to games tend to lose more games than teams that do not travel, or that fly west ( Leota 2022). Eastward travel has also been linked to points differences in American Football ( Worthen and Wade, 1999 ), team rankings and player performance in International Football ( Zacharko et al., 2020 ), and jump performance in elite skeleton athletes (Chapman et al., 2012 ).
Why is jet lag worse when we travel east?
As a rule of thumb, it takes about 24 hours for your internal rhythms to adjust for every hour of time zone that you have crossed. However, there is a lot of individual variation.
The symptoms of jet lag tend to be more severe if you are landing at a destination which is east, rather than west. This is because our internal clocks typically run on a rhythm which is just over 24 hours. We find it easier to extend our days, and stay awake for longer (also called a ‘phase delay’), than to compress our internal rhythm and fall asleep earlier. Some people will adjust by 1.5-2 hours per day when they fly west, but adjust more quickly when travelling east. This has led to the saying “West is best, and east is a beast.”
You will find it easier to adjust if you start your journey well rested, whereas stress can interfere with the rate of recovery.
How to reduce jet lag: light exposure is key
Bright light is the key signal that our bodies use to keep internal rhythms co-ordinated with each other, and our environment. Bright light lands on receptors at the back of eye and sends an alerting signal to a master clock in the brain called the suprachiasmatic nucleus (SCN). The master clock triggers the release of serotonin, and the brain becomes more alert. Darkness, or dim light, is the brain’s signal to produce melatonin, the hormone which helps to prepare the body for sleep.
- Being exposed to bright light at dawn or early morning in the time zone of departure has the effect of advancing the master clock and making us feel sleepy earlier. In other words, morning light helps us to behave more like an early bird. This is helpful if you’re flying east, such as when the Lionesses flew to Australia.
- Bright light late at night in the time zone of our departure has the effect of delaying the master clock, and making us sleepy later. This can be helpful if you’re flying west.
So...
If you’re flying East, e.g. New York to London (+5hrs), the effect on your body clock is to make the day shorter. You can start to go to bed and wake up an hour earlier 2 days before you fly, to help speed the transition..
On arrival, if it’s local bedtime, always dim the lights and see if you can switch off for sleep, but if not, ask yourself… what time is it for my body clock i.e. what time is it at the place you departed from? If it’s after sunrise and before sunset, seek out light. If it’s between sunset and dawn at your place of departure, avoid bright light by dimming the lights or wearing wrap around sunglasses.
Image: How to help adjustment to flying East
If you’re flying West, e.g. London to New York (-5hrs), the effect on your body clock is to make the day longer – you want to behave more like a night owl. You could start to go to bed an hour later and wake up an hour later 2 days before you fly.
On arrival, as always, if it’s bedtime, keep the lights low and see if you can drop off for sleep. If not, ask yourself… what time is it for my body clock i.e. what time is it at the place you departed from? Being exposed to light between sunset and dawn will delay the body clock. Minimising light in your old morning zone to help delay the clock.
Image: How to help adjustment to flying West
Try to time your arrival in the afternoon/evening in time to have a full night’s sleep at your new destination. Ideally, avoid cutting short your sleep on the day of departure, so that you fly after a good night’s sleep.
There are several apps and online programmes which offer tailored advice about when to seek out bright light, and when to avoid it, based on your schedule and flight times, such as the Timeshifter app and a free jet lag calculator from Sleepopolis.
Although light is the most important signal of time to your body clock, eating meals, intense physical activity and temperature changes can also alert the body clocks. These signals are called ‘Zeitgebers’, or time givers.
Avoid eating large meals or intensive exercise within the last few hours before your new bedtime. Aim to stick to regular mealtimes when you arrive. Getting outside for some gentle exercise in the days after you arrive will help the body clocks to adjust.
Sleeping on a plane: things to consider
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- Change your watch when you get on the plane, and stick to the sleeping and eating schedule that you’ll have on arrival. This may not be when you are served food on the flight. Aim to take snacks with you. An apple is good for slow release energy. If in doubt, skip a meal – it’ll be easier to adjust than overeating.
- Always travel with an eye mask and ear plugs. If you can’t sleep, you can still rest. I usually fly in comfortable clothing including a hooded sweatshirt so that I can pull the hood over my head and block out the outside world!
- Be wary of drinking more caffeine than usual, and ask for decaf if you’re planning to sleep on the plane.
- Alcohol will disrupt the quality of your sleep and make you more dehydrated.
- Stand up and move as frequently as possible when you’re not sleeping. This will reduce the risks of stiffness and blood clots. You can also do gentle stretching in your seat, even with the seatbelt sign switched on!
- Download some calming music and take comfortable headphones to help you block out in flight noise. You can use bluetooth headphones as long as you don’t use them during take off, landing or taxi-ing.
Why does travelling make you tired?
If you fly north-south, rather than east-west, you may still notice that you feel fatigued, even though you haven’t crossed any time zones. The process of travelling can still be exhausting.. late night packing, early starts, walking around the airport, sitting in a cramped position on the plane, breathing lower oxygen recycled air, dehydration, irregular sleep and eating patterns can all take their toll.
There is also the mental stress associated with uncertainty and a lack of control and familiarity. We know that when you sleep in a new place your sleep tends to be lighter as your brain stays on edge, looking for danger. This is called the ‘first night effect’.
Tips to reduce travel fatigue
- Write yourself a checklist for packing in advance. This is mostly so you don’t have to waste energy worrying about what you’ve forgotten, or buy yet another travel plug adaptor at the airport (I have 5). My list includes, passport, phone, eye mask, ear plugs, empty water bottle, lip balm, phone charger, wallet and printouts of travel insurance, flight details, and accommodation.
- Can you avoid an early flight? A 7am flight could mean waking up at 4am. The stress of anticipation inevitably means that you end up waking up at 2am, 3am and 3:55am, so you’re compressing your sleep before you’ve even started. Consider staying at the airport for a full night’s sleep, and wherever possible, bank extra sleep a few days before you fly.
- Allow for the unexpected, and leave plenty of time so that you’re not rushing. Trying to find an address when the wifi goes down or the battery runs out on your phone can get stressful, so take printouts of where you’re going!
- To make it easier to sleep in a new environment, try to repeat the same wind down routine that you use at home. A warm bath or shower, reading a familiar book, or a spot of meditation can help to detach from the excitement of the day, and get the mind and body ready for sleep.
- Take a few things which are familiar from home - favourite pyjamas, a book, photos, or even a pillow.
