Whether you’re planning a vacation with a long flight or gearing up for a business trip far away, jet lag may be on your mind. You know you’ll probably be hit with daytime grogginess, poor sleep, digestive issues, and low mood for the first part of your trip — and when you first get home, too. But how long exactly should you plan to feel off for?
The answer is a complicated one. Not only does it depend on how far you travel, which direction you fly in, your individual biology, age, chronotype, and sleep debt all play a part, too. Even the season you fly in can make a difference.
Below, we’ll explain how long you can expect jet lag to last for, and — more importantly — how you can make it last for as short a time as possible.
Jet lag, also called jet lag disorder, is a sleep disorder that happens when you fly across different time zones and your body takes time to catch up.
For example, if you fly from New York to London, you’re “jumping forward” five hours. It may be midnight in London, but it’s only 7 p.m. in your body, so you’re not tired yet. But then at 8 a.m. it feels like 3 a.m. for you, so you struggle to drag yourself out of bed, or you sleep in late. And the opposite happens when you fly back home.
You can learn more about what jet lag is here, but here’s a quick explainer to get you up to speed.
Jet lag is classed as a circadian rhythm sleep disorder as it‘s caused by your body‘s circadian rhythm. This is your internal body clock that runs on a roughly 24 hour cycle and dictates things like when you feel awake and sleepy, when your body temperature fluctuates, and when you produce certain hormones.
You have one master clock called the suprachiasmatic nucleus (SCN), which is found in the hypothalamus region of your brain. The SCN communicates with your body’s internal clocks, which can be found everywhere from your gut to your liver to your adrenal glands. These are called peripheral clocks.
When you cross time zones, your circadian rhythms take time to catch up and they adjust at different rates. While you adjust, you’ll be hit with the symptoms of jet lag.
While jet lag is mainly caused by being out of sync with your circadian rhythm, travel fatigue adds to the symptoms too as you easily rack up sleep debt while traveling. Sleep debt is how much sleep you owe your body over the last 14 nights. It’s compared to your sleep need, the individual and genetically determined amount of sleep you need each night.
The symptoms of jet lag include:
You can learn more about jet lag symptoms here.
How long jet lag lasts depends on the number of time zones you‘ve crossed. The general rule of thumb is that it takes almost a day for every time zone you cross to overcome jet lag. So, for that New York to London flight we mentioned earlier, you’d be crossing five time zones, so it could take you about five days to adjust.
However, research in rodents suggests the liver, lungs, and muscles can take nearly six times as long as the SCN to adjust to jet lag.
Plus, how fast you adjust depends on:
Let’s dive into what can affect your jet lag recovery time.
In general, it’s easier to adjust after traveling west than traveling east. When traveling west, you’re pushing your sleep-wake cycle backwards. This fits with how most of us are wired.
The human circadian rhythm isn’t 24 hours long exactly. The average length is slightly longer at 24.2 hours. So, for most of us, it’s easier to adjust to a longer day, by pushing our circadian rhythm back, than a shorter day.
In fact, your circadian rhythm can move back faster than it can be brought forward. It’s thought the fastest rate of adaption is about half a day per hour of time difference westwards, and a day per hour of time difference eastward. Other research suggests you can adjust 30% to 50% quicker after flying west than flying east.
It takes older adults longer to adjust to time zone changes and the symptoms of jet lag can feel worse.
One study compared young men with middle-aged men in a laboratory-created jet lag scenario where their schedules were brought forward six hours. The middle-aged participants reported more trouble sleeping, less alertness, and more weariness and effort needed to do daily tasks than the younger adults. However, the rate of adjustment wasn’t different between the two groups.
But research into age and jet lag is conflicting. A different study found older participants took longer to get over the sleep disruption and daytime sleepiness caused by jet lag compared to younger people.
Research also suggests adults over 60 find it harder to recover from jet lag, especially after eastbound flights, because of decreased and irregular melatonin rhythms. (Melatonin is the hormone responsible for priming your body for sleep.)
Older adults are also thought to be less “phase tolerant,” or their circadian rhythms are less able to handle being out of sync with their sleep-wake times.
Jet lag treatments might be less effective with age, too. A further study found light exposure in middle-aged participants was less effective at moving their circadian rhythm than it was in younger participants.
Your chronotype is whether you naturally tend to wake up and go to bed earlier or later, or in other words, whether you’re an early bird or a night owl.
Morning people have a slightly shorter than 24-hour circadian rhythm and night owls have a longer one. So, extreme morning people may find it easier to adjust to flying east, or bringing their sleep-wake cycle forward. Night owls, on the other hand, may find it easier to adjust after flying west, or pushing their sleep-wake cycle back.
Most of us sit somewhere in the middle, however, so how quickly we adjust to different travel directions can vary.
Believe it or not even the season you travel in can impact how long you take to recover from jet lag. That’s because you may land in darkness or in daylight in a destination depending on the season. And light — and getting and avoiding it at the right times — has the power to speed up how quickly you adjust (more on this soon).
One study found day length affected how quickly melatonin cycles adjusted after both westward and eastward flights. After flying west, you’ll get sunlight for longer in the evening in summer compared to winter. And when flying east, you’ll get more sunlight in the morning in summer compared to winter. Therefore, the study found participants’ melatonin rhythms resynchronized faster in summer than in winter for both westward and eastward flights.
You may find traveling in one direction harder in winter, while traveling in the opposite direction harder in summer. It all depends on when you land and how easy it is to get or avoid light when you need to do so.
If you’re starting your trip with high sleep debt, you’re more likely to feel the effects of jet lag. Plus, the sleep debt you build up while traveling can add to the symptoms of jet lag, especially low mood. You’ll probably rack up sleep debt when you arrive in your new location, too, as your circadian rhythm keeps you up past a reasonable bedtime, wakes you up too early, or frequently wakes you up in the night.
If you’re sleep deprived, you’re going to have reduced attention, grogginess, and lower cognitive function — and that’s just to name a few things. These symptoms will linger all the time your sleep debt is high.
You can speed up how long it takes to adjust to your new schedule with the help of zeitgebers. Zeitgebers, which is German for time-givers, are external cues that can synchronize your circadian rhythms to the outside world. These include things like light (the most powerful one), exercise, and meal timing.
You need to get the timing of these zeitgebers right, however. When done at certain times, they can push back or bring forward your circadian rhythms.
For example, researchers estimate if you get the timing of light exposure right after landing, you can bring your circadian rhythm forward by 1.5 hours a day and push it back by 2 hours a day. But not only are these numbers estimates, they depend on the person and the timing and intensity of light, too.
Further research shows those who stayed inside their hotel rooms after their flight, therefore not getting social interaction or sunlight, took four to six days longer to adjust than those who went outside. And a 2017 study in rats showed meal timings can speed up adjustment times.
Even without interventions, jet lag is usually a short-term problem. But there are some things you can do to reduce jet lag and how long you feel it for.
You can learn more about how to get over jet lag here, but here are three strategies to start with.
Light is the most powerful zeitgeber and getting the timing of your light exposure right can make or break your jet lag recovery. Aim for natural light whenever possible, but you can also turn to a light box if needed, it’s just not as powerful.
Here’s what one study recommends when it comes to light exposure and jet lag:
If flying east:
If flying west:
Getting the timing of light exposure right can be hard while traveling, though. Consider wearing sunglasses if you land during the day and need to avoid light at that time. And an eye mask can block out light while on the plane.
Bonus tip: Bring the power of light back home with you. Get at least 10 minutes of morning light as soon as possible after waking up to reset your circadian rhythm for the day. Then dim the lights and put on blue-light blocking glasses 90 minutes before bed to help your body produce enough melatonin to sleep soundly.
Melatonin is made in your brain and it tells your body bedtime is coming up, so it starts winding down and feeling drowsy. However, when you’re out of sync with your circadian clock, melatonin isn’t secreted at the right time for your new sleep schedule. That’s where melatonin supplements can help.
Here’s what one study recommends:
For eastbound flights up to 9 hours long:
For westbound flights up to 9 hours long:
For flights in either direction that are 10 to 14 hours long:
People with health conditions should speak to a health care professional before taking melatonin.
Heads-up: Avoid the temptation to reach for over-the-counter sleep aids. While sleeping pills can help you sleep in the moment, they come with side effects, long-term health risks, and they don’t help to move your circadian rhythm like melatonin does.
You’ll feel the effects of jet lag more if you’re sleep deprived, and sleep deprivation itself will add to the symptoms. What’s more, strategies to reduce how long jet lag lasts work best in well rested individuals.
However, it can be hard to meet your sleep need when traveling long distances and catching middle-of-the-night flights. Plus, as jet lag causes difficulty sleeping at appropriate local times, it can cause more sleep debt to build up when you’re in your destination.
To start from the best place, make a special effort to lower your sleep debt before your flight. RISE can work out how much sleep debt you have and keep track of it as you pay it back. We recommend keeping sleep debt below five hours to improve how you feel and function each day.
Got more sleep debt than that? You can pay it back by:
Keep track of your sleep debt in your destination, too, and lower it when possible to help you feel better while battling jet lag. When all the traveling is done, you can keep sleep debt low to improve everything from your productivity to your mood back home.
If you travel far enough, jet lag is an almost inevitable part of air travel. But how long you feel it for depends on everything from your age to your chronotype, your direction of travel to the season. However, there are a few things you can do to speed up your recovery time.
Use RISE to pay down sleep debt to start from a solid foundation. Then get well-timed light exposure and consider taking melatonin supplements. All this should help cut down the time it takes for your circadian rhythms to adjust to the new time zone.
You can’t cure jet lag, but you can reduce how long it takes to get over it with well-timed light exposure, exercise, and meals, as well as taking melatonin supplements and starting with low sleep debt.
When you have jet lag, you may feel daytime tiredness and have low mood, loss of appetite, stomach problems, and reduced performance, mentally and physically.
Depending on things like how far you’ve flown, the direction of travel, your age, and your chronotype, jet lag can last from a few days to a few weeks. High sleep debt may be causing feelings of jet lag three weeks after your flight, though.
Working out how long jet lag lasts depends on things like how many time zones you’ve crossed, your direction of travel, your age, your chronotype, and whether you try any interventions. While jet lag calculators do exist, they tend to only look at how many time zones you’re crossing, so they’re not always accurate. However, they can be helpful as a starting point. You can check out jet lag calculators from Sleepopolis, British Airways, and Timeshifter.
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