Everyone experiences jet lag differently, but we can all agree it’s not a fun experience. When you’re jet lagged, you might feel tired during the day, wide awake at night, and feel like everything from your concentration to your digestion to your mood is thrown off. But what’s causing these unwanted symptoms?
Below, we dive into the common jet lag symptoms and what’s behind them. Plus, we cover the long-term impacts of jet lag and some ways you can recover more quickly after your next flight.
Jet lag, also called jet lag disorder, happens when you fly across different time zones (usually two or more) and your body’s internal clocks take time to catch up.
For example, if you fly from New York to London, the local time jumps forward five hours. But your body can’t adjust that quickly. It may be 11 p.m. in London, but you’re still running on New York time. You’re not ready for bed as it feels like it’s only 6 p.m. for you.
Then in the morning, it might be impossible to drag yourself out of bed at 8 a.m. because it’s actually 3 a.m. for your body. And the opposite happens when you fly back home, suddenly going back five hours.
This all happens because of your circadian rhythm, or the roughly 24-hour internal body clock that dictates things like when you feel awake and sleepy, your body temperature fluctuations, and hormone production.
But you actually have more than one body clock. You have one master clock called the suprachiasmatic nucleus (SCN), found in the hypothalamus region of your brain. The SCN coordinates your other circadian clocks, called peripheral clocks, working in places like your liver, gut, and adrenal glands.
The timings of our circadian rhythms can change, but this happens slowly, not in the few hours it takes to jump time zones with air travel. Plus, they all adjust at different rates.
While most of the symptoms of jet lag come from being out of sync with these circadian rhythms, you can blame travel-related sleep deprivation for some of them, too.
Night flights and long-haul travel stop you from meeting your sleep need, the genetically determined amount of sleep you need each night. Plus being in circadian misalignment makes it harder to get enough sleep when you arrive in your new location. All this means sleep debt, the amount of sleep you owe your body over the last 14 nights, starts piling up.
You can learn more about what jet lag is here. Plus, you can use the RISE app to work out your individual sleep need — it’s not eight hours for everyone!
Jet lag symptoms vary from person to person. There’s even some lucky travelers (it’s thought to be about one-third) who don’t feel jet lag at all.
But for the rest of us, jet lag symptoms include:
Let’s dive into a few of these.
There’s a reason jet lag is a circadian rhythm sleep disorder — it messes with your sleep in all sorts of ways.
If you’re flying east, you’ll be jumping forward from your usual time zone. This means it might be 11 p.m. in your new local time, but your body clock thinks it’s 6 p.m., so you can’t fall asleep and you may feel wired late into the night.
If you’re flying west, you’re jumping back time zones, so you may feel sleepy at dinner time and struggle to stay awake until an acceptable bedtime. But then you’re wide awake at 3 a.m. and may struggle to get back to sleep.
Beyond your sleep-wake cycle, your sleep may be impacted by other disrupted cycles. For example, your urinary frequency may be thrown off, waking you up in the night with the need to use the bathroom.
All this makes it hard to meet your sleep need, meaning you’ll rack up sleep debt.
The other side of the jet lag coin is daytime sleepiness. This is caused in part by circadian misalignment as we mentioned above — if it’s daytime in your new destination but nighttime back home, you’ll inevitably feel tired as you’re still adjusting.
While your circadian rhythm is still working on the old time zone, it does things during the day that it would usually do at night, like secrete the sleep hormone melatonin, lower your body temperature, and slow your metabolism.
Daytime sleepiness can also be caused by travel fatigue and high sleep debt. You may have built up sleep debt on the flight and then continue to add to it while jet lag stops you from meeting your sleep need. When you’re sleep deprived, you’ll feel a whole host of symptoms like lowered alertness, loss of concentration, and poor performance mentally and physically, similar to jet lag.
Your mental performance — think attention, memory, and the ability to do simple calculations — also takes a hit when you’re jet lagged. This may not be a problem if you’re lounging by the pool, but if you’re traveling for work, traveling back home to get back to work, or simply want to feel mentally at your best on vacation, it can be frustrating.
While sleep deprivation after a long flight certainly contributes to this drop in mental ability, your circadian rhythm plays a role, too. That’s because your mental ability increases and decreases over a 24-hour cycle, just like your energy levels. And this is no longer in sync with the outside world.
Have you ever struggled with digestive issues after a time zone change? If so, you’re not alone. One study found 41% of airline crew members said they experienced them after long-distance flights.
What’s more, our appetite gets thrown out of whack, too. We might wake up in the middle of the night feeling hungry, but then don’t have an appetite at acceptable meal times.
Our body clocks are to blame for these symptoms, too. Your gastrointestinal system has its own circadian rhythm, meaning things like digestion and bowel function are working at times that don’t match your new time zone. You may feel things like constipation or indigestion while you adjust to the new schedule.
Plus, the hormones responsible for hunger are also controlled by your circadian rhythm, so the times you feel hungry will no longer match meal times, or even daytime.
The general rule is it takes almost one day for every time zone you’ve crossed to get over jet lag. Flying from New York to London crosses five time zones, so it may take you five days to fully adjust.
However, how long you feel the effects of jet lag for depends on:
Plus, research in rodents suggests peripheral clocks, like those of the metabolic, endocrine, and immune systems, may take almost six times as long to adjust as your SCN master clock.
You can learn more about how long jet lag lasts here.
Most of the time, jet lag is a short-term problem. You may feel off for a few days, but with time (and maybe a few interventions), you’ll be back to feeling yourself again as your circadian rhythms sync up with the local time.
However, chronic jet lag has long-term implications including:
Heads-up: These aren’t just the long-term health risks of jet lag. Studies show similar long-term effects for those who do shift work and even for those with social jet lag. Social jet lag is when your body clock is at odds with your social clock. This could happen if you stay up later at the weekend than during the week, for example. About 87% of us have social jet lag and go to bed at least two hours later than usual on weekends.
You can learn more about social jet lag and how to combat it here.
Luckily, jet lag doesn’t have to ruin the start of your trip or stop you getting back into daily life once back home. While there’s no cure, there are some things you can do to speed up how long it takes to recover from jet lag.
You can learn more about how to get over jet lag here. But here are some strategies to get you started:
Your SCN is attuned to the light-dark cycle, so getting light at the right times can help to bring forward or push back your circadian rhythm. Natural light is best, but you can turn to a light box if needed.
Here’s what one study recommends:
If flying east:
If flying west:
It can be tricky to get this right, though. Not only do you have to get the timings right, it can be almost impossible to avoid light exposure when you don’t want it on flights, in brightly lit airports, or when traveling to your hotel if you land during daylight hours. Sunglasses can help and an eye mask can block out light when trying to sleep on planes.
Bonus tip: Light isn’t just important when you travel. You can also harness the power of light back home to help reset your circadian rhythm each day. Get natural light as soon as possible after waking up and avoid bright artificial light 90 minutes before bed. RISE can tell you the best time to do light-based behaviors like put on blue-light blocking glasses each evening.
Melatonin is made by your brain to prime your body for sleep. But if you’re jet lagged, your body won’t be making melatonin at its usual times. This is where melatonin supplements come in. You can learn more about what melatonin does here.
For travel, melatonin has been shown to be successful at helping people overcome jet lag.
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. We dive deeper into how much melatonin to take for jet lag here.
Bonus tip: Avoid reaching for over-the-counter sleep aids while jet lagged. Sleeping pills come with many unwanted side effects, long-term health risks, and they don’t shift your circadian rhythm to help set up a new sleep pattern, they just force you into manufactured sleep.
It may be impossible to avoid sleep loss while traveling, but you can give your body the best chance of recovering quickly by reducing sleep debt before your trip.
RISE can work out how much sleep debt you have. Once you know your number, you can do something about it. We recommend keeping sleep debt below five hours to feel your best.
If you have high sleep debt, you can pay some back by:
As well as keeping sleep debt low before you trip, keep an eye on it while you’re away, too. Keeping sleep debt as low as possible will help you feel better, even while you’re adjusting to the new time zone.
We all experience jet lag differently. You may suffer from poor sleep, daytime sleepiness, subpar mental performance, or digestive issues. And it may take a few days for your circadian rhythms to adjust and for you to get back to feeling your best.
RISE can help. Use the app to lower your sleep debt before traveling and keep an eye on it while away to reduce the symptoms of high sleep debt, which makes jet lag feel worse.
Plus, you can see a prediction of your circadian rhythm each day. This will help you stay in sync up until your flight (or up until you start adjusting to your new time zone), and get back in sync once the traveling is done.
The time it takes to recover from jet lag depends on things like how many time zones you’ve crossed, which direction you flew in, your age, and your chronotype. In general, it takes almost one day for each time zone you cross to adjust.
The most common symptoms of jet lag are sleep problems (like struggling to fall asleep or waking up too early), daytime sleepiness, loss of appetite, low mood, and poor mental and physical performance.
You may feel sick while jet lagged, but this should go away in time. Chronic jet lag, however, can weaken your immune system and increase your risk of things like depression, obesity, metabolic syndrome, and cancer.
There’s no cure for jet lag, but you can speed up how long it takes to recover from it. Get the timing of your light exposure, exercise, and meals right, and consider taking melatonin supplements. Plus, keep your sleep debt as low as possible.
RISE makes it easy to improve your sleep and daily energy to reach your potential
RISE makes it easy to improve your sleep and daily energy to reach your potential
