How to cure jet lag - eastward edition
Travel seems like all fun and games, until you find yourself feeling exhausted, irritated, sleepy-yet-wired, and dull, and you wish you had never left home. Jet lag is miserable! Why do we get jet lagged, and how can we cure it so we can actually enjoy vacations?
Jet lag didn’t exist until humans figured out how to, ahem, jet across multiple time zones by plane. Our internal clocks, or circadian rhythms, are built into every cell in our bodies, and controlled by the “master” clock in the brain called the suprachiasmatic nucleus (SCN). Even when researchers have locked themselves in dark caves, they found that human circadian rhythms still tick on regularly, controlling when we can best sleep, eat, think, and exercise. Jet lag happens when our internal clocks mismatch with our environment due to rapid travel: not only do we feel “off” since we aren’t sleeping, eating, thinking, and exercising at the “right” times, there is the added frustration of not be able to sleep at night, and fatigue from sleep deprivation during the day.
A couple jet lag basics. It is typically worse when flying east than west, because there’s more sleep time lost. Some people get worse jet lag than others, it’s luck of the draw. Youth helps — children recover from jet lag faster than adults. More time zones means worse jet lag, and a longer recovery. Fortunately, our circadian rhythms aren’t set in stone, and eventually our clocks will adjust to the new place — this takes about a day per time zone. So for people traveling 7 times zones, that will be a week of jet lag, and if that is the duration of the trip, they will have to immediately reverse the process and have another week of jet lag when they return home!
So how can we cure jet lag (faster)? Use circadian science! ⏰🧪🎉 Here’s the science-backed guide for curing jet lag traveling east 6-8 time zones: US to Europe, or Europe to Asia. For illustration, let’s pretend we are traveling from St. Louis, Missouri (USA) to Paris, France, a 7-hour time difference. Of note, this guide assumes you sleep regularly approximately 11pm-7am at home. If your usual sleep schedule is very different, or you have significant sleep problems already, you will need more individualized advice from a sleep doctor. We will get to westward travel as well as opposite-side-of-world travel in future posts.
Here’s the science on how to shift our circadian rhythms:
Phase response curve to light and melatonin, in home time zone.
This is a phase response curve (PRC). On the X axis is time. On the Y axis, in the positive direction, are things that shift the circadian rhythm earlier (or advance it). In the negative direction are things that shift the circadian rhythm later (or delay it). Light and melatonin are the strongest forces on the circadian rhythm, so they are plotted here, light in yellow and melatonin in red. The key concept is that light and melatonin have different effects on the circadian rhythm depending on the time. As you can see, the big yellow trough shows that light will delay the circadian rhythm if given before 4-5am (the core temperature nadir, which is about 2 hours before wake time), but then the big yellow mountain shows that light will advance the circadian rhythm if given after this time. Timing is everything! The same goes for melatonin — when given at evening/night it will advance the circadian rhythm, but it will delay the rhythm if given during the morning — and it also generally has the opposite effects as light.
Now back to our Paris trip! Let’s all get on an imaginary plane. During the flight, try to get as much good sleep as you can: wear an eye mask, wear ear plugs or noise-canceling headphones, and avoid alcohol. If you have previously taken a short-acting sleep aid safely without problems, this might be a good time to do so. Note that most prescription sleep medications and over-the-counter antihistamines (e.g. dramamine, diphenhydramine/benadryl) last much longer in your system than the flight and should be avoided. I have had to medically assist fellow passengers on two separate flights because they got completely zonked and confused after taking a sleep medication they weren’t used to. If you are accustomed to it, regular (not slow-release) melatonin is also okay to take on the plane. In general, try your best, but it won’t be a great night of sleep. That’s ok.
Phase response curve to light and melatonin, after eastward travel 6 time zones.
When the plane lands, the time has changed! Look at the X axis on the new table, which has shifted 6 hours. Typically, a flight from North America to Europe is a “red eye,” so let’s say we have arrived at 8am Paris time. This lines up with the deep yellow trough in the phase response curve, meaning that light in the morning will delay your circadian rhythm, making your jet lag worse! So be prepared and wear sunglasses in the morning, as much as you can from when the plane windows are opened for landing, through the airport (except for the security check of course), and especially outdoors en route to your hotel.
Then the most important jet-lag cure: expose yourself to bright light, preferably sunlight, in the early-mid afternoon. As you can see on the graph, there is a yellow peak around 12-4pm, meaning that light exposure at that time will shift your circadian rhythm earlier. Wear sunscreen (!) but if you can tolerate it, take off any sunglasses and let the light hit your eyes in the afternoon. Note the very steep slope of the yellow line — the location of where that line crosses zero will vary depending on your home circadian rhythm. The more time zones you are going east, the later in the afternoon you should get bright light. For example, someone from Los Angeles going to Paris (9 hour difference) should wait to get bright light until around 2-3PM. Any earlier will have the opposite effect and make their jet lag worse. Again, timing is everything! Also, avoid napping in the afternoon, so that you build up your “sleep drive” for the nighttime when it will be harder to fall asleep with the time change.
Last but not least, you can boost the effect by taking melatonin right at bedtime (if you’re going to bed around 11pm to midnight) which is right around the red “hill” on the graph, meaning melatonin will also advance your circadian rhythm. Bonus: melatonin has a mild soporific (sleep-inducing) effect, which will help you fall asleep since internally, it will be the afternoon so it will be harder than usual to fall asleep. The exception is anyone who stays up partying until the wee hours of the morning… melatonin may have an opposite effect at this time, so just skip it.
Note that melatonin is considered a prescription medication in many countries, however lower doses (<2mg) can be sold over-the-counter in some European countries (e.g. Italy, Spain, France). The OTC melatonin in Europe is subject to much stricter regulations than in the USA, where melatonin is loosely overseen as a nutritional supplement, not a medication. So if you’re in one of those countries… this is a great opportunity to stock up on better melatonin! If you plan to pack melatonin from home, please check ahead to ensure it is legal at your destination. In terms of melatonin dose, a high-quality review of 10 clinical trials (link) found that 0.5 mg up to 5mg were effective, with the higher end being better for the sleep effect, and that slow-release formulations do NOT work well.
At nighttime, again, try your best with eye mask, ear plugs, etc to get the best sleep you can. The next day, again avoid bright light in the morning. You may benefit from a little extra cafe au lait with your pain au chocolat. Then, again for the next couple days, time your outdoor excursions for the early afternoon for the biggest circadian boost. Jet leg can’t be cured instantly, but with the right timing of light (and melatonin), you will recover a lot faster!
Recap: for travel eastward ~6-8 time zones:
🌞 Get light in the early afternoon (noon to 4pm)
🕶️ Avoid light in the morning. Prepare dark sunglasses for your flight arrival.
💊 Take melatonin right at bedtime.
It really works! Here I am on day 3 of my own St Louis-to-Paris trip, jet-lag-free and enjoying le printemps.
Additional tips:
Some people advance their circadian rhythms partially before departure for a day or two. You can do this by getting bright light first thing in the morning (at home) and taking melatonin a couple hours before bedtime (at home).
If you have a work presentation or similar event to be at peak performance for, consider partially pre-advancing your circadian rhythm (as in #1) and/or arriving a couple days early.
If you travel frequently and suffer a lot from jet lag, some prescription medications have been tested in clinical trials for this indication, so see a sleep doctor.
Bon voyages!!
PS: I don’t have space or time to go over all of the research studies that have been done on jet lag treatments, as I am skipping over the prescription medications (which the average person does not need for occasional travel), and many of the studies were done with “simulated” jet lag. Seriously, some studies had people sit in a lower-oxygen room in cramped conditions for the duration of a fake “flight”, then exposed them to a time zone change in the form of turning on the overhead lights at different times. Many studies are done on frequent air travelers (such as flight personnel) who are self-selected for not being badly affected by jet lag. Very few studies combine medication with appropriately-timed light exposure and avoidance, which is strange since light has the strongest effect on the circadian rhythm. One (in retrospect) humorous study was on 257 (!!!) Norwegian physicians who had flown from Norway to New York 5 days earlier for a medical conference, and different dosing schedules of melatonin were tested upon their eastward return flight to Norway. None of the melatonin doses worked better than placebo, which is no surprise since the study group’s circadian rhythms were already rattled by their recent travel west. Incidentally, the study researchers were at the New York Psychiatric Institute and Columbia P&S Medical school, and the first author of the study, Robert Spitzer, in addition to revolutionizing psychiatry by spearheading the Diagnostic and Statistical Manual of Mental Disorders (DSM-3), was later my psychiatry professor in medical school. It’s a small world!
