Much of the general malaise we may experience on long journeys may just be so-called ‘‘travel fatigue,’’ which can occur regardless of the time zone, leaving people feeling disorientated, generally weary, and headachy. Dehydration has been blamed. Radiation from the Sun and other factors.
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The cabin air isn’t just dry, but low in oxygen pressure—about what you’d get 10,000 feet above sea level, like twice as high as Denver. And that alone can make you feel not-so-great. Then, when you land, if you’ve crossed enough time zones, you can suffer from jet lag, which is the temporary disconnect between the new time at your destination, and that of your own internal body clock, which is still on home time. This is abnormal, since our internal clock is normally synced to the outside world. But, the symptoms of jet lag go away as your body becomes hip to the new time.
This usually takes, in days, “two-thirds the number of time zones crossed eastwards, compared with half the number of zones crossed westwards.” So, London is like six time zones east away from Chicago; so, flying there, it may take four days before you’re back to normal, whereas Londoners flying to Chicago should get over their jet lag in only three days. The reason it’s easier to go west, where the day is longer, than east is because our internal clock is naturally set for longer than 24 hours and has to be reset every day. That’s why they call the daily rhythm “circadian,” meaning “about a day.”
In fact, you can see this in Major League Baseball performance. Researchers churned through 40,000 games, mining 20 seasons, and found “surprisingly specific results of circadian misalignment”—jet lag, and, indeed, the problems arose most after eastward travel, with very limited effects after westward travel, consistent with the greater-than-24-hour cycle length of the human circadian clock. Okay, but how do you treat it?
First, you need to figure out if it needs treating at all. If you’re just traveling one or two time zones, you don’t have to worry about it. If you’re crossing three or more time zones, like traveling coast to coast, it then depends on how long you plan on staying. If it’s just a few days, it’s probably not worth treating it, since then you’ll have to switch back as soon as you get home. If you have control over your schedule, it’s better to “time appointments in the new time zone to coincide with daytime” back home. So, it’s pretty much common sense. If you travel east, your body will still think it should be sleeping in the morning. So, you should push stuff later, and vice versa.
But, if you are going to be gone for a while, you can adjust your body clock using behavioral methods and/or drugs, supplements, or foods. “There is only one sure fire way of avoiding jet lag altogether and that is to adapt to the new time zone before [your trip].” However, changing your home sleep schedule more than a few hours can be counterproductive by interfering with your pre-trip sleep, and you don’t want to be going into a long trip already sleep-deprived.
Before your trip, you want to maximize your sleep. In flight, the recommendation is to immediately “adjust…to [the] destination meal schedule”—easier said than done, and then, once you land, you want to try to “maintain [the] destination sleep schedule.” Try not to nap more than a few minutes, and you don’t want to be driving around when your body thinks it’s the middle of the night.
But, the key to treating jet lag is light therapy. Going east, you expose yourself to the bright light in the morning, and avoid bright light in the evening, and vice versa going west. But, it’s more complicated than that. The advice switches if you’ve traveling “through more than six time zones,” because “[y]our biological clock may then adjust in the wrong direction.” And, it’s even more complicated than that! “The effects of light acting upon the body clock” are actually only during a specific window around the time your body temperature bottoms out: usually around 4 am. You drop from 98.6 down to more like 97.6, even when you’re not sleeping—it’s just part of our circadian rhythm.
The bottom line is that here are the two cheat sheets you can take a snapshot of for future reference. So, for example, if you fly from LA to London, eight time zones east, you’d avoid light between 6 am and noon local time, and expose yourself to light between noon and 6 pm local, and the rest of the day, it doesn’t matter and won’t affect you either way. Okay, but that’s just on day one. “On subsequent days, the local times of light avoidance and exposure need to be advanced [earlier] by [one to two hours] each day, until light avoidance coincides with [when you’re sleeping].”
But, on those first few days after traveling east, you’ll note you’re going to want to be avoiding morning light, which can be difficult, if that’s when your flight gets in. One thing you can do is wear really dark glasses until you get indoors. But, if they’re too dark, you can’t really drive. So, that’s where these kinds of ugly orange lenses that block blue wavelengths can come in handy, preventing the dip in melatonin you can get just wearing regular sunglasses. Regardless, the next day, I know there’s the urge to get out and about, but that could actually make your jet lag worse, by taking you in the opposite direction.
What about if you’re flying more than eight time zones east? Then, you subtract the number from 24, and treat it as travel west. So, a ten-time zone trip to the east, like New York to Delhi, should be treated as a westward flight, requiring a delay of the body clock, across 14 time zones. In that case, it would be easy to get outside and get some sun. But if you just went four zones west, and need to get light in the middle of the night, what do you do?
A gadget company came up with like light-emitting headphones, the theory being you could bathe your brain in light directly through the ear canals. They stuck them on the heads of cadavers and did seem to get some light penetration, but you don’t know, until you…put it to the test. “This randomized, double-blind, placebo-controlled trial demonstrates that…transcranial bright light exposure via the ear canals [could] alleviate…jet lag symptoms.” Or, you could just turn on a lamp.
Transcranial bright light and symptoms of jet lag: a randomized, placebo-controlled trial.
Rapid travel over multiple time zones usually results in transient de-synchronization between environmental time and the biological clock of the individual. Common symptoms are increased daytime sleepiness, reduced sleep duration and quality, and performance impairments. Exposure to ocular bright light is known to alleviate jet lag symptoms and facilitate adaptation to a new time zone. Recently, transcranial bright light (TBL) via the ear canals has been shown to have antidepressant, anxiolytic, and psychomotor performance-enhancing effects. In this case we studied whether intermittent TBL exposure can alleviate jet lag symptoms in a randomized, double-blind, placebo-controlled study.
Intermittent light exposures (4 × 12 min; day 0: 08:00, 10:00, 12:00, 14:00; days 1-6: 10:00, 12:00, 14:00, 16:00) were administered during the 7-d post-travel period after an eastward transatlantic flight. The symptoms of jet lag were measured by the Visual Analog Scale (VAS), the Karolinska Sleepiness Scale (KSS), and the Profile of Mood States (POMS).
We found a significant reduction of overall jet lag symptoms (VAS), subjective sleepiness (KSS), and the fatigue, inertia, and forgetfulness subscales of the POMS when comparing the active TBL treatment group (N = 30) to the placebo group (N = 25). For example, the normalized values of VAS in the TBL, but not the placebo, group returned to pre-travel levels by the final post-travel day (6.16 vs. 15.34).
Results suggest a cumulative effect of TBL, as the effects emerged on post-travel days 3-4. Intermittent TBL seems to alleviate jet lag symptoms.
Come fly with me: jet lag and melatonin.