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Circadian Rhythm
Jet Lagged? Here's What to Do About It
Research helps explain how to feel yourself when you're far away from home.
Posted August 17, 2017
A few years ago, I found myself on a plane to Rome as I embarked on my first solo trip overseas. I thought I had come prepared—light luggage for backpacking across three countries, a refillable water bottle to keep me cool in the Mediterranean heat, even a phone charger compatible with the European electrical system. What I forgot to plan for, of course, was the heavy feeling of jet lag and just how long it would last.
Jet lag, or "circadian rhythmdesynchronosis", as it is known in the medical literature, is the experience of a constellation of symptoms resulting from high speed travel across time zones. Generally, the more time zones one crosses, the worse the symptoms get and the longer they persist, with the general guideline being that the number of time zones crossed is the number of days it will take to fully recover. Short term symptoms include daytime fatigue, impaired alertness, insomnia, appetite changes, gastrointestinal issues, poor psychomotor coordination, reduced cognitive skills, and depressed mood, whereas long term effects for frequent flyers crossing over multiple time zones, such as flight attendants, face an increased risk of cancer, amongst other maladies. For the six time zones crossed to get to Rome from Toronto, that meant six days until I fully felt like myself again.
Jet lag stems from the sudden disruption of a process known as 'circadian rhythms'; the physical, mental and behavioral patterns we cycle through each and every day based on the patterns of lightness and darkness in our environment. Circadian rhythms, interestingly enough, are not only inbuilt in humans (for which the time-frame per cycle is approximately every 24 hours), but are also found in many living things, including animals and even plants, and affect us down to our very molecules. According to the United States' National Institute of General Medical Sciences, these rhythms influence our sleep-wake cycles, hormone release, appetite, and body temperature, among other bodily functions, and have been found to be related to obesity, diabetes, depression, bipolar disorder and seasonal affective disorder, when abnormal. Because the human circadian rhythm is slightly longer than 24 hours (24 hours and 11 minutes, give or take 16 minutes), jet lag takes a larger toll on us flying east than flying west, because an already long day, from a rhythmic perspective, becomes even longer.
What drives our circadian rhythm is groupings of molecules in cells throughout the body, known as 'biological clocks', that are regulated by a 'master clock' in our brain. This 'master clock', or the suprachiasmatic nucleus (SCN), as it is scientifically known, is located just above the optic nerve in the hypothalamus and consists of approximately 20,000 densely packed nerve cells. As our SCN is closely tied to our vision, it interprets light through specialized cells in the retina of our eyes; when we see bright light, such as morning sunlight, our SCN outputs our physiological response, like waking up, for instance, as well as our behavior, such as feeling ready to eat breakfast. When the sunlight fades, our response changes to ready us for sleep by our SCN signaling the pineal gland to start producing melatonin, the chief hormone in charge of making us feel sleepy. These changes to light are particularly sensitive when functioning normally, yet are also quite resistant to change.
The explanation of light reactivity, however, isn't as simple as it seems; if it were, we would simply re-adjust to whatever time zone we happened to find ourselves in without any underlying symptoms. A clearer picture lies in our genes: As discovered by the Salk Institute for Biological, there is a single gene responsible for jet lag known as LHX1. After identifying 213 genes expressed within the SCN, researchers found that one gene was fully responsible for regulating the light-dark genes, including one that creates vasoactive intestinal peptide or "Vip", an essential compound which directly affects cell-to-cell communication. When experiencing jet lag, because the nerve cells are so tightly packed in the SCN, not all of them communicate the change in light immediately, but rather , gradually, causing long lasting symptoms. In studies done on mice with induced 8-hour jet lag, researchers found that mice with little LHX1 adjusted much faster to their new environments, partly because their neurons were so out of sync to begin with. Interestingly, by giving them artificial Vip, synchronicity in their cells was restored.
In another study done on mice, deleting LHX1 from cells in the SCN altogether found remarkable results: Regardless of being in constant light or constant darkness, the mice with the deleted gene still slept the same amount as other mice (12 hours cumulatively, which is considered standard for mice), however they slept with no pattern whatsoever, whereas they would previously have only slept, unlike humans, during light-heavy times, and their body temperatures, which normally increase by a degree in the afternoon, similarly to humans, fluctuated with no fixed time pattern. Curiously enough, when researchers induced a fever into the LHX1 impaired mice, their synchronicity returned.
Thus, the researchers suggest that finding a way to lower the traces of the Vip compound or briefly blocking LHX1 in humans and deregulating synchronicity prior to traveling could hypothetically help alleviate symptoms, particularly if renewing synchronicity is as simple as inducing a temperature or exposing heat. These scientific findings are nevertheless still new, and the potential effects of deregulating synchronicity by disrupting the production of Vip in human beings is yet to be determined.
Elsewhere, at Oxford University, a team of researchers discovered a protein (known as SIK1) which deactivates photosensitive cells (cells specialized to detect light) also affect light intake and could potentially be another way of curing jet lag.
Until altering our genes or disrupting proteins in our brain becomes a reality, scientists have already identified safe and effective ways to lessen the desynchronization of our circadian rhythms. As it turns out, it's actually pretty simple:
According to researchers Charmane I. Eastman and Helen J. Burgess, "the most effective treatments for jet lag rely on shifting the circadian clock to the new time zone as fast as possible." The only current way of doing this successfully, the researchers note, is to strategically expose yourself to bright lights at planned times prior to traveling to lessen the impact of the new time zone. For example, when traveling east, it is important to advance your sleep schedule (or, get to bed earlier), so that the new time zone you'll find yourself in does not come as a shock. This means gradually setting back your sleep schedule and exposing yourself to bright light (approximately 5000 lux) for the first 3.5 hours after waking. This bright light can be found in the form of light boxes, generally sold for the purposes of Seasonal Affective Disorder. So, if your travels take you eastbound, depending on the time zones crossed (approximately 5-6 for Europe), spend a few days prior to traveling, try to get to bed earlier, increasing bedtime earlier in hour-long increments each day, and exposing yourself to bright light upon waking. The same is true - in reverse - if traveling westbound; get to bed gradually later and later.
Along with resetting your sleep schedule, the researchers suggest taking over-the-counter melatonin supplements, which has found to be helpful in shifting the circadian rhythm, despite it not being FDA approved as a treatment for jet lag. The researchers recommend taking melatonin post-flight and approximately 30 minutes before bed, but only in flights which cross less than 7-8 times zones. For any longer distances, it should be taken 2-3 days before travels. They also suggest taking a 3 mg dose 7.5 hours before sleep , or a 0.5 mg dose 4.5 hours before. According to the Mayo clinic, however, "doses as small as 0.5 milligram seem just as effective as doses of 5 milligrams or higher, although higher doses have been shown by some studies to be more sleep promoting." In any case, consult with your medical doctor first before purchasing or trying melatonin, to avoid potential side effects.
So, as Eastman and Burgess estimate, in a scenario where a woman is traveling eastbound from Chicago to Paris—a roughly nine hour flight crossing seven time zones—"four days before the flight, she [should] takes 0.5 mg of melatonin 4.5 hours before her usual sleep onset. That night she goes to bed 1 hour earlier than usual, and wakes up 1 hour earlier than usual. She gets intermittent bright light in the morning, preferably by going outside. The whole schedule is advanced by 1 h/day, [meaning she goes to bed earlier and earlier each day before her trip]. After landing in Paris, all the bright outdoor light she receives will help advance her circadian clock…and her sleep schedule [will] remain aligned throughout, and she should have little or no jet lag." Anything else lauded as a potential cure to jet lag, apparently, is simply a fad.
The true secret to beating jet lag: Planning and prevention. Happy Travels!
References:
Srinivasan, V., Singh, J., Brzezinski, A., Zakaria, R., Shillcutt, S. D., & Brown, G. M. (2014). Jet lag: use of melatonin and melatonergic drugs. In Melatonin and Melatonergic Drugs in Clinical Practice (pp. 367-378). Springer India.
Hatori, M., Gill, S., Mure, L. S., Goulding, M., O'Leary, D. D., & Panda, S. (2014). Lhx1 maintains synchrony among circadian oscillator neurons of the SCN. Elife, 3, e03357.
Jagannath, A., Butler, R., Godinho, S. I., Couch, Y., Brown, L. A., Vasudevan, S. R., ... & Steiner, G. (2013). The CRTC1-SIK1 pathway regulates entrainment of the circadian clock. Cell, 154(5), 1100-1111.
Eastman, C. I., & Burgess, H. J. (2009). How to travel the world without jet lag. Sleep medicine clinics, 4(2), 241-255.
NIGMS. (2012, November). Circadian Rhythms Fact Sheet. Retrieved August 17, 2017, from http://www.citationmachine.net/apa/cite-a-website/manual
