With increasing travel and global connectivity, more individuals need to recover from jet lag sooner and faster. The challenge is that the abrupt switch in light-dark conditions causes misalignment between the internal body clock and the new local time zone. The body clock is only able to shift by approximately 0.5-1 hour per day (1). Eastward travel is more difficult than westward travel as it requires advancing the circadian clock (2). Two-thirds of people traveling two or more time zones will experience symptoms, with increasing symptomology when traveling five or more time zones (3).
Jet Lag, Jet Lag Disorder, and Associated Symptoms
A shift in our circadian rhythm (to earlier or later) can cause various symptoms most call ‘jet lag’. Jet lag, by definition, is a temporary impairment of sleep or wakefulness that occurs when traveling rapidly (i.e., airplane travel) across 3 or more time zones (4). Jet lag is not the same as travel fatigue, which can result most typically due to the stress of travel and may or may not include a change of time zones. Travel fatigue may include symptoms such as general fatigue and headache (5).
After traveling two time zones or more, an individual can be medically diagnosed with Jet Lag Disorder if insomnia, excessive daytime sleepiness, and daytime impairment or symptoms are present one to two days after travel (5). Jet Lag Disorder can be diagnosed when all three criteria are met (Table 1), according to The International Classification of Sleep Disorders, 3rd Edition (6). Even when the full diagnostic criteria aren’t met, the symptoms are disruptive and are worth addressing.
A new phrase “social jet lag” has recently entered the lexicon. Social jet lag is defined as significantly shifting your sleep-wake schedule several days a week, without changing time zones (7). It is quantified by at least a 2-hour difference in the mid-sleep time on work days versus free days (8). Changing the sleep-wake schedule effectively changes the light-dark cues (9). Social jet lag is ubiquitous among people of various ages, including 25% of preschool children (10). Social jet lag is associated with a wide range of increased health risks, including metabolic syndrome and gestational diabetes (11), covid-19 infection (33% higher risk compared to 20% in those without social jet lag) (8), and increased inflammation (12). Social jet lag of less than or equal to 2 hours also impairs prosocial behaviors (13), and is associated with mild depression (14) and emotional eating (15).
Symptoms of jet lag can be pervasive, extending throughout many systems. People with jet lag can experience somatic complaints such as nausea, gastrointestinal (GI) upset, and loss of appetite to psychological effects such as greater anxiety, depressed mood, difficulty concentrating, and irritability along with disturbed sleep and daytime fatigue, which are the most common concerns reported (4,7,16,17). Symptoms will tend to worsen with an increasing number of times zones crossed and eastward travel (4). Additionally, some people are more prone to jet lag, particularly seniors, shift workers, and morning types (5,17). Other factors that make jet lag worse include short sleep duration or disrupted sleep before travel, excessive caffeine or alcohol intake, prolonged sitting, and stress during travel (17).
Hormone profiles may also be impacted. For instance, the cortisol circadian pattern is altered after long-distance travel eastward, with the 8 am cortisol depressed and 11 pm cortisol elevated from baseline levels collected before travel (18). Brain imaging showed changes in the functional brain network, along with decreased melatonin and increased thyroid hormone (19). These hormonal shifts likely contribute to jet lag.
Flight attendants and Athletes—what they reveal about the impact of jet lag
The two populations that have been the most extensively studied for the effects of travel across time zones are flight staff and athletes, as they can frequently encounter changes in time zone. Clinically, we can learn from these two populations about the effect jet lag has on a number of health concerns.
A large cross-sectional study of 5,366 flight attendants was conducted comparing the disease prevalence of flight attendants to those in the NHANES (National Health and Nutrition Examination Survey) population. A significantly higher prevalence of mental health symptoms and health conditions were found in this population, including but not limited to, female reproductive cancers and other cancers (any), depression, fatigue, and sleep disorders (20). Further, subjective jet lag is found to be increased in those flight attendants with mood impairment (21).
An observational study followed Olympic support staff for fifteen days after a long-haul eastward flight across eight time zones. Sleep duration, sleep efficiency, and morning cortisol took seven nights to recover to baseline levels. Moods were significantly impacted, including increased confusion, fatigue, and depression for three to seven days. While jet lag and fatigue were improved by day 7-15, reduced vigor remained through day 15 (the length of this study) (22). An analysis of 17,088 National Hockey League games demonstrated that travel in both directions, particularly the number of hours of circadian shift, impacts total season points (23). The body of research into the effects of jet lag on physical performance shows that peak performance seems especially impaired, potentially demoting “Olympic Gold” to silver or bronze medals, particularly when athletes travel eastward (24).
The findings demonstrate a need to implement sleep strategies prior to travel (especially eastward), and have implications for public health (especially frequent business travelers) who may not have the medical guidance to mitigate the negative effects of jet lag (20,22–24).
Jet Lag Strategies
There are several effective strategies to address jet lag, although this area is where more research could help refine and standardize recommendations. Specific phase-shifting protocols support the sleep phase during travel across time zones. Therapeutics include precisely-timed melatonin, light, and dark. These protocols are best known by sleep specialists (6).
Many studies support melatonin’s use in reducing the ill effects of jet lag and speeding up the normalization of circadian rhythms. In a Cochrane review, nine out of ten trials found that melatonin effectively reduced jet lag symptoms in travelers, with the most benefit to those traveling eastward or over five time zones (25). Multiple reviews found that between 0.5 mg to 5 mg of regular-release melatonin taken at bedtime was effective in countering jet lag for both eastward and westward travel (25,26). However, quicker sleep onset and better sleep were observed with the higher dose of 5 mg. It is worth noting that slow-release formulas did not provide the same benefit (25). Multiple studies report the benefits of 3 mg dosing melatonin to counteract jet lag symptoms (27–29).
In addition to melatonin supplementation, precisely timed bright light and exercise (“zeitgebers”) are known to aid in shifting the circadian phase. Research is underway to evaluate this combination therapy for the treatment of jet lag (1). Phase advancing for three nights before travel using melatonin and light therapy will also reduce the symptoms of jet lag disorder by preserving sleep total and architecture (30).
Minimize Jet Lag
General strategies to minimize jet lag:
Adhere to the home-base schedule entirely or as much as possible. For example, occupations that are very briefly in the destination, such as pilots, may choose not to adjust to local time at all (31). For others, such as vacationers, simply keeping a later vacation schedule than a home/work schedule can reduce the amount of circadian adjustment needed. By planning to go to bed during vacation at midnight, rather than 10 pm, the amount of circadian adjustment needed is reduced by 2 hours.
Minimize light exposure before bed. Consider the use of blue light-blocking glasses for 1-2 hours before bedtime or eye masks when sleeping (32).
Increase outdoor light exposure in the morning when traveling eastward; outdoor light exposure in the evening when traveling westward (5). One hour of bright light (>8000 lux) in the first half of the day will advance the circadian phase by 1.20 hours while receiving that light cue in the evening will delay the body clock by 2.02 hours (33).
Utilize apps for mobile devices to help adjust time zones by giving optimal light-dark schedules. Those who more closely follow the recommendations report better mood (34).
Exercise at 7 am or between 1-4 pm will shift sleep earlier, and therefore could be helpful when traveling eastward. Exercise in the evening between 7-10 pm will delay sleep, and therefore can be helpful when traveling westward (35).
Implement general sleep hygiene techniques such as sleeping in a cool, dark room, using noise-canceling headphones, and avoiding caffeine and other stimulants.
Plan distinct meals without snacking in between. If you are suffering from GI upset due to jet lag, eating light, healthy meals may help. Meal timing will impact the body clock. Breakfast will phase advance the circadian rhythm, while late dinners will delay it (36).
Limit caffeine and alcohol intake in the afternoon and evening. Caffeine also impacts the circadian rhythm by extending tau, in effect causing a delay (37). For that reason, when traveling eastward it is best to avoid caffeine later in the day. Additionally, caffeine and melatonin are metabolized through the same enzymatic pathway, cytochrome (CYP) 1A2. Concurrent use of melatonin supplementation with caffeine can influence melatonin levels (38). Further, those with a genetic variation in CYP1A2, causing them to be a ‘fast metabolizer’ will impact the amount of melatonin that may be needed to offset symptoms of jet lag.
Additional strategies for traveling more than 6 time zones
When traveling more than six time zones, especially eastward, specific plans should take into account the travelers’ duration of stay, the purpose of travel, and schedule flexibility along with their habitual sleep patterns. A personalized plan can be designed based on the research findings available to date. In addition to the recommendations provided in Table 2:
For time zone changes of 7-11 hours eastward:
Begin advancing the sleep-wake schedule with low-dose melatonin, taken 6 hours before current location bedtime, three (3) nights before travel (30)
Take melatonin at bedtime upon arrival at the new location for four (4) nights.
For time zone changes of 12 hours eastward:
Follow all the above recommendations
Shift your circadian rhythm later by taking melatonin in the morning, and getting light in the evening (31).
Jet travel is a permanent feature of the modern lifestyle, with the number of flights increasing year over year. As our circadian rhythm is entrained to our local environment, rapid travel to a new environment causes circadian misalignment. The symptoms and consequences are due to the misalignment between our body clock and the light-dark cues provided in our new destination. Common immediate symptoms are wide-ranging from digestive upset and hormone changes to mood impairment and decreased vigor. The long-term consequences for people who travel regularly include an increased risk of some cancers, along with depression, fatigue, and sleep disorders.
Fortunately, strategies such as precisely timed melatonin, light exposure, and darkness aid in adjusting to the new destination, and minimizing symptoms. These strategies are best when personalized to the individual’s habitual sleep patterns, degree of the time change, and schedule on arrival.
Author: Catherine Darley, ND
Reviewers: Deanna Minich, PhD & Kim Ross, DCN
Last updated: February 13, 2023
1. Youngstedt SD, Elliott J, Patel S, Zi-Ching Mak N, Raiewski E, Malek E, et al. Circadian acclimatization of performance, sleep, and 6-sulfatoxymelatonin using multiple phase shifting stimuli. Front Endocrinol (Lausanne). 2022 Nov 16;13.
2. Herxheimer A. Jet lag. BMJ Clin Evid. 2014 Apr 29;2014.
3. Polymeropoulos CM, Polymeropoulos VM, Czeisler EL, Fisher MA, Smieszek SP, Xiao C, et al. Once-daily tasimelteon (VEC-162) for jet lag following transmeridian travel: A multicenter, randomized, double-blind, placebo-controlled trial. Front Neurol. 2022 Sep 15;13.
4. Janse van Rensburg DC, Jansen van Rensburg A, Fowler PM, Bender AM, Stevens D, Sullivan KO, et al. Managing Travel Fatigue and Jet Lag in Athletes: A Review and Consensus Statement. Vol. 51, Sports Medicine. 2021.
5. Ambesh P, Shetty V, Ambesh S, Gupta S, Kamholz S, Wolf L. Jet lag: Heuristics and therapeutics. J Family Med Prim Care. 2018;7(3).
6. Sateia MJ. International Classification of Sleep Disorders-Third Edition. Chest. 2014 Nov;146(5):1387–94.
7. Walker WH, Walton JC, DeVries AC, Nelson RJ. Circadian rhythm disruption and mental health. Vol. 10, Translational Psychiatry. 2020.
8. Coelho J, Micoulaud-Franchi JA, Wiet AS, Nguyen D, Taillard J, Philip P. Circadian misalignment is associated with Covid-19 infection. Sleep Med. 2022;93.
9. Diekman CO, Bose A. Beyond the limits of circadian entrainment: Non-24-h sleep-wake disorder, shift work, and social jet lag. J Theor Biol. 2022 Jul;545:111148.
10. Giannoumis M, Mok E, Borkhoff CM, Birken CS, Maguire J, Parkin PC, et al. Association of accelerometry-derived social jetlag and sleep with temperament in children less than 6 years of age. Journal of Clinical Sleep Medicine. 2022 Aug;18(8):1993–9.
11. Hashemipour S, Lalooha F, Ghorbani A, Habibi Nozari F, Badri M, Agha Abbaslou M, et al. Association of social jetlag with gestational diabetes: Qazvin Maternal and Neonatal Metabolic Study. Chronobiol Int. 2022 Sep 2;39(9):1226–32.
12. Girtman KL, Baylin A, O’Brien LM, Jansen EC. Later sleep timing and social jetlag are related to increased inflammation in a population with a high proportion of OSA: findings from the Cleveland Family Study. Journal of Clinical Sleep Medicine. 2022 Sep;18(9):2179–87.
13. Long Z, Zhao A, Chen Y, Li R, Xia Y, Guo Y, et al. The associations of chronotype and social jetlag with prosocial behavior problems among Chinese adolescents. Chronobiol Int. 2022 Nov 2;39(11):1498–507.
14. Qu Y, Li T, Xie Y, Tao S, Yang Y, Zou L, et al. Association of chronotype, social jetlag, sleep duration and depressive symptoms in Chinese college students. J Affect Disord. 2023 Jan;320:735–41.
15. Vrabec A, Yuhas M, Deyo A, Kidwell K. Social jet lag and eating styles in young adults. Chronobiol Int. 2022 Sep 2;39(9):1277–84.
16. Waterhouse J, Reilly T, Atkinson G, Edwards B. Jet lag: trends and coping strategies. Vol. 369, Lancet. 2007.
17. Srinivasan V, Spence DW, Pandi-Perumal SR, Trakht I, Cardinali DP. Jet lag: Therapeutic use of melatonin and possible application of melatonin analogs. Travel Med Infect Dis. 2008;6(1–2).
18. Paragliola RM, Corsello A, Troiani E, Locantore P, Papi G, Donnini G, et al. Cortisol circadian rhythm and jet-lag syndrome: evaluation of salivary cortisol rhythm in a group of eastward travelers. Endocrine. 2021;73(2).
19. Zhang F, Li W, Li H, Gao S, Sweeney JA, Jia Z, et al. The effect of jet lag on the human brain: A neuroimaging study. Hum Brain Mapp. 2020;41(9).
20. McNeely E, Mordukhovich I, Tideman S, Gale S, Coull B. Estimating the health consequences of flight attendant work: Comparing flight attendant health to the general population in a cross-sectional study. BMC Public Health. 2018;18(1).
21. Ruscitto C, Ogden J, Ellis JG. To what extent is circadian phase predictive of subjective jet lag in long-haul cabin crew pre- and post-trip? Appl Ergon. 2023 Jan;106:103882.
22. Rossiter A, Comyns TM, Sherwin I, Nevill AM, Campbell MJ, Warrington GD. Effects of long-haul transmeridian travel on physiological, sleep, perceptual and mood markers in Olympic team support staff. Chronobiol Int. 2022 Dec 2;39(12):1640–55.
23. Charest J, Cook JD, Bender AM, Walch O, Grandner MA, Samuels CH. Associations between time zone changes, travel distance and performance: A retrospective analysis of 2013–2020 National Hockey League Data. J Sci Med Sport. 2022 Dec;25(12):1008–16.
24. Jasper SC, Leenders MAAM, O’Shannassy T. Travel across time zones and the implications for human performance post pandemic: Insights from elite sport. Front Public Health. 2022 Dec 2;10.
25. Herxheimer A, Petrie KJ. Melatonin for the prevention and treatment of jet lag. Vol. 2010, Cochrane Database of Systematic Reviews. 2002.
26. Chan V, Wang L, Allman‐farinelli M. Efficacy of functional foods, beverages and supplements claiming to alleviate air travel symptoms: Systematic review and meta‐analysis. Vol. 13, Nutrients. 2021.
27. Eastman CI, Burgess HJ. How to Travel the World Without Jet Lag. Vol. 4, Sleep Medicine Clinics. 2009.
28. Takahashi T, Sasaki M, Itoh H, Ozone M, Yamadera W, Hayshida KI, et al. Effect of 3 mg melatonin on jet lag syndrome in an 8-h eastward flight. In: Psychiatry and Clinical Neurosciences. 2000.
29. Paul MA, Miller JC, Gray GW, Love RJ, Lieberman HR, Arendt J. Melatonin treatment for eastward and westward travel preparation. Psychopharmacology (Berl). 2010;208(3).
30. Garbellotto L, Petit E, Brunet E, Guirronnet S, Clolus Y, Gillet V, et al. Gradual Advance of Sleep-Wake Schedules Before an Eastward Flight and Phase Adjustment After Flight in Elite Cross-Country Mountain Bikers: Effects on Sleep and Performance. J Strength Cond Res. 2022 Sep 22;
31. Choy M, Salbu RL. Jet lag: current and potential therapies. P T. 2011 Apr;36(4):221–31.
32. Zerbini G, Kantermann T, Merrow M. Strategies to decrease social jetlag: Reducing evening blue light advances sleep and melatonin. European Journal of Neuroscience. 2020;51(12).
33. St Hilaire MA, Gooley JJ, Khalsa SBS, Kronauer RE, Czeisler CA, Lockley SW. Human phase response curve to a 1 h pulse of bright white light. Journal of Physiology. 2012;590(13).
34. Christensen S, Huang Y, Walch OJ, Forger DB. Optimal adjustment of the human circadian clock in the real world. PLoS Comput Biol. 2020;16(12 December).
35. Youngstedt SD, Elliott JA, Kripke DF. Human circadian phase–response curves for exercise. Journal of Physiology. 2019;597(8).
36. Takahashi M, Tahara Y. Timing of Food/Nutrient Intake and Its Health Benefits. J Nutr Sci Vitaminol (Tokyo). 2022 Nov 30;68(Supplement):S2–4.
37. Narishige S, Kuwahara M, Shinozaki A, Okada S, Ikeda Y, Kamagata M, et al. Effects of caffeine on circadian phase, amplitude and period evaluated in cells in vitro and peripheral organs in vivo in PER2::LUCIFERASE mice. Br J Pharmacol. 2014;171(24).
38. Minich DM, Henning M, Darley C, Fahoum M, Schuler CB, Frame J. Is Melatonin the “Next Vitamin D”?: A Review of Emerging Science, Clinical Uses, Safety, and Dietary Supplements. Nutrients [Internet]. 2022;14(19). Available from: https://www.mdpi.com/2072-6643/14/19/3934/htm