A friend of mine was going to do a two-week international trip flying from the United States to China with a time zone difference of more than 12 hours. Upon arrival, she would need to attend to some pressing family businesses, then head back to the United States (another 12-hour time difference) and plan to go to work the next day. Sounds like a typical international business trip or vacation.
Traveling across time zones can disrupt a person's natural rhythm, causing jet lag. It usually takes a few days to adjust, and the adaptation time depends on factors like the time difference and exposure to light. Eastbound flights tend to worsen symptoms compared to westbound ones. Research suggests that melatonin can help alleviate jet lag symptoms for travelers (1).
Melatonin is known as the hormone of darkness; in all mammals, it is secreted during the hours of darkness and falls precipitately with light onset. The circadian rhythm-generating system controls the secretion of melatonin from the pineal gland, but melatonin also influences the circadian system's regulation of rhythms. Several studies have reported the beneficial effect of melatonin on jet lag (1).
One study investigated the efficacy of oral melatonin in alleviating jet lag in flight crew after a series of international flights. The optimal time for taking melatonin in this group was also investigated. In a double-blind placebo-controlled trial, 52 international cabin crew were randomly assigned to three groups; early melatonin (5 mg started 3 days before arrival until 5 days after the trip); late melatonin (placebo for 3 days then 5 mg melatonin for 5 days); and placebo (2).
Daily ratings showed a trend in jet lag, mood, and sleepiness measures toward an improved recovery in the late melatonin group and a worse recovery in the early melatonin group as compared to placebo. Retrospective ratings made 6 days after arrival showed the late melatonin group reported significantly less jet lag (37.7 ± 28.8) and sleep disturbance (24.2 ± 24.2) following the flight compared to placebo (64.7 ± 24.3 and 53.9 ± 28.8, respectively, and p<0.05). The late melatonin group also showed a significantly faster recovery of energy and alertness than the early melatonin group, which reported a worse overall recovery than placebo. These findings showed that melatonin might have potential benefits for international air travel (2).
One study focused on elite athletes flying 12 time zones found that timely use of melatonin, exposure to light, and physical exercise helped in resynchronization. Upon arriving in Tokyo from Buenos Aires, soccer players and coaches took 3 mg of melatonin daily at their expected bedtime. Additionally, they engaged in outdoor physical exercise during specific times (from 08:00 to 11:00 hours in the morning and from 13:00 to 16:00 hours in the afternoon), avoiding sunlight or exercise at other times (3).
Notably, sleep quality and morning alertness in Tokyo were significantly linked to pre-flight 6-sulphatoxymelatonin (a melatonin metabolite) excretion. The average resynchronization rate of the sleep-wake cycle to the 12-hour time shift was 2.13 ± 0.88 days, much quicker than the expected minimum of 6 days after a 12-time-zones flight. These findings suggested that combining melatonin treatment, a well-timed environmental light schedule, and appropriate physical exercise could effectively help elite athletes overcome the effects of jet lag (3).
A retrospective study analyzed data from normal volunteers flying between Buenos Aires and Sydney via a transpolar route. The study included 75 volunteers (46 males) for the eastbound flight (Buenos Aires–Sydney) and 59 volunteers (34 males) for the westbound flight (Sydney–Buenos Aires). Participants were free from organic or psychiatric disorders, neurological history, and substance abuse (4).
For the eastbound study, all subjects received a fast-release preparation containing 3 mg of melatonin daily 30 minutes before the expected sleeping time at Sydney immediately after leaving Buenos Aires and for the time of the study. Upon arrival at Sydney, the subjects were advised to perform their routine normally and to walk outdoors for at least 30 minutes at two restricted periods (from 08:00 to 11:00 hour in the morning and from 13:00 to 16:00 hour in the afternoon). They were advised to maintain a symmetrical activity distribution (i.e., the same duration of exercise at both daily times). Exposure to sunlight at other times of the day was reduced by using regular dark sunglasses (4).
In the westbound study, volunteers returned to Buenos Aires on a transpolar flight, continuing melatonin use in Australia. On the flight day to Buenos Aires, they received a single 3 mg dose of melatonin at the expected bedtime and continued for 8 days. Similar to the eastbound study, participants maintained their routine, walked outdoors at specific times (from 08:00 to 11:00 hour in the morning and from 13:00 to 16:00 hour in the afternoon), and used sunglasses to reduce sunlight exposure during other times. Sleep log diaries were recorded from day -2 (in Sydney) to day 8 in Buenos Aires (4).
Diaries included sleep quality, bedtime, wake time, awakening episodes, and overall sleep information. Participants graphically rated daily sleep quality, morning freshness, and alertness on a scale from 0 to 10. Global assessments were derived, and individual actograms were constructed. The resynchronization rate, or the time taken to reach baseline, was calculated (4).
Results showed that the multifaceted approach (melatonin, light exposure, physical exercise) effectively hastened resynchronization for both eastbound and westbound flights. The average resynchronization rate was 2.27±1.1 days for the eastbound flight and 2.54 ±1.3 days for the westbound flight, notably faster than the expected 7–9 days without treatment after a 13-hour flight (4).
Overall, these findings suggest that taking melatonin at the recommended dose and timing, along with proper light exposure and physical activity, can greatly reduce the time it takes to overcome jet lag. So, it might be a good idea to consider using melatonin for future international trips.
References:
1. Gregory M. Brown; Seithikurippu R. Pandi-Perumal; Ilya Trakht; Daniel P. Cardinali (2009). Melatonin and its relevance to jet lag. , 7(2), 69–81. doi:10.1016/j.tmaid.2008.09.004
2. Petrie K, Dawson AG, Thompson L, Brook R. A double-blind trial of melatonin as a treatment for jet lag in international cabin crew. Biol Psychiatry. 1993 Apr 1;33(7):526-30. doi: 10.1016/0006-3223(93)90007-z. PMID: 8513037.
3. Cardinali DP, Bortman GP, Liotta G, Pérez Lloret S, Albornoz LE, Cutrera RA, Batista J, Ortega Gallo P. A multifactorial approach employing melatonin to accelerate resynchronization of sleep-wake cycle after a 12 time-zone westerly transmeridian flight in elite soccer athletes. J Pineal Res. 2002 Jan;32(1):41-6. doi: 10.1034/j.1600-079x.2002.10820.x. PMID: 11841599.
4. Cardinali DP, Furio AM, Reyes MP, Brusco LI. The use of chronobiotics in the resynchronization of the sleep-wake cycle. Cancer Causes Control. 2006 May;17(4):601-9. doi: 10.1007/s10552-005-9009-2. PMID: 16596316.
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