What Causes Jet Lag?


Jet lag occurs when a person's internal clock conflicts (1) with environmental cues like the sun rising or setting. This condition usually affects people who travel across many time zones (2). Most people who experience jet lag feel excessively fatigued or sleepy (3) in a new time zone.

What is Jet Lag?

Jet lag is the result of out-of-sync circadian rhythms. Circadian rhythms are the body's natural fluctuations in sleep, appetite, and other functions due to external day-and-night patterns. Jet lag affects people of all ages, but its effects are more pronounced in older adults (4), whose bodies typically take longer to readjust.

Why Do You Get Jet Lag?

Sleep deprivation and interrupted circadian rhythms cause jet lag. Under normal conditions, the body naturally induces sleep in the evening by reducing its core body temperature and increasing melatonin secretions. Melatonin is a sleep-promoting hormone (5). When a person's internal clock does not match the local timing of sunrise and sunset, core body temperature and melatonin levels do not signal the body to be sleepy or alert at appropriate times.

After a long flight, the body's internal clock needs time to adjust to the new time zone. Exposure to natural bright light can help the shift, but the change does not occur right away.

Certain factors affect the level of jet lag. The body's sleep-wake cycle is slightly more than 24 hours, and it is easier to lengthen a day than shorten it. Therefore, people who travel eastward have more difficulty with jet lag than westbound travelers.

The number of time zones traveled is another factor. Circadian disruptions become more severe as the distance increases. Travel time also impacts jet lag intensity.

An individual's circadian rhythms slowly adapt to the new time zone after a few days. Without any treatment for jet lag, eastbound travelers' circadian rhythms adjust by one time zone per day. Westward travelers usually adjust by 1.5 times zones per day.

What Are Jet Lag Symptoms?

As a result of jet lag, many people struggle to get uninterrupted sleep (6) and are not able to perform physical and mental tasks as effectively. Fatigue, depression, irritability, concentration difficulties, and digestive issues are additional symptoms.

People who fly east typically suffer poor sleep and can find it challenging to fall asleep. Travelers might rise too early after traveling west.

Jet lag may look like travel fatigue, but the two conditions are different. Traveling across three or fewer time zones might result in travel fatigue, which is generalized tiredness that quickly disappears. Travel fatigue is not related to disruptions in circadian rhythm.

How to Reduce Jet Lag

Fortunately, there are a number of approaches you can use to reduce the effect jet lag has on your mood and energy level while traveling. Consider the following methods before your next trip.

Make Preparations

In anticipation of travel (7), get exercise, eat healthy foods, and get enough sleep. To begin the time zone adjustment a few days before departure, try going to bed an hour or two earlier if traveling east or an hour or two later if traveling west. If schedules allow, get to your destination a day or two ahead of any planned events or activities so that you have time to adjust to the new time zone.

Take Care in the Air

While in an airplane, stick with smaller meals, and avoid caffeine. Alcohol can disrupt sleep, and should also be avoided. Talk to a doctor before taking sleep-inducing medications on a flight, as these medications could increase the likelihood of blood clots while flying.

Consider Trip Length

If you will be in the area for two or more days, follow the local day and night schedules if possible. If you will be spending two or fewer days in a new time zone, you might be better off keeping your home sleep-wake schedule in order to minimize jet lag's effects when you return.

Spend Time in the Sun

Sunlight exposure can offset jet lag. When natural light is limited, timed light exposure can help recalibrate circadian rhythms. After a westbound trip, travelers should get light exposure in the evening. Sunlight exposure in the morning is the best time after eastbound journeys.

Melatonin, Caffeine, and Medication

Short-term use of a melatonin supplement (8) may help with jet lag. It is best for travelers who have previous jet lag experience, travel across five or more time zones, and venture east. People who make shorter trips can also get relief from melatonin, especially if they take it in the afternoon or evening (9).

For people who travel shorter distances for one to two days, consuming caffeine to treat daytime fatigue might be a better option than taking melatonin at night.

Medications that help to induce sleepiness at night or that promote alertness during the day may be an option (10) for managing jet lag. Speak with your doctor if you are interested in these medication options in order to understand the potential risks and benefits.

Jet lag is a sleep disorder common among travelers of all ages. This condition can have some detrimental effects on cognition and motor skills. However, most travelers can take steps to reduce the impact of jet lag.


+ 10 Sources
  1. 1. Accessed on March 29, 2021.https://pubmed.ncbi.nlm.nih.gov/19147377/
  2. 2. Accessed on March 29, 2021.https://pubmed.ncbi.nlm.nih.gov/32066704/
  3. 3. Accessed on March 29, 2021.https://pubmed.ncbi.nlm.nih.gov/30112298/
  4. 4. Accessed on March 29, 2021.https://pubmed.ncbi.nlm.nih.gov/21572778/
  5. 5. Accessed on March 29, 2021.https://www.nccih.nih.gov/health/melatonin-what-you-need-to-know
  6. 6. Accessed on March 29, 2021.https://wwwnc.cdc.gov/travel/yellowbook/2020/travel-by-air-land-sea/jet-lag
  7. 7. Accessed on March 29, 2021.https://wwwnc.cdc.gov/travel/page/jet-lag
  8. 8. Accessed on March 29, 2021.https://pubmed.ncbi.nlm.nih.gov/12076414/
  9. 9. Accessed on March 29, 2021.https://pubmed.ncbi.nlm.nih.gov/12047605/
  10. 10. Accessed on March 29, 2021.https://pubmed.ncbi.nlm.nih.gov/30167980/

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