Jet lag

Definition, causes and symptoms

Jet lag, also known as hourly imbalance or dyssynchrony, is a change in the biological cycle or circadian rhythm after a time zone change, especially when traveling by plane. This biological cycle that lasts approximately 24 hours has an impact on sleep, mood, immune system and metabolism.
The more time zones a person crosses, the more severe the symptoms will be. Thus, a trip from São Paulo to Sydney (Australia) can be very tiring.

The main symptoms of jet lag are sleep disturbances, particularly trouble sleeping, especially when traveling east. For example, a person traveling from Paris to Beijing will likely find it difficult to sleep for the first few days as the day gets shorter. On the other hand, a trip west from São Paulo to Los Angeles will be a little easier as the day gets longer. In this case, however, the person may feel tired during the day.

These sleep disorders originate in the secretion of melatonin, a hormone that plays a crucial role in regulating sleep.

The consequences of sleep disorders are often tiredness during the day and also difficulty concentrating. Other symptoms such as digestion and intestinal transit disorders may also occur. Because of changes in cortisol secretion, the body may also suffer from physical or psychological symptoms.

Very young children tend to suffer more from jet lag than adults.

It is estimated that it takes about a day for the body to adapt to 1 hour of commuting. In other words, it will take 3 days to adapt to a new 3 hour time zone, 8 days to adapt to 8 hours, etc. It is important to point out that trips to the east are more difficult than those to the west.

But 2 time zones (usually 2 hours) can already lead to jet lag.


There are few effective drug treatments for this condition.

Doctors sometimes advise using melatonin. An amount of 0.5 mg of melatonin already seems to be enough to have an effect on sleep. It is advisable to take melatonin 30 minutes before going to sleep. It is also important to avoid consuming alcohol if you are taking melatonin.

The American newspaper Prevention estimated in a 2019 edition that the maximum amount of melatonin to be used in case of jet lag was 3 mg. A dose greater than 3 mg may have the opposite effect and disrupt the circadian rhythm.

Modafinil, a psychic stimulant drug sold in most countries by prescription, is sometimes prescribed by doctors in cases of jet lag to keep the person awake.

Sleeping pills – sleeping pills
Taking zolpidem or ramelteon (sold privately under the brand name Rozerem® in the US and Brazil) on the first night after traveling east for a period of 3 to 4 nights helped to improve sleep1.


– A few days before your departure, try to adapt to your new destination. For example, if you are traveling east (eg New York to Paris), 3 days before your departure, try to wake up early (30 minutes before your usual time) and sleep earlier, to be closer to the new timezone. Keep your bedroom dark throughout your sleep period.

– Avoid alcohol and coffee. Coffee may seem like a good ally in the fight against fatigue caused by jet lag, but it tends to disrupt sleep, especially at bedtime. While traveling east, during the flight and 1 to 2 days after arriving at your destination, avoid caffeine consumption.

– Drink plenty of water and eat a light diet (for example, fruits and vegetables). Avoid caffeine-rich products like soda and coffee .

– If you board a night flight, avoid taking sleeping pills. However, if you have a fear of flying or find it difficult to sleep in an airplane seat, consult your doctor, who may be able to prescribe something to help you sleep. You can also find over-the-counter sleeping pills at pharmacies, such as some antihistamines.

– Once at your destination, try to adapt to the new time zone, especially sleeping and waking times, and main meals. However, set aside the first day to rest.

However, for a person traveling only for a few days in a new time zone, such as during a business trip, it might be advisable, if possible, to stay in the rhythm of the time zone you live in. For example, a business person who lives in New York and has traveled a few days in Europe, instead of scheduling meetings in the morning around 08:00 or 09:00 (Paris time) could plan them for 11:00 or 12:00, a time closer to the start of the day in New York. This allows this person to be more rested and therefore more productive thanks to a longer night’s sleep.

– When taking a long-haul flight, if possible choose an overnight flight that arrives at your destination in the morning. You will benefit from an arrival in daylight, which will make it easier for you to pace yourself. Avoid sleeping during the day, even if you are tired, wait for the night to go to sleep when you are at your new destination. In case of extreme fatigue on the day of arrival, take a nap of a maximum of 1 hour and before 2 pm (time at the new destination).

Jeanne Kenney
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I’m a stylist trainer, a content creator, and an entrepreneur passion. Virgo sign and Pisces ascendant, I move easily between my dreams, the crazy world I want, and my feet on the ground to carry out my projects.

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