What is jet lag?
Jet lag is a temporary sleep problem that can affect anyone who quickly travels between time zones.
Our biological clock is usually synchronized with local time so that we feel hungry in the morning and sleepy in the evening.


Jet lag is a common condition that sometimes occurs after long distance flights. It is the result of your body finding it difficult to adjust to a new time zone. (1)

Symptoms
Symptoms of jet lag can vary. You may experience only one symptom, or you may have many (2). The symptoms of jet lag include:
• Fatigue
• Sleepiness
• Digestive upsets
• Memory lapses
• Irritability
Irregular periods
It's also quite common for women to see an impact on the timing of their menstrual cycles often delayed (3).
And for those who are taking oral contraception - or any other drugs - switching to the schedule of the new time zone may be a source of complications.

Expected Duration
For each time zone crossed during travel, it takes about one to three days to adjust to the new environment. For example, it can take up to three days for a person traveling from California to New York to feel "normal" again. If that person travels back to California after adjusting to New York time, it can take another three days to readjust to California time, approximately one day for each hour of time zone changes. Older people seem to be hit harder by jet lag and may require a little more time to adjust.


Long-term consequences
People who do not fly frequently are unlikely to develop more serious chronic physical problems as a result of jet lag.
But studies involving flight crews or shift workers have documented the debilitating physical health effects of repeated jet lag. The risk of gaining weight and of developing metabolic conditions like type 2 diabetes seems to be heightened.
 

Jet lag and professional athletes
Global travel and international  sport competition are inevitable for the modern-day athlete and sports team. Jet lag can cause disarray for the individual athlete as well as for the whole team (4).

Jet lag (and the resulting sleep loss) is one of the biggest contributors to decreased athletic performance after air travel, negatively affecting an athlete’s accuracy and reaction time, as well as increasing their chance of making errors (5).
it is likely that the symptoms of jet lag could result in decreased sports performance due to both physiological and emotional factors (6).

Jet lag and air crew
Pilots and aircrew often travel across time zones and work when others would normally be asleep. This can disrupt normal sleep patterns which can lead to fatigue,
and affect  performance. For crew members on duty during long-distance flights, this means that they are not always optimally rested at the beginning of their work and that periods of increased fatigue and decreased attention may occur.
The high velocity of aircraft is another reason for jetlag. If more than 15 to 22,5 meridians per day are not exceeded, the resulting temporal difference of 60 to 90 minutes may possibly be balanced by the adaptability of the human circadian rhythm. For this reason, jet-lag does not occur with travel by ship, train or automobile(7).


Tips to deal with jet lag
Get medical advice
If you have a medical condition that requires monitoring, such as diabetes or high blood pressure, or if you know you struggle with jet lag, consult your physician well in advance of your departure.

Before Travel
• Exercise eat a healthful diet and get plenty of rest.
• A few days before you travel, if you can, begin adjusting your body clock to the time zone at your destination. Go to bed an hour or two later than usual (if you are traveling west) or an hour or two earlier than usual (if you are traveling east) to get used to the time change (8) .
During Travel
During the flight, you should:
• Drink plenty of fluid - And Limit caffeine consumption.
• Keep active - if you are flying long distances, walk around the cabin occasionally and regularly stretch your arms and legs when you are sitting down.
• Change your watch when you board the plane so that it matches the time of your destination.
• Get some sleep - if it is night-time at your destination, try to get some sleep. You may find ear plugs or eye masks useful.
On Arrival at the Destination
• Adapt to the local schedule as soon as possible. However, if the travel period is 2 days or less, travelers should remain on home time.
• Optimize exposure to sunlight following arrival in either direction.
• Eat meals appropriate to the local time.

Medications, Alcohol and jet lag 
Using medication to prevent jetlag is controversial and should be discussed with your doctor. There have been reports of some benefits from melatonin or sedatives. However, The U.S. Food and Drug Administration (FDA) does not regulate melatonin and its safety is not established (9).

It is not recommended that you use sleeping tablets during your flight. Some travelers use alcohol to help them get to sleep, but this actually disrupts the normal sleep cycles and can prolong jet lag (10).


References
1- Harvard Health website, 2020, https://www.health.harvard.edu/a_to_z/jet-lag-a-to-z
2- Mayo clinic, 2021, https://www.mayoclinic.org/diseases-conditions/jet-lag/symptoms-causes/syc-20374027
3- Patient Website, UK, https://patient.info/news-and-features/
4- Aspetar Sports Medicine Journal 2021, https://www.aspetar.com/journal/viewarticle.aspx?id=474#.YDSsYuQ7YSl
5- Leaders website 2021. found on: https://leadersinsport.com/ performance
6- Verywell, Dotdash publishing 2021://www.verywellfit.com/does-jet-lag-decrease-athletic-performance-3120789
7- Institute of aerospace medicine, https://www.dlr.de/me/en/desktopdefault.aspx/tabid-2023/2958_read-4535/
8- Centers for Disease Control and Prevention US, 2019, https://wwwnc.cdc.gov/travel/page/jet-lag
9- Stat Pearls [Internet] 2021. https://www.ncbi.nlm.nih.gov/books/NBK534823/
10- Better Health, Victoria, Australia 2020, www.betterhealth.vic.gov.au/health/healthyliving/jet-lag