August 2020 | Reviewed by: Reeba Mathew, MD and Virginia Skiba, MD
What is jet lag?
Jet lag occurs when you travel across time zones and have trouble adjusting to the new schedule. It is most common after air travel, due to the speed with which time zones are crossed. When you arrive at your destination, your sleep-wake cycle may still be aligned with the previous time zone. Your body may expect to sleep when it is daytime in the new time zone or be awake when you are supposed to sleep.
Jet lag is a temporary condition. It may begin after you travel across at least two time zones. The severity of the jet lag depends on how many time zones you cross and which direction you traveled. Flying east is usually more difficult of an adjustment than westward travel. It is estimated that it takes one day per time zone for your body clock to fully adjust to local time.
You may have a difficult time functioning when you are jet lagged. You may not feel awake and alert when you need to do your job, socialize or sightsee. Anyone of any age can have jet lag, although older adults are likely to have more severe jet lag and may need a much longer time to recover. Some people can adjust more quickly than others to rapid shifts in time zones. Pilots, flight attendants and business travelers are most likely to have jet lag due to their lifestyle.
Jet lag can be worsened by:
- Sleep loss due to travel
- Spending a long time sitting in an uncomfortable position, such as in an airplane
- Caffeine and alcohol use
- Air pressure or poor air quality
Jet lag is a circadian rhythm sleep disorder. Your circadian rhythms are your body’s internal clock that signals when you are supposed to feel sleepy or alert. Your body’s clock operates on a roughly 24-hour schedule. It uses sunlight to determine how much of the sleep-promoting hormone melatonin to produce. Melatonin production is high during the evening and very low during the day. As a result, you are alert during the daytime and sleepy at night.