Jet lag is a circadian rhythm sleep disorder that occurs when your internal clock’s schedule does not match the wake-sleep cycle where you are currently located. Your body’s clock runs a roughly 24-hour cycle and uses sunlight to regulate melatonin production and release. Melatonin levels rise sharply during the evening and decline to very low levels during daylight hours.
Jet lag typically occurs with long-distance air travel when you are crossing three or more time zones. With circadian rhythm misalignment, you may have trouble adjusting your sleep-wake cycle and other bodily rhythms to the new time zone. This may lead to feeling sleepy during the day, having difficulty functioning during the day, or not being able to fall sleep at an appropriate time.
The severity of jet lag depends on how many time zones you cross and in which direction. Often flying east is much more disruptive than flying west. A rough estimation for the duration of the adjustment is one day per time zone crossed. The ability to adjust to jet lag also varies among individuals.
Jet lag is a temporary condition and resolves when the internal clock adjusts to the new time zone. However, for certain populations, such as pilots and business travelers, the chronic state of an out-of-sync circadian rhythm can lead to other sleep disorders, such as insomnia. Common sleep disorder symptoms may include:
According to the American Academy of Sleep Medicine, if you answer “yes” to the following questions, then you may have jet lag:1
Plan ahead—Getting sufficient or additional sleep several nights before travel can help you by “banking” sleep. Apps are available to help you plan for your adjustment to a new time zone, such as Jet Lag Rooster by Sleepopolis. Just input your departure city/date/time and arrival city/date/time, and the app provides a schedule of sleep and wake adjustments prior to departure to minimize the effects of jet lag.
Melatonin—Melatonin is produced by the pineal gland and signals the brain to fall sleep. It can be used to phase shift your sleep earlier by taking a melatonin tablet in the late afternoon or early evening; however, taking it at the wrong time can further misalign your internal clock. In the U.S., melatonin is sold as a supplement and is not well regulated so the actual content of melatonin relative to the dose on the label can vary.
Sun exposure and bright light therapy—The sun is the most powerful regulator of the sleep-wake cycle and can be used to shift the internal clock. Sun exposure after landing in a new location can assist in adjusting your body to the new time zone. Alternatively, artificial light at certain times can help reinforce your body’s interval clock. Scheduling early morning light therapy could be beneficial, if traveling east. Light therapy can be supplied by special light boxes or dawn simulators.
Importantly, mistiming exposure to light therapy can be detrimental to circadian alignment. At certain times, light exposure can either advance or delay your internal clock. Avoiding direct light in the evening and wearing blue-light filtering glasses can also help.
Minimize caffeine and alcohol consumption—It is recommended to reduce caffeine and alcohol intake during travel because it can impact your sleep-wake cycle and cause dehydration. Remember to drink plenty of water during flights.
Exercise—Some research suggests that moderate exercise as approved by your physician can help adjust to a new time zone and provides light exposure when performed outdoors at the right time.
When circadian rhythm misalignment is too severe to gradually shift, for example, a 10-hour shift, it may be best to simply try to adjust the new zone by exposing oneself to daylight and exercising moderately. If the trip is short, some may prefer to stay at their home time zone’s schedule, if possible, and not shift.