The Jet lag is “a condition that is characterized by various psychological and physiological effects (such as fatigue and irritability), occurs following long flight through several time zones (2 or more), and probably results from disruption of circadian rhythms in the human body”.
The body has its own internal clock, or circadian rhythm, that signals your body when to stay awake and when to sleep. Jet lag occurs because your body’s clock is still synced to your original time zone, instead of to the time zone where you’ve traveled. The more time zones crossed, the more likely you are to experience jet lag.
Jet lag can cause daytime fatigue, an unwell feeling, difficulty staying alert and gastrointestinal problems. Fortunately, there are steps you can take to help prevent or minimize jet lag.


Symptoms of jet lag can vary. You may experience only one symptom or you may have many. Jet lag is temporary, but it can significantly reduce your travel comfort. Jet lag symptoms can include:

  • Disturbed sleep: insomnia, early waking or excessive sleepiness
  • Daytime fatigue
  • Difficulty concentrating or functioning at your usual level
  • Stomach problems, constipation or diarrhea
  • A general feeling of not being well
  • Mood changes

Symptoms are likely to be worse or last longer the more time zones that you’ve crossed, especially if you travel in an easterly direction. It usually takes about a day to recover for each time zone crossed. Motor vehicle accidents caused by drowsy driving may be more likely in people who are jet-lagged.


  • A disruption to your circadian rhythms: crossing multiple time zones puts your internal clock or circadian rhythms, which regulate your sleep-wake cycle, out of sync with the time in your new locale.
  • The influence of sunlight: A key influence on your internal clock is sunlight. That’s because light influences the regulation of melatonin, a hormone that helps synchronize cells throughout the body (Light – Retina – Hypothalamus – Pineal gland – Melatonin). You can adjust faster your internal clock by exposing yourself to daylight in the new time zone.
  • Airline cabin pressure: changes in cabin pressure and high altitudes associated with air travel may contribute to some symptoms of jet lag, regardless of travel across time zones.
  • Airline cabin humidity: humidity levels are low in planes. If you don’t drink enough water during your flight, , dehydration may also contribute to some symptoms of jet lag.

Risk factors

Factors that increase the likelihood you’ll experience jet lag include:

  • Number of time zones crossed: the more time zones you cross, the more likely you are to be jet-lagged.
  • Flying east: it is harder to fly east, when you “lose” time, than to fly west, when you gain it back.
  • Being a frequent flyer: pilots, flight attendants and business travelers are most likely to experience jet lag.
  • Being an older adult: older adults may need more time to recover from jet lag than do younger adults.