Jet lag is a circadian rhythm sleep disorder, meaning it involves disruption to a person’s body clock and sleep. It causes fatigue and sleep issues after a person travels rapidly across time zones.

Jet lag is a circadian rhythm sleep disorder, meaning it involves disruption to a person’s body clock and sleep. It can cause fatigue and affect sleep, eating patterns, performance, concentration, and motivation. It can also affect digestion and lead an individual to feel generally unwell.

Sleep disorders and shift work can cause similar symptoms.

Tips for managing jet lag include adjusting the sleep schedule, using an eye mask, and exercising.

This article explores what jet lag means, the symptoms, how to minimize it, and why it happens.

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Jet lag can occur when a person’s sleep-wake patterns become disturbed. This may lead them to feel drowsy, tired, irritable, lethargic, and slightly disoriented.

The American Academy of Sleep Medicine defines jet lag as a syndrome that involves either excessive daytime sleepiness or an inability to sleep after traveling through two or more time zones.

The body can adjust naturally to 1 to 1.5 changes in time zones per day, but symptoms can arise if a person crosses two or more time zones in one day. The more time zones an individual crosses in a short period, the higher the likelihood of severe jet lag symptoms.

This effect tends to be greater when traveling eastward rather than westward, while symptoms are usually most severe on the day after arrival at a destination.

Some older research suggests that jet lag symptoms may become more challenging as people become older. This could be because circadian rhythms change with age.

However, not everyone gets jet lag — research suggests that around 1 in 3 people might not experience it.

The symptoms of jet lag vary, but they include:

  • difficulty sleeping at bedtime
  • problems waking up in the morning
  • fatigue
  • daytime sleepiness
  • poor sleep quality
  • difficulty focusing and remembering things
  • reduced mental and physical performance

Some people also experience:

  • digestive problems
  • nausea
  • dizziness
  • changes in appetite
  • mild anxiety
  • an excessive need to urinate during the night

Additionally, people who have traveled eastwards may find it harder to sleep at night, while those traveling westwards might find they wake up too early.

Individuals who regularly experience disruption to their body clock may also have a higher risk of various health conditions, although research has not yet confirmed this theory.

The best way to manage or limit jet lag is to target factors that contribute to it, such as the timing of meals and exercise.

Here are some tips that may minimize the effects of jet lag:

  • Go to bed 1–2 hours earlier than usual in the last few days before travel.
  • Drink plenty of water while traveling and limit the intake of caffeine and alcohol.
  • Keep active during the journey by stretching and exercising.
  • Try to sleep when traveling when it is nighttime at the destination.
  • Use an eye mask to limit light and encourage sleep.
  • Adopt a sleep and time schedule appropriate for the destination as soon as possible after arriving.
  • Spend time outdoors, as natural light will help with the adjustment.
  • Avoid sleeping late in the morning and sleeping in the day.
  • Exercise to maintain alertness after travel.
  • If necessary, take a nap on arrival but no longer than 20 minutes.
  • After traveling westward, seeking bright light in the evening may help; after traveling eastward, seek bright light in the morning.
  • On trips of 2–3 days only, try to keep the same sleeping and eating schedule as home.

Some people also take melatonin supplements to ease jet lag, but there is limited evidence to suggest they help.

A jet lag calculator, such as the British Airways jet lag advisor, can advise on balancing sleep and light exposure to minimize the impact of jet lag after specific journeys.

Jet lag has significant links to circadian rhythms.

What are circadian rhythms?

Circadian rhythms are 24-hour cycles involving the biochemical, physiological, and behavioral processes of our bodies. They regulate daily activities, such as sleep, waking, eating, and body temperature regulation.

Light exposure affects circadian rhythms and also plays a role in the development of jet lag. Time zone changes can be a factor in jet lag, although people who work in shifts can experience similar symptoms without traveling.

The body clock and the brain

Jet lag appears to involve a disruption in two separate but linked groups of neurons in the brain. These neurons are part of a structure called the suprachiasmatic nucleus (SCN), located in the anterior portion of the hypothalamus at the base of the brain.

Scientists say the SCN adjusts slowly to changes in time zone while other body clocks, or neuron groups, adapt at different rates.

One of these groups of neurons has links to deep sleep and the effects of physical fatigue. Another group controls the dream state of rapid eye movement (REM) sleep. The group involved in REM sleep finds it harder to adjust to the new cycle, and the two groups, or clocks, get out of sync.

What puts the body clock out of sync?

An internal time-keeping system drives the body clock. Changes in the light-dark cycle of night and day signal to the body that it needs to adjust. Changes in mealtimes, exercise, and other routines, can also contribute.

Situations that can cause the body clock to get out of sync include:

  • traveling across different time zones and changes in daylight and darkness cycles
  • working night shifts or frequently changing shifts
  • having certain sleep disorders

Jet lag will continue to disrupt sleeping, waking, eating, and other routines until the body clock recalibrates to suit the new environment.

Why is it harder to travel from west to east?

When traveling eastward, symptoms can feel more severe because the body has less time to recover. Traveling westward adds hours to a day, but traveling eastward reduces them. As a result, a person has less chance to catch up with sleep, which can delay recovery.

One study of 10 athletes found that jet lag continued to impact athletic performance up to 4 days after traveling across eight time zones from west to east. In contrast, their performance significantly recovered by day 2 after traveling the opposite way.

When traveling between north and south, changes in season may affect a person. However, for jet lag to occur, there must be an east-west or west-east movement. For example, flying directly south from Chicago to Santiago in Chile may cause discomfort, but it will not lead to jet lag.

Alcohol and caffeine

The World Health Organization (WHO) recommends limiting the consumption of alcohol or caffeine during or before flights, as they may worsen symptoms of jet lag.

They may exacerbate them by contributing to dehydration and affecting sleep quality. The WHO also recommends avoiding heavy meals, as these can add to a person’s discomfort.

Altitude sickness, oxygen, and dehydration

A 2017 study in mice found a possible link between environmental levels of oxygen and jet lag.

The pressure in an airplane’s cabin is lower than the pressure at sea level, so less oxygen may reach the brain when people fly. This could result in lethargy, which may worsen the symptoms of jet lag. The researchers suggested that oxygen modulation therapy could help reduce the effects of jet lag.

There is currently no treatment for jet lag and no medical approach that can cause the body clock to reset. However, researchers have looked at several options.

They include controlling light exposure, possibly with one or more of the following:

  • chronobiotic drugs, such as melatonin, which shift sleep rhythms
  • drugs, such as benzodiazepines, which enable people to sleep while traveling
  • stimulant drugs, such as caffeine
  • medicines that treat sleep apnea and other sleep disorders, such as modafinil (Provigil)
  • adjusting mealtimes during flights

Some people already use melatonin and sleep aids, but there is little evidence that they are effective, and they may actually have adverse effects.

Some early research has suggested using drugs that target genes that play a role in regulating the body clock. Mouse studies have indicated this might help, but such treatments will not be available for a long time, if ever.

Jet lag is a circadian rhythm sleep disorder that affects many people who travel across two or more time zones within a relatively short time. It occurs when the body clock gets out of sync with the environment and other body systems. It can cause fatigue, sleep disruption, gastrointestinal changes, and various other symptoms.

People who work night shifts or have frequent shift changes may experience similar symptoms, which can also affect individuals with certain sleep disorders.

While there is no medication to prevent or cure jet lag, managing sleep and light exposure and adjusting the routine for eating and exercising can help a person adapt more quickly.