Jet lag, also known as time zone change syndrome or desynchronosis, occurs when people travel rapidly across time zones or when their sleep is disrupted, for example, because of shift work.
It is a physiological condition that results from a disruption in the body’s circadian rhythms, also known as the body clock. It is seen as a circadian rhythm disorder.
Symptoms tend to be more severe when traveling eastward compared with westward.
Fast facts about jet lag
Jet lag can cause headaches, insomnia, and irritability.
Circadian rhythms regulate sleep and other bodily functions.
When circadian rhythms are significantly upset due to traveling, it is called jet lag.
Ways of reducing symptoms include changing your sleeping patterns, avoiding alcohol and caffeine, and getting enough sunlight on arrival.
What is jet lag?
Air travel can cause jet lag, especially long-haul flights going from west to east.
Jet lag can occur when sleep-wake patterns are disturbed. A person may feel drowsy, tired, irritable, lethargic, and slightly disoriented.
It can result from traveling across time zones or from doing shift work.
The more time zones a person crosses in a short period, the more severe the symptoms are likely to be.
Jet lag is related to a disruption in activity and a lack of synchronization in the brain cells of two parts of the brain.
The older a person is, the more severe their symptoms will normally be, and the longer it will take for their body clock to get back into sync.
Children usually have milder symptoms, and they recover faster.
To understand jet lag, we need to know about circadian rhythms.
What are circadian rhythms?
Circadian rhythms, or the body clock, are 24-hour cycles in the biochemical, physiological, and behavioral processes of our bodies. They regulate daily activities, such as sleep, waking, eating, and body temperature regulation.
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). The SCN is located below the hypothalamus at the base of the brain.
One of these groups of neurons is associated with deep sleep and the effects of physical fatigue. The other group controls the dream state of rapid eye movement (REM) sleep.
The group of neurons involved in REM sleep finds it harder to adjust to the new cycle, and the two groups become out of sync.
What puts the body clock out of synch?
The body clock is driven by an internal time-keeping system, but it is affected by external environmental factors, such as the light-dark cycle of night and day.
When the body clock gets out of synch and needs to be reset, jet lag results.
Traveling across different time zones and going through daylight and darkness cycles that are different from the rhythms we are used to can cause our body clock to get out of synch. Other causes include shift work and some sleeping disorders.
Jet lag affects patterns of sleeping and waking and of eating and working.
Hormone regulation is key to body clock synchronization. When jet lag happens, hormone levels get out of sync with the environment. Body temperature also varies according to the body clock.
Jet lag will continue until all these factors can respond properly to the new environment.
Why is it harder to travel from west to east?
When travelling eastward, symptoms feel more severe, because our bodies have less time to recover. Travelling westward adds hours to our days whereas travelling eastward reduces them. This means that our bodies have less time to adjust and synch up with a circadian rhthym when flying east.
Traveling from north to south or south to north can cause additional problems, as the seasons are different.
However, for jet lag to occur, there must be an east-west or west-east movement. Flying directly south from Chicago to Santiago in Chile may cause discomfort, but it will not lead to jet lag.
In addition, jet lag does not usually occur after crossing just one or two time zones. The more time zones one crosses, the worse the symptoms may be.
Alcohol and caffeine