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Why does one suffer from jet lag?

Updated: Jan 29, 2021

Jet lag, also known as desynchronosis, is a physiological condition that occurs as a result of a disruption in the body’s circadian rhythms, also known as the body clock. Disruptions include rapid crossing of multiple time zones or when one’s sleeping pattern is disrupted, such as when the individual performs shift work.

Jet lag is also known as circadian rhythm disorder. There are many side effects of jet lag, which includes an individual feeling drowsy, tired, irritable, lethargic and slightly disoriented. The more time zones one crosses in a short period, the more severe the symptoms are likely to be and age also plays a part in the severity of jet lag on each individual.

Symptoms of jet lag

Jet lag has a variety of symptoms and different individuals will suffer from different symptoms and different severity depending on one’s body systems and the number of time zones that they have just crossed. The most common symptoms that arise from jet lag are the following.

  1. Sleeping disturbances, insomnia, fatigue and lethargy

  2. Headaches or discomfort feeling in one’s head

  3. Irritability, confusion and difficulty in focusing

  4. Mood swings

  5. Loss of appetite

  6. Gastrointestinal disturbances such as constipation

  7. Dizziness or unsettled feeling

There isn’t a treatment for jet lag currently, but a range of actions can be taken to reduce the impact of jet lag.

Circadian rhythm

Circadian rhythms are 24- hour cycles that form part of the body’s internal clock in the background running to carry out many essential functions and processes such as coordinating the digestive system to produce proteins to match the usual meal timings of an individual. Different systems of the body will follow circadian rhythms that are synchronised with a master clock located in one’s brain. This master clock is directly influenced by one’s environmental cues such as the presence of light, which is why circadian rhythm is related to the day & night cycle.

When properly aligned, a circadian rhythm can promote consistent and restorative sleep, but when the rhythm is thrown off, it could create significant sleeping issues for an individual such as insomnia.

Body clock & the brain

Jet lag appears to be a result of a disruption in two separate but linked groups of neurons in the brain and these neurons are part of a structure called the suprachiasmatic nucleus (SCN). The SCN is located below the hypothalamus at the brain’s base.

One of these groups of neurons is commonly associated with deep sleep and the effects of physical fatigue while the other group manages and control the dream state of rapid eye movement (REM) sleep.

The second group of neurons, or those commonly associated the control of REM sleep, finds it harder to adjust to the new cycle and hence the 2 groups become out of sync and the individual will suffer from jet lag.

What puts the body clock out of sync?

An individual’s body clock is driven by an internal time-keeping system but is affected by external environmental factors that can get it out of sync such as the light dark cycle of night and day and hence when the clock is out of sync, jet lag occurs.

Traveling across different time zones and going through light dark cycles of night and day that differs from one’s usual day can cause their body clock to get out of sync. Other causes include some sleeping disorders such as insomnia and shift work.

When jet lag occurs, sleeping patterns are affected alongside other patterns such as eating pattern and working patterns, and will continue till the body clock adapts to the new environment and returns to sync.

Alcohol & caffeine

The world health organisation or WHO has pointed out that the consumption of alcohol or caffeine before or during the flight may worsen the symptoms of jet lag. It is also pointed out that these can both lead to dehydration and since the air inside an airplane cabin is comparatively drier than natural air at ground level, it can worsen jet lag symptoms for the individual.

The consumption of alcohol will increase the need to urinate which is a factor that can disrupt sleep. Also, although alcohol can induce sleep in an individual, the quality of sleep will be lower and furthermore, the hangover effect of alcohol could worsen the effects of jet lag and travel fatigue on a passenger.

Caffeine can also disrupt sleep patterns as it blocks the adenosine receptor present in our body to detect the high levels of adenosine in our blood. Adenosine has an important function to perform in many biochemical processes and is one of many neurotransmitters and neuromodulators in the human’s body that affects one’s complex behaviour towards sleep, especially the initiation of sleep.

In the brain, adenosine performs its role as an inhibitory neurotransmitter, which means that it acts as a depressant for the central nervous system and inhibits many processes commonly associated with wakefulness. Adenosine levels in the brain increase every hour that one is awake and hence is believed to be responsible for increasing levels of sleepiness that develops for as long as a person stays awake for the day.

Therefore, when these adenosine chemicals aren’t pick up by the receptors present in our body due to the presence of caffeine, one will tend to find it harder to fall asleep.

Altitude sickness, oxygen and dehydration

As the planes of today typically fly at a good FL300 and above, the pressure in the airplane’s cabin will be lower than what it is at sea level. This indicates that passengers might face a condition known as hypoxia, or deficiency in oxygen levels at the tissues level. The reduced air pressure on airline flights can reduce the amount of oxygen in passenger’s blood by 6 to 25%.

Studies has shown that short-term exposure to altitudes of at least 10,000ft can lead to fatigue although the effects can begin at lower altitudes for some individuals.

Why is it harder to travel from west to east?

Symptoms also tend to feel more severe when one travels eastward as the individual’s body will have less time to recover. This is because westward travel will add hours to our days while eastward travel reduces the number of hours in our days and hence it means that our bodies have less time to adjust and sync up with a circadian rhythm when flying eastward.

Prevention of jet lag

There is no treatment for jet lag but there are lifestyle adjustments and preventive measures to reduce the impacts of jet lag in order to have a more comfortable trip.

Some lifestyle adjustments include:

Physical fitness and health: People who keep physically fit, receive sufficient rest and have a well-balanced diet appear to have fewer and less severe symptoms than those who do not maintain their physical fitness and health.

Controlling underlying medical conditions: Doctor’s advice should be seek before making a long-haul trip for passengers with underlying medical conditions such as lung disease, heart disease and diabetics as these conditions can affect the severity of jet lag symptoms.

Other preventive measures include:

Choice of flight: Choose a flight that arrives early evening local time, which allows the individual to try sleeping at around 2200 hours. Breaking down a flight into many segments such a scheduling a stopover if possible, will give one’s body the required time to adapt to a new environment and hence reduces the impact of jet lag.

Sleep preparation: Prepare for a eastward flight by getting to bed and waking up earlier a few days prior to the flight and westward flight travellers can prepare themselves by getting to bed and waking up later a few days prior to the flight.

Time tuning: Change your watch timing to the destination time zone as soon as you board the plane so that you can regulate your activities on the plane based on destination local time.

Keeping active: Stay active during the flight by doing exercises or walking along the aisle.

Strategic napping: Use eye mask and ear plugs to aim for strategic napping. It is advisable to sleep when it is nighttime at the destination and catch a nap at other point in time to reduce sleepiness.

Hydration: Consume more water during the flight and avoid alcohol and caffeine to prevent dehydration.

Upon arrival, there are also preventive measures that can be taken to reduce the effects of jet lag such as:

  1. Avoid heavy meals or strenuous exercise

  2. Spend time outdoors preferably in sunlight

  3. Sleep at a “normal” time at the destination’s time zone

These methods can only reduce the effects of jet lag but will not cure jet lag. The sooner one’s body can adapt to the new time difference, the faster one will recover from the effects of jet lag.

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