Jet lag refers to disturbances in an individual’s regular sleep pattern[1] due to a misalignment between their natural sleep-wake cycle (known as the ‘circadian rhythm’) and the travel destination time zone.
While jet lag symptoms typically go away on their own, the process can take several days depending on factors such as the number of time zones crossed while travelling and whether the affected individual uses a jet lag treatment.
During this time, the individual’s sleep, energy levels and key cognitive functions can be affected, resulting in jet lag symptoms such as tiredness and fatigue.
This guide covers the main steps to take before travelling, during the flight, at layover stops and after reaching the destination to overcome jet lag symptoms as quickly as possible.
The guide also provides comprehensive answers to common questions about overcoming jet lag, based on the latest scientific research on the condition.
What causes jet lag?
Jet lag occurs when an individual crosses multiple time zones within a short period and experiences a misalignment between the destination time zone and their circadian rhythm[2], which refers to a 24-hour cycle in which the individual sleeps, wakes up, eats and remains active.
The greater the number of time zones crossed, the higher the probability of jet lag occurring. Additionally, travelling eastward is more likely to cause jet lag than travelling westward, as the body’s natural circadian rhythm is slightly longer than 24 hours, making it more difficult to adjust to an earlier (advanced) time zone associated with travelling east.
What does jet lag feel like?
Jet lag can make the affected individual feel tired, sleepy and foggy after arriving at their travel destination.
Some of the most common jet lag symptoms include:
- Sleep deprivation - Individuals who have crossed multiple time zones but whose circadian rhythm lags behind the destination time zone are likely to experience difficulties falling asleep. This can also increase the probability of waking up during the night, reducing overall sleep quality.
- Fatigue - The sleep deprivation associated with jet lag can prevent the affected individual from getting adequate rest and recovery. This can add to the tiredness felt after taking a long flight, resulting in excessive fatigue.
- Impaired cognitive function - The brain consolidates memories and repairs neural connections necessary for optimal cognitive performance during the deeper, non-rapid eye movement (NREM) stage of sleep[3]. Therefore, sleep deprivation associated with jet lag can affect cognitive performance, causing the affected individual to feel foggy. For more information, read our expert guide to what happens to your body when you are sleeping.
- Headaches - Prolonged exposure to dry cabin air can cause dehydration, which shifts fluid out of the brain, exerting pressure on the brain’s protective cover and stimulating pain receptors, resulting in a headache[4]. In some cases, sleep disturbances due to jet lag can also affect the balance of neurotransmitters such as serotonin, which influence pain perception. This can trigger a headache affecting specific sides of the head, known as a migraine.
How long does it take to overcome jet lag?
The time it takes for an individual to overcome jet lag depends on:
- The number of time zones crossed - The greater the number of time zones an individual crosses while travelling, the bigger the difference between the local time at their departure location and their destination location. This substantial time difference requires a larger adjustment in circadian rhythm, prolonging jet lag.
- The direction of travel - Travelling eastward, such as from the USA to the UK, results in more severe jet lag symptoms, as you must ‘advance’ your body clock to match the new time zone. This can mean trying to go to bed when it is night-time at the destination, even though you are wide awake. In comparison, travelling westward often results in milder symptoms, making it easier and quicker to recover from jet lag.
- Individual differences in circadian rhythm adaptability - An individual’s age, health and sleep patterns affect how quickly their circadian rhythms adapt to changes in time zones while travelling. Individuals who are younger and follow a regular sleep schedule are more likely to adjust quickly, while older adults or those with irregular sleep habits may experience prolonged jet lag symptoms.
- The use of a jet lag treatment - Jet lag treatments such as Melatonin are proven to help with falling asleep at the correct time after travelling, enabling the body’s internal clock to adjust to the new time zone faster and more effectively. Melatonin should be taken at your intended bedtime in the new time zone, between the hours of 8 pm and 4 am and for no longer than 5 days. For more information, watch our video guide to Melatonin, which explains how this treatment aids jet lag recovery.
Why is jet lag worse coming home to the UK when travelling eastward?
Jet lag is more severe when coming home to the UK from a country that lies to the west of the UK, such as the United States, due to the biological functioning of the body’s internal clock.
Human beings have evolved in a way that makes it easier for the body to adapt to a delayed sleep time, as opposed to advancing to an earlier sleep time.
Therefore, travelling eastwards to come home to the UK makes it harder to overcome jet lag, as the body struggles to adjust to the advanced time.
Does crossing multiple time zones make it harder to recover from jet lag?
Yes, crossing multiple time zones can make it more challenging to recover from jet lag.
The greater the number of time zones crossed, the bigger the misalignment between the body's internal clock and the local time at the destination, leading to more pronounced symptoms and a longer adjustment period.
Does drinking coffee make it harder to get over jet lag?
The effects of caffeine consumption on jet lag recovery depend on the amount of caffeine consumed and the time of day.
Caffeine is a stimulant that promotes alertness by blocking adenosine receptors in the brain, which are responsible for making us feel tired.
Therefore, consuming a small amount of caffeine early in the day after travelling can help with overcoming untimely sleepiness, aiding the adjustment of the body’s circadian rhythm to the new time zone.
Conversely, consuming a larger amount of caffeine later in the day after travelling can exacerbate jet lag, as the effects of caffeine can last for several hours, potentially delaying the onset of sleep at night.
This further disrupts the process of adjusting to the new time zone, exacerbating jet lag symptoms and prolonging jet lag recovery.
Does drinking alcohol make it harder to get over jet lag?
Alcohol disrupts the deeper stages of sleep, such as REM sleep. Therefore, drinking alcohol can reduce overall sleep quality, causing you to feel tired and disoriented upon waking. These feelings can add to the discomfort of jet lag symptoms such as fatigue and grogginess.
It is also important to note that alcohol is a diuretic, which means it speeds up the loss of fluids by increasing urine production. This can result in dehydration, subsequently affecting the body's ability to regulate its core temperature and perform essential physiological processes.
These mechanisms can add to the difficulty of falling asleep after travelling, prolonging the time taken for the circadian rhythm to adjust to the new time zone, and delaying jet lag recovery.
Key takeaways
Jet lag occurs when your body’s circadian rhythm becomes misaligned with the destination time zone after crossing multiple time zones.
While jet lag symptoms such as fatigue and impaired cognitive function can be uncomfortable, implementing the strategies outlined in this guide and taking a jet lag treatment such as Melatonin after arriving at the destination can help speed up the jet lag recovery process.
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