Jet lag occurs when rapid travel across multiple time zones disrupts the body's internal clock, also known as circadian rhythms. This mismatch between the body's internal time and the local time can lead to a range of symptoms including disturbed sleep, daytime sleepiness, irritability, and difficulty concentrating.
Dr. Nina Rzechorzek, a researcher at the University of Cambridge focusing on human brain temperature, sleep, and circadian rhythms, explains that jet lag is experienced when the body's internal biological time remains aligned with the departure time zone while individuals attempt to sleep, eat, and function according to the destination's local time. This internal desynchronization is closely tied to the body's natural 24-hour cycle.
"Almost all the cells in our body maintain their own 24-hour clock, which are synchronised by a master clock in the brain," says Dr. Anna Edmondson of the University of Cambridge's Laboratory of Molecular Biology. This master clock is primarily regulated by environmental cues, with daily cycles of sunlight and darkness being the most significant. When individuals travel across several time zones, the timing of these light and dark cycles changes abruptly. It can take several days for the master clock to adjust to the new time, resulting in the symptoms of jet lag.
Traveling east is often associated with more pronounced jet lag effects than traveling west. The infographic notes that flying west can make it difficult to stay awake in the evening, while flying east can lead to difficulties waking up in the morning. This is because the body's internal clock is more easily adjusted to a longer day (traveling west) than a shorter day (traveling east).
The infographic also visually represents how jet lag effects increase with the number of time zones crossed, illustrating flight paths from the UK to the US (westward) and the UK to Thailand (eastward) to demonstrate these differences.
While the provided notes focus on the physiological cause of jet lag, strategies for mitigating its effects often involve carefully managing exposure to light and adjusting meal times to help realign the body's internal clock with the new local time. These strategies aim to synchronize the body's master clock with the environmental cues of the destination, thereby reducing the period of internal desynchronization and its associated symptoms.