In general, travelling eastward is considered worse for jet lag than travelling westward. This is because when you travel east, you are “losing” time, and your body has to adjust to an earlier time zone. This can be more difficult for your body to adapt to because it requires you to go to bed and wake up earlier than you are used to.
For example, if you fly from New York to London, you travel across five time zones and arrive at your destination 5 hours ahead of your body’s internal clock. This can lead to difficulty falling asleep and feeling tired during the day.
On the other hand, when you travel westward, you are “gaining” time, and your body has to adjust to a later time zone. This can be easier for your body to adapt to because it allows you to go to bed and wake up later than you are used to.
That would partly explain my severe jet lag when we made the east-to-west trip to Iceland. It also explains why I did not suffer any significant jet lag when we made our world trip through multiple time zones, west to east.
Jet lag is a condition that occurs when your body’s internal clock, or circadian rhythm, is disrupted due to travelling across multiple time zones. This disruption can lead to various symptoms, such as fatigue, difficulty sleeping, irritability, and digestive issues.
The leading cause of jet lag is the mismatch between your internal circadian rhythm and external time cues at your destination, such as daylight and meal times. Your body has a 24-hour cycle that regulates many biological processes, including sleep and wakefulness, hormone production, and body temperature.
When you travel across multiple time zones, your body’s clock becomes out of sync with the local time at your destination. For example, if you travel from New York to London, you might experience daytime fatigue and difficulty sleeping because your body thinks it’s still nighttime in New York.
The body’s circadian rhythm is regulated by a group of cells in the brain called the suprachiasmatic nucleus (SCN), which responds to light cues from the eyes. When you travel to a new time zone, your eyes receive light cues that are out of sync with your body’s internal clock, which can disrupt your sleep-wake cycle.