Why Jet Lag Is Worse When You’re Travelling East

We’ve told you before that it’s harder to adjust to time zones when you’re travelling east. A new study explains why, exactly, and also sheds some light on how long it takes to recover from jet lag.

Photo by Nicolas Alejandro.

In a study published in Chaos studied the relationship between circadian rhythm and the direction of travel. Basically, it comes down to the fact that our internal clocks are just over 24 hours, and when we travel east, the days are shortened, which means our circadian rhythms needs to do more to catch up. One of the study’s authors told Travel + Leisure:

“You expect to advance your internal clock if you travel east and backward if you travel west,” Girvan added. “However, if you travel a large number of time zones eastward, your internal clock doesn’t phase advance like you would expect. Instead, it phase delays.”

For non-scientists, “phase advance” is your bedtime and wake-up time moving earlier in the day, and “phase delay” is your bedtime and wake-up time moving later.

Generally, they discovered that travelling east across three time zones takes almost four days to recover completely, compared with just three days if you’re travelling westward. And if you’re travelling eastward across nine time zones, it takes almost two weeks to recover, compared with less than eight days if you’re travelling westward.

We’ve told you how to fight jet lag in general, and for more detail, head to the links below.

Resynchronization of circadian oscillators and the east-west asymmetry of jet-lag [Chaos via Travel + Leisure]