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Science Figured Out That Jet Lag Is Worse For East-Bound Travellers

Science Figured Out That Jet Lag Is Worse For East-Bound Travellers

Is recovery from jet lag is harder when you’re headed to America or Europe? For many of us, jet lag means a mixture of sleepless nights and inescapable afternoon naps – so is it really worse depending on whether you’re headed east or west? Well according to science it does.

recent study in the scientific journal Chaos has revealed that jet lag is actually a lot harder if you’re headed east. To explain this we first need a quick explainer on jet lag in general.

Jet lag occurs when your sleeping patterns aren’t matched with your circadian rhythm, a.k.a. your body’s internal clock. The circadian rhythm is a 24-hour cycle of physiological activity, and is controlled by hormones that determine whether you’re awake or asleep at any given time. Disruptions to this cycle are why jet lag or a bad night’s sleep can alter your appetite and sleep patterns for days after.


Now, researchers say they’ve identified the main reason why travellers have more difficulty adjusting when flying east rather than west. Basically, there’s a thing called the “eastward-westward asymmetry” which plays on your circadian clock – a clock which has a natural period that’s a little longer than 24 hours. For most of us, our internal clock can be 23.5 hours long, or even 24.5 hours long – if your internal clock has an additional 30 minutes, the study found that it has an effect on how you handle jet lag.


In general, you’d expect your internal clock to advance forward if you travel east and fall backward if you travel west – so if you travel to Auckland, which is two hours ahead of Sydney or Melbourne, your body would adjust to that two hour time difference. Same deal if you went in the opposite direction and travelled to Perth from the east coast of Australia (Perth is two hours behind the east coast).

However, if you travel across a number of time zones eastward (like we would if we were to travel to Rome which is eight hours behind), our internal clock doesn’t change like we think it should. You’d think it would “phase advance”, meaning your bedtime and wake-up time would move earlier in the day. But instead, your circadian rhythm decided to throw a 180 on you and “phase delay” meaning your bedtime and wake-up time actually move later. This is what causes you to experience more severe jet lag.


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In general, the study found that eastward travel across three different time zones meant you’d require more than four days to completely recover. But if you travelled westward over the same number of time zones, you’d only need a little less than three days. Cool!

So what have we learnt? Aside from jet lag being the most unwelcome part of travel, we have determined that if we’re desperate to diminish the effects of jet lag, we can opt to head west instead of east. (But don’t get me started on the whole date line thing… that’s a whole other mountain to climb).

Oh and if you’re desperate, here’s a handy app to use to help you defeat jet lag like a champ.

(h/t Travel + Leisure)

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