Jet lag is the condition in which, as a result of travelling quickly through multiple time zones, your inner sense of daily rhythms no longer matches the local rhythms at your destination.
People normally live in a 24-hour rhythm. While we sleep, our heart and breathing rates slow, our blood pressure drops, our muscles relax and our mental and psychomotor efficiency decline significantly. Light is one of the main guides that our body uses to maintain its sense of time. The brightness of day and the darkness of night are the prime means by which we manage our “internal clock”.
A rapid journey through multiple time zones will put our internal clock out of sync with the local day-and-night rhythm. Our internal clock will be confused, because it now needs to adapt to a new time, a new light-and-dark rhythm and a new activity/inactivity cycle. And it’s not only our sleep/wake rhythm that is upset here: the shift also affects many other regular bodily functions that are subject to the same 24-hour cycle.
Different bodily functions also take different lengths of time to adapt. Adapting to the new sleep/wake rhythm, for example, can take less time than it takes your body temperature to adapt. You may find that your digestive system is still in another time zone, too. And it is this confusion of the internal clock that causes the physical and mental problems that are associated with the jet lag phenomenon.
The effects of jet lag
Jet lag tends to have a stronger effect on people travelling east than on those going west. This is because our "internal clock" actually works to a rhythm of a little over 24 hours. If you fly from east to west (e.g. from Switzerland to the USA), the “longer” day you experience will thus be more suited to your natural body rhythm than the “shorter” day you will experience when travelling east (e.g. from Switzerland to Thailand). Indeed, the human body adjusts to the new time zone about 20% faster after a westbound flight than after an eastbound one.
General tips for coping with jet lag
Change your watch to the time at your destination while you are still inflight, to enable yourself to mentally prepare for the new time rhythm.
- Try to adopt the local daily rhythm as much as you can: eat at the local times, and don’t go to bed until the sun goes down.
- Try to get enough sleep the first night after you arrive.
- Avoid physical exertion in the first two days, to help your body get used to the new time rhythm.
- Avoid taking sleeping pills or melatonin: these can confuse your body even more!
- Spend as much time as you can out of doors: the daylight will help your body to get used more quickly to the new local rhythms.
Dealing with jet lag during short stays
Your internal clock can take between a few days and several weeks to adjust to a new time zone. In view of this, if you are only staying at your destination for a short period (up to 72 hours), it may make sense to remain on the time and in the daily rhythm of your home country throughout your stay.
How to keep to the time of your home country
Keeping to the time of your home country takes more of an effort, but it may well be worth it:
- Calculate the time difference between your home country and your destination.
- Think of the times you would normally sleep and be awake at home, and convert these to the corresponding times at your destination.
- Note the times at your destination when you would be at your tiredest at home (i.e. the equivalents of 03:00-05:00 and [to a lesser extent] 15:00-17:00 at home), and try to avoid planning any business meetings at these times.
- Try to avoid light at your destination when it would be dark at home. This is best done by staying in windowless rooms indoors during such times, and/or wearing sunglasses if you have to go out.
- Plan your meals at the equivalent times of your meal times at home. If it’s dinner time at the destination when it would be breakfast time at home, try to eat something light, to help your digestive system.