Sleep models applied to jet lag

Are you having problems with “jet lag” as a result of your galivanting around the world?

Are you falling asleep or waking up, or both, at odd times after zipping westward or, often worse, eastward across time zones?

Many people do and having a model for the workings of sleep can provide a basis for deciding what to do.

Sleeping and waking

The model that I use is based on the guideline that, for each hour that we sleep, we store up two hours of wakefulness. This makes approximate sense as people who are getting enough sleep are asleep for about 8 hours and awake for about 16 hours per day.

Also, another guideline is that we can only store a maximum of 16 hours of wakefulness. So if we start at zero wakefulness, e.g at the end of a normal day, we can sleep for only about 8 hours, then we wake up. We cannot sleep longer than normal in an attempt to store more wakefulness and, therefore, to stay awake for longer than about 16 hours without becoming tired.

However, of course, we can stay awake for longer periods, in which case we can go into negative wakefulness, also known as “sleep deficit”. In that case, we can sleep for longer to catch up; and we need to sleep for longer to get back into positive stored wakefulness.

Dealing with “jet lag”

On this basis, one way to try to deal with jet lag is to start by calculating how much wakefulness you have stored now. This can be done by knowing what state you were in at some reference time in the past, and calculating how much time has elapsed since then, and how much sleep you have had during that time.

Then, based on how much wakefulness you need to have stored to be in a normal state at some future time (perhaps 24 hours from now, or perhaps at your normal bedtime today or tomorrow), you can calculate how much sleep you need between now and then to get back into synch.

One of the difficulties is that the body gets into a habit of sleeping for a constant length of time and then waking up. When trying to deal with jet lag, some people sleep for too long and therefore take longer to get back into synch. If you calculate that you need to sleep for less time then you normally sleep, you need an alarm clock or someone to wake you up. On the other hand, if you calculate that you need to sleep for longer than you normally sleep and are waking up too soon, then you might need to do it in two separate periods of sleep, with a (shorter than normal) gap between.

I hope that this makes some sense to you.

There’s more …

By the way, if you are interested, there is additional complexity to this and many people believe that it is important to have your eyes open in daylight for enough time at the right times in the sleep cycle. This makes some sense, as the outer layer of photo-sensitive cells in our retinas die during sleep and are discarded to expose a new outer layer on each sleep cycle. Further indication of this is that I have heard, but not confirmed, that: blind people do not get jet lag. If so, that is fascinating!

Background

I originally wrote this for someone who reported that they were suffering from jet lag; and I’m posting it here because someone else is reporting similar suffering, and it might be of some use of other people too.

Of course, as an amateur at this, I must point out that this is not medical advice and you must take responsibility for your own bedtimes! Also this is not a description that I have developed or have scientifically researched, it is however a model that I learnt about during the human factors part of my flying training. If you are “jet lagged” and have stayed awake long enough to read this, I hope that you find it helpful.