Dr. Matt Walker

Others, 120 minutes.

Is it consistent with an individual?

It is variable.

relatively stable within an individual.

So I would say that the size of the difference from one individual to the next is much bigger than the size of the difference within an individual from one night to the next to the next.

Immensely.

And what's also interesting is that speaking about some sex specific things, there are sex differences.

So on average, men, if you look at them, will have a sleep cycle that's about 15 to 20 minutes longer than women, which on a 90 minute average is actually quite a lot.

And I bring this point up because you may have seen some of those sort of claims or devices out there.

Well, firstly, probably on social media and people send me these things and say, is this true?

which is you really have to structure your wake up time at these very distinct 90 minute on the clock when the clock strikes the 90 minute midnight, that's when you have to be waking up and you should set your alarm.

Right, that there's something uniquely special about the completion of a 90-minute cycle that will have you ejected out of sleep feeling like an Energizer bunny, kind of, that's some of the claims that they- And if I were to ask you now, true or false?

False.

So sleep for as much as you possibly can sleep.

Don't terminate that sleep artificially on the basis of anyone telling you that there is this kind of Da Vinci code magic 90 minutes.

That's unfortunately not true.

And I, you know, I've been guilty of saying, you know, it's a 90 minute cycle and repeating that.

So if I didn't know any better, I would.

believe that.

So I'm not trying to, you know, chastise anyone.