Dr. Matt Walker

because otherwise this person is just going to still be a little bit too wired.

I would say it's one of the things that I would advocate in terms of a good sleep optimized routine, and we can come on to that.

Even if you don't think you're necessarily someone who's sensitive to that.

Now, it turns out I am someone who is sensitive to that.

It can really quite trigger me, so I stay away from it.

We often see this...

with insomnia too, and we call it the tired but wired phenomenon.

And people will say to me, look, I am just so tired.

I am so, so tired, but I'm just so wired that I can't fall asleep.

I'm desperate for sleep.

I know I want sleep.

but I can't fall asleep because I'm just so wired.

And that is a sympathetic hyper cortisol state.

And you can see it in their physiology.

But coming back to your question, cortisol will drop naturally throughout the night,

but then it starts to rise back up and will start to produce its fantastic sort of peak climbing rate right at the moment when you would naturally again want to wake up.

So what we're mapping here is this wonderful tapestry, this kaleidoscope of coordinated biology

that your adenosine levels are finally coming to their lowest point.

Your circadian rhythm is starting to rise.

Your cortisol levels are starting to rise.