Dr. Matt Walker

looking at cortisol across now a full 24 hour period.

And sure enough, when you look at healthy controls who can sleep well and insomnia patients, they look almost identical across the day.

But then when it comes to falling asleep right around that bedtime period, the healthy controls are going all the way down.

The insomnia patients go down and down and down, and then they have a rise back up right around that sleep onset period.

And then they start to drop back down again, just as the control group.

But then they also often will have a spike in the middle of the night, which then comes down.

And then both of them are staying low throughout the early morning period.

And then it starts to rise back up.

So it's not as though net net overall, there is a higher level of cortisol in people with insomnia.

It seems to be right at those trigger zones that map very nicely to sleep onset problems, sleep maintenance problems.

Yeah, I often think that sleep maintenance insomnia that you've just described is the revenge of daytime emotions unresolved.

That's a great way to put it, yeah.

So that would be, so we've spoken about regularity, we've spoken about darkness, and we've spoken about the inverse of that in the morning, which is light, a little bit of cortisol.

So the third out of the five is going to be temperature.

And the advice here is keep it cool.

As we mentioned a little bit in the first episode, and we will go into great detail when we speak not just about these conventional and unconventional tips, but we're also going to go into the future of science and where sleep science is taking us to, in fact, optimize and even enhance our sleep.

We will speak a lot about temperature.

Suffice to say that you need to drop your core body temperature and your brain temperature by a little less than one degree Celsius, two to three degrees Fahrenheit, to get to sleep and stay asleep.

The general target that we have in sleep science, if you look across the literature, is somewhere around about the 67 degree Fahrenheit, or I'm trying to do the calculation, maybe 18.5-ish degrees Celsius.

Now I know that that sounds cold, and cold it is, but you can also wear thick socks to bed.