Matt: Yeah, the duration. So there are essentially four ingredients, and this is probably going to be my next book, which is essentially the four pillars of sleep: depth, duration, continuity, regularity. If you shortchange sleep on any one of those, you get a compromised deficit in brain and body. So depth is what we were speaking about. It really should be depth/quality of sleep. You need both the depth of those deep sleep brainwaves but you also need all of these different brainwave oscillations, these things called sleep spindles, and slow waves, and the coordination between those two. It's all about the electrical quality of your sleep.

So you can have the duration of sleep, you can have eight hours of sleep, but if it's not of the right electrical quality or depth, you get deficits. But you can get lots of high quality sleep, but if you're only getting four hours of it, it's not going to be enough. So it's duration. Depth, duration.

Then it's also about continuity. This has been probably, in the past five years, one of the explosions in the sleep field. If you were to get eight hours of sleep but across a nine-hour period because you are awake for, you know, 5 minutes here, 10 minutes here, 30 minutes here, 15 minutes here, that's very fragmented sleep, which, by the way, alcohol is another thing that will fragment your sleep very much like that. So the continuity of your sleep is poor. It's not continuous. It's fragmented.

And even if you get eight hours of sleep in a nine-hour period but it's fragmented versus you get eight hours of sleep all in a nice one bout within eight hours, so in both of those scenarios, it's the same duration of sleep, maybe it's even the same electrical quality of sleep, but if it's fragmented and littered and punctured with many awakenings, the continuity of sleep is poor. And that's not good either.

And then, finally, the part is regularity. This means going to bed and waking up at the same time no matter whether it's the weekend or the weekday. Go to bed at the same time, wake up at the same time. Those are the four key pillars that we know of for sleep. And you can hold any three constant and manipulate one of them and you get a deficit.

Now we can't quite weigh the complete, you know, is it, you know, this one is worth, you know, 40%. This one is worth sort of 20%. We can't yet do that. But it's very clear that those are the four pillars of good sleep.