The Science Of Perfect Sleep - Dr Matthew Walker - #883

**Chris Williamson** (0:00)
You might be the British man with the best hair that I know at the moment.

**Matthew P. Walker** (0:04)
I think it is the greatest cry of a midlife crisis that you are ever going to see. It's a total train wreck. I'm suggesting that no one told me the pandemic was over and that you can get your hair cut. This is the consequence of it. So for anyone who is watching, any therapy bills that you have to have after seeing me and being confronted by me, send them to me, and I will pay for them. Oh my goodness.

**Chris Williamson** (0:30)
Fantastic.

**Matthew P. Walker** (0:31)
Well, what a good opening to it.

**Chris Williamson** (0:32)
Look, it is what it is. Talking about sleep today, we had a lot of conversations about it on the show previously, but I really want to dig into some sort of more rare insights that people probably know that they need to know, but don't yet know. So just to get started, how do you come to think about what good sleep is? How do we conceptualize good sleep?

**Matthew P. Walker** (0:52)
Yeah, it's an interesting question because I think everyone, most mornings, let's say you've got a significant other, you come down the stairs and you say, you know, how do you sleep? And they'll say, I slept well or I didn't sleep well. So everyone themselves has a subjective estimate of what this thing called good versus bad sleep is. Science is a little different though. And medicine teaches us that there are essentially what I would describe as the four macros of good sleep. And so three macros of food, fat, carbohydrate and protein, four of sleep. And you can remember it by the acronym QQRT, quantity, quality, regularity, timing. And there's all sorts of stuff on the internet about, take this supplement, do this particular thing. And it's the Shangri-La of all good sleep. And you'll have this utopian blissful night. Honestly, if you just focus on these four main principles, you're 80% of the way there. So quantity is what we used to espouse in sleep, as the measure of good sleep, which is somewhere between 7 to 9 hours for the average adult. And there is variability.
The next one is quality. And I think this is probably...

**Chris Williamson** (2:04)
Actually, I need to jump in on the quantity before you even move on.

**Matthew P. Walker** (2:07)
Yeah.

**Chris Williamson** (2:08)
Quantity of sleep, time in bed, time asleep.

**Matthew P. Walker** (2:11)
Hmm, astute question. Most of us conflate the former for the latter and it's potentially dangerous. So if you are a good sleeper, you will have what we call a sleep efficiency of at least 85%. Which means, so sleep efficiency of the time that you're in bed, what percent of that time are you asleep? And really good sleepers will have, let's say, 80 to 90% sleep efficiency. So even if you're in bed for seven hours, you're not getting seven hours of sleep.

**Chris Williamson** (2:45)
You're looking at close to six.

**Matthew P. Walker** (2:46)
Correct. So to get at least the minimum, according to the CDC, of seven hours, you actually have to be, on average, in bed maybe about eight, eight hours and 15 minutes. So it's a really astute point that we sort of misconstrued the question of total sleep duration as total time in bed. And you have to subtract one from the other. And that's why I think there is some legitimacy in looking at, say, sleep tracking data, because at least that will tell you total sleep time.

**Chris Williamson** (3:18)
I mean, that was the...

**Matthew P. Walker** (3:19)
Absent of, you know.

**Chris Williamson** (3:20)
Exactly. That was the biggest realization. I looked at my end of year review for Whoop, and I've worn this thing for 1,600 nights, since way before they were a partner on the show. And the biggest realization, I've said, I think Whoop's great and you can sign up for it if you want, but I can tell you what the realization is, the main realization that you're all gonna come to, which is eight hours in bed does not mean eight hours of sleep. That's the biggest realization. Everybody comes away from it. They go, well, I was sure I was in bed for eight. I thought I got eight hours. And he goes, well, he told me that I was actually only in bed for seven and a half. I kind of had a bit of a bad night's sleep. So I had like six, 15 of sleep last night. I thought I was in bed for eight. You go, that's a red pill that everybody needs to take.