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everyone. Welcome to ask me anything. Episode number 31. I'm joined. Once again by Bob Kaplan. Although, as you'll learn at the end of this episode. This will be the last time we're joined by Bob Kaplan, but let's not get ahead of ourselves. In today's episode. We talk about really two things in detail. One is HRV, heart rate, variability. We've had so many questions.
Strings on this subject for the past couple of years and we've just been slowly kind of collecting questions until we thought we had enough to do kind of one of our theme attic shows on it. And the second thing we talk about is ethanol all things related to ethanol. So how does it affect HRV? Is really our segue. But then also what are the effects of alcohol on sleep? And we really go after mortality probably, where we spend most of our time and we talked about it through the lens of all of the epidemiology as most of you are met. So, you know, there's a
It's a confusing body of literature out there that suggests that maybe some alcohol is good for you. And no alcohol is not as good for you. And so we go really deep on this subject matter. So again, if you have any questions about alcohol or if you drink at all, and if you are, if you don't drink and you're wondering if you should be drinking, I think this episode will be very helpful for you. So one thing I want to point out for this episode. This episode was just due to some limitations of timing when we recorded it. This was not recorded in video. So we will only be doing this in audio. That might
Show notes a little more important. Although we didn't really have a lot of content here that necessitated being able to see. So I think you're going to be fine listening to this an audio. But obviously, the show notes will have any of the graphs and other images that we talked about. Now, if you're not a subscriber, of course, you can get a sneak peek of this as usual, then you'll have to obviously subscribe if you want to in to enjoy the full content. So without further delay. I hope you enjoy. Am a number 31.
Hey Bob, how's it going?
Today? Gone? Well, Peter, how are you?
It's good. It's a little unusual. Today. We're doing this a little bit on the old school tip. No video. Today. We're going to be a little bit more descriptive in our terms since people can't watch our facial expressions. Although that somehow provided any value. We won't do any screen sharing.
I think we can
manage what you have in store for us today.
So I aggregated a whole bunch of questions around HRV.
Variability and alcohol. Many questions on both those topics.
I know this has been something you've been asking me about for a year. When are we going to do one on HRV when we're going to do one on each RV? So I think the answer is
now. All right, we'll dive in. First question, seems relevant. What is HRV?
And it's funny. This, a tougher question to answer without an image, but I'll do my best. So as you pointed out a second ago, HRV stands for heart rate.
Variability and that's a pretty descriptive term because what it measures is the variation in time between heartbeats and that's measured in milliseconds. So 1000 milliseconds is one second. So if a person's heart is beating 60 times per minute, you might say well there's a thousand milliseconds between every beat but it turns out that it's not really that way. You see it.
If your heart is beating, 60 times per minute or once per second between the first beat and the second beat, it might be a thousand ten milliseconds. And between that beat and the next beat, it might be nine hundred and 60 milliseconds in between that beat and the beat thereafter. It might be 1027. Milliseconds. When you start looking at this thing at the level of thousands of a second. You realize that there is
actually some variability if anybody's ever seen in EKG, which I'm sure everybody has seen. But maybe you haven't thought so much about what all the little squiggly lines mean without going into the details of what the P wave and the QRS and T waves mean think most people will recognize that there is a very big spike for each of those beets. And that's actually the our Spike. If you now measure the distance between the ours, we call that the RR interval and you
The root mean square of the successive differences between the heart beats. So that means you calculate, the time difference between each RR interval. Each of those values is squared. So X itself and the result is averaged before the square root of the total is obtained. So, it's just kind of mathematical method for trying to approximate differences. You get What's called the are mssd again, if you just think about that and units you
Took something that was in Ms. U squared it. So it became Ms. Squared, you added them all up. It was still Ms. Squared. You took the square root of it. It's back to Ms. So our mssd is reported in milliseconds. If anybody's been paying attention to wearables, a number of these things will calculate your heart rate variability. Typically while you're sleeping and you'll notice it gives you a number in milliseconds. I think prior to the Advent of wearables. This was typically just done with an EKG or
Another sort of chest strap like device that was very accurately measuring, the electrical activity of the
heart. The next question is, probably why do we measure HRV? So you talked about heart rate, think people would understand measuring heart rate and maybe why that matters know why you might want to lower heart rate in general. Why do we measure HRV? What does it tell us? Or what? Can it tell us? Possibly,
as I alluded to above the heart, even when your heart rate is not changing? And if you're at rest, which is
When we measure HRV, so we don't really measure HRV, when you're out and about moving around because just the movement itself that you're undergoing is going to change your heart rate. So if I stand up from my desk and go and walk over to the kitchen and do something well at that's going to increase my heart rate just because I stood up and if I'm exercising, obviously my heart rate is changing quite a bit. So this is really something that we care about when you're at rest. But as I said, there is variability between those beats and it turns out that that variability is heavily influenced by which of the autonomic
Nervous systems is most dominant. So this probably warrants a slight detour. So we have broadly broadly speaking to nervous systems. We have one that is under our control and one that is not under our control and that's a very good thing if you want to reach for and grab a pencil or walk, obviously that requires voluntary control. You want to be in control of those nerves firing and making muscles do their thing.
But you certainly don't want to have to be thinking, and consciously making things happen that need to happen constantly. You certainly wouldn't want to have to think about breathing, certainly wouldn't want to have to think about your heart beating. You certainly wouldn't want to have to think about digesting food. You certainly wouldn't want to have to think about a lot of things that take place beneath the surface. So all of those things are regulated by. This thing called the autonomic nervous system. We further divide this autonomic nervous system into two branches. One is
The sympathetic system and the other is called the parasympathetic system. The parasympathetic system the way we would always learn to remember this in medical school was this was the rest and digest system. So this is the down-regulating system. It conserves energy. It aids in digestion. It slows heart rate. Our favorite little fact was it was responsible for erections, but not ejaculation ejaculations. Somehow came from this.
Sympathetic system. So the sympathetic system of course is the fight or flight system. So it's making energy more available. It's dilating the pupils right? It's getting you ready to see as much information as possible. It's slowing digestion and peristalsis. Meaning it's slowing down. Anything that's not essential and it's increasing heart rate. Let's just think about what this looks like from a practical standpoint. If you're laying in bed and you hear a loud, bang in your house, you have no idea if it's an intruder or if a picture fell off the wall.
You don't even have to worry about the your brain isn't going to even force you to make that decision. It's going to make a decision for you, which is, this is a threat. And so your heart rates going to shoot up your pupils will dilate any amount of digestive energy going on right now will cease and your liver is going to start cranking out glucose and making you available for fighter flight. Okay. So what does this do? They HRV? It turns out when the sympathetic system is revved up HRV goes down. And when the parasympathetic
System is in control. HRV goes up and I think it's easy to think about this, right? As the heart rate speeds up, which is what's happening under sympathetic tone. There's less variability between the Beats when the heart rate slows down when the body is relaxing. There's more variability between beats
that enough that's intuitive or not. I was thinking about that. If you have over the course of a minute and your beats per minute is say your I don't know Lance Armstrong when he's at the height of his powers. I don't know what
that is.
Probably 30 beats per minute. Yeah,
30 and then you've got somebody else who has 100 beats per minute. Just the RR intervals, whatever you call it. There's just less time between them intuitively. I would think there would be less room for variation between each beat, that makes sense. Yeah. I mean, I don't know how strong the
correlation is between resting heart rate in HRV. It's almost undoubtedly positive, but I don't know what the r squared is on that. Is that a fair explanation? Bob? Does that make sense on why we would care about
HRV.
Yes, I think so as a knock-on to that when you get your HR be output, if it's high or low. What is that telling us or how does that inform us? What do we do with that information?
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