The Peter Attia Drive - January 31, 2022


#193 - AMA #31： Heart rate variability (HRV), alcohol, sleep, and more


Episode Stats


Length

14 minutes

Words per minute

168.98405

Word count

2,378

Sentence count

69


Summary

Summaries generated with gmurro/bart-large-finetuned-filtered-spotify-podcast-summ .

In this episode, Dr. Bob Kaplan joins Dr. Atia to talk about heart rate variability (HRV) and the effects of alcohol on sleep. Dr. Kaplan discusses the importance of HRV and the role of ethanol in these phenomena.

Transcript

Transcript generated with Whisper (turbo).
00:00:00.000 hey everyone welcome to a sneak peek ask me anything or ama episode of the drive podcast
00:00:16.400 i'm your host peter atia at the end of this short episode i'll explain how you can access
00:00:20.840 the ama episodes in full along with a ton of other membership benefits we've created
00:00:25.460 or you can learn more now by going to peter atia md.com forward slash subscribe so without further
00:00:32.140 delay here's today's sneak peek of the ask me anything episode
00:00:35.880 hey everyone welcome to ask me anything episode number 31 i'm joined once again by bob kaplan
00:00:46.780 although as you'll learn at the end of this episode this will be the last time we're joined by bob
00:00:51.200 kaplan but let's not get ahead of ourselves in today's episode we talk about really two things
00:00:55.620 in detail one is hrv heart rate variability we've had so many questions on this subject for the past
00:01:02.000 couple of years and we've just been slowly kind of collecting questions until we thought we had
00:01:06.880 enough to do kind of one of our thematic shows on it and the second thing we talk about is ethanol
00:01:11.660 all things related to ethanol so how does it affect hrv is really our segue but then also what are the
00:01:16.980 effects of alcohol on sleep and we really go after mortality probably where we spend most of our time
00:01:22.500 and we talk about it through the lens of all of the epidemiology as most of you or may some of you know
00:01:29.060 there's a confusing body of literature out there that suggests that maybe some alcohol is good for
00:01:34.200 you and no alcohol is not as good for you and so we go really deep on this subject matter so
00:01:39.960 again if you have any questions about alcohol or if you drink at all and if you or if you don't drink
00:01:44.600 and you're wondering if you should be drinking i think this episode will be very helpful for you
00:01:48.660 so one thing i want to point out for this episode this episode was just due to some limitations of
00:01:53.780 timing when we recorded this was not recorded in video so we will only be doing this in audio that
00:01:59.540 might make the show notes a little more important although we didn't really have a lot of content here
00:02:04.100 that necessitated being able to see so i think you're going to be fine listening to this in audio but
00:02:09.160 obviously the show notes will have any of the graphs and other images that we talk about now if you're not a
00:02:13.840 subscriber of course you can get a sneak peek of this as usual and then you'll have to obviously
00:02:18.460 subscribe if you want to enjoy the full content so without further delay i hope you enjoy ama number 31
00:02:24.960 hey bob how's it going today going well peter how are you it's good it's a little unusual today we're
00:02:36.620 doing this a little bit on the old school tip no video today we're gonna have to be a little bit
00:02:41.000 more descriptive in our terms since people can't watch our facial expressions although that somehow
00:02:46.600 provided any value we won't do any screen sharing i think we can manage what do you have in store for
00:02:53.280 us today so i aggregated a whole bunch of questions around hrv heart rate variability and alcohol many
00:03:02.800 questions on both those topics i know this has been something you've been asking me about for a year
00:03:07.960 when are we going to do one on hrv when are we going to do one on hrv so i think the answer is
00:03:12.020 now all right we'll dive in first question seems relevant what is hrv and it's funny this is a tougher
00:03:21.660 question to answer without an image but i'll do my best so as you pointed out a second ago hrv stands
00:03:28.760 for heart rate variability and that's a pretty descriptive term because what it measures is the variation in
00:03:35.260 time between heartbeats and that's measured in milliseconds so a thousand milliseconds is one
00:03:41.600 second so if a person's heart is beating 60 times per minute you might say well there's a thousand
00:03:51.600 milliseconds between every beat but it turns out that it's not really that way you see even if your
00:04:00.220 heart is beating 60 times per minute or once per second between the first beat and the second beat
00:04:06.660 it might be a thousand ten milliseconds and between that beat and the next beat it might be 960 milliseconds
00:04:18.120 and between that beat and the beat thereafter it might be a thousand 27 milliseconds when you start
00:04:24.520 looking at this thing at the level of thousandths of a second you realize that there is actually some
00:04:30.600 variability if anybody has ever seen an ekg which i'm sure everybody has seen but maybe you haven't
00:04:35.920 thought so much about what all the little squiggly lines mean without going into the details of what the
00:04:40.760 p wave and the q r s and t waves mean i think most people will recognize that there is a very big
00:04:47.020 spike for each of those beats and that's actually the r spike if you now measure the distance between
00:04:55.520 the r's we call that the rr interval and you take the root mean square of the successive differences
00:05:03.460 between the heartbeats so that means you calculate the time difference between each rr interval each of
00:05:11.600 those values is squared so multiplied by itself then the result is averaged before the square root of
00:05:18.920 the total is obtained so this is kind of a mathematical method for trying to approximate
00:05:23.880 differences you get what's called the rmssd again if you just think about that in units you took
00:05:29.880 something that was in milliseconds you squared it so it became milliseconds squared you added them all up
00:05:34.520 it was still milliseconds squared you took the square root of it it's back to milliseconds so
00:05:38.180 rmssd is reported in milliseconds if anybody's been paying attention to wearables a number of
00:05:46.340 these things will calculate your heart rate variability typically while you're sleeping
00:05:49.420 and you'll notice it gives you a number in milliseconds i think prior to the advent of wearables this
00:05:56.420 was typically just done with an ekg or another sort of chest strap like device that was very accurately
00:06:04.060 measuring the electrical activity of the heart the next question is probably why do we measure hrv so
00:06:10.180 you talked about heart rate i think people would understand measuring heart rate and maybe why that
00:06:14.980 matters why you might want to lower heart rate in general why do we measure hrv what does it tell us
00:06:20.720 or what can it tell us possibly as i alluded to above the heart even when your heart rate is not changing
00:06:27.400 and if you're at rest which is when we measure hrv so we don't really measure hrv
00:06:32.400 when you're out and about moving around because just the movement itself that you're undergoing is
00:06:38.180 going to change your heart rate so if i stand up from my desk and go and walk over to the kitchen and
00:06:42.080 do something well that's going to increase my heart rate just because i stood up and if i'm exercising
00:06:46.580 obviously my heart rate is changing quite a bit so this is really something that we care about when
00:06:50.680 you're at rest but as i said there is variability between those beats and it turns out that that
00:06:55.500 variability is heavily influenced by which of the autonomic nervous systems is most dominant so this
00:07:03.100 probably warrants a slight detour so we have broadly broadly speaking two nervous systems we have one that
00:07:11.180 is under our control and one that is not under our control and that's a very good thing if you want to
00:07:19.020 reach for and grab a pencil or walk obviously that requires voluntary control you want to be in
00:07:25.400 control of those nerves firing and making muscles do their thing but you certainly don't want to have
00:07:30.860 to be thinking and consciously making things happen that need to happen constantly you certainly wouldn't
00:07:36.780 want to have to think about breathing you certainly wouldn't want to have to think about your heart
00:07:41.120 beating you certainly wouldn't want to have to think about digesting food you certainly wouldn't want to
00:07:46.020 have to think about a lot of things that take place beneath the surface. So all of those things
00:07:51.100 are regulated by this thing called the autonomic nervous system. We further divide this autonomic
00:07:56.700 nervous system into two branches. One is called the sympathetic system and the other is called
00:08:02.220 the parasympathetic system. The parasympathetic system, the way we would always learn to remember
00:08:08.880 this in medical school was this was the rest and digest system. So this is the down-regulating
00:08:16.580 system. It conserves energy. It aids in digestion. It slows heart rate. Our favorite little fact was
00:08:24.620 it was responsible for erections, but not ejaculation. Ejaculation somehow came from the sympathetic
00:08:29.980 system. So the sympathetic system, of course, is the fight or flight system. So it's making energy
00:08:35.740 more available. It's dilating the pupils, right? It's getting you ready to see as much information
00:08:41.040 as possible. It's slowing digestion and peristalsis, meaning it's slowing down anything that's not
00:08:47.000 essential and it's increasing heart rate. Let's just think about what this looks like from a
00:08:50.920 practical standpoint. If you're laying in bed and you hear a loud bang in your house, you have no
00:08:56.840 idea if it's an intruder or if a picture fell off the wall, but you don't even have to worry about
00:09:01.460 your brain isn't going to even force you to make that decision. It's going to make the decision for
00:09:05.660 you, which is this is a threat. And so your heart rate's going to shoot up. Your pupils will dilate.
00:09:10.720 Any amount of digestive energy going on right now will cease and your liver is going to start
00:09:15.520 cranking out glucose and making you available for fight or flight. Okay. So what does this have to do
00:09:20.340 with HRV? It turns out when the sympathetic system is revved up, HRV goes down. And when the
00:09:28.760 parasympathetic system is in control, HRV goes up. And I think it's easy to think about this, right?
00:09:34.280 As the heart rate speeds up, which is what's happening under sympathetic tone,
00:09:38.720 there's less variability between the beats. When the heart rate slows down, when the body is
00:09:44.860 relaxing, there's more variability between beats. I don't know if that's intuitive or not. I was
00:09:49.460 thinking about that. If you have over the course of a minute and your beats per minute is say,
00:09:54.420 you're, I don't know, Lance Armstrong when he's at the height of his powers. I don't even know what
00:09:59.300 that is. Yeah, probably 30 beats per minute. Yeah. 30. And then you've got somebody else who
00:10:03.160 has a hundred beats per minute, just the R, R intervals, whatever you call it. There's just
00:10:07.040 less time between them. Intuitively, I would think there would be less room for variation between
00:10:12.060 each beat. If that makes sense. Yeah. I mean, I don't know how strong the correlation is between
00:10:17.760 resting heart rate and HRV. It's almost undoubtedly positive, but I don't know what the R squared is
00:10:23.420 on that. Is that a fair explanation, Bob? Does that make sense on why we would care about HRV?
00:10:29.580 Yes, I think so. As a knock on to that, when you get your HRV output, if it's high or low,
00:10:35.600 what is that telling us? Or how does that inform us? What do we do with that information?
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