#176 - AMA #27： The importance of muscle mass, strength, and cardiorespiratory fitness for longevity
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Summary
In episode 27 of the Ask Me Anything podcast, Dr. Bob Kaplan and I discuss all things related to the outputs of exercise and morbidity and mortality. Specifically, we go into great detail around the benefits one gets from a high degree of cardiorespiratory fitness, and the benefits that one will derive from a large amount of muscle mass and muscle strength. And conversely, what happens when you don't have those things? We also tease apart as best we can the relative contributions of each of those things.
Transcript
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Hey everyone, welcome to a sneak peek, ask me anything or AMA episode of the drive podcast.
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I'm your host, Peter Atiyah. At the end of this short episode, I'll explain how you can
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access the AMA episodes in full, along with a ton of other membership benefits we've created,
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or you can learn more now by going to peteratiyahmd.com forward slash subscribe. So without
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further delay, here's today's sneak peek of the ask me anything episode.
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Welcome to ask me anything episode number 27. I'm once again joined by Bob Kaplan. In today's
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episode, we discuss all things related to basically the outputs of exercise and morbidity and mortality.
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So specifically, we go into great detail around the benefits that one gets from a high degree of
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cardiorespiratory fitness and the benefits that one will derive from a high amount of muscle mass and
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muscle strength. And conversely, what happens when you don't have those things. We also tease apart
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as best we can, the relative contributions of each of those things. So is it more about muscle mass?
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Is it more about muscle strength? If you are optimizing to get the best health benefit in
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the least amount of effort, not something I recommend, where do you get the most bang for
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your buck? Is it strength? Is it cardiorespiratory fitness, et cetera? So anyway, this one is a really
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fun episode. I would encourage you to watch this one. So obviously it is available as any podcast is
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via audio, but this is one where I think the data being presented and we go through a lot of this
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by showing the figures. It just makes a heck of a lot more sense if you can see what we're talking
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about. So if you're a subscriber and you want to watch the full video, which I hope you do,
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you can find it on the show notes page. If you're not a subscriber, you will watch a sneak peek of this
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video on the YouTube page, but potentially this is the episode that gets you to subscribe. So without
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further delay, I hope you enjoy AMA number 27. All right, Bob, we got a pretty fun AMA today here,
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but before we do, I don't think I realized until looking at your background that the Boston Bruins
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had a 30 year drought in which they did not win their division, 1940 to 1970.
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Oh, I'm glad I missed that drought. Is that 1940, was that when there was fewer teams? I mean,
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it'd be really embarrassing. That's embarrassing. Well, it's not as embarrassing as the Maple Leafs
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who haven't won the Stanley Cup since I think 1967. Oh my goodness. If any team deserves a
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Stanley Cup, it's Toronto. I enjoyed, I think I sent you a video of a guy talking about,
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you know, that's bad enough, but was it a year ago or a couple of years ago? They lost to a
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backup goaltender, it was a Zamboni driver. Yeah, right. At the ACC.
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Yeah, that's a beautiful story though. Yeah. All right. So we've got a pretty fun topic,
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an important topic on the docket today, which is effectively kind of scratching the exercise
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itch as it pertains to longevity, but at a, probably a deeper level than folks who are used to. So
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where should we start? I think we should start with, well, aerobic fitness or cardiorespiratory
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fitness. Cause I think we've got a few of things that these questions have come in. I think a bunch
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of questions related to this, which is studies that look at how much lean mass you have and
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whether that is a predictor of longevity. And then there's also studies that talk about muscle
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strength, not just muscle mass and whether that predicts longevity and whether one of those is
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better than the other. But I think a good place to start is with cardiorespiratory fitness with
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similar question, you know, is, does better lead to less mortality and does lower cardiorespiratory
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fitness lead to higher mortality or is it at least associated? Okay. So let's start by kind of
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explaining to folks the metrics that we're going to talk about through this. So the most common thing
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I think we see in the literature is either METs, metabolic equivalents or VO2 max. And I think part of
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that is it's quite objective. So if anybody's had a VO2 max test, they'll understand how objective and
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unpleasant it is. I think we've talked about this before. So you are hooked up to an indirect
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calorimeter. So it's a device that provides complete occlusion around your mouth and your nose.
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Typically this device also sort of plugs your nose. So you're only breathing through your mouth.
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And the important thing is that the device has two sensors on it. One sensor measures the
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concentration of oxygen that is being expelled. And for the purpose of this discussion, that's the
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more important of the sensors, but for what it's worth, the other one is also measuring the
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concentration of carbon dioxide that's expelled. So because we know the concentration of oxygen and
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CO2 on the way in by knowing what comes out and obviously oxygen will be lower, CO2 will be higher.
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We know how much carbon dioxide was produced and how much oxygen was consumed. And knowing those two
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things gives you a flow rate, a VO2 and a VCO2. Those two pieces of information alone tell you how much
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energy you're utilizing via something called the Fick equation, if I'm not mistaken. So total energy
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consumption is 3.94 times VO2 plus I think it's 1.11 times VCO2 at any point in time. So if you have
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for this minute VO2 was this, VCO2 was that, you apply it to that equation and it will tell you
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you were utilizing 10 kilocalories per minute, which would be, you know, 600 kilocalories per hour,
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which is, you know, I do this sometimes when I'm doing my zone two, my zone two tends to be
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about 780 kilocalories per hour. So interesting, but again, that's not how I test zone two. I'm
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using lactate for zone two. But now what we're talking about is something different, which is
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what is the maximum utilization of oxygen? So if you make somebody work harder and harder and harder,
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so if they're on a bike and you keep adding wattage to the bike and they have to pedal against more and
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more resistance, or if they're on a treadmill and you make them run faster and faster and up at higher
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and higher incline, at some point they will reach a maximum, at which point they can no longer
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utilize more oxygen. Now we're not going to go into the why right now, but I believe that Alex
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Hutchinson and I covered that in some depth in our podcast, you may recall. And we talked about
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some of the alveolar limitations, how much of that is being limited at the gas exchange surface
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versus how much is being exchanged in the actual, pardon, how much of that is being limited in the
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muscle. But regardless of which of those it is, and it's possible it's a combination or it's possible
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that at low levels of fitness, it's more in the muscle and at high levels of fitness, it might be
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more in the lung. But that number is the VO2 max. When you're doing the test, it's measured typically
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in liters per minute, but then we normalize it by body weight. So we normalize it as liters per,
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well, we do it actually as milliliters per kilogram per minute. So when you start to hear the numbers
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that people kick around, the fittest of the fit are going to be North of 80, but what does that
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mean? It means they're North of 80 milliliters of oxygen per kilogram per minute. And I think
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actually Alex and I talked about that on the podcast, right? The highest ever recorded person
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was probably about 96 or so. And any sort of elite athlete, elite cardiac type athlete, right? So
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runner, cyclist, rower, those sorts of athletes, they're generally going to be above 70. So what does
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that number tell us about mortality, right? I mean, I think that's a question. And I think we've got
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some data to talk about that. So do you want to, you want to pull out one of these slides here?
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Okay. So this took a group of people, do you recall how old they were?
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And it ran them through a VO2 max test and then it ranked them and low were people who scored,
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I believe in the bottom 25th percentile. These are non equally weighted groups if my memory serves me
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correctly. But I think that low were the people in the bottom 25th percentile. Check me on that. Below
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average, I think was 25th to 50 percentile. And then 50 to 75th percentile was above average and high was
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like 75th to maybe 95th. And elite was just that top 5 percent. I'm probably off by a little bit, but
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directionally that's true. I just want to make sure people don't look at these and think that each of them
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Yeah. I think that's directionally accurate. I'm looking at the third table one, their patient
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demographics. It's interesting. So it's a total of 122,000 patients. And if you look at the low,
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below average and above average and high, they're all about 30,000 participants in each one of those
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groups. And then you've got the elite and there's a little over 3,500 versus the 30,000 that's split
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Got it. Yep. Okay. So that's about what we just said there. And we're looking at all cause mortality
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here and you can see a pretty clear trend. The two things that stand out are there's kind of a
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monotonic relationship between fitness and mortality. But the second thing that stands
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out is by far the biggest gap is between the people in the bottom 25 percent, which are categorized as
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low fitness and basically everyone above them. So if you go to the next figure, Bob, I think we get
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to see this in a little bit more detail. I like this figure, frankly, more because it allows us to see
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a bit more interesting stuff. So here we can see both for all patients. So lumping everyone in
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together, male and female, if you have low fitness and then comparing it to everybody else, what's the
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risk reduction? So if you go from low to below average to above average to high to elite, you can see
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what is the hazard ratio. So it's interesting going from just being low to being below average is a
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50 percent reduction in mortality over a decade if you're starting in your 50s. We're going to come back
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to that, but that is so important. It is. It seems like a weird message to give to somebody that, you
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know, I want you to be below average, but that is definitely a step up from low in terms of how they
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categorize these. That's right. If you then go from low to above average, it's about a 60 percent
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or 70 percent reduction in mortality. And it just continues monotonically to increase. Again,
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the lowest improvement is going from high to elite. That doesn't buy you a whole heck of a lot.
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It is still statistically significant. And that's to see that you have to look at figure C. Again,
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this is going to be one of those podcasts where it's really going to be better to watch this over
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video because, you know, the data just speak for themselves. And of course, the show notes are going
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to include all of these. So make sure you're looking at this. But remember, the hazard ratio for
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mortality is the reciprocal of the hazard ratio of risk reduction. So tables A and C are basically
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showing you similar things in the group comparison. So again, when I said that going from high to elite
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didn't have as much of a benefit, you can see it has the smallest hazard ratio of improvement in
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benefit or the reduction going from high to elite. It's 29 percent. But notice that the confidence
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interval does not cross one and therefore the P value is less than 0.05. Now, here's what's
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interesting. What they've done, and you can see all of these listed, right? So if you compare someone
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of low fitness to elite, it is a five fold difference in mortality over a decade, which is
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pretty remarkable. And that's what they show you above. They give you context. They put this in the
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context of other things that we commonly understand as being problematic for mortality.
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Namely, smoking, coronary artery disease, type 2 diabetes, hypertension, and end-stage renal disease.
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So look at these differences, right? And I believe, Bob, this is not just for someone who's
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currently smoking. This is if you've ever smoked, right? Yes. I think it was previously used or used
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tobacco. So they're really looking at the difference between never smokers. So you've never smoked in your
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lifetime to if you've ever smoked. Okay. And that's a 41 percent increase in mortality over the decade.
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Coronary artery disease, 29 percent. Diabetes, 40 percent. High blood pressure, 21 percent. And the
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most of all of these things, end-stage renal disease, about 280 percent increase in mortality.
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Now, we all understand what that means, but now when you compare that to the differences in these
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fitness levels, it gives you, at least in my opinion, a greater appreciation for how much
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improvement in mortality comes from improving your fitness. So if you look at the biggest driver
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of mortality, which would be end-stage renal disease in this cohort, it's the same as going from
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low cardiorespiratory fitness to above average cardiorespiratory fitness. So going from the bottom
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25th percentile to being in the 50th to 75th percentile, which is a totally achievable feat,
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as you'll see in a moment. Anything else you want to say about this, Bob, aside from the fact that it's
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sort of stunning? It is. It's really striking. So one little pro tip or amateur tip is when Peter
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was talking about the reciprocals, is that if you look at figure 2A and then you look at figure 2C,
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and you look at the group comparisons, if you want to see that plotted point, for example,
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on the right-hand side of figure 2A, elite versus low, you can look at figure 2C, where it says low
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versus elite, and the hazard ratio is 5. The reciprocal is just take 1 divided by 5, and you
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get 0.2. And then if you look at that, so then when you look at the chart, it makes sense. And then
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high versus low, for example, it's 3.9 for hazard ratio, which is about 4. So 1 divided by 4 is about
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0.25. That checks out. So just a little pro tip for the fans out there. That's helpful because these
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graphs have a log linear axis. So it's not intuitive to look at these things. Going from low to below
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average gives you half of the benefit, but you'll never get the remaining half ever, because that
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would imply immortality, which obviously isn't happening. Okay. Now let's put some numbers to
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this, because this is one of those things that we use a lot with our patients, because we want most of
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our patients, we want all of them doing this, but not all of them are willing to do it. But we
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certainly want everybody to have a VO2 max test so that we can kind of benchmark them on their way to
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their centenarian Olympics. So let's actually see what these numbers look like. Thank you for listening
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