Could a decreased heartrate thanks to better hemoglobin lead to an increased lifespan?

Question

When looking at mammals and their heart rates one can find a correlation between the lifespan of a mammal and their heart rate. Namely most mammals seem to get about 1 billion (the American one) of heartbeats in their life (with some slight discrepancies).

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Now mammals, such as humans, use blood to transport oxygen. When they enter increased physical activity, e.g. running, their heart rate increases to transport more oxygen to organs and muscles.

My idea is that if we can increase the oxygen transported by the blood we could decrease the heart rate necessary to transport enough oxygen, thus increasing life-expectancy as we have more beats left.

A possible way to achieve that increase in oxygen transported in blood is to use the hemoglobin of lugworms, which can transport ~40 times as much oxygen as human hemoglobin.

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Q: Could this increase in oxygen-carrying-capacity in blood lead to a decreased heart rate and thus to an increased lifespan?

Bonus: How many additional years could I get?

Answer 1

Probably not.

This idea that heart-rate inversely correlates with life span, also called the rate of living theory While some studies have showns a correlation between heart rate and life span, this doesn't imply a causal relationship. In fact it's more likely that heart rate and life span are both a function of the size of the animal. Larger animals having larger more efficient hearts that need to beat less.

A 2007 study on the subject found no correlation between metabolic rate and average life span birds and mammals. They concluded:

Body Mass Is Likely Associated With Longevity due to Ecological Constraints

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Of course in the degenerate case there definitely isn't a link between low heart rate and a longer lifespan, since with a heart rate of 0 a lifespan of 0 is likely.

Answer 2

There is a lot of work done in science to see if there is a correlation between heart rate and longevity, but as the previous answer shows, this is not held to be the case.

The longevity of the heart though is only one thing that can kill you. Ironically enough, the molecule that seems to have the most to do with our ageing process is oxygen itself. In that sense, it's probably more likely that cumulative oxygen exposure is likely to kill you more than heart rate.

But (I hear you all say), exercise makes our heart beat faster, gets us breathing harder, and generally makes us use MORE oxygen and is also supposed to be good for you, right?

Well, exercise is good for us, but the truth is that anaerobic exercise is good for us because it actually causes a form of hypoxia; we're using energy faster than the oxygen in our system can be replaced to generate more energy within our system. It's only mild so it's not the life threatening form of hypoxia associated with suffocation and it's self tuning insofar as when we're exhausted we can't continue the exercise.

One way that exercise increases our fitness is by acclimating us to less oxygen in our bodies. That means when we are not working as hard, we can go for longer on the same amount of oxygen. This is exemplified the most by high altitude African long distance runners who come down to sea level and higher atmospheric pressures and run marathons with higher saturations of oxygen than they're used to, allowing them to run for longer without getting as tired.

Breathing excess oxygen generates what are called Free Radicals in our bodies, that can be harmful to our cellular structures. This is one of the reasons that anti-oxidants are touted as such a solution to the ageing process. They reduce free radicals out of our system and ensure that the amount of oxygen in our system is balanced a little better to our energy needs.

So, instead of making hemoglobin more efficient, perhaps the secret to longevity is making it less efficient. If we can reduce oxygen levels to those that we use at rest during normal breathing, and use increased heart rate and breathing to increase our oxygen levels during exertion, then several things will happen.

First, free radicals will be (radically) reduced. If we use all the oxygen we can absorb, then there's less of a chance of free radicals being present in our system. This means less overall damage to our bodies in normal day to day life.

Second, there will be an upper limit on what exercise or physical exertion we can actually do. This is not so bad a thing as one might think. In the past, we had to exert ourselves to eat and get out of danger. We've changed our environment so much that we have machines helping us get food and no natural dangers to speak of. Sure, we won't be able to out run a bullet, but we can't now so in some respects nothing would change except that we would all be a little slower.

Finally, our bodies would not age as fast because we're not processing as much oxygen (and carbohydrates) to produce energy. This is really one of those 'the light that burns half as bright burns half as long' situations. We know that oxygen causes ageing in our bodies, and we know that the animals that seem to be longest lived in our environment are those which are specialised to low oxygen environments, like the Naked Mole Rat (Underground) and the Bowhead Whale (DEEP underwater).

All this said...
It is important to note that a longer life is not necessarily a more fulfilling one. You'll be slower, doing less with your life (No one with lower oxygen absorption rates is climbing Everest for instance) and if all our tech dies one day, so do we. (But, that's arguably the case for most of us anyway if that happens.) Also, oxygen is not the only factor here. Assuming that we live longer with regular heart rate (say only 5% reduction in O2 absorption) then our heart has to beat more often. That may well end up one of the limiting factors. Not to mention mental disorders like Alzheimer's and Parkinson's disease. There are a range of things that could still kill us long before our cells naturally 'age'.

When you get right down to it, the human body is a marvel of bio-engineering. It is staggeringly complex, and it is that very complexity that causes part of this problem. Natural ageing, either by oxygen processing or the breakdown of any of the other 'critical' processing systems like kidneys, liver, heart, brain; the list goes on. The one thing that is sure is that evolution has built a body that is capable of far more energy expenditure than is currently needed with our current technologies to survive. As such, in a technical society, dialing back our oxygen intake may slow us down and lengthen our lives. Is that a good thing? Ultimately, if the choice was made to us, it would be up to each one of us to decide for ourselves.

Answer 3

You are too focusing on heart rate. If blood had 40x capacity for oxygen it could extend lifespan in many ways (not related to heart rate), decreased heart rate would be just side effect (that would probably lower that capacity).

Increased oxygen capacity would help in cases of heart and brain attacks where fast intervention is required. Looking at mortality rates , A1 (Coronary artery disease) and A2 (Brain stroke) categories contribute to 7,4% of deaths (if my calculations are right). Indirectly it would help with survivability in other categories too.

On its own (without medical intervention) heart has some regenerative abilities so with better oxygen supply it could cope with damage better.

Answer 4

As a hypothetical feature of superhumanoid physiology, genetic manipulation, or a sci-fi explanation for improved longevity, yes.

"Is this possible even if implausible?" Yes, it is possible.

I'm not much of a mathematician, please forgive the loose mathematics to estimate an answer to "How much longer do they live?"*new info

The original calculations have been redacted in light of newer findings. You could estimate based on the tool at the bottom of this post a decrease in estimated age of 3 years for an 8% decrease in VO2 max (I've heard it quoted 1%/year in various clubs). The average is quoted as 40 for fitness enthusiasts and 24 for the average person in fitness and health clubs. Age affects oxygen-carrying capacity moreso than the other way around, and not as a given/established causal relationship, only as a correlation.

You could in the name of fiction form an estimate from those numbers, like, say "if a 150yo wanted a fitness age of 34 with a 208 heart rate, they'd need 150-34=116/3=38.67, so 40*1.08^38.67=40^19.6, a VO2 max of around 784" but you see how quickly that got out of hand. That could be the equivalent of a human with an elephant or whale's oxygen-carrying capacity.

The caveat to that is bigger isn't always better (think horses and cheetahs and dogs, which all have higher VO2 max than humans, with supportive anatomies for the levels they do have, and humans outlive all of them). I've never found a study that supported it, the dogs racing the Iditarod are said to be near 225 or 230 for VO2 max.

In science!-based reality, no. *Partial edit, somewhat more plausible, but still limited to the entirety of thenstructure supporting it. You'd need something like Greed from FMA's body structure (not Brotherhood).

http://www.dailygalaxy.com/my_weblog/2010/11/sherpa-genetics-human-evolution-at-work.html "Even at elevations of 14,000 feet above sea level or higher, where the atmosphere contains much less oxygen than at sea level, most Tibetans do not overproduce red blood cells..."

Instead, they adapted to negate polycythemia, the body's response to oxygen deprivation (creating too many more red blood cells.

http://www.nature.com/articles/nature13408 In an environment in which scientists (biologists) had anticipated higher red blood cell count to facilitate greater efficiency in oxygen-carrying capacity, humanity had instead adapted by way of genetics and interbreeding to mitigate the effects of hypoxia.

Human adaptation was thus primarily negating negatives (hypoxia & polycythemia) rather than bestowing positives (increased oxygenation, carrying capacity). Humanity adapts by nerfing environmental hazards moreso than outright buffing.

sphennings made an excellent point, results of studies do not necessarily mean a causal relationship between heart rate and lifespan. Athletes are the best example for both forced inclinations in oxygen-carrying capacity (supplements) and natural inclination of lower resting heart rates & higher oxygen-carrying capacity.

The base or resting heartrates of active individuals -- professional and elite athletes especially -- appears to inversely correlate with oxygen-carrying capacity measured as VO2 Max.

While this is estimated by scientists and doctors as the "common sense/advice" that healthy/fit individuals live longer, heart rate and oxygen-carrying capacity are -- I'm going to stop this here and finish the edit when I have a desktop in 4 days.

As per the above information on athletic correlation, I found fitness.mercola.com/sites/fitness/archive/2014/11/07/amp/how-fitness-age-indicate-longevity.aspx to disprove where I was originally going (that despite fitness and healthiness plenty of athletes die earlier than comparatively less fit or healthy individuals) but the more I search the more similar articles, journals, and studies I find.

https://www.worldfitnesslevel.org/#/ This tool from the mercola article told me that despite my age, 34, and low VO2 max (31), my "real" count is actually <20 and about 59 for VO2 max. With the same max heart rate, it shows a loss of about 3 years & 8% VO2 max for picking the most sedentary choices. I tried with different info and it came out to be about the same.