Living Longer is Not the Point

Average life expectancy in the UK has risen from roughly 50 years to over 80 in the last century. That is not a small thing. But the average person will spend their final 8 to 12 years living with significant functional limitation – unable to get off the floor unassisted, unable to carry their own shopping, unable to walk at a pace that would let them cross a road in the time the light gives them.

Medicine has become extraordinarily good at keeping people alive. It has not yet become equivalently good at keeping them capable. And the conversation about longevity, as it exists publicly, is almost always about duration. When people hear the word they hear "more years." The question that actually matters is what those years will contain – and the answer is determined not at 70, but at 40.

Muscle mass declines by 3 to 8 percent per decade after 30. VO₂max declines by roughly 10 percent per decade. Bone mineral density peaks at around 30 and falls thereafter. None of this is disease, and most of it will not show up on a blood test. It is the background rate at which capacity is being spent in every adult who is not actively working against it.

You can find a companion essay for this podcast episode at dmitrysokolovmd.com.

Transcript

SPEAKER_00 0:00

Living longer is not the point. And many people, including many doctors, get the two things that matter here confused. One is duration, the other is capacity. They are not the same, and they don't necessarily move in the same direction. Over the last century, medicine has achieved something remarkable. Average life expectancy in the UK has risen from roughly 50 years to over 80. That's not a small thing. Antibiotics, sanitation, vaccination, surgery, anesthesia, intensive care, the cumulative effect of a century of medical progress is that more human beings reach old age than at any point in history. But here's what that number obscures. The average person in this country will spend their final 8 to 12 years living with significant functional limitation. Not dying living, but unable to get off the floor unassisted, unable to carry their own shopping, unable to walk at a pace that will let them cross the road in the time the light gives them. Cognitively present, perhaps, but physically unable to do things that constitute a life worth living. Playing with grandchildren, traveling, cooking, walking without fear of falling, getting out of a chair without thinking about it. We have become extraordinarily good at keeping people alive, but not yet equivalently good at keeping them capable. There is a common version of history that says people in the Middle Ages lived to 30 or 35. That figure is real, but it's an average life expectancy at birth, almost entirely driven by infant and childhood mortality. Somewhere between 30 and 50% of children did not survive to adulthood. But if you made it to 21 in medieval England, you could reasonably expect to reach your early 60s. What modern medicine has done is not so much extend the human ceiling as fill in the survival curve beneath it. More people nowadays reach old age, but the functional quality of that final chapter has not improved at the same rate. In some ways, it has even deteriorated, because we're now sustaining biological life in bodies whose capacity to use that life has eroded substantially. And this is where the conversation about longevity goes wrong. When people hear the word, they hear more years. When I hear it, I hear what will those years contain? And the answer to that question is not determined at 70, but rather at 40. Capacity is the word that changes the conversation. Physical, cognitive, emotional capacity, the ability to do specific, measurable things that make our life functional and independent. Capacity has a trajectory. It rises through childhood and early adulthood, peaks somewhere between 25 and 35 depending on the domain, and then, unless something is done about it, declines. Muscle mass declines by roughly 3 to 8% per decade after 30. VO2 max, the single strongest predictor of all cause mortality we have, declines by approximately 10% per decade. Bone mineral density peaks at around 30 and falls thereafter, and cognitive processing speed begins to slow in the 40s. None of this is a disease, and most of it will not show up on a blood test or trigger a referral. It's the background rate of biological decline that's happening in every adult who is not actively, deliberately, and consistently working against it. The critical insight is this. If someone has poor capacity at 40, expecting the same capacity, let alone better at 80 is not optimism, but arithmetic that simply doesn't work. Because the decline is not linear, it accelerates. The difference between your fitness at 40 and at 50 is smaller than the difference between 50 and 60, which is smaller than the difference between 60 and 70. The curve steepens. And by the time it becomes obvious, by the time someone cannot get off the floor, cannot carry a bag, cannot walk briskly, the window for building meaningful reserve has narrowed considerably. This is where the concept of banking becomes essential. And I do mean it in the financial sense, because if you're watching this, you almost certainly understand compounding. Bone mineral density, built in your 20s and 30s, is a reserve you draw on for the rest of your life. You cannot easily deposit new bone at 65, although some options exist even then, but you're better arriving at 65 with a larger account you've built decades earlier. Muscle mass follows the same logic. The lean tissue you carry into your 50s determines what you have available to lose in your 70s and 80s. And cognitive reserve, the structural and functional resilience of the brain, is built through decades of sustained intellectual engagement, physical exercise, social connection, and sleep quality. It's not something you can suddenly acquire in retirement. The parallel to finance is precise. If you were a financial advisor, you would not advise a client to begin saving for retirement at 63, although even that may be better than nothing. You would tell them to begin as early as possible because the compounding is the mechanism. The same is true of physiological reserve. Every year of structured training, adequate protein intake, quality sleep, and cognitive engagement in your 30s and 40s is a deposit into an account you will desperately need in your 70s and 80s. And the interest compounds in both directions. Build early and the reserve sustains you. Neglect early and the deficit accelerates. But there is a distinction I want to draw between the two modes of effort because I think it changes how people relate to this. Maintaining capacity means you're fighting a decline. If your mindset is to maintain, you're holding a line. You're trying not to lose what you have. And while that is vastly better than doing nothing, the psychological experience of maintenance is defensive. You are aware that the direction of travel is downward and you're resisting it. Developing capacity is different. When the focus shifts from maintenance to improving something, getting stronger, increasing VO2 max, deepening a skill, building endurance you didn't have previously, you're no longer fighting decline. You're fighting stagnation. You're pushing off a horizontal line, not a descending one. And the subjective experience of that is fundamentally different. The person who is trying to hold their current fitness feels like they're losing a slow battle. The person who is trying to run a faster 5k deadlift 10 kilos more than the last quarter, they feel they're building something new. Both are doing the same physiological work, but the actual frame changes everything about adherence, motivation, and the long-term sustainability of the effort. I tell every person I work with, do not try to maintain. Instead, develop and the maintenance will happen as a side effect. There's also another practical dimension to this that I think is underappreciated. People assume they know whether they are in a good physical condition. They feel fine, they function at work, they can walk up a few flights of stairs without distress, so they take this as evidence that their capacity is adequate. Well, it's adequate, but for the demands of their current life, which for a desk-based professional are extremely low. But the question is not only whether you can meet today's demands, the question is whether you have sufficient reserve to absorb the demands of aging, illness, injury, or surgery that may and will come in 20 or 30 years. In my own practice, I use a small set of functional assessments as a midterm audit. These are not validated clinical thresholds with published cutoffs, but rather a handful of practical tests that give a useful insight in the status quo of our physical capacity, including if it matches what we'll need later in life. A dead hang from a bar. Can you hold your own body weight for 90 seconds to 2 minutes? This will test your grip strength, shoulder integrity, and the upper body endurance that predicts your ability to catch yourself in the fall, carry objects, and maintain independence. A wall set. Can you hold a seated position with your back against the wall for 90 seconds to 2 minutes? This tests your quad endurance, the muscle group most directly linked to getting out of a chair, climbing stairs, and recovering from a fall or preventing one. A farmer carry, walking with a weight equal to half your body weight for 2 minutes. This will test loaded carry capacity, grip endurance, trunk stability, and the integrated strength pattern that most closely mirrors real-world functional demand. Grip strength, measured with a simple dynamometer, is the most validated physical marker of all cause mortality in the published literature. It takes only 20 seconds. In my practice, the clinical floor, below which I'm concerned about sarcopenia, is 27 kg for a man and 16 kg for a woman. Those are the European consensus thresholds, but the floor is not the target. The target is substantially above that. The floor tells you something is already wrong, but what I want to see is reserve. If you cannot touch your toes or sit in a full squat, if your dead hang lasts less than 30 seconds before your grip fails, these are not the targets I've just described. These are the signals well below targets that your capacity at this point is meaningfully low for someone who expects to be independent at 80. And the honest message is not that this is a crisis, this is information. It's a midterm report on a process that has been running since you were born and will continue running until you die. And the question the report answers is simple. At this rate of change, where does the curve put you in 30 years? The longevity conversation as it exists publicly is oftentimes about duration. How to live to 120, how to add years, how to slow aging, and there is real science in some of that. But the question that actually matters, the one I think about when I see a patient in their 40s, who feels fine, whose blood tests are normal, and who has no idea that their functional capacity is already on the trajectory they don't want to take, is not how long they will live. It is what they will be able to do when they get there. Living longer is not the point. Living capable is the point. And this capability is not something you purchase suddenly at 65 when you notice it's missing. It is something you build or fail to build in the decades when it doesn't yet seem urgent.