Imagine that every fixable part of aging got fixed tomorrow.
Worn-out cells cleared away on schedule. Cell batteries running like new. The protective caps on your chromosomes restored. Inflammation quieted, hormones balanced, tissue repair working the way it did at 25. Everything about aging that can in principle be undone, undone.
How long would you live?
That sounds like a question for a science fiction novel, but a research team in Moscow has just answered it with real numbers. Their paper, in press at the journal npj Aging, takes the one part of aging that cannot be reversed, follows it to its logical end, and reports a figure.
The answer is about 156 years.
The number is interesting. What the researchers found along the way is more interesting still, and it has something to say about how each of us cares for the body we have.
The one kind of damage you cannot undo
Most of what we call aging is wear and tear. Things accumulate that should not, or things run down that should not. Wear and tear is fixable in principle, and much of it is at least partly fixable in practice.
There is one exception, and it is the subject of this study.
Every cell in your body carries a copy of your DNA, which is essentially a very long instruction manual. Every time a cell repairs itself, copies itself, or divides, there is a small chance of introducing a typo. Not an inherited typo, the kind you were born with, but a brand new one that appears in one cell during your lifetime. Scientists call these somatic mutations. I will just call them typos.
Typos pile up. A neuron in your brain picks up roughly 17 of them a year. A heart muscle cell picks up about 36. Most are harmless, landing in stretches of the manual that particular cell never reads. But occasionally a typo lands in a critical instruction, and that cell dies.
Here is why this matters more than the other kinds of aging damage. You cannot un-typo a genome. Once the instruction is scrambled in a given cell, the original text is gone from that cell forever. There is no backup copy to restore from. Editing every cell in a living human body is theoretically imaginable and nowhere close to real.
So if you want to know the true ceiling on human lifespan, this is where to look. Everything else can, at least on paper, be repaired. This cannot.
Starting with a body that never ages
The researchers built their answer in layers, and the first layer is the one I find most illuminating.
They asked what life expectancy looks like if aging simply does not happen at all.
A body that does not age is not immortal. People still die of car accidents, infections, falls, and bad luck. What makes it non-aging is that the risk of dying does not climb as the years pass. A 400-year-old faces exactly the same odds in any given year as a 30-year-old.
So the team took national mortality records from 16 countries, picked Switzerland (which has the lowest background risk among countries with long modern records), and froze the death rate at its age-30 level. Thirty is a deliberate choice. It describes someone in good health, fully out in the world and exposed to all its ordinary hazards, but not yet carrying the diseases of later life.
Freeze the risk there, and half the population would still be alive at 1,759 years. One in 100,000 would reach roughly 29,000.
Two smaller findings from this baseline stayed with me. Freeze the risk at its lowest point in all of life, around age 8, and the median climbs past 10,000 years. And freeze it at the level a 110-year-old actually faces, and the median remaining lifespan is one more year. That second number is a quiet reminder that what kills people at extreme age is the accumulated risk itself, not some hard wall at 122.
The cells you never get back
With that baseline established, the researchers added exactly one thing: cells dying from DNA typos, in the parts of the body that cannot make replacements.
This is the heart of the problem. Brain cells and heart muscle cells are, for practical purposes, the ones you were issued at the beginning. The front part of your brain holds roughly 3.5 billion nerve cells. The heart holds roughly 3.2 billion muscle cells. Neither pool is meaningfully restocked over a lifetime.
Working out how often a typo actually kills one of these cells took considerable effort. The team pulled DNA readings from individual cells taken from healthy donors, measured how fast typos accumulated with donor age, then worked out which parts of the instruction manual are genuinely essential for that particular cell type and how likely a typo in each spot would be to break something vital.
The answer, for both brain and heart cells, comes out to roughly one cell in 400 dying per year from this cause. A small number. Over centuries, not small at all.
The researchers also had to decide what counts as organ failure, and they sensibly set it well before the last cell dies. For the brain, they used the 30-50% loss of nerve cells at which cognitive problems become the rule in dementia, and placed the failure point at 60% of the starting count. For the heart, losing 40% or more of the main pumping chamber’s muscle is dire, so they set the failure point at 55%.
Run the clock forward, and the brain crosses that line at roughly 198 years, the heart at 212. Factor in ordinary background risk, and brain aging alone gives a median lifespan of 194 years. Heart aging alone gives 208.
Consider what that means. One single mechanism, acting by itself, cuts the median from 1,759 years down to under 200. Typos in cells you cannot replace are not a footnote in aging. They are the main event.
The organs that barely notice
Then the researchers added the ability to replace lost cells, and the picture flipped completely.
The liver was modeled first with only its main working cells, which divide and replace their own losses but have a built-in limit on how many times they can do so. Even in that stripped-down version, the liver does not reach failure until a median of nearly 38,000 years.
Then they added the liver’s reserve repair cells, the quiet backup crew that steps in after major damage. In that version, not one simulated life reached liver failure within 100,000 years. Not a single one.
The airway was modeled with the repair cells that line your breathing passages. These are a middle case. They can replace losses, but they have no backup crew of their own, so every division uses up part of a fixed budget. Their numbers hold nearly flat for thousands of years, then decline as the budget runs out, reaching failure around 4,400 years. Enough to matter eventually. Not enough to matter for anyone reading this.
That contrast is the real finding of the study. Tissues that can replace themselves are, against DNA typos alone, essentially untouchable. Damaged cells simply get swapped out for clean ones, and the damage never compounds. Tissues that cannot replace themselves have nowhere to hide.
There is something worth noticing in that arrangement. The organs asked to handle the body’s dirtiest work, the liver processing everything you swallow, the airway meeting the outside world with every breath, were built with deep reserves for repair. The organs that carry your memory, your personality, and the beat of your life were built for endurance instead. They endure remarkably well. They do not endure forever.
Putting the body back together
The last step was to reassemble the four organs into a whole person. The rule is simple and unforgiving: if any critical organ fails, the person dies.
With brain, heart, liver, and airway all aging together from DNA typos alone, and ordinary background risk included, the median lifespan comes out to 156 years. That is roughly twice the 79 years Swiss residents actually live. The far edge, the age reached by one in 100,000, comes out to 470 years.
Because organs do not really age in isolation, the team also calculated the extremes of what any pattern of connection between them could produce. That range runs from 146 years at one end to 194 at the other. So the honest answer is a median somewhere in the 146-194 range, with 156 as the best single estimate.
The half we can still do something about
Here is the part I keep coming back to, and it is not the ceiling.
If you fixed every fixable form of aging and left only the DNA typos, you would roughly double median lifespan, from about 79 to about 156. Which means the typos account for something like half the gap between what we actually live and what we could live in a body that did not age at all.
The other half belongs to everything else. Worn-out cells, failing cell batteries, chronic inflammation, hormonal drift, exhausted repair systems, metabolic dysfunction.
That is genuinely good news, because the second half responds to how we live. The unfixable half sets a ceiling we cannot presently move. The fixable half is what is costing us decades right now, and it answers to food, movement, sleep, muscle, blood sugar, and inflammation. Those are not future therapies waiting on a laboratory. They are available this afternoon.
It also means the more breathless longevity predictions, the ones promising we will outrun aging entirely, do not survive contact with this study. The researchers say so plainly. Even in the best imaginable case, the brain eventually runs out.
What the study does not claim
The authors are refreshingly honest about their limits, and their honesty deserves as much attention as their headline.
Their model counts only typos that kill a cell outright. Typos that leave a cell alive but working poorly are not counted, and there are surely far more of those. Cancer is set aside entirely, on the assumption that the immune system catches it. Only four organs were included, which leaves out the kidneys, the gut, the pancreas, the immune system, and the blood vessels.
Every one of those omissions pushes in the same direction. Adding any of them would lower the estimate, not raise it. This is a ceiling, not a forecast. It describes what DNA typos permit, not what anyone is going to achieve.
What I take from this
Three things, none of which are new to me, but all of which this study sharpens.
First, the difference between tissue you can replace and tissue you cannot is the most important structural fact about aging. Your liver will forgive you a great deal. Your brain and heart keep a permanent record. Anything that reduces the load on those two organs is protecting cells that are never coming back, and this study puts a number on what that permanence costs.
Second, the damage you take on is written into that record. The researchers point out that both brain and heart cells carry unusually high internal oxidative stress, and that Alzheimer’s disease, multiple sclerosis, and heart disease each speed typo accumulation beyond the normal rate. Disease is not only a downstream result of the damage. It feeds back and raises the rate. Tobacco smoke, unnecessary radiation, and long-running untreated inflammation are all writing into a document that cannot be edited afterward.
Third, and most practically: if the ceiling sits near 156 and we are living to 79, the distance between those two numbers is where good daily decisions do their work. Not in some future clinic. In the body each of us has been given to look after.
The ceiling is real. Almost none of us are anywhere near it.
