Medicine is treating your age, not your body – How organ-aging clocks could predict trouble years before standard blood tests

In 2015 I was 43 years old and my blood work said I was generally fine.

Total cholesterol: 190 mg/dL

LDL cholesterol: 119 mg/dL

HDL cholesterol: 40 mg/dL

Triglycerides: 237 mg/dL (above the 150 threshold, which is why I was advised to improve my diet)

HbA1c: 5.9% (pre-diabetic, but the aforementioned diet would take care of this)

Lp(a): 12 mg/dL (minimal to no genetic risk of heart disease)

Nothing on that page said stop what you are doing or raised a red flag; a yellow flag at best. The fact that I weighed 161 lbs (73 kgs) for my height (6 feet) and I was playing competitive soccer twice a week helped the narrative that I was a couple of dietary tweaks away from everything being fine. And the medical guidelines that drive diagnostic and therapeutic interventions suggested that at 43 I was still years short of the birthday at which things like a coronary artery calcium score or a stress test needed to be done, especially in the absence of any symptoms showing up.

Then, by chance, I walked into the South Asian Heart Center. They ordered a coronary calcium scan even though I had no symptoms and no complaints, largely motivated by the founder’s desire to understand why so many South Asians were being diagnosed with heart disease at increasingly younger ages. (Thank you, Ashish Mathur). My score came back at 266. That put me in the 98th percentile for my age. Ninety-eight men out of a hundred my age had less calcium in their arteries than I did, and every blood test I had ever taken had missed it. Everything I have done with my health since started with that scan. And that scan happened by luck.

My blood test in an alternate universe

Imagine a different type of report being generated every year that I did my standard blood test. In addition to the reported biomarkers, such as cholesterol, triglycerides, etc., it also has an aging pace for each of my organs. An age for my lungs, kidneys, liver, brain, etc., all in line with my calendar age of 43; some a couple of years older, while others a bit younger. But the age of my heart would probably read 53. And that would be the flag that would trigger a calcium scan. The protocol would now be personalized based on what’s happening to me rather than driven by a generic protocol that’s based on age.

That is the difference between what actually happened to me and what could one day actually happen. But here’s the good news: this isn’t a hypothetical scenario any more; that world is close. Two papers published this year, a review by Eric Topol and Tony Wyss-Coray, as well as the study referenced in it, which read the aging signature of dozens of cell types across 60,000 people, mean this report could soon actually be produced.

Wow!! Really? Tell me more about how this works.

So glad you asked. Organs do not age together. When we eventually succumb, it’s usually because one organ gave way. So in theory, if we could avoid any runaway organ that is our weakest link because it is aging way faster than the others, we could potentially live healthier for longer.

The cleanest proof comes from a group of British people all born in the same week of March 1946 and followed ever since. When they were 63, researchers measured the aging of six organs in each of them. The spread was about ten years! So while they were all 63 as their chronological age, some of them had organs like those of a 53 year old, while others had organs that were the equivalent of a 73 year old’s. And even more interestingly, the same person had organs that were easily 10 years apart in age.

The key insight here is that chronological age cannot be the sole driver of medical protocols.

Hold on! How do you get an age for my liver out of a tube of blood?

Fair question, and the answer is simpler than you would expect. Every organ leaks proteins into your bloodstream, and it turns out that a meaningful number of them come predominantly from a single organ; one protein is mostly from the liver, another is mostly from the brain, another is mostly from the heart. Measure the levels of those organ-specific proteins, then compare the pattern against thousands of people whose ages are already known. If your liver proteins look like those of a typical 60 year old and you are 50, your liver clock reads 60.

Same blood draw. Same fifteen minutes in the chair. A completely different question asked of it. That is also why this can plausibly become routine rather than exotic. It doesn’t need a new machine in every clinic. It needs the sample you were already giving.

But doesn’t my standard blood test already indicate how healthy my organs are?

Your standard panel measures what your body is doing right now. Cholesterol is what is circulating today. HbA1c is the last three months of sugar. Good snapshots, which is why we use them. An organ clock measures something different. Not the level today, but how fast that organ is wearing out. Not the position, but rather the trajectory.

That gap is exactly where I fell through. My LDL cholesterol of 119 mg/dL was a snapshot, and the snapshot was unremarkable. What it could not tell me was that my arteries had been slowly but surely deteriorating for a decade, while I felt strong.

The study shows this pattern again and again. Immune cell aging predicted future diabetes in people whose blood sugar was still completely normal. As a comparison, HbA1c is used to determine if you are diabetic today, while fasting insulin is used to determine the same thing about five years in advance. The age of the immune system can potentially help explain a lot of such issues significantly better and earlier. Similarly, lung cell aging predicted cancer even after accounting for whether someone smoked, meaning the cells knew something that smoking status did not. This is a pretty big one, given Post #66, where I spoke about the fact that 25% of lung cancer cases are happening in non-smokers, and given that current protocols don’t support screening for lung cancer in non-smokers, mortality rates in that group are very high because the cancer is diagnosed only after symptoms show up. Therefore lung cell aging can make a meaningful impact in a way we have never had before.

So the regular blood markers and organ aging are complementary. Your cholesterol tells you what to treat today. The organ clock tells you which part of you is heading somewhere you will not like. You want both.

This is amazing! Give me one more example that illustrates the power of this approach.

I see you are as excited about this as I am. So here’s one more. Alzheimer’s risk turns out to hinge not on the brain in general but on one supporting cell called an astrocyte. Its job is to keep your neurons fed and cleaned up.

Take two people. Both sixty-two. Both carrying two copies of APOE4, the gene we have treated for years as close to a sentence for Alzheimer’s. Our current system would regard them as effectively having the same risk. However, their astrocyte clocks can be very different. Over fifteen years, the carriers with older astrocytes developed Alzheimer’s about 38% of the time, while the ones with normally aging astrocytes came in at 13%. And among the 23 carriers of the same APOE4 gene whose astrocytes were youngest, not one developed Alzheimer’s. Zero.

The same pattern shows up in survival: people whose brain and immune clocks run normally do remarkably well over fifteen years even when their other organs are aging badly. It’s not established exactly why those two organ clocks play an inordinately larger role, but the consensus is that they are, after all, the master regulators of the body. The brain identifies the issues and the immune system takes care of them.

Excellent! So is this reversible?

The answer to that is yes… but.

Researchers went back after ten years to see whether fast aging organs stay fast aging. Mostly, they do. These clocks are sticky. This is not a dial you spin on a Sunday afternoon. But the same work compared about a thousand people living genuinely well (never smoked, healthy weight, seven hours of sleep, exercise five days a week) against a thousand who smoked and carried obesity. The healthy group was biologically younger broadly, across many cell types at once. Both are true. These clocks resist quick fixes but respond to sustained ones.

I get it. I need to be consistent. So what should I focus on starting tomorrow?

Ideally you would start by ordering this test. Unfortunately, these clocks are not commercially available yet, except in some research institutions. The UK Biobank has already measured thousands of blood proteins at roughly $50 a person at scale. If I had to guess, this should be available in a year or two. There are some epigenetic age tests available and I have done them myself. But frankly, they are more for entertainment purposes, and while they provide directional guidance, they are quite expensive. So only do them if you want to do it for fun.

Here is what I would suggest, especially if you are over 40 or have a family history of early heart disease:

A coronary calcium scan. A few hundred dollars in the US, a few thousand rupees in India, ten minutes, no needle. It looks directly at your arteries rather than inferring from your blood. A score of zero is genuinely reassuring. Anything above zero means disease is already present and the conversation changes from prevention to treatment. Mine was 266 at 43 with unremarkable lipids, which is the entire argument for asking.

Lp(a), once in your life. It is largely genetic, it does not move much, and roughly one in five people carry a level that meaningfully raises their risk. Most have never been tested. Mine was 12, which is fine, and knowing that changed how aggressively I treated everything else.

ApoB and fasting insulin. LDL-C measures cholesterol. ApoB counts the particles carrying it, and the particle count is what actually collides with your artery wall. Two people with identical LDL can have very different ApoB. Fasting insulin is the other one almost nobody orders. Your pancreas compensates for insulin resistance for years by simply making more insulin, and during those years your HbA1c stays normal. With my HbA1c sitting at 5.9, this is the test I most wish someone had run on me in 2015.

On the cancer side I am deliberately not adding anything exotic, because the highest-value thing available to you today is unglamorous: being on time for the screenings that already exist. Colonoscopy from 45. Mammography from 40. Cervical screening. Low-dose CT if you have a real smoking history. Take ten minutes this week and check your dates.

I understand from a diagnostics perspective. But from a lifestyle intervention perspective, what should I focus on?

Eleven years on, I am 54 and I am in the best shape of my life. What that took was not clever. It was Zone 2 cardio most days, strength training twice a week, soccer on weekends, a focus on fiber, protein, unsaturated fats, complex carbs, fruits (especially berries) and veggies, protecting my sleep, and tracking my recovery, so that I am watching trend lines rather than waiting for the next annual panel to tell me something.

Honestly, you have thought about this way too much.

Shucks, thanks! I am choosing to hear that as a compliment. In fairness, I did not choose this. A calcium score of 266 chose it for me. I did not have any of this insight in 2015. I hope you don’t count on luck alone, and are more proactive on both the diagnostics and lifestyle fronts, and then let’s hope the new organ aging test hits the market soon.

In fact, here is a checklist of things that summarizes what I have written about above, in a two-page format. Hope you find it helpful.

As always, I would love to hear your thoughts and experiences in the comments.

Nickhil Jakatdar is the CEO of GenePath Diagnostics and the founder of PreventiveHealth.ai, working to make advanced diagnostics and credible health guidance more accessible, affordable, and actionable. A PhD in EECS from UC Berkeley and the youngest recipient of the UC Berkeley Distinguished Alumnus Award, he has founded and led multiple tech companies. He holds 60 patents, and serves on several academic, healthcare, and innovation boards. To follow his thinking on preventive health, technology, and systems that scale expertise, join his private WhatsApp community and subscribe to his Substack.

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