The secret for living longer is in two systems

Let's be honest here. Everybody's dream is to be able to go to the doctor and instead of just checking your cholesterol or blood pressure, they tell you exactly how you are aging. For instance, they might tell you: “Hey, your brain is 5 years younger than average”, or, if things don't go as well as planned, you might hear: ”You should do something about your lungs, because they are aging twice as fast”. Well, that’s not science fiction anymore. It’s the direction aging research is heading, thanks to a study published in [Nature Medicine] by a team of researchers at Stanford University and collaborators. The study reveals that proteins floating in our blood can reveal the “biological age” of different organs, and that the state of two organs in particular, the brain and the immune system, may hold the keys to living a longer, healthier life. We usually think of age as a single number: the candles on your birthday cake. But biologists have long known that our bodies don’t all age in lockstep. Your liver might be spry while your kidneys are lagging behind. Some 70-year-olds are sharp and active, while others struggle with multiple chronic illnesses. What’s been missing is a reliable way to measure *biological age*, how old your body really is, organ by organ. Traditional tools like MRI scans, DNA methylation tests (“epigenetic clocks”), or general blood chemistry gave pieces of the puzzle but not the full picture. The Stanford team, led by Hamilton Se-Hwee Oh and Tony Wyss-Coray, turned to **plasma proteomics**, the study of thousands of proteins circulating in the blood. Since many of these proteins come from specific organs, they can act like reporters, carrying news from inside your brain, liver, heart, or lungs straight into your veins. The researchers analyzed blood samples from nearly 45,000 people in the UK Biobank, a massive health study that has followed volunteers for decades. Using machine learning, they trained models to estimate the biological age of 11 major organs including the brain, heart, liver, kidney, lungs, pancreas, and immune system based on levels of almost 3,000 proteins. They asked several questions, including the following. Do these organ “age gaps” predict future disease? Do they influence how long people live? Can lifestyle or medications slow down, or even reverse, organ aging? The answers were multifaceted, but the key point is that your brain and immune system matter most. In fact, while all organs’ biological ages mattered for health, two stood out in the study, the brain and the immune system. **People with an “aged brain” were three times more likely to develop Alzheimer’s disease**, similar to the risk from carrying one copy of the APOE4 gene, the strongest known genetic risk factor. A “youthful brain,” on the other hand, cut Alzheimer’s risk by 74%, as protective as carrying two copies of APOE2, the rare “good gene” variant. Having multiple aged organs stacked the odds against you. With 8 or more aged organs, people had an **eightfold higher risk of death** within 15 years. But here’s the good news: **individuals with youthful brains and immune systems together had about half the risk of dying compared to their peers**. In other words, while every organ’s health matters, protecting your brain and immune system may give you the biggest return on investment for living longer. One of the most encouraging findings is that organ aging isn’t set in stone. The study showed that lifestyle choices directly shape how fast organs age. Factors that contribute to faster aging include smoking, heavy drinking, processed meat, poor sleep, and socioeconomic stress. Instead, if you want to slow down aging, you should aim for vigorous exercise, eating oily fish and poultry, and higher education levels. Even medications and supplements made a difference. Ibuprofen, glucosamine (a joint supplement), cod liver oil, multivitamins, and vitamin C were all linked to more youthful organs in certain cases. Estrogen treatment in women after menopause also seemed to slow the aging of some organs. It’s a reminder that the choices we make every day leave molecular fingerprints in our blood. Think of this research as the prototype for a “blood test of aging.” In the near future, a simple blood draw might tell you not just your cholesterol levels but whether your brain, heart, or kidneys are aging faster than average and whether lifestyle changes or treatments are making a difference. This could transform medicine. Instead of waiting until disease shows up, doctors could track organ health proactively. Imagine adjusting your diet or exercise and seeing your organ age scores improve, like watching your fitness tracker but at a molecular level. The implications of this research ripple far beyond the lab. For individuals, it opens the possibility of personalized aging profiles, knowing where you’re most vulnerable and how to strengthen it. For medicine, it provides a new set of biomarkers that could guide prevention and treatment, especially for age-related diseases like Alzheimer’s, heart failure, or COPD. For our society as a whole, it shifts the focus from lifespan (just adding years) to healthspan, making sure those years are good ones. It also highlights an elegant truth: aging isn’t uniform. We don’t all decline the same way, and by understanding which organs matter most, we can make smarter choices and design better interventions. Of course, while the blood tests are powerful, they don’t yet replace traditional diagnostics for specific diseases. Still, the vision is clear: one day, routine bloodwork could come with an “organ aging report card,” showing not just how old you are, but how old your organs feel. And if your brain and immune system come back looking youthful, you might just have bought yourself more healthy years. Now, if you could measure the hidden age of your organs, would you want to know? Thanks to this groundbreaking work, that question may not stay hypothetical for long. The science suggests that by protecting our brains and calming our immune systems, we might not just add years to our lives—we might add life to our years. And perhaps the most empowering message is this: your choices matter. From what you eat, to how you move, to how you rest, your daily habits are written in your blood, shaping not just how long you live, but how well. If you want to learn more, the original article titled "lasma proteomics links brain and immune system aging with healthspan and longevity" on [Nature Medicine] at [https://doi.org/10.1038/s41591-025-03798-1](https://doi.org/10.1038/s41591-025-03798-1). [Nature Medicine]: https://doi.org/10.1038/s41591-025-03798-1

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