When you blow out your birthday candles each year, you’re marking the passage of time but not necessarily the passage of age. Chronological age is one thing (and scientists increasingly agree it’s just a number), but what matters more is biological age (how old your cells behave). The difference between biological and chronological age is denoted as the “age gap”.
What’s even more surprising is that biological aging isn’t uniform across the body. According to a new study led by Stanford University neurologist Tony Wyss-Coray, our organs can age differently. The researchers have now devised a blood test that measures how fast individual organs in your body are aging. This is not merely a snapshot of how you’re doing today. It’s a molecular window into your health years from now.
“The brain is the gatekeeper of longevity,” said Wyss-Coray. “If you’ve got an old brain, you have an increased likelihood of mortality. If you’ve got a young brain, you’re probably going to live longer.”
A Clock for Your Organs
The team used blood samples from more than 44,000 volunteers enrolled in the UK Biobank, a massive biomedical database that has tracked participants for up to 17 years. These individuals were between 40 and 70 years old when sampled.
Using an advanced lab tool called Olink, which quantifies proteins in the blood, the researchers analyzed nearly 3,000 proteins, many of which originate from specific organs. Some of these molecules are released from the heart, others from the brain, kidneys, liver, and so on.
The team used machine learning (a type of AI) to link each protein signature to one of 11 organ systems, including the brain, immune system, heart, lungs, and kidneys, and estimate how “old” that organ was relative to the person’s actual chronological age. The bigger the deviation from the norm, the more “extremely aged” or “extremely youthful” an organ was considered.
Their findings were sobering. About one in three participants had at least one organ aging faster than expected. One in four had multiple aged organs.
Predicting Disease Before It Starts
Aged organs foretold real-world outcomes. People with older-than-expected hearts had significantly higher risk of heart failure or atrial fibrillation. Aged lungs predicted chronic obstructive pulmonary disease (COPD). And those with an older brain were more than three times as likely to develop Alzheimer’s disease compared to those with a normally aging brain.
Remarkably, people with especially youthful brains were 74% less likely to develop Alzheimer’s. This level of protection was on par with carrying two copies of the APOE2 gene variant, long known to guard against the disease.
“Someone with a biologically old brain is approximately 12 times as likely to receive a new diagnosis of Alzheimer’s over the next decade or so as someone the same age with a biologically young brain,” Wyss-Coray said.
This held true even when the researchers controlled for APOE genotype, sex, and chronological age.
The test also predicted who would die. People with a biologically aged brain had a 182% higher risk of dying within 15 years. Meanwhile, individuals with youthful brains had a 40% reduction in mortality risk.
And if someone had multiple aged organs — say, eight or more — their odds of dying shot up more than eight-fold compared to people whose organs matched their age.
Can We Slow Down Organ Aging?
The study hinted at possible solutions. Organ aging turned out to be sensitive to lifestyle. Smokers, heavy drinkers, and people with insomnia tended to have older organs. Those who exercised vigorously, slept well, or consumed oily fish had more youthful profiles.
Certain medications and supplements also correlated with youth in some organs, notably ibuprofen, cod liver oil, multivitamins, glucosamine, and vitamin C.
Among women, the hormone treatment Premarin, often prescribed for menopause, was linked to more youthful immune, artery, and liver profiles. These findings, in particular, raise questions about how estrogen might slow aging post-menopause.
“This is, ideally, the future of medicine,” said Wyss-Coray. “Today, you go to the doctor because something aches, and they take a look to see what’s broken. We’re trying to shift from sick care to health care and intervene before people get organ-specific disease.”
Indeed, the most tantalizing prospect is that this test could become a tool for prevention. If doctors can spot an aging brain before symptoms arise, they might have a window to delay or even stop the onset of dementia.
Why Brain Aging Matters Most
Not all organs are equal when it comes to predicting longevity.
The brain and the immune system emerged as the strongest predictors of survival. That shouldn’t be too much of a surprise. You are your brain, you are not your kidney or liver. People with both a youthful brain and immune system had a 56% lower risk of death over the next 17 years compared to those with normally aging counterparts.
Interestingly, aging in the brain seemed to ripple across the body. People with aged brains also faced higher risks of chronic obstructive pulmonary disease (COPD) and heart failure, suggesting a broader role in systemic health.
“It’s similar to bringing your car to the garage once a year, when they use a computer diagnostic to show if all the different parts of your car are okay,” Wyss-Coray said, describing his team’s new blood test with an analogy. “What is nice here is that this potentially gives people something in their hands that they can change.”
For now, the test remains a research tool. But Wyss-Coray has co-founded two spinoff companies (Teal Omics and Vero Bioscience) aimed at commercializing it. He estimates that a consumer version could be available within two to three years.
Doctors could use a simple blood test to monitor not just heart or kidney function, but the molecular creep of aging — and maybe do something about it.
The findings were reported in the journal Nature Medicine.
