New Blood Test Reveals How Fast Your Organs Are Aging

Your birthday candles reflect your chronological age, but they say little about how old your organs actually are. A new study by Stanford Medicine investigators, published in Nature Medicine, has developed a blood-based method for assessing the biological age of 11 distinct organ systems—and predicting which diseases a person is likely to develop over the following decade.

The research, led by senior author Tony Wyss-Coray, analyzed blood samples from 44,498 participants aged 40 to 70 drawn from UK Biobank, monitoring them for up to 17 years. The team measured nearly 3,000 proteins in each participant's blood, using the levels of organ-specific proteins to generate a biological age estimate for each of 11 organ systems: brain, muscle, heart, lung, arteries, liver, kidneys, pancreas, immune system, intestine and fat.

"We've developed a blood-based indicator of the age of your organs," Wyss-Coray said. "With this indicator, we can assess the age of an organ today and predict the odds of your getting a disease associated with that organ 10 years later."

One in three participants had at least one organ that deviated significantly from the average for their chronological age, earning it an "extremely aged" or "extremely youthful" designation. The strongest associations ran between an organ's biological age and the likelihood of developing a disease tied to that organ—aged lungs predicted heightened COPD risk, an aged heart predicted higher risk of atrial fibrillation or heart failure, and an aged brain was a particularly powerful predictor of Alzheimer's disease.

Compared to someone with a normally aging brain, a person with a biologically old brain is approximately 12 times as likely to receive an Alzheimer's diagnosis over the next decade. Brain age also proved to be the best single predictor of overall mortality: an extremely aged brain increased the risk of dying by 182% over roughly 15 years, while an extremely youthful brain was associated with a 40% reduction.

"The brain is the gatekeeper of longevity," Wyss-Coray said. "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 second study published the same day in Nature Medicine extends this work to individual cell types, finding, for example, that people carrying two copies of the APOE4 genotype—a major Alzheimer's risk factor—tend to have biologically older astrocytes, but that those with youthful astrocytes appear to have their elevated risk neutralized.

"This is, ideally, the future of medicine," Wyss-Coray said. "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."