Age is just a number, they say. But being young at heart might be less important than being “young” in other places.
Chronological age and biological age are known to diverge over our lifetimes, as our genetics and the way we live can influence how much damage our cells accumulate. A new type of experimental blood test is now zeroing in on the biological age of different organs in our bodies. And it’s not the heart, liver, or lungs that seems to hold the biggest predictive power over our lifespans, but the brain—the seat of our thoughts, actions, and emotions.
“The brain is the gatekeeper of longevity,” said Tony Wyss-Coray, a Stanford University neurology professor and author of a new study in Nature.
Wyss-Coray and colleagues studied blood samples and medical reports spanning 17 years for nearly 45,000 individuals aged 40 to 70. The researchers tallied the relative concentrations of 3,000 different proteins in the individuals’ blood that relay the health and functioning of various organs. Then they created a machine learning model that could predict chronological age based on the protein signatures and calculated the age gap for each individual, creating a relative biological age rating for each of the different organs and organ systems. The algorithm was then able to predict future health, organ by organ.
People with an “extremely aged” brain relative to their same-aged peers, based on the protein profiles, were nearly twice as likely to die in a 15-year period. But people with an extremely youthful brain relative to same-aged peers—at the opposite end of the scale in terms of protein profiles—reduced a person’s risk of dying by 40 percent over that same period. One of the proteins that had the strongest weight in this brain aging profile was neurofilament light chain—a biomarker that can signal degeneration in axons in the brain and is often measured in clinical trials of Alzheimer’s disease.
Wyss-Coray hopes this type of blood screen could also provide information about the risks for more than a dozen diseases—from Alzheimer’s to liver disease to osteoarthritis—based on biological organ ages. “Today, you go to the doctor because something aches, and they take a look to see what’s broken,” he said. But this organ-aging approach may help focus future research on longevity where it matters most in the body. “We’re trying to shift from sick care to health care.” 
Lead image: N Universe / Shutterstock
