Your birth certificate assigns the same age to every part of your body, but the cells inside it do not all grow old at the same pace. The cells supporting your brain may be aging quickly while some of your immune cells remain exceptionally youthful.
Researchers already knew that organs such as the brain, heart, and lungs can have different biological ages. A new Stanford Medicine study, published in Nature Medicine, takes that idea further by examining whether the biological ages of individual cell types are associated with future disease risk.
The researchers connected the apparent ages of certain cells with the later development of Alzheimer’s disease and amyotrophic lateral sclerosis, or ALS. Some of those differences were detectable years before a diagnosis, raising the possibility that a blood test could eventually identify accelerated aging before symptoms emerge.
“This is, ideally, the future of medicine,” said senior author Tony Wyss-Coray in a press release. “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.”
How Blood Proteins Can Measure the Age of Cells
Chronological age measures how many years a person has lived. Biological age instead attempts to capture the condition of a body part and whether it appears older or younger than expected.
For the study, researchers examined proteins circulating in the blood. Many of those proteins can be traced to particular organs and cell types, allowing the team to create protein signatures linked to different parts of the body.
The researchers compared each person’s protein patterns with those typically found in people of the same chronological age. From the differences, they estimated whether individual cell types appeared biologically older or younger than average.
The method builds on a 2025 study from the same Stanford team, which used blood proteins from more than 44,000 people to estimate the biological ages of 11 organs and organ systems. Those estimates were associated with future disease and mortality, with brain age emerging as the strongest single predictor of a person’s risk of dying.
Read More: A Popular Anti-Aging Drug Combo Triggers Severe Brain Damage in Mice
Younger Brain Cells May Affect Alzheimer’s Risk
The Alzheimer’s findings centered on APOE4, a genetic variant strongly associated with the disease. People who inherit two copies have an especially high risk of developing Alzheimer’s.
Participants with two APOE4 copies generally had biologically older astrocytes, support cells that help neurons function and maintain a stable environment in the brain. Among people whose astrocytes appeared biologically youthful, however, the heightened Alzheimer’s risk normally associated with two APOE4 copies was effectively neutralized.
The result does not mean that younger astrocytes prevent Alzheimer’s. It does indicate that two people with the same high-risk genetic profile may not face identical outcomes, and that the condition of certain brain cells could help explain some of that difference.
The same participants also tended to have younger macrophages, immune cells that fight pathogens and help repair damaged tissue. Someone could therefore have older-than-expected brain-support cells and younger-than-expected immune cells at the same time.
Muscle-Cell Age May Signal ALS Risk
The researchers also linked the biological age of skeletal muscle cells with ALS. The disease occurred 12.7 times as often among people with an aged muscle-cell profile as among those whose muscle cells appeared youthful.
The difference was detectable more than three years before participants received an ALS diagnosis based on symptoms.
The blood-based method remains available only for research. Researchers could eventually use it to test whether medications, diet, exercise, or other interventions affect aging in particular cell types.
Rather than assigning the entire body one biological age, this approach could show which cells appear most vulnerable and which remain comparatively healthy. That more detailed view may one day help doctors identify disease risk while there is still time to respond.
Read More: Shingles Vaccine May Also Slow Biological Aging — Not Just Prevent a Painful Rash
This article is not offering medical advice and should be used for informational purposes only.
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- This article references information from a study published in Nature Medicine: Plasma proteomic signatures of cellular aging predict human disease
