Blood proteins hint at which cells are ageing fastest

What was found

A team led from Stanford measured more than 7,000 proteins in the blood of 60,542 people and built computer models that estimate the "biological age" of more than 40 cell types, from nerve and immune cells to muscle and lung cells.

Most people were not ageing evenly. About a fifth to a quarter showed one cell type ageing faster than expected; 1 to 3% showed ten or more. These cell-by-cell signatures were linked to disease and to survival over up to 15 years. One example: astrocytes, the brain's support cells, looked older in people carrying the APOE4 gene variant, and in people with two copies, the oldest-looking astrocytes went with about three times the risk of later Alzheimer's disease.

Why it matters

It suggests a blood sample can say something about specific cells, not just the body as a whole, including cells inside the brain. It adds to the evidence that proteins from the brain reach the blood and carry information about it, which is why researchers keep looking at blood for brain health.

How sure we are

A large, peer-reviewed study in Nature Medicine, with long follow-up. But it is an early framework, not a clinical test: the cell-type labels rest on existing protein atlases, blood proteins do not always mirror what happens inside cells, and most participants were older and of European ancestry. The authors call for validation in broader populations.