A newly developed blood test from Stanford can determine the biological age of cells and detect diseases like Alzheimer and ALS early.
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A study published in “Nature Medicine” shows that our cells age completely asynchronously. The test predicts Alzheimer’s and ALS years in advance.
Two people with the same chronological age, as noted on their birth certificates, may still have different biological ages. This fundamental truth has been confirmed by a team from Stanford University led by neurology professor Tony Wyss-Coray, promising to revolutionize longevity research.
Understanding Biological Age
The study examined over 60,000 individuals from three independent cohorts, analyzing more than 7,000 plasma proteins. Machine-learning models were trained to estimate the biological age of over 40 cell types from a single blood sample. The findings indicate that not organs, but rather individual cell populations determine which diseases a person may face.
Years before a disease manifests, the risk of its development can be detected through a blood analysis. Each cell type in the body releases specific proteins into the bloodstream, with different proteins produced by astrocytes in the brain, skeletal muscle cells, and lung epithelial cells.
The Stanford team utilized the Human Protein Atlas to assign each measured protein to its cellular origin, inputting the data into Elastic-Net regression models. The algorithms identified a specific “age gap” for each cell type: how much does the biological age of this cell population deviate from the average of peers?
Alzheimer’s Risk: Young Astrocytes as Protectors
One of the study’s most striking discoveries relates to the brain. Individuals with extremely aged astrocytes, the support cells that maintain the blood-brain barrier and clear toxic metabolic products like amyloid-beta, demonstrated over a 15-year period a 12.59-fold higher risk of developing Alzheimer’s compared to those with younger astrocytes. This risk level is on par with the strongest known genetic risk factor, the APOE4 gene variant.
Notably, among APOE4 homozygotes—those carrying two copies of the Alzheimer’s risk allele—38% developed dementia within 15 years with extreme astrocyte aging, compared to only 12% with normal aging. Encouragingly, none of the 23 APOE4 homozygotes with youthful astrocytes developed the condition.
ALS Early Detection: Muscle Cells Signal Danger
The dataset’s strongest single association actually relates to muscle, not the brain. Individuals with extremely aged skeletal muscle cells had a 12.74-fold increased risk of developing amyotrophic lateral sclerosis (ALS), observed more than three years prior to clinical diagnosis. This finding indicates a possible diagnostic window that did not previously exist.
In lung cancer, the approach also revealed significant stratification. In smokers, extreme aging of the airway epithelium identified a 58% higher risk of cancer than smoking history alone, irrespective of pack-years. This suggests that two smokers with identical histories but differing cellular age profiles have vastly different risks.
The PARS Score: Cellular Age Determines Lifespan
The study distilled data from all cell types into a Polycellular Aging Risk Score (PARS), integrating cumulative aging into a single mortality value. The dose-response relationship is stark: individuals with normal profiles survived around 90% over 15 years, while those with extreme aging across more than 20 cell types had only a 34% survival rate.
Challenges and Future Directions
While the results are intriguing, limitations must be recognized. The cohorts primarily comprised older white individuals, leaving questions about how effectively the models might apply to younger or ethnically diverse populations. More critically, the study was observational, necessitating further research into whether targeted interventions against astrocyte aging truly prevent Alzheimer’s.
In clinical settings, physicians may struggle to interpret high-dimensional cellular aging profiles without standardized guidelines, risking both over- and under-diagnoses. Traditional tools like cognitive scores and imaging examine symptoms after they occur, whereas cell-type aging clocks can detect biological drift years before clinical manifestation, offering a fundamentally new approach to diagnosis.
Wyss-Coray is pushing for commercialization through two spin-offs: Teal Omics for drug screening and Vero Bioscience for consumer products, aiming to make tests available within two to three years. However, regulatory hurdles in Europe concerning in-vitro diagnostics and AI may stall practical application.
