Did you know that you’re as old as your oldest organ?

Forget your date of birth. A new study has demonstrated that organs age at vastly different rates, and these ages can vary from your actual lifetime.

Stanford Medicine (CA, USA) investigators have discovered that organs in the human body age at varying rates, influencing an individual’s susceptibility to diseases associated with specific organs as well as overall mortality.

Previous research indicates that biological age (your age implied by various aging biomarkers) does indeed differ from chronological age (how long you have existed). One study revealed that approximately 20% of health adults aged 50 or older possess at least one organ exhibiting aging at a significantly accelerated rate. Building on these earlier investigations, the Stanford Medicine team have demonstrated that it is now possible to estimate the biological age of any organ in the body using a simple blood test.

The research, based on a study of 5,678 people, involved distinct assessments for 11 key organs, organ systems or tissues: heart, lung, fat, immune system, kidney, liver, pancreas, intestine, muscle, brain and vasculature.

“When we compared each of these organs’ biological age for each individual with its counterparts among a large group of people without obvious severe diseases, we found that 18.4% of those age 50 or older had at least one organ aging significantly more rapidly than the average,” senior author Tony Wyss-Coray explained. “And we found that these individuals are at heightened risk for disease in that particular organ in the next 15 years.”

The team also discovered that individuals with two organs aging significantly more rapidly than the average had a mortality risk that was 6.5 times greater than individuals without any pronouncedly aged organs.

Using commercially available technologies and a custom machine-learning algorithm, the researchers analyzed thousands of proteins in the participants’ blood, identifying almost 1,000 organ-specific proteins that at abnormal levels, were linked to accelerated aging and susceptibility to diseases and mortality. The machine-learning algorithm, trained to estimate age based on the levels of around 5,000 proteins, was verified for accuracy using an additional sample of ~4,000 people who were representative of the U.S. population.

The study revealed an “age gap” for each organ, representing the difference between its actual age and the estimated age based on the algorithm’s calculations. Notably, the age gaps for 10 of the 11 organs studied (excluding the intestine) were significantly associated with a higher risk of death from all causes over a 15-year follow-up period.

Having an accelerated-aging organ was linked to a 15% to 50% higher mortality risk over the next 15 years, depending on the affected organ. For instance, compared to individuals with normally aging hearts and brains, accelerated heart aging correlated with a 2.5 times higher risk of heart failure, while accelerated brain aging correlated with a 1.8 times higher risk of cognitive decline and Alzheimer’s disease progression.

The researchers suggest that by monitoring the health of individual organs in apparently healthy people, it may be possible to identify accelerated aging and therapeutically intervene before the onset of diseases.

These findings could potentially revolutionize preventive healthcare and open avenues for new drug targets based on organ-specific proteins indicating excessive organ aging. The next steps involve validating these findings in larger populations to pave the way for widespread application in healthcare monitoring and early intervention.