Blood Test to Determine Organ Age Could Help Predict Disease Risk

How old are we inside? A new blood test reveals how old our various organs are. Because the heart, brain, or muscles do not always age at the same rate as the rest of our body, In around 20 percent of people over 50, at least one organ is older than it should be, as the levels of certain proteins in the blood reveal. This in turn increases the risk of developing an organ-specific disease or dying from it by up to 50 percent, as the team reports in “Nature.”

As we age, our biological age does not always correspond to our chronological age. Depending on genetic predisposition, lifestyle, and environmental influences, our tissues, organs, and cells change more or less quickly. And the rate at which individual organs in our body age is not the same either. The liver, for example, remains young throughout our lives thanks to its rapid cell regeneration. Our brain cells, on the other hand, can live for more than 100 years. However, the age of the individual organs in our body could previously only be determined using complex tissue samples.

Organ-specific Proteins in the Blood as an Age Indicator

People with a prematurely aged organ and with more than one "too old" organ.
People with a prematurely aged organ and with more than one “too old” organ. Image: © Wyss-Coray et al./ Nature, CC-by 4.0.

The age of eleven different organs can now be determined solely based on a blood sample, thanks to a method developed by researchers led by Tony Wyss-Coray from Stanford University. The rationale behind this approach is rooted in the understanding that the age of organs correlates with changes in their gene activity and the production of specific proteins. The team hypothesized that quantifying organ-specific proteins in blood plasma would provide minimally invasive insights into the aging of each organ.

In their study, researchers initially determined the content of 4,979 different proteins in blood samples from 1,400 healthy individuals of middle to older age. Subsequently, they identified which proteins originated from specific organs, considering proteins as organ indicators if they were produced four times more strongly in one organ compared to all others. The team identified a total of 858 such organ-specific proteins in human blood.

In the next step, scientists employed artificial intelligence, training it to recognize age-specific differences in the quantity of various organ proteins. The analysis focused on eleven organs whose contributions to age-related diseases are well-researched, including the heart, lungs, kidneys, liver, muscles, pancreas, brain, blood vessels, immune system, and adipose tissue. Utilizing this AI, the team then determined the organ age of over 4,000 individuals based on blood values.

20 Percent of Over-50s Have an Organ That Is Too Old

Connection between organs that have aged at an above-average rate and various diseases
Connection between organs that have aged at an above-average rate and various diseases. © Wyss-Coray et al./ Nature, CC-by 4.0

The result: “With this method, we can determine the biological age of individual organs in a person,” says Wyss-Coray. The data confirm that the organ-specific age can significantly vary both among individuals of the same age and among different organs. While a certain range is considered normal, there are also cases of organs aging significantly prematurely, as reported by the team. This occurs when an organ is more than one standard deviation older than the organ average in individuals of the same age.

Specifically, nearly 20 percent of people over 50 years old have at least one organ that is significantly older than the rest of the body. One in 60 people even has two prematurely aged organs. However, the specific organs affected can vary widely. For about two percent of the test subjects, the heart was several years older than it should be, while in others, the kidneys, lungs, or vascular system were affected.

Increased Risk of Illness and Death

But what are the consequences if one of our organs ages prematurely? Wyss-Coray and his team have determined this based on the health history of their test subjects since the blood samples were taken around 15 years ago. The results showed: “People with one or more prematurely aged organs have an increased risk of developing an organ-specific disease in the next 15 years,” reports Wyss-Coray. The risk of premature death also increases—by 20 to 50 percent, as the team determined.

For example, people with a prematurely aged heart are two and a half times more likely to die of a heart attack or other heart disease than people with a normal-aged heart. If the brain has aged prematurely, there is a 1.8-fold higher risk of developing dementia in the next five years. The same applies to aged blood vessels, as the researchers report. There are also very clear links between a severely aged kidney, high blood pressure, and diabetes.

“Organ Clock” as an Opportunity for Better Early Detection

According to scientists, such a blood test opens new possibilities for detecting disease risks earlier and intervening in a timely manner. By examining the condition of individual organs in ostensibly healthy individuals, we could identify organs that age prematurely. Treating these individuals before they become ill is a potential outcome. However, the blood test needs further testing in larger human cohorts before implementation.

Researchers not directly involved in the study share a similar perspective. André Fischer from the German Center for Neurodegenerative Diseases (DZNE) in Göttingen emphasizes the importance of developing minimally invasive biomarkers that provide insights into the risk of complex diseases like Alzheimer’s. While the presented data is promising, it does not yet constitute a predictive blood test. Instead, the data serves as a crucial building block for developing protein-based blood tests for early disease detection.

Furthermore, Joris Deelen from the Max Planck Institute for Biology of Aging in Cologne notes that the measurement is relatively expensive, requiring optimization for practical clinical use. Despite the cost, the results are compelling, and the creation of organ-based age scores is an innovative method for examining the aging of individual organs.