Scientists have found that the biological age of key organs like the brain and immune system could be stronger predictors of lifespan than previously known genetic factors. The findings, published in the journal Nature Medicine, come from a large-scale study that examined the blood of over 44,000 UK adults to estimate the ageing of individual organs based on thousands of proteins circulating in the bloodstream.
The research shows that while all organs contribute to ageing, the condition of the brain and immune system plays an outsized role in determining a person’s overall health and longevity. People with a biologically “older” brain were found to have a significantly higher risk of developing Alzheimer’s disease and dying earlier, regardless of their actual age or genetic predisposition. In contrast, those with younger-looking brain and immune system profiles had markedly lower risks.
Unlike chronological age, biological age reflects how fast or slowly the body is ageing at a molecular level. In this study, scientists measured the levels of over 2,900 proteins in participants’ blood samples and used machine learning to estimate the biological age of 11 organs. These included the brain, heart, lungs, kidneys, and immune system. They then tracked the health outcomes of participants over a period of up to 17 years.
A key finding was that individuals with particularly youthful brains had a 74% reduced risk of developing Alzheimer’s disease. This level of protection was similar to that seen in people with two copies of APOE2, a gene variant known for reducing the risk of Alzheimer’s. On the other hand, having an older brain biologically tripled the risk of developing the disease, comparable to carrying one copy of APOE4, the gene most linked with increased Alzheimer’s risk.
Researchers also found that accumulating aged organs had a compounding effect on mortality. People with five to seven aged organs were four-and-a-half times more likely to die early than those with normal organ profiles. But those with youthful brain and immune systems had a significantly lower risk of early death. In fact, individuals with both a young brain and immune system had a 56% lower risk of dying during the follow-up period.
The study also showed that biological age was not set in stone. Lifestyle factors such as exercise, diet, smoking, and even certain medications influenced how organs aged. For example, people who regularly consumed oily fish or exercised vigorously tended to have younger organ profiles, while smoking, poor sleep, and high alcohol intake were associated with faster ageing.
The findings open new possibilities for using blood tests to monitor organ health and identify those most at risk of future illness. They also point to the potential of developing treatments that target ageing in specific organs, especially the brain and immune system, as a means of promoting longer and healthier lives.
