For many years, doctors believed that the thymus, a small organ located in the chest, was only important during childhood.
It helps train the immune system by producing special cells called T cells, which protect the body from infections and disease. After puberty, the thymus becomes smaller, and scientists thought it no longer played an important role in adult health.
However, two new studies from researchers at Mass General Brigham have challenged this long-standing belief.
The studies, both published in the journal Nature, suggest that the thymus may still be very important in adulthood. In fact, having a healthier thymus may be linked to living longer and having a lower risk of serious diseases such as heart disease and cancer.
In these studies, researchers used artificial intelligence to analyze routine CT scans. CT scans are commonly used in medical care, and the researchers found a way to use them to study the thymus in large numbers of people. This allowed them to examine the organ in much greater detail than before.
The team looked at data from more than 25,000 adults who took part in a national lung cancer screening trial, as well as over 2,500 people from the well-known Framingham Heart Study. By studying the size, shape, and tissue of the thymus, the researchers created a “thymic health” score for each person.
The results were surprising. People with better thymic health had about a 50 percent lower risk of death compared to those with poorer thymus condition. They also had a 63 percent lower risk of dying from heart disease and a 36 percent lower risk of developing lung cancer. These findings remained strong even after taking into account age and other health factors.
The researchers believe this may be because the thymus plays a key role in maintaining a strong and flexible immune system. As people age, the immune system often becomes weaker and less able to respond to new threats. If the thymus is healthier, it may help the body better fight diseases, including cancer.
The studies also found that certain lifestyle factors may affect thymic health. Smoking, being overweight, and having long-term inflammation in the body were linked to poorer thymus condition. This suggests that daily habits and overall health may influence how well the immune system works over time.
In a second study, the researchers focused on people who were receiving immunotherapy for cancer. Immunotherapy is a modern treatment that helps the body’s own immune system fight cancer. The success of this treatment depends heavily on how strong the immune system is.
The researchers studied more than 1,200 cancer patients who received immunotherapy. They found that those with healthier thymuses had better outcomes. These patients had about a 37 percent lower risk of their cancer getting worse and a 44 percent lower risk of death compared to those with poorer thymic health.
This suggests that the thymus may play an important role in determining how well patients respond to cancer treatment. If doctors can measure thymic health, they may be able to predict which patients are more likely to benefit from immunotherapy.
These findings open up new possibilities for medicine. In the future, doctors may be able to use thymic health as a way to assess disease risk or guide treatment decisions. It could also lead to new strategies for strengthening the immune system as people age.
However, the researchers also point out some limitations. These studies show strong connections, but they do not prove that thymic health directly causes these outcomes. More research is needed to confirm the findings. In addition, the method used to measure thymic health is not yet ready for everyday clinical use.
Another important point is that while lifestyle factors were linked to thymic health, the studies did not test whether improving these habits can directly improve the thymus. Future research will need to explore this question.
Overall, these studies provide a new way of thinking about aging and the immune system. They suggest that the thymus, once thought to be unimportant in adulthood, may actually be a key factor in how people age and respond to disease.
If these findings are confirmed, they could have a major impact on how doctors understand health, prevent disease, and treat cancer in the future. Paying attention to this small and often ignored organ may help unlock new ways to support longer and healthier lives.
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