Hidden system, big impact: THIS forgotten organ could predict how long you live, study finds

Scientists at Mass General Brigham have discovered that the thymus, a small immune system organ which is believed to lose its relevance after childhood, likely plays a significant role in adult health. Two new studies have revealed that adults with healthier thymuses are expected to live longer and are less likely to develop serious diseases. In addition, they also suggested that thymic health might influence how well cancer patients respond to immunotherapy.

The findings were published in the issue of "Nature and challenge decades of assumptions about the thymus". The results suggested that the organ remains significant throughout adulthood and could eventually assist in preventing diseases, strategies and decisions of cancer treatment.

"The thymus has been overlooked for decades and may be a missing piece in explaining why people age differently, and why cancer treatments fail in some patients," said Hugo Aerts, PhD, corresponding author on the papers and director of the Artificial Intelligence in Medicine (AIM) Program at Mass General Brigham. "Our findings suggest thymic health deserves much more attention and may open new avenues for understanding how to protect the immune system as we age."

How thymus function in our body?

The chest-located thymus trains disease-fighting T cells; however, its post-puberty shrinkage leads scientists to assume it plays a minimal role in adult health. Consequently, large population studies historically ignored the organ. While past research linked T cell diversity to ageing and fading immunity, those studies were small and limited to blood samples.

Breaking this trend, a new, broader study analysed data from over 25,000 adults in a national lung cancer screening trial, alongside more than 2,500 healthy participants from the long-running Framingham Heart Study to better understand the organ's long-term health impact.

AI Reveals Links to Longevity and Disease Risk

Using AI, the researchers measured the size, structure, and composition of the thymus to evaluate routine CT scans, creating a "thymic health" score. Researchers have also found that people with healthier thymus glands had markedly better long-term health outcomes. Those with higher thymic health scores were about 50% less likely to die from any cause, 63 per cent less likely to die from cardiovascular disease, and 36 per cent less likely to develop lung cancer compared with those with poorer thymic health.

The associations remained strong even after adjusting for age and other health factors. Scientists believe declining thymic health reduces T-cell diversity, weakening the immune system's ability to fight diseases. Chronic inflammation, smoking, and higher body weight were identified as key factors linked to poorer thymic health.

In a separate study, after examining CT scans and clinical outcomes from over 1,200 cancer patients treated with immunotherapy, the team found that patients with healthier thymuses tended to respond better to treatment. They experienced about a 37 per cent lower risk of cancer progression and a 44 per cent lower risk of death, even after adjustment for differences in patients, tumours, and treatment approaches. These findings also underscore a potentially important role, along with previously underrecognised, for the thymus in finding how effectively modern cancer immunotherapies work.

Scientists react to assessing thymic health

Researchers caution that further studies are needed to confirm the findings, and the imaging method used to assess thymic health is not yet suitable for routine clinical use. While lifestyle factors were linked to thymic health, it remains unclear whether changing them can improve thymus function.

Ongoing research is also examining whether incidental radiation exposure during lung cancer treatment affects thymic health and patient outcomes. "Improving our understanding and monitoring of thymic health could eventually help physicians better assess disease risk and guide treatment decisions," said Aerts.