More preserved thymic tissue is linked to lower mortality and lung cancer incidence in older adults with heavy smoking histories. Digest
The thymus establishes a diverse immune defense early in life, yet much of its tissue is gradually replaced by fat with aging. A new study examined whether adults who retain more of that tissue have different long-term health outcomes than those who don't.
Researchers analyzed chest scans and health records from more than 27,000 participants in two large studies, one focused on lung cancer screening and the other on cardiovascular health. Using artificial intelligence (AI), the researchers assessed how well thymic tissue was preserved on chest scans as a potential indicator of thymus function. They then compared people with the highest and lowest scores to see whether they differed in their risk of dying over the next 12 years or developing lung cancer over six years.
- Participants with higher thymus scores had a substantially lower risk of dying over 12 years. In the lung screening group, mortality was 13.4% compared with 25.5% among those with the lowest scores.
- Those with higher scores were less likely to develop lung cancer over six years, with rates of 3.4% versus 5.3%.
- Cardiovascular mortality was also lower among participants with higher scores, at 2.9% versus 7.5% over 12 years.
- Lower thymus scores were associated with heavier smoking, obesity, lower physical activity, elevated inflammatory markers, and less favorable metabolic markers, including higher blood sugar, triglycerides, and blood pressure. Higher HDL cholesterol was associated with higher scores.
The T cells that mature in the thymus are a type of immune cell that does more than fight infections. They also help recognize cancer cells and regulate inflammation, which plays an important role in atherosclerosis. But chronic inflammation may also accelerate thymus decline. This could help explain the links with lifestyle factors, since smoking and obesity tend to promote inflammation, while physical activity can help reduce it. However, it remains unclear whether lifestyle changes can actually preserve thymus function.
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If thymic decline contributes to the development of disease, it may represent a shared vulnerability across several age-related conditions, rather than just another sign of aging. This raises the possibility that preserving thymus function could help maintain immune defenses as we age.