Running Low on Red: Does a Falling Red Blood Cell Count Set a Ceiling on Human Lifespan? (opens in new tab)

In a cohort enriched for exceptional longevity, people whose red blood cell count fell below roughly 3.8 trillion cells per litre saw their already steep, age-driven mortality risk amplified sharply. The authors argue that the lifelong, replication-intensive job of making red blood cells eventually outstrips the body’s regenerative capacity — and that this decline may be one of the biological brakes on the human lifespan. We are used to thinking of red blood cells as humble oxygen couriers. A...