Delaying disease in other age groups could show that aging has slowed, while extending the lifespan limit requires people to outlive the current record: aging researcher Max Unfried distinguished these two tests in a debate over a prediction that humans will live for 300 years or more

Delaying disease in other age groups could show that aging has slowed, while extending the lifespan limit requires people to outlive the current record: aging researcher Max Unfried distinguished these two tests in a debate over a prediction that humans will live for 300 years or more

On October 30, cancer physician Jason Williams wrote on X that humans will live for 300 years or more. Biomedical engineer Patrick Heizer challenged him on October 31, and Unfried and Alan Dail continued the discussion on November 1.

Williams believes that people can be kept at a biological age of 25–35 years, as judged by the condition of their bodies. At that age, he writes, people almost never die from disease; they die in accidents. He gave his reasoning in the same post: “We see this in animal experiments, from mice to dogs and primates, and I don’t think there is a limit.” In a reply to a reader, he identified proof as the hardest part:

“It will take 300 years to prove a lifespan of 300 years, so we will act on animal data long before we can confirm the findings in humans.”

Heizer, quoting that post, wrote: “I think we need to get at least one person to 125 before making such outrageous claims about longevity.” In explaining his choice of 125 years, he cited Jeanne Calment, the longest-lived person with a verified age, who lived for 122 years and 164 days.

Unfried agreed with Heizer: we need to test the current lifespan limit and see whether it can be extended, and “hardly any biotechnology currently in development is likely to extend it.” Dail replied that only five living people are aged 115 or older. The oldest, Britain’s Ethel Caterham, will turn 125 on August 21, 2034, almost eight years away, if she survives that long. If none of the five agrees to try life-extension interventions, Dail added, the wait for someone to reach 125 will exceed ten years, whereas slower aging could be demonstrated in people younger than those five.

Unfried replied to Dail that slower aging could manifest in other groups of people as a delay in several age-related diseases, along the lines of the TAME trial design. The design rests on the premise that a drug that delays these diseases together acts on aging itself. Metformin, a diabetes drug, will be compared with a placebo over six years in more than three thousand people aged 65–79 without diabetes. The endpoint is the first occurrence of heart disease, cancer, dementia, or death, and the trial’s launch awaits funding.

Extending the lifespan limit, Unfried said, is “a separate, though related, question”: demonstrating it requires people who live beyond the current record. “There is no biomarker for maximum lifespan, and extending it requires more than avoiding disease: that is necessary but insufficient” (a biomarker is a measurable indicator that predicts a treatment outcome). Unfried explained why avoiding disease is insufficient in a talk at the ARDD aging conference: mice and humans both develop cancer, yet he estimates that their lifespan limits differ by tens of times, suggesting that something else also affects the limit. He proposes investigating what that might be by comparing tissues from 200 mammalian species.

Dail replied that a test is needed that does not require years of waiting: “If something really affects lifespan, it should also be able to extend it in shorter-lived species. Our pets, for example, could be used for such a test.” Delaying age-related decline and disease, he added, would be a huge success even if the 122-year barrier remains unbroken for the foreseeable future.