A study of 3,836 centenarians in Italy finds that the increase in the risk of dying during a given year slows in extremely old age, leveling off to about a 50:50 risk after age 105. The researchers who reported the evidence today (June 28) in Science say the finding provides support for the idea that humans have not yet reached the extent of human longevity.
“The increasing number of exceptionally long-lived people and the fact that their mortality beyond 105 is seen to be declining across [the] cohort—lowering the mortality plateau or postponing the age when it appears—strongly suggest that longevity is continuing to increase over time and that a limit, if any, has not been reached,” the authors write in their study.
Scientists who study human aging have been debating whether there is in fact a maximum lifespan, or whether it’s possible to keep pushing the boundary. For instance, a 2016 report concluded that 115 years was just about as long as people could make it. The following year, five rebuttals poked holes in that argument.
In the current study, the investigators looked to a large, single-country database of people born from 1896 to 1910. It’s widely appreciated that the risk of death doubles each year during adulthood, but the mortality rate began to slow down for the subjects of this study and eventually plateaued.
Coauthor Kenneth Wachter of the University of California, Berkeley, says that the aim of the study was to settle the debate, and “[w]e think we have settled it,” he tells The Washington Post.
The data haven’t convinced researchers studying aging that the trend seen in this investigation is universal. “This paper makes sense in that the doubling cannot continue indefinitely. If mortality is at 60 percent, it cannot eventually double to 120 percent—that is mathematically impossible,” Brandon Milholland, an aging researcher at Albert Einstein College of Medicine, tells Gizmodo. “However, this paper models late-life mortality as suddenly stopping in its tracks and remaining completely flat. That is highly implausible.”