Supposing that disease can be treated and accidents avoided, what is the upper limit of how long a human can live? According to an international group of researchers, perhaps indefinitely.
In a study published in the Science, Elisabetta Barbi of Sapienza University, Rome, and her co-authors use statistics from a group of 3,836 Italians aged 105 and above to lay out a case in support of the hotly contested theory that our risk of death plateaus after we reach extreme old age.
It is well accepted that the likelihood of dying increases with every year beginning in adulthood and continuing up to about age 80. What happens after that, however, depends on who you ask. After demographic sources became more reliable (one needs accurate birth and death records for such analyses) around the 1990s, a handful of investigations concluded that death rates in developed nations had begun to decelerate in individuals entering their eighth, ninth, 10th, and even 11th decades – the so-called supercentenarians – of life.
Combined with the undeniable evidence that modern medicine is allowing more and more people to reach advanced ages and observation of similar longevity patterns in animals, many scientists began to speculate that our species has no set expiration date.
Yet others refuted these findings by citing data collection issues or contending that there is a natural limit to the durability of the human body.
Then, in 2016, a study that examined the age-at-death of centenarians in nations with the highest life expectancies reported that the insurmountable number is 115 years; any cases of longer-lived individuals were said to be mere outliers. But despite its publication in the esteemed journal Nature, many in the field immediately – and savagely – criticized the researchers’ statistical methods.
Hoping to address the puzzling topic using the most reliably sourced data, the authors of the current study turned to the thoroughly verified and continually updated Italian National Institute of Statistics’ database of elderly residents.
Their analysis suggests that after reaching 105 years, humans’ steep risk of dying before their next birthday levels off; becoming about 50-50.
“The increasing number of exceptionally long-lived people and the fact that their mortality beyond 105 is seen to be declining across cohorts—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,” Barbi’s team wrote.
"Our results contribute to a recently rekindled debate about the existence of a fixed maximum lifespan for humans, underwriting doubt that any limit is as yet in view.”
Responding to the skepticism their paper has already sparked, co-author Ken Wachter told Nature: “We have the advantage of better data. If we can get data of this quality for other countries, I expect we’re going to see much the same pattern.”
[H/T: Nature News]