A study questions the belief that the chance of dying increases as people aged. They proposed that the human lifespan has no limit.
The new study examined the pattern among deaths of nearly 4,000 Italians who were aged 105 and older between 2009 and 2015. These people were both supercentenarians and semi-supercentenarians born between 1896 and 1910.
A Plateau To Human Aging
The study found that if people made it past 105 years old, the probability of dying and living evens out. They call this a "plateau" to human aging.
The team noted that semi-supercentenarians, or those between the ages of 105 and 109, have a 50/50 chance of dying within the year. On the other hand, their expected additional lifespan is only 1.5 years. This rate continues until the age of 110 years old, hence the plateau or the leveling out.
On the other hand, the nonagenarians, or those who reached the age of 90, have a 15 percent chance of dying the following year. However, even if they were much younger compared to the semi-supercentenarians, they are only expected to live for the next six years on the average. Now, if these people made it to 95 years old, their chances of dying within the year increased by 24 percent and their average life expectancy decrease to 3.7 years, almost half of their life expectancy when they were 90 years old.
Any person, however, has an increased chance of getting to 110 years old if he or she survives until the age of 105.
To date, the oldest human on record died at the age of 122.
Researchers from UC Berkeley and the Sapienza University of Rome published the findings of the said life expectancy study in the journal Science on June 29.
Based on these calculations, the team concluded that there is no time limit as far as the human lifespan is concerned. There is no way to say, for example, that a person can only live up to 200 years old.
Not counting diseases and other unforeseeable factors, a strong, healthy individual may live on and on, at least based on this present study. If a limit exists, it has never been observed or calculated yet, the researchers argued.
The records acquired from the Italian National Institute of Statistics has a validation system that calculates age at the time of death to the nearest day.
"Our data tell us that there is no fixed limit to the human lifespan yet in sight," said Kenneth Wachter, the senior author for the study.
"Not only do we see mortality rates that stop getting worse with age, we see them getting slightly better over time," he added.
The Gompertz Law Of Mortality
In 1825, Benjamin Gompertz, a British mathematician, observed that the risk of dying increases more rapidly as people became older. Once a person reaches his or her adulthood, his or her chance of dying becomes double every eight years, according to Gompertz. Scientists who have been studying life expectancy in humans treated Gompertz's conclusions with high regard.
Wachter and his team, however, is challenging the Gompertz Law Of Mortality, saying that it is no longer applicable when a person reached the age of 105.
"The increasing number of exceptionally long-lived people and the fact that their mortality beyond 105 is seen to be declining across cohorts strongly suggest that longevity is continuing to increase over time and that a limit, if any, has not been reached," the team wrote in their paper.