New research is calling into question the notion that humans are close to reaching a fixed biological limit on lifespan.

Despite rising lifespans overall, a study in 2016 suggested that survival rates for people aged over 100 were not seeing a corresponding increase.They found that maximum age of death had actually plateaued in the mid-1990s, according to Forbes. For 20 years, Jeanne Calment, who died in 1997 after a life of 122 years, has held the record for the longest lifespan verified with reliable records.

That study suggested 115 years as the average maximum human lifespan.

Yet a new study, published in the journal Science, has found that death rates actually slow at 80 years, and plateau at 105. The researchers interpret the data to mean that we are not yet approaching a firm limit to biological lifespan. 

The data tracked 3,836 Italians aged 105 and older, between 2009 and 2015. They found that contrary to past research that found increasing risk of death with age, risk of death plateaued at 50 percent, starting at 105. This means that at 108, the risk of death was not substantially higher than at 105. 

Studies had previously shown that the risk of death plateaus in a similar fashion in other animals, but it was unclear whether the same principle applied to human lifespans.

“The aim was to settle a controversy about whether human mortality has the same shape as mortality in many other species,” according to one of the study’s authors, Professor Emeritus of demography and statistics Kenneth Wachter, of UC Berkeley. “We think we have settled it.”

While the likelihood of living to these ages is still quite low, with only 2 in 100,000 women and 2 in 1,000,000 men living to 110, the data suggests that mortality rates stop accelerating at these ages.

The national registry in Italy is considered more accurate than US Social Security data, since it is updated annually.

“Italy is likely to have the best data we have,” according to Wachter.

The study was limited by its relatively small population sample, and the fact that such statistical analyses can only indicate general associations. Researchers did not factor in cause of death, and the data only examined one nation.

However, the researchers argue the data reveals the bigger picture of human lifespan potential.

According to another of the study’s authors, Elisabetta Barbi, a University of Rome demographer, “If there’s a fixed biological limit, we are not close to it.”

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