Study explores upper limit of human lifespan
Jeanne Louise Calment lived for 122 years and 164 days, the oldest verified age of any person, ever. Her interviews revealed a portrait of the centenarian in high spirits: “I’ve only ever had one wrinkle, and I’m sitting on it,” she told reporters when she turned 110.
Calment died in 1997 in Arles, France, where she spent much of her impressively long life. No one else, according to accurate records, has lived beyond 120 years.
Whether there’s a limit to the human life span is an age-old question. An actuary named Benjamin Gompertz proposed in 1825 that mortality rates accelerate exponentially as we grow older. Under what is known as the Gompertz law, the odds of dying double every eight years. That seems to be the rule for people ages 30 to 80.
But researchers disagree about what happens to mortality rates very late in life. A new study, published Thursday in the journal Science, indicates that the Grim Reaper suddenly eases off the accelerator.
“The aim was to settle a controversy about whether human mortality has the same shape as mortality in many other species,” said study author Kenneth Wachter, professor emeritus of demography and statistics at the University of California at Berkeley. Mortality rates have been found to level off in lab animals, such as Mediter- ranean fruit flies and nematode worms. “We think we have settled it,” he said.
Mortality rates accelerate to age 80, decelerate and then plateau between ages 105 to 110, the study authors concluded. The Gompertz law, in this view, ends in a flat line.
To be very clear, we’re talking about the acceleration of mortality rates, not the odds themselves. Those still aren’t good. Only 2 in 100,000 women live to 110; for men, the chances of becoming a supercentenarian are 2 in 1,000,000. At age 105, according to the new study, the odds of surviving to your 106th birthday are in the ballpark of 50 percent. It’s another 5050 coin flip to 107, then again to 108, 109 and 110.
Led by Elisabetta Barbi at the Sapienza University of Rome and experts at the Italian National Institute of Statistics, the new research tracked everyone in Italy born between 1896 and 1910 who lived to age 105 or beyond. The data included 3,836 people, of whom 3,373 were women and 463 were men. The national Italian registry, which requires yearly updates from citizens, provides more accurate information than U.S. Social Security data. “Italy is likely to have the best data we have,” Wachter said.
Statistician Holger Rootzen at the Chalmers University of Technology in Sweden called the study a “very careful and good analysis” that reveals a mortality plateau between ages 105 and 110.