Study ex­plores up­per limit of hu­man life­span

The Charlotte Observer (Sunday) - - Insight - BY BEN GUARINO Wash­ing­ton Post

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.

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