Very old flies cease to age, at least under the definition of aging as the rise of mortality rate with age. Very old flies have a high mortality rate, but that rate plateaus. There has been some back and forth over the years as to whether such a late life plateau in mortality rates can be observed in humans. Presently the consensus is that it is not apparent. It is, however, challenging to draw any robust conclusions on human mortality past the age of 110, as there are so very few survivors to that late stage of life. All of this is fascinating from a scientific point of view, but something of a sideshow when it comes to the treatment of aging as a medical condition. Earnest therapies for aging are needed at half the age of interest here, and given good approaches to repair the underlying damage of aging, it becomes somewhat irrelevant as to what happens when those therapies are not used.
The validity of conclusions about mortality at extreme age depends crucially on the quality of the data on which they are based, as age misrepresentation for the very old is common even in countries with otherwise reliable statistical data. Motivated by this, demographic researchers from 13 countries contribute to the International Database on Longevity (IDL), the third (August 2021) release of which contained 1119 individually validated life lengths of supercentenarians, i.e. those reaching age 110 or more; the data, which cover different time periods for different countries, can be obtained from www.supercentenarians.org. For some countries, the IDL now also includes data on semi-supercentenarians, i.e. people living to an age of at least 105. Since October 2019, IDL has contained French data on 9571 semi-supercentenarians and 241 supercentenarians who died between 1 January 1987 and 31 December 2016. We call these the France 2019 data; all these supercentenarians but only some of the semi-supercentenarians were validated.
We use a combination of extreme value statistics, survival analysis, and computer-intensive methods to analyse the mortality of Italian and French semi-supercentenarians. After accounting for the effects of the sampling frame, extreme-value modelling leads to the conclusion that constant force of mortality beyond 108 years describes the data well and there is no evidence of differences between countries and cohorts. These findings are consistent with use of a Gompertz model and with previous analysis of the International Database on Longevity and suggest that any physical upper bound for the human lifespan is so large that it is unlikely to be approached. Power calculations make it implausible that there is an upper bound below 130 years. There is no evidence of differences in survival between women and men after age 108 in the Italian data and the International Database on Longevity, but survival is lower for men in the French data.