The risk of death for humans and most animals is described by a pattern known as the Gompertz distribution, which was formulated back in the 19th century. It states that the probability of death increases exponentially with age. However, in the twentieth century, when the life expectancy of people in many countries increased significantly, it became clear that the Gompertz law well describes mortality statistics only at the age of up to 80 years, and after this milestone the rate of contraction of the old part of the population slows down.
Since recently the number of very old people has grown, scientists have the opportunity to build demographic models on a large amount of data. While earlier scientists still believed that the risk of death continues to grow with age, although more slowly, recent studies suggest that after a certain age that was earlier designated at 110 years, this risk goes to the plateau. In the new work, the scientists confirmed this hypothesis with the example of Italian long-livers, while reducing the "borderline" age to 105 years.
Statistics from several Roman universities and the University of California at Berkeley with the participation of the famous European demographer James Vaupel (James Vaupel) used the data of the National Institute of Statistics of Italy on residents who, by the beginning of the observation period were 105 years or more, from 2009 to 2015. In total, the database contained records of 3836 such people, of whom there were only 463 men. During the observation of them, 2,883 people died.
Researchers noted that in previous works their colleagues used data where all people older than a certain age (for example, 110) were assigned to one cohort, and in their work the analysis was carried out in more detail by year. For ages less than 105 years, the authors used the Human Mortality Database (HMD), which includes information about residents of many countries, including Italians.
Based on the collected data, the researchers built their model, linking mortality from all causes with age, for people over 65 years. The resulting curve of up to 80 years was in good agreement with the Gompertz law, but after that the probability of mortality began to decline and by 105 years had reached the plateau.
According to the authors of the work, their data say that the limit of the duration of human life has not been reached and will eventually move away. Explanations for the phenomenon found from the point of view of modern theories of aging, however, they do not. To date, the oldest person, whose age was documented, remains Jeanne Kalman, who died in 1997 at 122 years.
Earlier, mathematicians suggested, based on the trend of increasing life expectancy from 1970 to 2010, that the maximum age of a person can be limited to 115 years. Nevertheless, critics of the work, among which was James Vopel, said that in many countries the peak of the increase in life expectancy has not yet reached its maximum.