How long can we live?
A research letter published in Nature at the beginning of the month studies data from a variety of databases to conclude that there is a limit to the human lifespan. Even more, the results suggests that we,ve already reached the limit: 115 years. According to the paper, it is unlikely that the maximum age at death will rise in the future. The maximum documented age of death worldwide is that of Jeanne Calment, a French woman who died in 1997 at 122 years. The oldest individual in UK was Charlotte Hughes, who died in 1993 at the age of 115. Today, the oldest living person in UK is 112 years old. In view of the new study, it is not probable for a human to live longer than Mrs. Calment.
The authors of the paper are from the Albert Einstein College of Medicine in New York. Their motivation was to settle a long term controversy in the field of aging: is there a natural limit to the human lifespan? Using statistical techniques, the authors conclude that the maximum lifespan is 115 years, and that it was reached in the 1990s; the chance of a human dying at an age of 125 years is less than 1 over 10000 in any given year.
Already in the 1980s it was suggested that the duration of life may be limited. Upper limits for human maximum lifespan were already estimated but the lack of data did not allow definite conclusions to be made. There are many confounders that make the analysis of aging data difficult; the most important one is that only a few countries in the world have high-quality, long term mortality records, and in consequence only a small number of maximum ages at death can be studied. To conclude that the humans reached our maximum lifespan, Xiao Dong and his colleagues studied two types of data. First, they observed that the life expectancy is generally increasing since the beginning of the 20th century in most of the developed countries. Furthermore, the number of individuals per 100000 living until old age is also increasing steadily. But if one focuses on what age group is growing faster, it turns out that after a steep increase during the 1970s, since 1980 the fastest growing group of people are between 95 and 100 years old.
To further confirm their findings, the authors studied a second type of data: the maximum age at death in several countries, including UK. They charted the maximum age at death for each year since 1960, and observed that since the mid 1990s the values are not increasing anymore.
The study is not free of controversy. James W. Vaupel, from the Max Planck Institute Odense Center on the Biodemography of Aging and the curator of one of the databases that provided the data for the new study, rejects the conclusion of the paper, claiming that it just repeats mistakes from the past.