The ceiling of life

Natalia Reznik, "Trinity Variant"

Centenarians who have crossed the centenary milestone are already used to these days. And they have met in the past. The English peasant Thomas Parr (1483-1635) entered history. He married twice, at the age of 80 and at the age of 122, had children. When Parr turned 152, King Charles I found out about him and summoned him as a curiosity to his palace. There the elder died: the change of conditions did not benefit him.

Thomas Parr. Portrait of the work of an unknown artist
from the London National Portrait Gallery (Wikipedia)

The year of birth of Parr, like many other centenarians, has not been documented, and officially the oldest inhabitant of the planet is considered to be a Frenchwoman Jeanne Kalman, who died in 1997 at the age of 122 years. The age is respectable, to be sure. But is this the limit? And does this limit even exist?

Supporters of its existence call different numbers, from 85 to 200 years. Opponents of this point of view believe that the duration of human life can be significantly increased by improving its conditions, improving medicine, modifying the genome and eating right, and all these benefits undoubtedly await some part of humanity in the future. After all, the average life expectancy of people in developed countries has been steadily increasing for many decades. As for the maximum life expectancy, in Sweden, for example, it increased from 101 years in the 1860s to 108 years in the 1990s. In France, it is also growing smoothly, therefore, it can increase further.

Recently, the limits of human longevity were investigated by Professor Jan Vijg, head of the Department of Genetics at Albert Einstein College, and his colleagues [1]. Scientists analyzed the Human Mortality Database, collected by experts from Germany and the United States and containing information about 40 countries. From these data, it follows that the average life expectancy has been increasing since the beginning of the twentieth century due to a reduction in early mortality (Fig. 1). Those who did not die before 30 have a good chance of living to 70-80.

Fig. 1. Life expectancy is increasing year by year.
The exception is the two World Wars (here and below are the drawings from [1])

However, the maximum life expectancy increases due to an increase in survival in the oldest age group. Indeed, in the twentieth century, this indicator grew quite rapidly, but in 1980 it peaked and did not increase any more. In other words, human life can have a natural limit. Scientists tested this hypothesis by following the changes in the maximum life expectancy in the XX–XXI centuries: it practically stopped growing, reaching a plateau equal to 114-115 years (Fig. 2). This age has hardly changed for several decades, and the life limit was very clearly marked on the graph. And this is despite the increase in the size of the elderly population as a whole, which in itself should push back the limit of maximum life expectancy.

Fig. 2. The maximum life span seems to have reached the ceiling

Jan Vij and his team tested their findings on data from France, Japan, the UK and the USA, the countries with the largest number of people over 110 years. From 1968 to 2006, there were 534 such people. Between 1970 and 1990, the maximum life expectancy in these countries increased rapidly and reached the limit between 1995 and 1997. Moreover, in 1968-1994, the maximum life expectancy increased by 0.15 years annually, and after 1995 it decreased by 0.28 (Fig. 3). Scientists obtained similar results by analyzing the database of the Gerontological Research Group. They came to the conclusion that the natural limit of life exists, and humanity has almost reached it. The probability of breaking through this ceiling and living to 125 years is one ten thousandth. Jeanne Kalman belonged to such rare people.

Fig. 3. Maximum life expectancy
in France, Japan, the UK and the USA it increased until 1995,
and in subsequent years it slowly decreases

If there is a natural limit to life, it must have a biological cause. According to the authors of the study, this barrier cannot be a consequence of the work of genetic programs that determine aging and death. There are no such programs, the biological clock measures the time of development and puberty. Perhaps the limit of life is a by-product of the activity of these clocks. It is possible that some ongoing research will help to increase the maximum life expectancy a little more.

Of course, not all gerontologists and geneticists agree with the conclusions of Jan Vij and his team. Among the main opponents are James W. Vaupel, director of the Institute for Demographic Research of the German Max Planck Society, referring to his 2010 article [2]. In this publication, Vopel notes that the growth of maximum life expectancy in some countries is still ongoing. The number of women over 100 years old in Sweden has been growing from 1861 to 2008, the number of Japanese women over 105 years old has been increasing from 1947 to 2007, and these figures have not reached a plateau. He also cites the results of his own research in the 1990s on the life expectancy of several thousand pairs of Danish twins born in 1870-1920. The researchers did not find any signs of a genetically programmed limit of life expectancy in them. They didn't find it in animals either. Therefore, there is no limit. Since animal experiments have proven that changes in diet and lifestyle, as well as genetic modifications, can delay aging, these measures should also be effective for humans. According to Vopel, the problem of age-related diseases is also solvable. Life expectancy is increasing largely due to the improvement of the elderly. According to demographic data, age-related changes that used to occur at the age of 70 now manifest themselves at 80, and diseases of 80-year-olds wait for 90 years.

This proponent of endless old age is convinced that the reasons for longevity are a secure life, the opportunity to spend a lot of money on the development of healthcare and payment for medical services, a high level of education (educated people live longer). Medicine is progressing, people in good health are reaching an increasingly advanced age, so the maximum life expectancy is growing and will continue to grow. James Vopel believes that in most countries with a high life expectancy, children born after 2000 will celebrate their hundredth birthday in the XXII century.

Epidemiologist and statistician Jay Olshansky, professor at the University of Illinois at Chicago, is convinced of the existence of the natural limit of life [3]. In his opinion, relying on still unknown biotechnological achievements that will help slow down aging, leading to a significant increase in average and maximum life expectancy, cannot serve as convincing evidence. Scientists who study life expectancy know that this indicator is quite constant for each species. In ideal conditions, in the absence of an external threat, mice live for about a thousand days, dogs — about 5 thousand, people — about 29 thousand. Obviously, for each species, such a life expectancy is biologically justified, and there is no reason to think that people could live significantly longer than they do now.

Indeed, the average life expectancy in developed countries has increased significantly, for the first time in history, most people live to an advanced age. Death is now the lot of mostly people from 65 to 90 years old. But without further biomedical advances, the growth of average life expectancy slowed down, Professor Olshansky predicted this back in the 1990s and turned out to be right. In his opinion, the growth of average life expectancy will continue to slow down.

Olshansky agrees with Jan Vij that the limitation of life expectancy is not the result of the work of a special genetic program. It arose as a by-product of the work of the body's growth and development programs. This means that the limit of life is set by restrictions imposed by other factors. The absence of aging and death programs opens the door to non-genetic influences that improve health and life expectancy. However, diet and exercise prolong life for a short time, just as a new, improved training method allows an athlete to run a little faster, but does not dramatically affect his speed. Jan Vij and his colleagues reminded us that humanity has approached the natural limit of life expectancy. And we must admit this, although people are concerned about its extension. So we will work to close the gap between the average and maximum duration. This is a more realistic task than the endless prolongation of old age.

Literature:

1. Dong X., Milholland B., Vijg J. Evidence for a limit to human lifespan // Nature. 2016. 538. 257–259. 
2. Vaupel J. W. Biodemography of human ageing // Nature. 2010. 464. 536–542. 
3. Olshansky S. J. Measuring our narrow strip of life // Nature. 2016. 538. 175–176. 

Portal "Eternal youth" http://vechnayamolodost.ru  23.11.2016