Life Expectancy: All You Can Age

6. December 2016

Is there an upper limit to longevity? Researchers claim as much in a recent study. Colleagues do not skimp in their criticism. Only 100 years ago, sceptics believed that life expectancy would never exceed 65 years.

At the end of November, Emma Martina Luigia Morano-Martinuzzi celebrated her 117th birthday. The Italian lady is considered the oldest surviving person with well-documented birth records. She may well have several more years ahead: Jeanne Louise Calment (1875- 1997) reached 122. Regularly eating pastries with milk, one raw and one boiled egg, pasta and meat: scientists cast doubt on Morano-Martinuzzi’s advice on how to reach a biblical age. They wonder whether there is a biological limit to age.

It’s on the way up

Over the past 125 years, life expectancy has virtually doubled. While the figure for newborns in 1895 stood at 40 years, it is now 78 (for men) and 83 years (for women). An end to this trend has not as yet made itself evident. Is there an upper limit?

Where the steam starts running out

Jan Vijg from the Albert Einstein College of Medicine in New York has been grappling with just this question. Together with colleagues he evaluated the data on births and deaths in the Human Mortality Database in detail. Many “super centenarians” come from Japan, France, Great Britain and the USA. “Demographers and biologists have argued that there is no reason to assume that the current increase in maximum lifespan will end soon”, explains Vijg. “Yet our data suggest that this has already happened”.

He found out that maximum age increased by 0.15 years annually until the mid-1990s. Since then, the figure has decreased by 0.28 years per year. Researchers verified these findings using data from the Gerontology Research Group. Here also, from 1972 until1994 an annual increase in maximum age of 0.12 years was made evident. Subsequent to this, longevity has decreased by 0.14 years per year. An explanation is however not offered by Vijg.

Emma Martina Luigia Morano-Martinuzzi (116), predict researchers, would hardly manage to make it much past 122. This amounts to a chance of less than one in 10,000. Maximum life expectancy is between 113.1 and 116.7 years for all people. Outliers are possible but statistically improbable. In summarising: “Further progress in the control of infectious and chronic diseases may continue to increase the average life expectancy, but not the maximum life expectancy,” the authors write.

Researchers making mistakes

This view is not one shared by Professor James W. Vaupel. The director of Germany’s Max Planck Institute for Demographic Research expresses serious criticism about the study. “It’s disheartening, how many times the same error can be made in science and published in prestigious scientific journals”,  says Vaupel. He criticises the “selective use of data” and talks about “one-sided conclusions”. Information on the biological limits of life has not been noted by the expert in any case. He refers to similar misconceptions in earlier times: “100 years ago, it was assumed that average life expectancy would never exceed 65 years. As the counter evidence became visible, the upper limit was shifted again and again”.

Richard Faragher, biogerontologist at University of Brighton, refers to  molecular-based options. “Of course there are limits to human life if we do not intervene”, Faragher says. With worms, mice and flies we have already managed to increase this figure through the suppression of various genes. Low-calorie diets have had similar effects. In human ageing telomerases first and foremost play an important role.

Immortal molecules

The backdrop to this: in being structural elements telomeres stabilise the DNA. They shorten with each cell division. Reduced beyond a critical length, the cell is destroyed. Telomerases counteract this phenomenon; they make cells theoretically immortal. When researchers switched off telomerase in mice the animals aged rapidly. The activation or reactivation led to remarkable rejuvenation of the rodents. They could suddenly perceive odours with a precision that normally occurs only with young animals.

Hai Yan from Durham showed how important the TERT gene (telomerase reverse transcriptase) is in this context. It occurs in the genetic material of all cells. Many tumours, for example glioblastomas,  activate TERT promoter genes and thereby secure decisive advantages. Felix Sahm, Heidelberg, also recently found mutations in TERT promoter genes in meningiomas.

These studies show why many researchers have doubts as to whether telomerase is the key to understanding ageing processes. Does its activation extend life – or would cancers be triggered? Whatever the case, sport also seems to have an influence on telomerase activity. All of a sudden a long known fact can also be verified at the molecular level.

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General medicine, Medicine

1 comment:

Mr William Bradley
Mr William Bradley

The article shows that there is really still some confusion on whether or not we can increase longevity. Comparing average life expectancey does not really tell us very much as it it is based on populations not individuals. The lowered life expectancy of years ago was skewed because of early deaths caused mainly by disease. Looking at my ancestry records, death rate was high in up to the late teens. The majority of others died between 50 and 70, probably because of the environmental conditions they lived in, but we had several who lived well into their 80’s and 90’s even when going back into sixteenth century. As some of these longevities seemed to run in families, there is most likely a genetic factor involved. As research has shown that genetic factors can influence certain “disease” conditions, it is likely that a long life span will be always be restricted to a few unless we are able to get reliable genetic manipulation.

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