Are Humans Likely To Live Beyond 125
All good things come to an end. Old civilisations that were admired and celebrated, fell inexplicably. Old age can be a little monotonous on its own; but pep it up with the ravages of time, it has all the unpredictable peaks and troughs ploughed in on human face. Those of you old enough to know or young enough not to care, would be shocked at the transformation of the face of a lovely and petite Nimmi from Agra, who came into the limelight when she played an innocent Kashmiri teenage girl in the Bollywood hit film Barsat, with Raj Kapoor and Nargis. Though blitzed by her 83-year life span, she is still going strong in suburban Mumbai.
And, what could be more disheartening for those who do not play golf, and for some like me, who played golf for 22 years, but only with a very high handicap that, the University of Edinburgh has found out people who play golf ‘above par’ can add five years to their life.
Despite better hygiene and nutrition, and advances in medical sciences, we can’t go on forever. Living human cells have a limit of dividing and replacing our lost tissue. But the question is how far western science can push it up the greasy slope of life. This subject to the indulgent scrutiny is baffling though there is meat to the argument.
We shed so many skin cells every day that a new replacement set of skin cells are needed every 30 days. As we get older we lose collagen (protein that binds tissue together – the stuff that form gelatine when you boil tissue such as muscle, bone, and from which medical capsules are made) from the tissue under your skin.
We remain intact because the corresponding cells keep dividing to replace them. From the beginning of evolution, healthy humans were born and died as the cells in the body ran out of energy to multiply. Even the inorganic Sun whose energy came from nuclear fission inside, will burn itself out and die in about 5 billion years. It has been burning for 4.5 billion years.
There is no stopping in the march of time since it began at the “Big Bang” 14 billion years ago, when the universe was “concentrated almost to a single, furiously hot infinitesimal point” from which it expanded in a cosmic revolution.
The most commonly used noun in English language is ‘time’. We could not have lived without time – London time, Indian time and so on, since it began. And with time, living and non-living things perished. Human beings are no exception.
I’ve written in the past that life expectancy has been continually increasing globally. A baby born today in the West, is expected to live until it reached 81, in contrast to an average 50 in 1900 (equivalent to about 30 in Manipur). Life expectancy in Manipur also seems to be increasing from empirical evidence that, people surviving above 65 are on the rise.
Published recently in the journal Nature, David Sinclair, professor of Longevity Science at Harvard, US, whose job is to find ‘cure for ageing’, says he believes modern medicine can significantly extend the human lifespan and we expect people to live to 120 and beyond within our life time, and there will be a world where people can look forward to living at least beyond 100. It will be not uncommon where people can live to 120. Every time we say that there’s a natural limit, we develop technology to push us further.”
“Simple organisms, even yeast cells and fruit flies, have ‘longevity genes’ that can be switched on by low calorie diets and exercise. When these genes are ‘switched on’, they can protect the organism and help them live longer. We have many of these genes in our bodies and we’re just starting to learn that they do help us live longer and healthier. There are drugs already in clinical trials and, so far, they seem to be safe and showing early signs of success,” says Sinclair.
Sinclair is talking about making pills that would prevent diseases such as Alzheimer’s, bowel diseases and a whole lot of ailments. He has been able to do it in mice so far. The question is according to him: “Can we do that in people, and how soon? Giving cholesterol to prevent heart diseases or stroke helps but not a lot. No matter how much we say that it’s good for you to be thin and to exercise, it doesn’t seem to help for most people as most people just do not make the effort. He says “If we could have a simple pill that our doctor could prescribe to take with breakfast, that could have our lifestyle, it would be great. I’m not saying we should just sit on the couch and get fat and take a pill, that’s not the point. But we can supplement what our bodies naturally need and that’s going to help keep us young.”
Controversially, a new study by Jan Vijg, a geneticist at Albert Einstein College of Medicine, in New York, and his colleagues have concluded that human beings are not likely to live more than 125 years. They believe that we have already hit our target on longevity, and upward trajectory does have a ceiling. Life expectancy probably peaked in 1997 when Jeanne Calment died in France aged 122, as the oldest person on record. Her record will never be broken.
The way these researchers came to this conclusion was from an analysis of information from the Human Mortality Database, which compiles mortality and population database from more than 38 countries and is jointly run by US and German demographers. They found that since 1900, the number of people surviving past 70 has been increasing, which has led to a surge in life expectancy, but when the researchers looked at survival improvements for people aged 100 and above they found that gains in survival declined rapidly. The age has since increased by a very small amount.
They further found that age at death of supercentenarians strongly increased between 1970s and early 1990s but reached a plateau (ie the rising curve line flattened) around 1995 at 110 years of age. The age that Clement died, 122, is very much close to that predicted by the Hayflick Limit, which states there is a finite number of times that human cell population can divide before stopping. Dr Jan Vijg says: “Our data strongly suggest that it has already been attained and that this happened in the 1990s. Further progress against infection and chronic diseases may continue boosting average life expectancy, but not maximum lifespan.”
Vijg’s team deduces that there is a natural limit to human life span at about 115 years. There will still be occasional outliers like Calment, but the probability of a person exceeding 125 in any given year is less than 1 in 10,000. The limit is surprising even to Vijg, who says, given the world’s population is increasing, supplying an ever-increasing pool of people who could live longer, and that nutrition and general health have improved. “If anything, you would have expected more Jeanne Calments in recent years, but there aren’t.”
Some scientists question Vijg’s interpretation. They point out that data used in the analysis are not equivocal, and that the paper doesn’t account for future advances in medicine. James Vaupel, founding director of Max Plank Institute of for demographic research in Rostock, Germany, argues that the age experiencing the greatest increase in survival may have plateaued in many countries, but it has not yet plateaued in some that are particularly relevant to this research, namely, Japan, which has the world’s highest life expectancy – 83.7 years in those born in 2015, nor in France or Italy, which have large populations of high life expectancy. But Vijg argues that the increase in the survival age even in these three countries has significantly slowed down in recent years and so seem to be trending towards no increase.
Richard Fraghar, a biogentologist at the University of Brighton, UK, agrees with Vaupel: “Of course there are limits to human lifespan if you don’t interfere, but future developments in medicine could further increase maximum lifespan, which the paper has omitted.” He gives instances: “In worms, mice and flies, researchers have radically extended lifespan by suppressing genes involved in growth-factor signalling, or by restricting food. Human cells have been rejuvenated by delivering RNA encoding – a protein that extends telomeres, protective caps on the ends of chromosomes that are associated with ageing and disease. If it wasn’t possible to extend the maximum lifespan in humans, this would make us different from every other experimental species we’ve tried.”
Vijg disputes that, findings in model organisms aren’t necessarily applicable to humans because these animals are bred to have certain traits. Our lifespan is controlled by too many genes.
Biomedical gerontologist Aubrey de Grey, chief science officer of the SENS Research Foundation, California that develops and promotes rejuvenation biotechnologies, is more hopeful of longer lifespan. “The result in this paper is absolutely correct, but it says nothing about the potential of future medicine, only the performance of today’s and yesterday’s medicine.”