Senescence results from a cumulative imbalance between damage and repair. Progress in reducing damage by improving living conditions and preventing disease, together with medical interventions, are fundamental causes of increased longevity. But myths apart, only around fifty people in human history have been verified as reaching the age of 114. Fewer than twenty of those who got to 114 have reached the age of 115. Worldwide there are estimated to be between 300 and 450 living supercentenarians—that is, over 110 years old—but as of June 2010 there is a list of only 79 validated supercentarians, and only three are male. Just how content they are is not clear.
Currently the oldest person is a Japanese lady Kama Chinen who is just short of 115 years. The title of the oldest verified person in history belongs to Frenchwoman Jeanne Calment (122 years and 164 days old), who died on 4 August 1997. She was born in Arles, France on 21 February 1875. Her genes may have contributed to her longevity as her father lived to the age of 94 and her mother to the age of 86. She rode a bicycle to the age of 100 and smoked till she was 117.
While the oldest woman was 122, the oldest man so far was 115. He was Christian Mortensen (1882–1998), a Danish-American whose age is undisputed, although the Guinness Book of World Records still ranks him second to the disputed case of Shigechiyo Izumi, 120, as the oldest man ever. Recently the oldest man alive, Henry Allingham, died at 113 in July 2009. There was much in the news about him; he had 6 grandchildren, 12 great grandchildren, 14 great-great grandchildren, and one great-great-great grandchild. He had had two mental breakdowns caused, he claimed, by working too hard. He lived in a home for blind ex-servicemen.
New evidence studying the genomes of 1055 centenarians found that it is now possible to predict if someone can live to 100 with a 77 per cent accuracy. The result is based on analysis of 150 mutations. It was found that 90 per cent of the centenarians possessed a particular genetic signature of mutations in the relevant genes. However, one must remember that this genetic test will not tell someone how long they will live, as genetics only accounts for about a quarter or a third of our lifespan; it could tell someone how long they might live.
The oldest known mothers are thought to be two Indian women, Rajo Devi and Omkari Panwar, who were allegedly both 70 when they had babies in 2008 following fertility treatment. But neither has a birth certificate to verify their age. The world’s oldest father, Indian farmer Nanu Ram Jogi, fathered a child in 2007 at the age of 90. He is married to his fourth wife, boasts he does not want to stop, and plans to continue producing children until he is 100. Mr Jogi admits he is not certain how many children his series of four wives have borne him—but counts at least 12 sons and nine daughters and 20 grandchildren.
Alice Sommer was born in Prague 106 years ago and is the oldest person I know. She lives very close to me and is famed as a piano player and teacher—she still plays for several hours a day. She lives alone in quite good health, but goes out little, usually taken by her grandson. When asked how she felt about being old she replied:
There are very good things. Experience. Looking backwards and enjoying knowledge. Only when we are so old can we appreciate the beauty of life. We are surrounded by miracles. Memories are so important. There are no bad things about growing old. None at all, and I am not at all afraid of death as that is the natural order of things. I was lucky to have been born with a very good temperament. When I am faced with a bad situation I immediately find something good in it. I do not think about how old I would like to get.
How is she cared for?
I am looked after extraordinarily well—a girl comes in the morning for half an hour and then another for half an hour in the evening. And I get meals on wheels from the council. I use a magnifying glass to read so do not read much but Bach is my philosopher of music.
Those who pass beyond 90 do seem often to cope well, and centenarians can have daily lives that are as good as those ten years their junior. Being independent is a strong indicator for living long. In several studies, over one third of supercentenarians were still independent and able to care for themselves. In general it seems that this very old group are less well than the younger old, but then come to death rapidly. For example, only about 4 per cent die of cancer compared to 40 per cent of those around 50. They also have very low rates of heart disease, though there are stories that some are smoking heavily. There is a high incidence of some form of dementia, but not Alzheimer’s, though their brains have the signs of that disease.
Of those who reach 100, a study found that about one half avoided chronic disease till they were over 80, and about one fifth escaped all the main chronic diseases. Children of centenarians suffer less from cancer and heart disease. A variation in the gene FOXO3A, a key regulator of the insulin-IGF1 signalling pathway, has a positive effect on the life expectancy of humans, and is found much more often in people living to a hundred and beyond—this appears to be true worldwide. The ApoE gene can also help with respect to dementia. Failing to give up smoking or to control blood pressure and cholesterol were reported to reduce life expectancy by 10 to 15 years. However, Clement Freud commented: ‘If you resolve to give up smoking, drinking and loving, you don’t actually live any longer, it just seems longer.’
Studies of twins and long-lived families have indicated that genes can explain about one third of maximum lifespan, but even identical twins age differently and this may be partly due to random switching on and off of some of their genes due to environmental influences. The other determinants are how one lives and chance factors like accidents and infections. Siblings of centenarians have a significantly higher chance of becoming a centenarian themselves. We have seen that the insulin IGF-1 system is involved in determining lifespan in model organism, so could reduction in its activity increase lifespan in humans? The answer seems to be yes. Mutations known to impair IGF-1 receptor function are overrepresented in a cohort of Ashkenazi Jewish centenarians, and DNA variants in the insulin receptor gene are linked to longevity in a number of groups located throughout the world. Increased activity of sirtuins, related to ageing in yeast, prompted by the drug resveratol has not been shown to extend lifespan in mammals.
In model organisms, such as the worm, fruit fly and mouse, changes in genes can dramatically increase their lifespan as much as fivefold. The equivalent life-extending effect in humans would result in an average lifespan of 400 years, and a maximum lifespan of over 600 years. But how healthy would such individuals be, and would they not have the effects of ageing? Never forget Tithonus. Many of the pathways regulating lifespan in model organisms are conserved throughout evolution, yet the genes that could dramatically increase human lifespan have not been identified.
How long would we like to live? Polls show that on average people want to live to about 90, though some 15 per cent had no idea how long they wished to live. Many were rightly very concerned about health as they aged, and one half, for example, feared the inability to drive their car. The elderly were less fearful than the young. Only about half of the public want scientists to work on mechanisms of age extension.
The Japanese artist Hokusai made his famous wood-block print of The Great Wave off Kanagawa in the 1820s at the age of around 65. Even after reaching the age of eighty, he was busy producing many fine prints. He often expressed his desire to live beyond the age of 90, and just before he died at the age of 88 he sighed and said his last words: ‘If heaven gives me ten more years, or an extension of even five years, I shall surely become a true artist.’ He also wrote: