Picture for a moment a young child that you know. Perhaps your 8-year-old sister or 10-year-old daughter, perhaps a nephew or a young boy who lives nearby. You can see their wonderful childish enthusiasm and energy for life, and you can imagine their freedom from responsibilities and obligations. It is reassuring to think that, even as the world changes, children all over the world still display those life-affirming characteristics – and, of course, they help remind you of your own childhood.
Yet you can also see how their childhood will differ from your own as they take for granted, and seem to intuitively accept, many of the technological innovations that astound you. But it is not just their childhood that will differ from your own – it is also their adulthood. One of the parameters of their adult life is illustrated in Figure 1.1
. These are the calculations demographers have made of their probable length of life. If the child you are thinking about was born in the US, Canada, Italy or France, there is a 50 per cent chance that they will live until at least 104. If the child you have in mind was born in Japan, then they can reasonably be expected to live to a staggering 107 years.
Figure 1.1 Oldest age at which 50% of babies born in 2007 are predicted to still be alive.
Human Mortality Database, University of California, Berkeley (USA) and Max Planck Institute for Demographic Research (Germany). Available at www.mortality.org
You probably found it fairly easy to think of an 8-year-old. But let us ask you to identify another age group. How many centenarians do you know? Perhaps you don’t know any, or perhaps you can think with considerable pride of a grandmother who reached 100. But the very fact that you know so few, and feel such understandable pride about those you do, reveals how exceptional it is. To understand this difference between 8-year-olds and centenarians, let’s contrast the future-orientated data in Figure 1.1
with past data. Looking back to 1914, the probability that someone born that year would live to 100 was 1 per cent – and that’s precisely why you found it so hard to identify centenarians alive today. The odds were simply stacked against them.
But look again at Figure 1.1
– in the year 2107, being a centenarian will no longer be a rarity. In fact it will be the norm, and considerably more than half of those 8-year-olds you know will still be alive.
What is behind this extraordinary shift in longevity is neither one single simple causal factor nor indeed a sudden change. In fact, for most of the last two hundred years there has been a steady increase in life expectancy. More precisely, the best data currently available suggests that since 1840 there has been an increase in life expectancy of three months for every year. That’s two to three years of life added for every decade. Figure 1.2
documents this staggering impact from the 1850s onwards. What is really extraordinary is the constancy of the gains in life expectancy over this period of time. If we focus on the highest average life expectancy around the world in any one year (what demographers refer to as best practice
it really is well characterized by a straight line. And perhaps more importantly, there is no sign that the trend is levelling off, suggesting that this phenomenon will continue into the near future. So a child born in Japan in 2007 has a 50 per cent chance of living to 107. By 2014, that chance has already improved, and
the new-born babies joyously received in Japanese maternity wards that year have a 50 per cent chance of living to 109 rather than 107.
Figure 1.2 Best Practice Life Expectancy
Calculated using data from Human Mortality Database, University of California, Berkeley (USA) and Max Planck Institute for Demographic Research (Germany). Availability at www.mortality.org
. For an explanation, see ‘Broken Limits to Life Expectancy’ by Jim Oeppen and James Vaupel, Science, May 2002, vol. 296.
A hundred years ago the chances of living to 100 were slight; for those who are 8 years old now the chances are high. What about those in between? What does it mean for you? The simple answer is that the younger you are now, the longer you are likely to live. Take another look at the curve in Figure 1.2
to see the trajectory of this change. Basically in every decade since 1840, life expectancy has increased by two to three years. So if a child born in 2007 has a 50 per cent probability of living to 104, then a child born a decade earlier (1997) has a 50% chance of reaching 101 or 102; a decade earlier (1987) the range is 98 to 100; a decade earlier (1977) 95 to 98; for 1967 it is to 92 to 96; and a decade earlier still (1957) the range is 89 to 94, and so on.
The steady improvements in life expectancy shown in Figure 1.2
have been achieved through a variety of distinct phases. The first substantial increases in life expectancy came from tackling infant mortality. If you live in a developed country now, it is almost impossible to imagine what a terrible scourge child mortality had been in the past. The classic writers of Victorian England poignantly captured these young tragedies: Little Nell dies at the end of The Old Curiosity Shop
at the age of 14, while in Jane Eyre,
Lowood School has a typhoid epidemic and Jane cradles her dearest friend Helen as she dies in her arms. These were not dramatic stories of exceptional events; Charles Dickens and Charlotte Brontë were simply recounting the commonplace events they saw around them. From the 1920s onwards, it was reductions in child and infant mortality that accounted for the majority of improvements in life expectancy seen in Figure 1.2
. The infectious diseases that killed Little Nell and Helen, such as TB, smallpox, diphtheria and typhoid, began to be eliminated. Governments instigated innovations in healthcare provisions, standards of nutrition improved, and people were educated into more healthy lifestyles.
The second substantial increase in life expectancy came from tackling the chronic diseases of middle age and beyond – in particular cardiovascular problems and cancer. Twentieth-century novelists no longer described the tragedy of childhood mortality, but they themselves were touched by the chronic diseases of their age. Sherlock Holmes’
creator Sir Arthur Conan Doyle died of pneumonia in 1930 aged 71, while James Bond’s creator Ian Fleming died in 1964 from a heart attack at 56. Over time, earlier diagnosis, better treatments and intervention, and better public education, especially around the health-related challenges of smoking, helped drive improvements in health. As Nobel Laureate Professor Angus Deaton notes, this epidemiological transition occurred as fatal diseases moved out of the bowels and chests of infants into the arteries of the elderly.1
The next substantial increase in life expectancy will come from tackling the diseases of old age. Indeed there have already been sharp improvements in life expectancy for the elderly. The probability of an 80-year-old man dying in England in 1950 was 14 per cent and has now fallen to 8 per cent; for a 90-year-old the probability has fallen from 30 per cent to 20 per cent. Reaching 100 years of age used to be sufficiently rare that many countries took steps to recognize it. In
Japan, for example, anyone reaching 100 was entitled to receive a silver sake dish, a sakazuki
. When this practice was introduced in 1963 there were just 153 centenarians but by 2014 more than 29,350 were issued. In the UK, a message from the Queen has been the way the country acknowledges its centenarians. A decade ago one person took responsibility for the cards; it now takes seven people, as the number of cards has increased by 70 per cent. A glance at Figure 1.2
would predict that the manufacture of sakazuki
and the number of letter writers is set to increase significantly – indeed in 2015 the sakazuki
tradition was discontinued.
There are, of course, myriad causal factors at work behind this increase in life expectancy: better health, better nutrition, better medical care, better education, better technology, better sanitation and better income. Demographers debate which of these factors is most important. To the extent that any consensus exists, it is probably best reflected in the influential work of Samuel Preston. He estimates that while rising income and better nutrition account for around 25 per cent of the increase, the major factors are new public health innovations around vector control, drugs and immunization.2
The role of public health and education is a crucial factor in this improvement – consider, for, instance the impact of public awareness campaigns around smoking and life expectancy.
You will live longer wherever you are born
It’s noticeable that all the data in Figures 1.1
are drawn from the richer and more developed countries. Right now in developing countries, fewer children born today can expect to live for 100 years. However, looking forward, the very same forces that have raised life expectancy in the developed countries are now leading to rising life expectancy in developing countries. Just as child mortality fell in the West with rising income, better nutrition and better healthcare, so too a similar phenomenon is happening around the world. Poorer countries start with lower life expectancy than rich countries, but are benefiting in general from the same increases.
Take for example India, where in 1900 life expectancy was 24 years, compared with 49 years in the US. By 1960, US life expectancy had
risen to 70 years while India had only risen to 41 years; the gap in longevity between these two nations was widening. However as India’s economic success picked up, the gap narrowed. By 2014, India’s life expectancy was 67 years and UN demographic forecasters estimate that this should increase at the rate of around two years every decade. India may start with a lower life expectancy than the US, but it is rising in much the same way. In many countries across the world the same is true – the 100-year life is becoming a global phenomenon, although it’s the rich countries that are experiencing it first.
Will you live forever?
Glance back to Figure 1.2
and let your eyes imagine how the longevity trajectory could continue upwards. You may ask yourself whether, as life expectancy has increased at the rate of two to three years every decade, there is any limit to how long people will live. The majority of children born in the West today can be expected to live beyond 100. But why stop there? Why not 150, or 200, or even beyond?
As with most scientific debates, there is a wide range of opposing views. Much discussion focuses on whether there is a natural limit to human life, and if there is, what that might be.3
The pessimists argue that improvements in nutrition and the big breakthrough in tackling infant mortality are complete, and that the diseases of prosperity, a more sedentary lifestyle and rising obesity will curtail any further increase in life expectancy.
Others take a more optimistic view, arguing that public education will continue to be a powerful lever in boosting life expectancy and, combined with technological innovations, will continue to push longevity. Historically the combination of public education, the benefits of technology, early diagnosis and more effective treatments have all helped overcome previous barriers to life expectancy. Why wouldn’t they continue to do so going forward? Indeed within this group of optimists are those who take an almost fantastical view, arguing there is no natural limit to human life, and scientific progress and technology will create life expectancies that approach many hundreds of years.
That is the view of Ray Kurzweil, who became director of engineering at Google, where he leads a team on Artificial Intelligence. In his book,4
co-authored with his physician Terry Grossman, he describes three crucial bridges to a multi-century lifespan. The first bridge is to follow best practice medical advice so as to extend life sufficiently to benefit from the second bridge, which is created by the coming medical revolution in biotechnology, and then onwards to the third bridge, which enables one to benefit from nanotechnology innovations where Artificial Intelligence and robots rebuild ageing bodies at a molecular level. These are the optimists of gerontology, arguing that the natural limits to life are an order of magnitude greater than anything yet imagined.
Which of these schools of thought is right clearly has enormous consequences. Figure 1.2
suggests that if there is a limit, we don’t seem to be close to reaching it. Best practice life expectancy would start to level off if longevity is indeed approaching a peak, but as the graph shows, the rate of progress continues at the same rate as in the past two centuries. Personally the authors tend to agree with the moderate optimists: we imagine that the rises in life expectancy will begin to slow down, perhaps at ages of 110 or 120. Of course, no one can know. But for us, the most important fact to remember is that the concept of the 100-yea...