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The Real Risk

Life expectancy: How long will you live?

About the author

David Spiegelhalter is Winton Professor of the Public Understanding of Risk at the University of Cambridge, UK. His professional background is in medical statistics. He is a frequent contributor to the media, and has been an advisor on risk issues as diverse as breast implants, volcanic ash, clinical trials, surgical mortality, and the inquiry into mass murderer Harold Shipman. He is a Fellow of the Royal Society and was awarded an OBE in 2006. You can see more of David’s explorations of risk at the Understanding Uncertainty website, or follow him on Twitter at @undunc

(Copyright: Thinkstock)

(Copyright: Thinkstock)

Behind the cold columns of statistics regarding when we are likely to die lie insights into social changes, global events, and future ageing trends.

My last column looked at death in the workplace, and at the risk of sounding overly fatalistic I now want to examine how long we are likely to live. When we talk about longevity, it is usually described in terms of “life expectancy” – the average length of life – but averages can be misleading. After all, people in the UK have on average one testicle each.

For instance, the 90th Psalm declares, at least in the King James version of the Bible, that “the days of our years are three-score years and ten”, although up to recently you had to be fairly lucky to reach this biblical sell-by date. Some historical figures did manage it: Augustus Caesar conquered that barrier to reach 75, while Michelangelo hammered on to the amazing age of 88.

Since the ancient Greeks, there was also a superstition about the risks of ages that are multiples of seven – the “climacteric years” of 49 and 63 were seen to be positively dangerous. Partly in order to combat this belief, in 1689 a priest in Breslau in Silesia (now Wroclaw in Poland) collected the ages at which people died. These data eventually found their way to Edmond Halley in England, who took time off from discovering comets to construct the first serious life table in 1693, which uses estimates of the annual risk of dying to work out the chances of living to any age.

There was no evidence of any increased risk at age 49 or 63, so Halley neatly demolished the idea of climacteric years. Unlike the Bible’s declaration, Halley’s life tables went up to 84. He estimated there was a 2% chance of reaching this age, and just to prove it he died when he was 85, thus by some margin outliving Bill Haley, also of Comet fame, who only lived until 55.

Fab (sixty-)four factor

But in the case of survival, life expectancy is strongly influenced by a lot of deaths in childhood – the average will be low, but the survivors may then live to a good age. So perhaps taking another cue from the music world might provide a better way of assessing life and death.

Paul McCartney was 16 when he wrote When I’m 64 – an age when 64 seemed as old as old. But if we look at the chances of surviving childhood and getting to 16, and then the chance of such a survivor getting to 64, we can get a better picture of what has changed over the decades.

For example, if we consult wonderful resources such as the Human Mortality Database, we find that back in 1841 (the first year we have data for), 31% of children born in England and Wales died before they were 16, but if you did survive there was nearly a 50% chance of reaching 64.

When the Beatles recorded When I’m 64 in 1966, 2.5% of children died before 16, and surviving girls had an 85% chance of reaching 64: for boys it was only 74%, the difference reflecting the unhealthy lifestyles of so many men. By 2009, the last year we have measurements for, less than 1% of children died before 16, and the chance of reaching 64 rose to 92% for women and 87% for men. This gives an overall life expectancy of 82 for women and 78 for men.   

Global events

Life-expectancy figures do have a value, though, as behind the cold columns of numbers in historical tables lie powerful events. Apart from the World Wars, Napoleon’s march on Moscow, which killed 400,000 men, temporarily reduced life expectancy to 23, the influenza epidemics of 1918-1919 took 10 years off life-expectancy for females in France, while Aids has meant life expectancy in South Africa declined from 63 in 1990 to 54 in 2010.

Extraordinary changes have occurred elsewhere. In 1970 Vietnam had a life expectancy of 48, and it is 75 now – it took England and Wales from 1894 to 1986 to make this transition. We can also see the effects of inequality within a country. For instance, in 1901 life expectancy for Black men in the US was 32, with 43% dying before 20 – for White men the corresponding figures were 48 and 24%. After 100 years and a civil rights movement, the gap in life expectancy was still visible, though it had narrowed from 16 years to five.

Ageing future

Looking forward, we are told that the global population is at seven billion and rapidly rising, and we can also make some reasonable guesses for the life expectancy of people born now. If we allow for future improvements in health, the “principle projections” estimate that males born now in England and Wales can on average expect to live until 90, and for females it is 94, with 32% of males and 39% of females expected to reach 100 in 2112.

The mind boggles at these figures. But these projections are, understandably, rather controversial. Is there some inbuilt ageing process, and can it be reversed? Or is there some natural ceiling that we are going to bang our wrinkled heads against?

One thing is certain for children born in the future – there are going to be a lot of old people around for them to look after, as those already plodding through their middle-age are not going to go away. The UN estimates that the proportion of people over 60 will double between 2007 and 2050, as people will live longer and lower fertility rates mean fewer young people. There will be two billion people over 60 in the world by 2050, and around 400 million over 80.

But what sort of state are all these old people going to be in? After the bit about three-score years and ten; Psalm 90 continues with “and if by reason of strength they be fourscore years, yet is their strength labour and sorrow; for it is soon cut off, and we fly away”, which does not exactly paint an encouraging picture of ageing. Are we making all this effort to live longer, just so that we can spend even more time sitting round the edge of a room, television blaring, struggling to grasp what reluctant visitors are shouting at us?  

In fact, it does not look so bad: in 2008 UK men at age 65 had around 17 years of life expectancy left, 10 of which would be considered as “good” or “very good” health, and this is quite a stringent criterion. Women had more than 20 years left on average, 11 of which would be classed as being “healthy”.

All of which is something of a comfort to me. I will be 64 in a few years, and I have already lost most of my hair. But I am aiming to wait as long as possible before entering “Dunsummin”, the retirement home for statisticians.

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