My dad died last month. I’ve got over the immediate emotional impact, but I still miss him, of course. I hope I always will. What I’ll miss most, I think, is the feeling of being the man in the middle, with dad on one side of me and my son on the other. Only after dad died, did it occur to me that we have no photo showing us like that. Just one of many things that went undone or unsaid, and now never will. I’m the old man now.
My dad was 83 when he died. Some people commented that he was still quite young. Well, it certainly is true that plenty of people live longer than that nowadays, but was his life below average length? I was surprised how hard it was to figure this out. Although there are plenty of statistics available , these don’t answer that exact question. The UK Office for National Statistics (ONS) publishes things like life expectancy at birth or at age 65 for various years, but what I wanted to know was something like “the median lifespan of British males born in 1931”. If half the men born in 1931 (the year of my dad’s birth) are already dead, then that statistic is a matter of historical fact. I presume the ONS has the data, but I didn’t see that exact statistic. Still, from looking around, I reckoned the “average” (that is, mean) lifespan of British men born on 1931 to be about 79 years (though I suppose the mean is subject to change while there are still survivors). Anyway, by that reckoning, my dad lived a bit longer than the average for men born in 1931.

It’s well-known that people live much longer now than they used to and there’s an on-going debate as to the extent to which human life an be extended. This paper explains that while there have been regular claims that absolute limits have been reached, these supposed limits have been broken over and over again by increases in lifespan that continue to progress steadily. ONS statistics show the history of advancing longevity on Britain. The following graph illustrates number of deaths by age among British males in various years between 1850 and 2010.

Number of Deaths by Age from the Period Life Tables for England and Wales, Males.
Source: Office for National Statistics – http://www.ons.gov.uk/ons/dcp171776_292196.pdf
I have focused on male statistics here just to keep things simple and because this discussion started with a consideration of my father. Comparable female statistics can be seen in the ONS paper. The features I’ve discussed here generally apply to females as well as males, although child (under 10 years) mortality during the nineteenth century was not so brutal for females as for males and female adults have throughout lived slightly longer on average than males.

Several features of this plot illustrate how mortality has changed since 1850:

  1. Mortality before the age of 50 has plumetted since 1900.
  2. Until 1900, modal age(s) of death were not particularly distinct, but few survived beyond 75 years.
  3. In the twentieth century, mortality under the age of 50 fell, resulting in the emergence of a well-defined modal age of death for adults;
  4. From 1925 until 1975 the modal age of death for adults remained fixed at about 75 years.
  5. Since 1975 the modal age of death for adults has increased, reaching 85 years in 2010.

The graph above doesn’t show mortalities below age 10, but these can be seen in the following plot of the number of males surviving per 100,000 by age for various years of birth.

Number of Survivors by Age, from the Period Life Tables, England and Wales, Males.
Source: Office for National Statistics – http://www.ons.gov.uk/ons/dcp171776_292196.pdf

In the nineteenth century, almost 30% of male children died before their tenth birthday. By 1925, however, this had improved markedly and by 1950, levels of child mortality were comparable to what we have today.

What these statistics seem to show is that during the twentieth century, patterns of mortality changed markedly and that this took place in two phases. The first half of the century saw a dramatic fall in mortality among children and reduced mortality among young adults so that lifespans became more consistent. While developments in medicine no doubt played a part in this, it’s quite likely that improvements in nutrition, housing, sanitation and hygiene as well as greater awareness of and precautions against accidents were all important too. That the modal age of mortality of 75 years remained fixed over the half-century from 1925 to 1975 might quite reasonably have been taken to suggest a ‘natural’ limit to human lifespan of around 75 years. Since 1975, however, we seem to have entered another phase in the story as the modal age of mortality has started to advance, gaining 10 years between 1975 and 2010. This is consistent with the global rate described by Oeppen and Vaupel. This illustrates the pitfalls of hypothesizing limits to human longevity from mortality statistics alone. To hypothesize a limit, you really ought to propose a mechanism that limits lifespan independently of any external influence. The half-century reign of the 75-year modal lifespan appears to be the result of certain causes of death that were different from anything encountered earlier but that became hard to avoid after you passed 70. Many of those can no doubt be alleviated by new medical techniques. It appears that, in the 1970s, medical practise caught up with the increasing numbers of aged people in the population. The causes of mortality that had imposed the 75-year “limit” were alleviated and people started surviving even longer. It remains to be seen whether it will be biological or economic limits that turn out to be more critical in determining how far human lifespans can be extended.

During the last three years of his life, my dad was in almost continual poor health and his life had become largely a matter of going from one medical appointment to the next. He spent that last two weeks of his life in hospital. Having attended what was meant to be an outpatient appointment (in and out the same day), he was sent to A&E and, from there was circulated between various departments over the following two weeks. Two days before he died, he underwent a surgical procedure intended to improve circulation in his left leg. As far as I can tell, there was a good medical case for this: his quality of life and perhaps life expectancy too could have been improved; the risks were well understood and procedures for dealing with the resulting emergencies well-established. My dad understood all this and had given his consent. Nevertheless, he suffered a serious bleed and was transferred to a tertiary care hospital. It seems his ischaemic heart couldn’t cope with the shock and finally gave up two days later.

That dad ever made it to the age he did is probably thanks to modern medicine. Nevertheless, since his death was essentially the consequence of medical intervention, it was also modern medical practices that determined the timing of his death. Lifespan is a good objective measure of overall lifetime health, but there comes a point where prolonging life becomes an end in itself, independent of health. As the population ages, medicine will be keeping alive more and more people whose prospects of returning to independent good health or of ever being economically productive is essentially nil. Increasingly, our culture will have to be built around such people. What then will be the core value of our culture?

Goodbye, dad. I love you. Thanks so much for making me possible. You gave me more than I’ll ever be able to say. This one’s for you.

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