I went to a pair of talks last night. The overall title for the evening was “Why are we living longer”. The title started from an assumption that we are living longer, and looked for the cause.
But I was keen to ask a prior question: “Are we living longer?” And to ask for evidence to support the claim. Ok, if that was established, then we could ask why?
You see, I’m not sure we are living longer. And the talks confirmed my suspicion.
The first speaker, Prof Tom Kirkwood, started with a slide showing a near linear increase in life expectancy for human beings over the last 50 to 60 years. His implication was that this linear increase should go on for ever. He hinted at the possibility. For the UK, life expectancy is now in the high 70s, and increasing.
But hold on. Humans have always had individuals who had life spans into the 70s and 80s. The second speaker, Prof Richard Faragher pointed this out. Research on the age of ancient skeletons found around Europe shows this 70-year lifespans stretch back through millennia. He concluded that we are not living longer.
The issue is who was meant by the ‘we’ in the title. Does it refer to us as individuals or species.
At an individual level, more of us are making it to the 80s and 90s – yes, we are living longer. At a species level, there is no evidence that the number of people entering super old age. The list of established supercentenarians (people over 110) currently contains only 70 names, with only 3 over 114. None are over 115. The record for a human is 122.
I asked for evidence that there is a mass of people about to join the list. There may be hunches, or beliefs or wishes – but as yet no evidence.
The evening was put on by the Medical Journalists’ Association. I’m a member, and I value our goals to make complex matters clear. So let’s be clear. At the moment the evidence that more people will live to 80 and 90 is clear. The evidence that the human species is about to stretch to new lengths is at best unclear – certainly not a certainty.
Yes, individual life expectancy is going up. No, as yet, the human species hasn’t changed.
The issue is more than academic. It rapidly becomes political and financial. For example, if you think the species limits are about to change, then there is a deeply troubling pension problem. If you think that we are going to have more 90-year olds, then yes, there is an issue, but it is of a much lower magnitude.
Correct representation of data is important.