Life Expectations v Longevity

On the radio yesterday I heard a discussion about the increase in life expectancy during the 20th century. One commentator observed, rather depressingly, that we hadn’t extended life, we had extended death.

For some people, we find ways to keep them alive, without also making that life enjoyable and meaningful. In effect, we were just dragging out the process of dying.

It is, our belief that AgeTech can play an important part in making those extra years both enjoyable and meaningful. But it may also be that in some cases the right path for someone is not a long time in hospital undergoing treatment but a shorter time back in their own home. A place where they are surrounded by the people and things that they love. And where they are able to say goodbye to friends and family both near and far away. My mother had signed an advanced directive because life had become painful and difficult for her. When she had a heart attack just before her 90th birthday, she was not treated, nor artificially fed or hydrated. She passed away in a few days, without further pain or much distress. I have found that a wonderful example of clear thinking, courage, and stoicism which I hope to emulate.

But let’s talk about life expectancy. People think they understand what we mean by “life expectancy” but most people don’t. Ask someone how they would calculate life expectancy, or what a quoted figure for life expectancy means, and they’ll mostly give the wrong answer. We can calculate the average age of people dying of natural causes over a period of time. Suppose we did that for the year just ended and came up with a number. People tend to think that number is the life expectancy of someone born right now. But it’s not. The people who died last year were mostly born over 70 years ago, and at the time they were born the average age of death was probably in the 60s for the UK. So the average of death at a point in time is certainly not the same as life expectancy for those born at that time. The problem, of course, is that life expectancy changes over time, and mostly increases. So someone born today could reasonably expect to live longer than the people who are dying right now (ignoring the possible effects of climate change, antibiotic resistance, and an asteroid impact). We can try to project forward to estimate the true life expectancy for someone born today, and that’s what we usually do, but we’ll be wrong – perhaps very.

And what does the quoted figure of life expectancy mean for someone who is already relatively old? We could estimate the life expectancy for someone born in a given historical year that doesn’t give us the correct figure for the number of further years of life they probably have left. A significant number of people die as babies, children, adolescents, etc, so the life expectancy at birth for people born in any given year is lowered by this component. If life expectancy for someone born 70 years ago was, say 76 years, that does not mean that they should now only expect an average of 6 more years, they should expect a few years more than that. This is one of the reasons that the Office for National Statistics produces life expectancy figures for people born today, and for people at the age of 65 (and they could calculate a figure for any age, but it wouldn’t add much value). These “extra years” of life expectancy for those that are already relatively old are diminishing. That’s because infant mortality and childhood death have drastically decreased and hence the figures for life expectancy at birth and age 65 are slowly converging.

If you look at published life expectancy figures you will tend to find two types quoted:

  1. Period life expectancy, which is simply the average age of death by natural causes at the moment someone is born. It ignores the fact that health care will improve during their lifetime and they will probably live longer than their predecessors.
  2. Cohort life expectancy, which is either the actual average number of years lived by people born in a given year (for years before say 1920), or the estimated average age of death for that cohort projecting into the future based on previous trends.

A decade or so ago we went through a period where life expectancy was increasing by about one year for every year that passed. This suggested that immortality was near – if we could increase life expectancy faster than time was passing then some people might never die. But over the last few years, life expectancy increases in the UK have stalled (but life expectancy has not decreased).

I don’t think many people are truly interested in living forever, but I do think we are all interested in living well. That needs to be the goal of medicine, elder care, and AgeTech. It also needs to be the goal of people themselves. If people don’t make efforts to stay healthy then it greatly limits what can be done for them. Fortunately, I think we are living in a time when obesity perhaps aside, people are making a real effort. Efforts to improve their diet, take exercise, give up smoking, reduce alcohol and take an interest in planet Earth too. If we can make life worth living to the very end, then the increases in life expectancy truly become something to celebrate. 

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