In 1952, the new Queen Elizabeth issued around 250 birthday telegrams. After 50 years on the throne, this had risen fifteenfold, to almost 4,000. The Queen was born in the ‘magic cohort’ year of 1926. If she survives to 2026, she can expect to be issuing 15,000 telegrams by then. Thank goodness that the world has gone digital.
Pause for a few moments to consider what this means.
We are told that life expectancy is rising. But, are fewer people’s lifespans being cut short by a ‘premature’ death? Or, more dramatically, are some extreme long-lived people pushing out the boundaries of what has been considered in the past to be a limit on human lifespan? Perhaps, both are occurring?
Biological orthodoxy
The latter phenomenon goes against the orthodoxy for many biologists, who believe in a biological limit on lifespan for all animals, including humans. But the pace at which ageing occurs clearly varies from person to person, so we would never expect everyone to live for the same length of time. There will always be an element of chance.
Population Change
Setting aside the biology theory, do population statistics give us any pointers? Sadly, information on longest lived people is sparse and often unreliable, but the UK has been preparing regular mortality tables since Queen Victoria, based on population censuses.
These can be used to reveal dramatic changes in death rates at individual ages. Suppose that we have a group of 100,000 births (in this case all boys). We can work out when they would theoretically have died if they had all followed the average rates for each age in that era. This reveals the change in the shape of the distribution of lifespans. The chart plots three lines for their expected lifespans for the mid 1800s (green), the early 1970s (pink) and the early 2000s (blue).
By 1970, there were far fewer short lifespans, primarily due to the almost complete eradication of infant mortality and vast falls in deaths from infectious diseases, like tuberculosis. Alexander Fleming’s discovery of penicillin was a big step forward, but so were more mundane advances like better appreciation of the benefits of cleanliness and good nutrition.
In the last 30 years, the improvement has switched from the young to the over 60s, mainly thanks to big falls in deaths from heart disease and strokes. The appreciation that smoking tobacco is not good for you has also helped. The improvement in life expectancy is stark, with annual falls in death rates of 2% or more occurring at many ages.
For pension providers, the changes since 1970 have particularly affected the funding dynamics. Until 1970, there was little change in average pensioner life expectancies for those who reached retirement. However, since then we have seen dramatic falls in death rates, particularly for younger pensioners, pushing up the cost of pension provision.
Three Score Year and Ten?
In the 1850s, only 22% of new births would have reached their 70th birthday. By 1970, this had risen to 57%, and in the space of just 30 years, this has now risen to a quite remarkable 77%. Even with no further falls in mortality, 15% of boys born today will survive beyond their 90th birthday.
If we zoom in on the over 70s, we see dramatic change since 1970. The age at which most deaths happen has risen from around 75 to almost 85, and more occur at the most common age too. In the clinical language of demographers, this phenomenon is known as “compression of mortality”: there is a shorter window in which most deaths will occur.
But there is a shift in the bell-shaped curve to the right too. Does this lend weight to the argument that there is no limit on life? Perhaps.
Or, could it just be a statistical quirk? Today, there are many more older people who have the chance to go onto ripe old age. This means that we would expect to see more people living to extreme ages than before: the most extreme ages could just be statistical outliers in what remains a random process. This might explain some of the shift to the right.
If there is a hard limit, it is a lot higher than age 100: the biological evidence on ageing would suggest that individual lifespans are elastic and that there will always be some dispersion around the average life expectancy.
So, for now, the jury remains out. Watch this space.