One of the biggest questions in ageing research is whether there is a ceiling on how long human beings can live. A recent study, published in Science, suggests there isn’t. The study measured the survival probabilities of 3,896 people in Italy aged 105 and older. It found that, while we are much more likely to die at 75 than at 55, once we reach about 105, the odds of death remain about the same each year of life.

This effect is often referred to as a “mortality plateau”. If it were impossible to live past a certain age, we would expect mortality rates to continue rising as people age, rather than plateau. The fact that the odds of dying don’t appear to increase past 105 suggests that we have not yet approached our maximum lifespan as a species. But is potentially living for over a century something we ought to look forward to? Here, philosophy can offer some important insights.

Of course, we still don’t know for sure that there is no ceiling. Some researchers argue that there is a natural “expiration date” for human beings, at about 125 years. Chiyo Miyako is currently the oldest known person in the world, at 117 years old. Jeanne Calment, who died in 1997, had the longest recorded lifespan, at 122 years.

In the UK, the number of people over the age of 100 has more than doubled since 2002, and could reach 36,000 by 2030. If there is a mortality plateau, by the year 2300 the oldest person alive could be about 150 years old.

Pleasure versus pain

Would a maximum lifespan of 150 make our lives better or just longer? One way of thinking about this is in terms of pleasure and pain: the more pleasure (and the less pain) we have over the course of our lives, the better our lives are. Other things being equal, a life which lasts 100 years is better than one that lasts 80 years, as long as the extra 20 years contain more pleasure than they do pain.

How likely an outcome is this? As people age, they are much more likely to develop degenerative conditions that could lead to a lower quality of life. But these conditions can be mitigated by a healthy lifestyle and adequate support services. While elderly life may be restricted in some ways, there is no reason that it cannot be, on balance, pleasurable.

On the other hand, an extended lifespan might influence our earlier quality of life. In 2017, there were about 3.5 people of working age (16-64) for every person over age 65, but this ratio is expected to fall to 2.1 to one by 2040. This means that there will be relatively more people claiming pension benefits, and fewer people in the workforce paying taxes to support them. This could lead to the working population being required to pay additional taxes and remain in the workforce for longer, or a reduction in other services to cover pension costs.

An unwanted postscript

We might also think that our lives go better when we get the things we want. Having a longer life might give us more time to accomplish our goals and projects. But we might also think that a desirable life is one with a certain narrative structure.

The late philosopher Ronald Dworkin distinguished between “experiential interests” and “critical interests” to shed light on how people may view their life goals. Experiential interests are for things like pleasure – anything we enjoy. Critical interests are those what we value becoming a reality – essential to what we think constitutes a good life. This could be a parent’s interest in the happiness of their child, for example.

We can imagine a person having a critical interest in avoiding the perceived indignity of dementia, which may accompany extreme old age. Even if the person doesn’t seem bothered by their cognitive decline in the moment, this may not have been how they wanted their life to go. We might think it would be better for this person, taking the whole of their life into account, if they had died prior to this period of decline.

In other words, there could be many circumstances in which we might live for too long. Sometimes it might be better for us to die earlier than we otherwise might have, if doing so is more consistent with the “life story” we wanted for ourselves – for example, being active and independent throughout our lives.

Declining desires?

A similar concern has been raised by the late philosopher Bernard Williams. Williams argued that the things which give meaning to our lives are “categorical desires”, which are essential to our identity. They include things like writing a novel, raising children or pulling off a charity project. These sit alongside more “meaningless” desires, such as the need for food or sex, which he argued can’t make us happy in the long run.

Joseph Sohm

Williams believed that, if we live long enough, we will fulfil all our categorical desires – losing an important driver of our happiness. We are then faced with a remaining life of oppressive boredom, or replacing our fundamental desires and radically changing who we are.

However, as I see it, life can remain rich and complex even for the very elderly, and taking on new projects need not undermine who we are. This is especially true if our friends and loved ones are living longer as well. While our desires and interests may change, connection to others can help to promote continuity among the various stages of our lives.

What each of these views shows is that living longer does not in itself make us better off. As our population continues to age, we will need to make important and potentially difficult choices about how we want to care for the elderly. Crucially, strategies to promote healthy ageing may not only ease the burdens on society, but help to ensure that our longer lives are better lives – even in a philosophical sense.