Life extension has been a human goal for millennia, and research into ageing is providing grounds for optimism that this goal can be achieved. But are there any reasons we should be wary of extending lifespan? In general, living longer is thought to be a good thing. Indeed life expectancy is one of the criteria on which we judge whether a nation is doing well or badly.

Despite this, the prospect of increasingly longer lives raises a number of concerns with an ethical dimension: Would increases in quantity of life be accompanied by increases in quality? Would the products of life extension research be distributed fairly? And would a society of people with much longer lives pose social problems, such as a potentially unsustainable population of unhealthy and dependent elderly citizens?

It is impossible to provide clear answers to these important questions about longer lives without significant research into the particular means that will be used to extend lifespan. Fortunately there is a growing body of scientific literature yielding clearer ideas about the potential benefits and drawbacks of life-prolonging technologies.

Life extension and caloric restriction
Thus far caloric restriction (CR) is the only intervention has been shown to slow ageing, consistently and substantially extending average and maximum lifespan in a wide variety of organisms. If similarly effective in humans it could result in a substantial increase in average and maximum lifespan, perhaps raising average lifespan to around 100, and increasing maximum lifespan well above the 122 years achieved by Jeanne Calment.

Caloric restriction mimetics
The effectiveness of CR has, unsurprisingly, led to an effort to develop CR mimetics (CRMs)—drugs that would replicate the effects of CR without the need to restrict calories. Such is the interest in CRMs, that the pharmaceutical giant GlaxoSmithKline bought Sirtris, a biotechnology company aimed at creating effective CRMs, for $720 million—an amount indicative of the potential demand for such drugs.

Life extension and quality of life
Research on CR and CRMs presents the possibility of revisiting ethical questions about life extension with empirical evidence in hand. The results of this research are extremely positive in terms of quality of life, fairness, and the welfare of society. In animal subjects, CR increases healthy lifespan. Similar results have been observed in human groups such as the Okinawan centenarians. Not only do they live longer, but they are healthier, with a reduced incidence of diseases such as cancer, cardiovascular disease and diabetes. A drug that mimicked CR appears likely to improve quality as well as quantity of life.

Life extension and fairness
Although CRMs may be beneficial for individuals, simply allowing those with greater wealth and education to buy such drugs would result in grave disparities of healthy lifespan. If a national health service has a strong focus on preventing or postponing disease, and if a CRM is proven to be cost-effective, there are good reasons to think it should be fairly provided to all.

Life extension and the good of society
Benefits from research on CRMs could also transfer to society. With a population that is healthier for longer, healthcare expenditure would at least be deferred, and perhaps the overall spend would be reduced. Moreover, increased healthspan provides the potential for citizens to work for longer.

Conclusion
Extending lifespan is not unconditionally an ethical goal. As individuals, we want to know what the quality of additional years will be like. As a society, we want to know that the intervention won’t undermine goals like equality and solidarity. Moreover, we need to know that longer lives will not place unsustainable demands on future generations.
Research on CR and CRMs is an important step towards providing the requisite knowledge. The available studies strongly suggest that CRMs could contribute to biological potential for longer, healthier and more productive lives. Moreover, this promise appears compatible with, and could further, ends that are important for individuals and societies. Empirically-informed individual choices and policies will enable the realisation of these benefits.

Further reading

• Gems, D. 2011. Tragedy and delight: the ethics of decelerated ageing. Philosophical Transactions of the Royal Society of London - Series B: Biological Sciences 366 (1561): 108-112.
• Speakman, J., and S. Mitchell. 2011. Caloric Restriction. Molecular Aspects of Medicine 32 (3): 159-221.
• Temkin, L. 2008. Is Living Longer Living Better? Journal of Applied Philosophy 25 (3): 193-210.
• Wareham, C. 2012. Life Extension and Mental Ageing. Philosophical Papers 41 (3): 455–477.