Life expectancy in the developed world has rapidly increased throughout the last century due to rising living standards, better education, and healthier nutrition. However, we now face a new challenge from the degenerative diseases associated with ageing, which include cancer, diabetes, cardiovascular disease, and dementia. These cost the economy billions and affect almost everyone who lives into old age, and have a devastating impact on quality of life.

Current research often focuses on individually targeting these age-related diseases, but it can be argued that preventing one disease simply increases the risk of contracting another. As a result, some scientists have taken a new approach, attempting to find a drug that targets the process of ageing itself. Although a ‘cure for ageing’ may seem like a fantasy, certain treatments have already been found to have lifespan-extending effects in the lab, and it is possible that these could one day be used on humans.

One potential approach to extending the human lifespan is through severely restricting caloric intake. The link between caloric restriction and longer lifespan was first observed eighty years ago in rats, and similar effects have been reported in a diverse range of organisms including worms, fruit flies, and mice. There is evidence that this principle might also apply in humans: the Okinawan population of Japan, who have traditionally survived on a low-calorie diet, have an extremely high life expectancy. The apparent link between reduced food intake and longevity has spawned a fasting craze in the start-ups of Silicon Valley, with enthusiasts claiming fasting promotes their productivity, as well as potentially enabling them to live longer. These theories must, however, be treated with caution, considering the dangerous impact of eating disorders, many of which involve restrictive eating.

In reality, most of us are unwilling to commit to the 40% reduction in caloric intake trialled in many of these animal studies. Caloric restriction in humans can also lead to unwelcome side effects such as infertility and decreased bone density. As a result, scientists are attempting to create a drug that mimics the effects of caloric restriction, enabling increased lifespan without the harmful side effects or decreased quality of life associated with severely reducing food intake.

One possible candidate is resveratrol, a compound found in some fruit and in red wine. Resveratrol was previously thought to be a solution to the ‘French paradox’ – the observation that French people have low incidence of heart disease despite their diet being rich in saturated fats – but a study has since shown that the levels of resveratrol in red wine are too low to have any significant effect.  High doses, however, have been shown to extend lifespan in several organisms – including worms, fish, and honeybees – due to the effect of the drug on the activity of sirtuins, enzymes which control several biological pathways and are known to be linked with the ageing process. While studies on the effect of resveratrol in humans have not shown very promising results, the development of more potent synthetic compounds which target the same cellular pathways holds hope for the future.

Another potential avenue for drug development lies in testing whether some chemical present in the blood of the young is able to rejuvenate the elderly. This theory stems from experiments using parabiosis, a research technique which involves surgically attaching the vasculature of two mice so that they share their blood. It was found that damage to liver or muscle in an older mouse healed faster in the presence of blood from an attached younger individual. This led to the founding of Alkahest, a biotechnology company, by Tony Wyss-Coray, one of the scientists responsible for this initial experiment.

Alkahest are currently investigating the use of plasma taken from men under 30 to treat Alzheimer’s in the elderly. As the US Food and Drug Administration has already certified plasma transfusion as safe, this approach has a head start in the clinical trials process. However, there remain concerns regarding this method. Plasma donation is a time-consuming process and donors are often financially compensated, raising fears of a future where desperate young people sell their blood to the highest bidder. A potential alternative approach is to identify the substance present in the blood responsible for these rejuvenating effects and use that specific compound as a drug, avoiding the need to ‘harvest’ blood from younger people.

It’s clear that a drug capable of curing ageing is still a long way off, and there are many potential difficulties which must be overcome: clinical trials for lifespan-extending drugs could take decades, and it is important to ensure that any years added to people’s lives are healthy ones.

Despite these problems, it is an exciting time for the field of ageing research, with Google having helped to found Calico - a biotech company with the aim of combating ageing – in 2013, with plans to build a $1.5 billion research and development centre. If lifespan extension is ever achieved, the huge impact on society would surely make this level of investment worthwhile.