Until the mid-nineties it was not thought that the process of ageing was subject to any general control. It was thought likely to involve hundreds if not thousands of genes and would also be influenced by many environmental factors. That view has now started to change. One reason is the discovery that calorie-restricted diets can extend healthy life in a range of animals. Another key finding was made in 1993, when work by Cynthia Kenyon on roundworms showed that altering a single gene, daf-2, could double their lifespan, slow their ageing and allow them to live longer lives as vigorous, young, worms.
These sorts of discoveries sparked a flurry of work into ageing, and the growing understanding that there are biological levers in a range of species, including humans, that can be pulled to extend life. Scientists have tinkered with the lifespan of many animals by modifying their genes, giving them different kinds of drugs, and putting them on calorie-restricted diets. The rare few humans who live beyond 100 seem to have been born with a lucky genetic endowment (and lived a good life) that appears to allow them to age more slowly. For many the next obvious step is to figure out whether it would be possible to create an anti-ageing drug for humans, something that would also slow down the arrival of age-related diseases such as cancer, dementia and cardiovascular disease. 
Luckily the world might not have to wait for science to develop a drug from scratch. There is already a candidate anti-ageing drug, a generic called metformin that has been widely used by diabetics around the world. It works to lower insulin levels in the blood and triggers a range of other molecular pathways that are likely to influence the ageing process. The way it works inside the cell is not completely understood but it is thought to favourably influence metabolic and cellular processes associated with the development of age-related conditions such as inflammation, autophagy (when broken bits of cell are recycled) and cell senescence (when they are unable to grow and divide any longer). In humans, those who take metformin seem to have improved risk factors for cardiovascular disease. Epidemiological work suggests that its use is associated with reduced incidence of cancer and mortality. There is some evidence it may reduce the risk of mild cognitive impairment.
Nir Barzilai of the Albert Einstein College of Medicine in New York wants to test the drug in thousands of people who already have, or are at risk of, cancer, heart disease or cognitive impairment. There are many other possible anti-ageing drugs, and also growing interest in stem cells as therapies for age-related conditions. Metformin however may be able to pass an important test with American drug regulators if a study focused on short-term endpoints (such as lowering the chances of getting cancer) can show that they are having an overall effect on ageing. If the metformin trial succeeds, ageing is shown to be an indication for which drugs might be developed, then a flurry of research funding into anti-ageing therapies is likely to follow as drug companies will see a route to market. If Mr Barzilai's study goes ahead he says that those on the study could gain an additional two years on their "healthspan". This is the term that longevity researchers use to talk about therapies that they hope will extend lifespan, but without the additional years of disability that have been a reliable feature of the longer lives that medicine has already brought.

Source: The Economics