The £400 test that tells you how long you'll live

A blood test that can show how fast someone is ageing – and offers the tantalising possibility of estimating how long they have left to live – is to go on sale to the general public in Britain later this year.

Graphic: How the test works

The controversial test measures vital structures on the tips of a person's chromosomes, called telomeres, which scientists believe are one of the most important and accurate indicators of the speed at which a person is ageing.

Scientists behind the €500 (£435) test said it will be possible to tell whether a person's "biological age", as measured by the length of their telomeres, is older or younger than their actual chronological age.

Medical researchers believe that telomere testing will become widespread within the next five or 10 years, but there are already some scientists who question its value and whether there should be stronger ethical controls over its wider use. In addition to concerns about how people will react to a test for how "old" they really are, some scientists are worried that telomere testing may be hijacked by unscrupulous organisations trying to peddle unproven anti-ageing remedies and other fake elixirs of life.

The results of the tests might also be of interest to companies offering life-insurance policies or medical cover that depend on a person's lifetime risk of falling seriously ill or dying prematurely. However, there is a growing body of scientific opinion that says testing the length of a person's telomeres could provide vital insights into the risk of dying prematurely from a range of age-related disorders, from cardiovascular disease to Alzheimer's and cancer. "We know that people who are born with shorter telomeres than normal also have a shorter lifespan. We know that shorter telomeres can cause a shorter lifespan," said Maria Blasco of the Spanish National Cancer Research Centre in Madrid, who is the inventor of the new commercial telomere test. "But we don't know whether longer telomeres are going to give you a longer lifespan. That's not really known in humans," she added.

"What is new about this test is that it is very precise. We can detect very small differences in telomere length and it is a very simple and fast technique where many samples can be analysed at the same time. Most importantly, we are able to determine the presence of dangerous telomeres – those that are very short."

Dr Blasco's company, Life Length, is in talks with medical diagnostic companies across Europe, including the UK, to market the test and collect blood samples for analysis in Spain. A deal with a company operating in Britain is likely within a year, she said.

"We need to have a clinical company to send us the blood [samples]. We are in contact with several groups in the UK who are interested," Dr Blasco said.

Life Length is anticipating hundreds of requests from people wanting to have their telomeres tested and is expecting demand from thousands more once the company is able to bring down the cost of the test as public demand increases.

Although Life Length is not the only company selling telomere tests, it is the only one gearing up for over-the-counter sales to the public and the only company with an accurate-enough test to be of practical use, said Professor Jerry Shay of the University of Texas Southwestern Medical Centre in Dallas.

"This test devised by Blasco is so accurate that it is likely to provide more useful information than some of the other tests out there right now," said Professor Shay, who is a scientific consultant for Life Length. "What's important in ageing is the shortest telomeres. What makes cells stop growing is the shortest telomeres, not the average telomere length, which is what other tests look at.

"Everyone talks about the chronological age, but there is also a biological age, and telomere length is actually a pretty good representation of your biological age. Telomeres are important – there is no question of that," he said.

Asked why the general public would be interested in taking a telomere test, Dr Shay said: "I think people are just basically curious about their own mortality. If you ask people what they worry about, most people would say they are worried about dying."

He added: "People might say 'If I know I'm going to die in 10 years I'll spend all my money now', or 'If I'm going to live for 40 more years I'll be more conservative in my lifestyle'. The worrying thing is that if this information ever got to a point where it is believable, insurance companies would start requiring it in terms of insuring people.

"If you smoke or you're obese your insurance rates are higher, and if you have short telomeres your insurance rates might be higher too."

Scientists do not yet believe they can narrow down the test prediction to calculate the exact number of months and years a person has yet to live, but several studies have indicated that individuals with telomeres that shorter than normal are likely to die younger than those with longer telomeres. Telomere research is considered to be one of the most exciting areas in biomedical science and last year the Nobel Prize in medicine was shared between three scientists who are pioneers in the field.

Interestingly, one of the Nobel laureates, Elizabeth Blackburn of the University of California San Francisco, is an enthusiastic proponent of telomere testing while another of the prize-winners, Carol Greider of Harvard Medical School, is more sceptical of its benefits.

"Do I think it's useful to have a bunch of companies offering to measure telomere length so people can find out how old they are? No," Dr Greider recently told the journal Science.

Dr Blasco, a former post-doctoral student in Dr Greider's laboratory, is more certain of the benefits. "It will be useful for you to know your biological age and maybe to change your lifestyle habits if you find you have short telomeres," she said.

Telomeres: a short history

* 2003 Scientists studying 20-year-old blood samples from 143 people show that telomere length is good indicator of whether someone is likely to live for 15 years or more once they reach 60.

* 2004 Women living with stress of having a sick child are found to have shorter telomeres. Other research suggests that meditation or other forms of stress reduction may lengthen telomeres.

* 2007 Study of men in Scotland shows those with the longest telomeres were half as likely to develop heart disease than those with shorter telomeres. Telomere length was as good as cholesterol levels at predicting the risk of developing cardiovascular disease.

* 2009 Short telomeres linked with inherited bone marrow disease.

* 2010 GM mice with no telomerase, an enzyme that elongates telomeres in some cells, age prematurely compared to normal mice. The ageing effects were reversed after injections of telomerase.

* 2011 Study of civil servants in the UK shows that those with few educational qualifications have shorter telomeres than those with higher educational qualifications. People with poor backgrounds are known to age faster and suffer more age-related diseases.

Vox pop: So, would you take the test?

Trevor Salmon, 53, musician

It is a brilliant breakthrough because we spend every day of our lives trying to live longer. The idea that time is finite is a very hard reality to accept. If this is accurate, then it will enable us to make preparations and refine our lives accordingly.

Samira Melloul, 28, entrepreneur

My curiosity would make me pay for it. But I would need to be convinced by the the firm's credentials. I don't like the idea that such critical DNA data would be with a company that could store it or sell it on to third parties. In the future, this type of information will become very valuable.

Narek Sarkissian, 27, engineer

I don't trust it. Life is about chance and you could die crossing the street tomorrow. What's the point of a DNA test when our true fate is out of our hands? Offering to predict these things with an element of certainty is ambitious and simply not worth my time. There are much better things I could spend that money on.

Natalie Burger, 60, retired

I wouldn't want to know when I was going to die. I'm 60 now and I keep thinking maybe I have another 15 years. But perhaps I have less than that. I don't make plans and have to accept that when my time has come, it's over. Some of this information is all too frightening and is better left alone.