A new blood test could potentially offer some proof that many people really are older than they look.
The test, set to go on sale to the British public later this year, measures the length of a person's telomeres, which are the pieces of DNA at the ends of chromosomes. As cells keep dividing with age, the telomeres get shorter and shorter. By measuring telomeres, some scientists believe they can determine biological age, which doesn't always equal chronological age.
"That means some people may be biologically older or younger than their age," said Jerry Shay, professor and vice chairman of cell biology at UT Southwestern Medical Center in Dallas. Shay is also on the scientific advisory board of Life Length, the manufacturer of the test about to be sold in the United Kingdom. "The test will tell you within about a decade what your biological age is."
Research on telomeres is an expanding and important scientific area, as evidenced by the awarding of the 2009 Nobel Prize in medicine to three American geneticists who studied these small DNA segments.
Anyone interested in taking the 500 euro (about $700) test needs to see a doctor to get blood drawn. The blood will then be sent to a laboratory, and results are generally available in about a month, though the company says it can get results in about a week if necessary. Other companies sell telomere tests as well.
Shay stressed that although the test is an indicator of biological age and is possibly a factor in determining life span, it cannot definitively predict how long a person will live.
"If you have really short telomeres, that doesn't mean you're going to die in the next year or two," Shay said. "It's really for the average person who's just curious his or her general health."
Debate Over Usefulness of Test
While Shay and other proponents of the test say it can provide people with valuable information that can encourage them to adopt healthier lifestyles, others say it is little more than a waste of money.
"If your telomeres are much shorter than most people your age, that could be a red flag that perhaps you need to do something to try and reverse the conditions that led to that," said Shay, such as adopting a healthier lifestyle.
"You don't need a 500 euro test to tell you that you need to exercise and eat right," said Dr. James Evans, editor-in-chief of Genetics in Medicine, the journal of the American College of Medical Genetics.
The results may not be very useful to most people since many factors affect longevity.
"Research has shown that lifespan is determined by both genetic and environmental factors and therefore a test examining one measurement, may not accurately predict this process," said Heidi Tissenbaum, an associate professor at the University of Massachusetts Medical School. "More research is needed to show the connections between telomere length and a person's life span."
"Telomere reserves are just one of many genetic elements that one would need to catalog in order to provide robust information on life span and, as importantly, years of healthy living," said Dr. Ronald DePinho, professor of medicine at Harvard Medical School in Boston.
Others say it may be too early to really be able to evaluate how useful telomere data are.
"It will be interesting and important to examine telomere length in a population and then assemble all the other epidemiological information like race, lifestyle, diet, geographic origin, etc.," said Kerry Bloom, a professor of biology at the University of North Carolina at Chapel Hill. "There are many factors that are likely to influence the results. Only until we have large data sets can we start to anwer the question.
Need to Use Data Carefully
One of the problems that could arise from this test is the misuse of information. If the test becomes more widely available, people need to make sure they purchase it from a reputable company.
"This is likely to spur a whole bunch of snake oil," said Shay, meaning unscrupulous companies selling the test could also try and sell other items purported to offer longevity or other false benefits.
People also need to be sure insurance companies don't get hold of the data.
"If it's found you have shorter telomeres, companies may look at that and start charging higher rates," Shay said.
While it's important to protect people's results, Evans doesn't think the test poses any real ethical concerns.
"I don't think it will cause any dramatic harm to people who have the test done," he said.
Until more is known about what life span secrets the telomere holds, Evans believes people should focus on more important ways to reliably increase longevity.
"The things that matter are not smoking, drinking in moderation, exercising, eating a reasonable diet, maintaining a reasonable weight and wearing a seat belt," he said. "This is the vast bulk of things you can alter to increase your life span."
Additional reporting by ABC News' Jane Kurtzman and Bojana Zupan.