Published online 28 May 2011 | Nature | doi:10.1038/news.2011.330

News: Q&A

Spit test offers guide to health

Telomeres may not predict how long we'll live, but they can still revolutionise medicine, says Nobel laureate Elizabeth Blackburn.

BlackburnElizabeth BlackburnTONI ALBIR/epa/Corbis

A test that claims to measure a person's "biological age" using the length of a person's telomeres — the DNA caps that protect the ends of our chromosomes — marketed by the Spanish company Life Length in Madrid, caused a media storm last week, inspiring wild headlines such as 'The £400 test that tells you how long you'll live'. But will testing the length of our telomeres soon be as routine as measuring cholesterol levels or blood pressure when it comes to assessing our health?

Intricately connected with ageing, telomeres shorten inexorably as cells divide, unless an enzyme called telomerase builds them back up again. As more studies link shortened telomeres with an increased risk of developing a daunting range of diseases — not to mention a reduced lifespan — perhaps it is not surprising that companies are lining up to offer commercial telomere tests.

Even the eminent Elizabeth Blackburn, who shared the 2009 Nobel Prize in Physiology or Medicine for her work on telomeres, is getting in on the act. She co-founded a company, Telome Health based in Menlo Park, California, which has developed its own test to measure telomere length in samples of saliva.

Blackburn spoke about the future of the field at a Berzelius Symposium on telomere biology in Stockholm, Sweden, this week. Nature asked her what she makes of the recent media claims, and what she believes telomere tests will do for medicine.

Can a telomere test predict how long you will live?

That's just silly, isn't it? It is statistical. Yes, there are mortality connections, but it's silly to say this will tell you your life length. You need to take it in context with other information.

So what can it tell you?

We and other groups are seeing clear statistical links between telomere shortness and risk for a variety of diseases that are becoming very common, such as cardiovascular disease, diabetes and certain cancers. We have also looked at chronic psychological stress, including depression and post-traumatic stress disorder, and more and more we see associations with telomere shortness. There are even links with education — in one study telomere shortness was related to not finishing school.

The emerging science is looking at changes in telomere length over time. We're seeing the data unfolding in front of us. A lot of them are not published yet, but in one study, we looked at ageing adults1. Those whose telomere length fell over a 2.5-year period were three times more likely to die from heart disease over the subsequent nine years than those whose telomere length went up or was maintained.

How can telomere tests be useful in medicine?

You get a statistical association with risks for common diseases. In the past, most of the big medical problems have been specific, drastic things — infectious diseases, broken legs — that you had to fix. Medicine has been successful by treating diseases in a very specific way once the damage is done. But telomere length integrates a lot of factors together and gives you an overall picture of risk for what is now emerging as a lot of diseases that tend to occur together, such as diabetes and heart disease. That is not a familiar model to the medical world.

Interventions might include doing things that allow people to cope with their stress, for example, and encouraging exercise, which emerging studies show is associated with telomere maintenance.

But we already know that if we exercise and reduce stress, we will have lower disease risk.

This gives a form to it. It is seen as a bit 'loosey goosey' to talk about lifestyle and things like that. This gives a very concrete — albeit statistical — readout of how you are doing. We have a study going on now and people were beating down the doors to be in it. So this seems to be a useful measure that people can relate to.

Having something where you can see changes may be particularly useful. For example, if you exercise, perhaps this could give you a physiological biomarker for how you are doing.

Apart from prescribing a healthy lifestyle, how might a doctor use this information?

I'll give you an example: a very interesting study in which researchers looked at Scottish men who had one or more risk factors for cardiovascular disease2. They looked at telomere length, then gave statins [which lower the risk of heart disease] or placebo and asked, how protective in the subsequent years was the statin? Well, it made no difference to people whose telomere length was in the top third — it was essentially wasted on a third of the people. We are also finding interesting relationships between telomerase activity and whether people respond to antidepressant medication.

Your test measures telomere length in white blood cells, why?

For convenience — those are the cells in saliva. Telomere length is not the same for every cell type, but someone who is short for one category generally is shorter for the others. However, there is also very good disease relevance for using white blood cells. It turns out that the status of your immune system is probably quite related to the diseases we are talking about. For example, heart disease is associated with activation of the inflammatory branch of the immune system. It's the body's basic response to wounds and infection but if it's switched on long-term, for example by stress, it can be very damaging to the body's tissues and is associated with chronic diseases like heart disease.

So telomere length could be more than just a biomarker?

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The conservative statement is that telomere length is a biomarker, but it's probably not passive. There are some very intimate relationships between things such as molecular markers for inflammation and telomere health. We've just published a big analysis that relates a couple of inflammatory markers, interleukin-6 and tumour necrosis factor-α, to telomere shortness3. Those in turn have been related to high levels of inflammation and cardiovascular disease.

Could we develop drugs to protect or lengthen our telomeres?

My colleagues and I are not interested in making drugs at this point, although I'm sure people will want to do this. Everyone wants a magic pill, but it's a long road to develop any kind of pill. It's not a stupid idea, but let's be realistic about how long it'll take.

What are the next questions for research?

Telomere length has an interesting statistical predictive value, so the question for future research is what's the biology, what's going on? How do we tease out the different components of effects — which are genetic and which are non-genetic; which are causal and which are related? Challenges in medicine are moving from 'treat the symptoms after the house is on fire' to 'can we preserve the house intact?' Can we use what we learn about disease processes to think about prevention and earlier interception? 

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