The little tips of chromosomes get shorter every time a cell divides, and this shortening is a mark of cellular aging. If they get short enough, the cell dies or stops dividing. Elizabeth Blackburn, who won the 2009 Nobel Prize in Physiology or Medicine for her studies on telomeres with colleagues Carol Greider and Jack Szostak, has spent the better part of her career trying to figure out why. In recent years, Blackburn has expanded on that initial work to show that these gauges of cellular health serve as barometers of environmental and emotional stress and predictors of various diseases. In this expansion of an interview in the October issue of Scientific American, Blackburn talks about additional ways that this research has started to branch out.

Most of your studies look at telomere length in white-blood cells, but you've started looking at cells in saliva. Why?
We're involved in a very large study that's federally funded and being done with Kaiser Permanente, and saliva is a very non-invasive way to get cells from the body. UCSF [University of California, San Francisco]'s Institute for Human Genetics is participating, too, looking at genome-sequence variations. We're collecting about 100,000 telomere lengths in saliva samples and then looking at how those relate to both the extensive longitudinal clinical records that Kaiser is collecting and the genome sequence variations. This will eventually become a publicly available database. The first stage of the study, genotyping the DNA and measuring the telomere lengths, was completed in July.

I understand your new UCSF robot, called ATLAS (the Automated Telomere Length Analysis System), is being used for that giant study, as it can measure several thousand samples a day as opposed to the hundred you could do before. What's the timetable on the database?
Well, it's not going to be next week, that's for sure. We're still refining and getting our data sets. Basically, in the next few years.

What do the telomere lengths of white blood cells, which are dividing cells, tell us about what's happening in non-dividing cells, such as heart-muscle cells? In other words, what can they tell us about the health status of the entire person?
Well, first of all, it's hard to look at non-dividing cells in people because the heart cells and the brain cells—people have a way of wanting to hang onto them. Can't imagine why! So, for ethical reasons, you don't look at them in humans. Basically, when you look at different types of cells, such as fibroblasts, which form connective tissue, or epithelial cells, from saliva, you see general correlations within a person. If telomeres are up for one cell type, they're up for others overall. What we don't know yet, because the data sets have mostly been collected on blood cells, is which will turn out to be better in terms of predictive power for disease risk.