BOSTON The great promise of the Human Genome Project is that if we can crack the genetic code in each of our cells, we may be able to predict what diseases we might get and prevent them. But more than a decade into this project, no medical miracles have been produced. Now, a new study by the Harvard School of Public Health has more disappointing news. WBURs All Things Considered host Sacha Pfeiffer spoke with the studys senior author, Peter Kraft, an associate professor of epidemiology at Harvard.

Sacha Pfeiffer: Your study looked at one of the possible key reasons for why simply mapping the human genome as huge a scientific accomplishment as that is might not alone be enough to start curing or preventing diseases. What else have researchers thought might be necessary to do that?

Peter Kraft: Weve actually been fabulously successful, in the last five years especially, in finding genetic variants that are associated with disease risk. But when people looked and asked the question, Do these actually help us predict whos going to be at high risk? the answer was mostly no. And one of reasons that might have been is that people looked at these variants in isolation, one at a time. But if you considered how they work together, and how they work together with the environment, to influence cancer risk or disease risk generally, people thought that might help boost the predictive ability.

So in terms of how genes work with other genes, or how genes react if you smoke, or if youre overweight, or if youve taken hormones that kind of thing?

Right, exactly. So the models up till now have assumed that a gene is a gene and its effect is the same whether you smoke or not. But, of course, that may not be the case and in fact probably isnt the case.

And so in your study you took those factors into account environmental and lifestyle factors. What did you find?

We sort of played a thought experiment and said, What if we knew how actually these things worked together? And given that information we tried to predict who was at high risk and who was at low risk. And we found that even knowing that information, which were a long way from knowing and understanding but even if we knew it, the change in the risk estimates would not be all that great. Its giving us a 1 to 3 percent increase of our ability to detect people who are at high risk.

Is that not a very useful increase?

Well, it depends on the context, but not necessarily. It seems to be in the range where your decision as a patient and your clinicians recommendations wouldnt really change that much. So given what they knew before they drew your blood and looked at your genetics, their recommendation would probably be the same.

So your study tells us that if we get our genes mapped, we might learn a little bit more if were at risk of a disease, but not very much to help our doctors. So where does that leave us in terms of our hopes for the Humane Genome Project and this idea that we could create personalized medicine customized for every individual?

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Study: Knowing Genetic Makeup May Not Help Predict Disease Risk

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