Genetic Tests Not Helpful for Predicting Heart Disease

There's no proof that most of the genes that researchers have linked to an increased risk of heart disease do in fact cause heart disease, according to a comprehensive new analysis of the data, which was published in the Journal of the American Medical Association (JAMA). This conclusion deserves a lot more attention than it's getting in the mainstream media because it reveals one of the major blind spots in health research and reporting today.

The belief that your genes determine your destiny is so ingrained amongst journalists, the general public and indeed many medical staffers that it's accepted as a universal truth. And of course, some genetic variants--like the one for Huntington's disease--are so detrimental that they are always bad news.

But when it comes to heart disease and other chronic conditions, the combination of genetic and lifestyle risk factors is so complex that it can be very tough figuring out what the true culprits are.

Trouble is, as this highly worthwhile news item from Nature makes clear, we're already lining up for genetic tests to try to learn our predisposition for heart disease and other chronic conditions. One common test, for a genetic variant called apolipoprotein E-4, is supposed to show that you have an increased risk for heart disease. The link has shown up in a number of small studies.

And yet the association (remember, associations do not prove causation) disappeared in the JAMA analysis, which looked at much larger groups of patients.

This is not to say that there are no genetic risk factors for heart disease--just that we're not as clever at finding them as we think.

One more thing: the JAMA study technically applies only to Caucasians since the researchers included only Caucasian populations in their analysis. They didn't want to have to account for the possibility that race plays a role as well in predisposition to heart disease as well.

That's understandable in terms of scientific design--it's very difficult to study two things at once. But it doesn't describe the complex, real world in which we live.

Source: Nonvalidation of Reported Genetic Risk Factors for Acute Coronary Syndrome in a Large-Scale Replication Study, TM Morgan et al, JAMA 2007;297:1551-1561 (available in full for free as of April 11)

Women and Heart Disease

You've got to understand risk if you want to stay healthy. Why do women fear breast cancer more than heart disease? As a group, women have a 4% chance of dying from breast cancer vs. a 38% chance of dying from heart disease. But because women are less likely than men to develop heart disease in their 40s, they (and their doctors) often assume they don't need to worry too much about cardiac problems.

So, the American Heart Association has come up with new guidelines on preventing heart disease that emphasize a woman's lifetime risk. The idea is for women to understand their real risks better and, hopefully, to motivate them to exercise more and adopt a healthier diet. Indeed, there's probably more you can do to prevent heart disease than to prevent breast cancer anyway.