Strong DNA link found to heart attacks

Changes on chromosome 9 increase heart attack risk by 40%
Heart disease still remains the number one killer in the U.S. So listen to your doctor. Watch your cholesterol. Get some exercise. And have your DNA checked. Wait a minute. Have your DNA checked? When did that piece of advice pop up? Well, that isn't the advice yet. But your doctor may be suggesting it in the near future. Two groups pinpointed a change on chromosome 9 that correlates with an increased risk for a heart attack. If you have this difference, then you are 40% more likely to have a heart attack. On its own, knowing about this DNA difference is not necessarily that useful. This is because although the risk is real, it is pretty small. But as a part of some future panel of DNA tests, knowing this information could prove to be very useful in helping to figure out a person's overall risk for having a heart attack. And if scientists ever figure out what is going on with this DNA change, then they may be able to design medicines that can help.
A small but real risk
Heart disease definitely seems to run in families. If you have a relative who had an early heart attack, then you are at a higher risk of having one yourself. For example if you have a parent or brother or sister who had a heart attack before the age of 50, your risk of a heart attack is increased by 33%. Two relatives like this and your risk increases by 50%. Some scientists decided to try to find out what is going on in our DNA that can cause this increased risk. Two groups did very similar work with different populations and found that the same DNA region was important. So most likely the result reflects a real indicator of increased risk. What they found was a certain DNA change on chromosome 9 was common to many people who had heart attacks. This DNA change is pretty common in Caucasians. Both papers predicted that around 20-25% of Caucasians have two copies of this DNA change*. The DNA change puts all of these folks at a 30-40% higher risk for a heart attack. That's an awful lot of people and the risk sounds significant. But with all of these percentages, it can be hard to figure out what is really going on. Especially without knowing your risk to begin with! So I contacted Dr. Ruth McPherson, one of the key researchers involved in the work. I asked what is my real risk if I have two copies of the DNA difference. Here was her reply: We estimate a person's 10 year risk of having a heart attack or dying from heart disease based on conventional risk factors such as age, sex, smoking, cholesterol, HDL-C, BP and clinical history of heart problems or diabetes (Framingham risk score). So if based on these known risk factors, a 50 year old man has an estimated 10% risk of developing heart disease in the next 10 years, if he carries 2 copies of the high risk allele (genetic variant), his real risk is about 40% higher or (1.4 X 10% = 14%). In other words, your chances for a heart attack would go from 10% to 14%. This is not enough to explain the fact that heart attacks can run in families. It is most likely just one of many possible DNA differences that all contribute to some overall risk. In other words, many different DNA differences can each increase or decrease someone's chances of having a heart attack. Adding together all of these risks would give someone a true picture of their risk from DNA. So researchers need to work to find all of those DNA differences. Perhaps they can do this by focusing in on families with more than one heart attack. Then they may find less common but more significant DNA differences. And when they do, maybe a panel of tests could be done to really calculate someone's risk of heart attack because of what's in their DNA. *Remember, we all have two copies of each chromosome.

More Information

Certain DNA changes
increase your risk
for a heart attack.
And the DNA change does…
OK, so what does the DNA change do? Well, they couldn't figure that out. What scientists have done is to create a huge database of hundreds of thousands of DNA differences. They don't know what (if anything) these DNA differences do. The scientists just know they are there. They can use this database to compare people's DNA and see which differences they share. And which ones they don't. When scientists look at very large groups, all of the differences that aren't near regions important for what they are comparing fall out. Leaving only the statistically significant ones. This is just what the scientists did in these studies. They compared the DNA of people who had heart attacks with those who didn't. Both groups of researchers looked at hundreds of thousands of DNA differences in tens of thousands of patients. For example, one group compared the DNA of 1607 heart attack patients to 6728 people who hadn't had heart attacks. They looked at 305,953 DNA differences. Three DNA differences stood out, all on chromosome 9 very close to each other. They then expanded their study to look at four other groups of patients and found the same results. The other group did a similar study with 23,000 people and 100,000 DNA differences and found the same DNA differences on chromosome 9. But neither group knows what these DNA differences do. Or even if they are important for what they were studying. What they can learn is that somewhere around the DNA differences is something that makes a heart attack more likely. So the next step will be to really home in on this region and try to find out what is going on. The scientists do know that there are two genes in the region. The two genes might be involved in heart attack risk since they are involved in cell growth and death. These processes are definitely involved in heart attacks. But the little bit of work they've done hasn't shown any differences in the genes. So they'll need to keep looking. We do know, though, that something here is important. And when scientists figure it out, they may be able to make new medicines based on what they learned. A final note. None of this work would have been possible without the human genome project. This sort of large scale analysis could not be done without knowing all of the letters in a human's DNA. So that we can see where the differences are. The human genome project is definitely bearing fruit. Money well spent.