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.