When cholesterol accumulates inside blood vessels, they sometimes burst into clots that block the flow of blood to a person's brain. This is what we call a stroke. But even though doctors have understood what goes on during these events for quite some time, researchers still don't fully grasp what causes heart attacks and strokes to happen in the first place. Now, two new studies, published independently yesterday in The New England Journal of Medicine, may yield some clues, as researchers have found that patients who posses a broken version of a gene that normally transforms fat particles into triglycerides are 40% less likely to experience a stroke, or a heart attack.

In the first study, researchers mapped the genes of 3,734 Americans, two thirds of whom were white. With this information, the scientists were able to identify a gene, called APOC3, that appears to play a role in cardiovascular health. When it was broken because of a mutation — and was therefore unable to transform fats into triglycerides — people's risk of heart attacks were greatly reduced. The other study, which involved a lot more participants, had similar results. Using data from 75,725 participants, the researchers were able to demonstrate that having low triglyceride levels can reduce a person's heart attack risk by 36 percent. Moreover, people with low triglyceride levels appeared to have mutations that destroy APOC3.

Amish people with broken APOC3 genes could eat foods loaded with fat

These findings were actually hinted at in a much smaller study, published in 2008. In that study, researchers discovered that Amish people with broken APOC3 genes were able to keep their triglyceride levels stable, even when they ate foods loaded with fat. "Nobody has been absolutely sure of the role of triglycerides in heart disease," Steven Nissen, chair of cardiology at the Cleveland Clinic, told Forbes. Nissen said these studies are a big deal, because even though they "don't prove triglyceride-lowering heart drugs will work, they do lay the groundwork."

About 720,000 Americans experience heart attacks every year. Currently, many Americans take statins, a class of drug that reduces low-density lipoprotein — or LDL cholesterol — to lower their risk. These drugs are controversial, however, because although they reduce a patient's risk of having a heart attack, many experience them anyway. As a result, researchers have spent a lot of time looking for new drugs, but with little success. Moreover, drug companies have focused a lot energy on HDL cholesterol — the type is widely referred to as "good cholesterol." This may change, some researchers say, because these new studies hint that HDL cholesterol might not be a protective as we once thought.

"We probably had it backwards."

"We probably had it backwards," Ethan J. Weiss, a cardiovascular research at the University of California San Francisco, told Forbes. "we should be paying attention to triglycerides and ignoring HDL."

Weiss may be right, but years of research will be needed before doctors can say so for sure. Any new finding takes time to validate, but this one might be especially tricky because previous studies that have involved lowering triglyceride levels did not demonstrate that doing so reduces a patient's risk of heart attack or stroke. So, although some drugs already lower triglycerides, or act on the APOC3 gene, doctors won't prescribe them for this purpose just yet. But as the lead author of the first study, Sekar Kathiresan, told The New York Times, researchers now have "a route to heart attacks that is independent of LDL [cholesterol]." And that new route may be reason enough to hope.