It’s one of the most vexing issues facing the treatment of heart disease: Why do women fare worse than men after suffering a heart attack?

Heart disease is the leading cause of death for both women and men in the United States. Yet, women are more likely to die within a year after suffering a heart attack. And within five years of a heart attack, nearly half of women will have heart failure, a stroke or die, compared with about a third of men.

There are no easy explanations for the differences. However, a recent study can help lay the foundation for more research into the differences in order to develop better diagnostic tools and treatments for women with heart disease.

It may all come down to plaque, the fatty substance that can clog arteries and lead to heart disease. Researchers found that characteristics of plaque varied significantly between the sexes. Plaque in women, for example, was more evenly distributed through the arteries and contained less cholesterol — a major risk factor for heart disease.

“Right now we don’t change treatment depending on what gender you are,” said Stephen Nicholls, M.D., Ph.D., the study’s senior author and a cardiology professor at the South Australian Health and Medical Research Institute. “Maybe that will be different.”

The research, published last August in Circulation: Cardiovascular Imaging, made the American Heart Association’s list of top 10 heart and stroke science advances of 2016.

Better diagnostic tools are helping doctors amass more knowledge. The study examined plaque in 297 men and 138 women using high-resolution intravascular imaging. This method uses focused beams of light instead of relying on ultrasounds, giving researchers the ability to see minute details of the plaque and artery lining that had previously only been available from autopsies.

The researchers found that plaque in women was much more likely to erode than rupture. Both erosions and ruptures can lead to serious problems, said Harmony Reynolds, M.D., an associate professor of medicine at New York University School of Medicine and co-director of the Sarah Ross Soter Center for Women’s Cardiovascular Research. Reynolds was not involved in the study.

She explained that a rupture leaves behind a gooey mess much like a broken egg. The erosion looks more like a skinned knee.

In addition, women’s plaque contained less cholesterol and was more evenly distributed throughout the artery, while in men the substance was more likely to be in the earliest part of the artery. Women’s plaque was also smaller.

Now, the challenge is building on the findings to improve treatments for women.

“We need a better understanding of the erosion,” said Nicholls. He also said the lower levels of cholesterol in women’s plaque suggested that future research should investigate whether statins are as important in treating women with heart disease as they are for men. Perhaps blood thinners will prove to be more crucial for women, he offered.

“If we can understand what is driving an event in an individual, then that may indicate which combination of therapies is best positioned to reduce their subsequent risk,” Nicholls said.

For now, Nicholls stressed the study won’t influence how he treats patients.

Reynolds agreed. She said many people still consider heart disease a man’s problem, and that it is vital to continue educating women about their risks and how they can protect themselves by adopting a healthy lifestyle.

Editor’s note: This is one in a 10-part series of the top medical research advances of 2016 as determined by the American Heart Association.