Postmenopausal women may be at higher risk of having a stroke than they think. A new study by researchers at NYU Langone Medical Center and colleagues found that traditional risk factors for stroke -- such as high cholesterol -- are not as accurate at predicting risk in postmenopausal women as previously thought. Instead, researchers say doctors should refocus their attention on triglyceride levels to determine which women are at highest risk of suffering a devastating and potentially fatal cardiovascular event.

The study appears online February 3 in the journal Stroke.

"Every year, hundreds of thousands of people are affected by stroke and there is a tremendous emphasis on identifying people at increased risk," said lead author Jeffrey S. Berger, MD, assistant professor of medicine and director of Cardiovascular Thrombosis at NYU School of Medicine, part of NYU Langone Medical Center. "This study revealed that what we've been using to evaluate risk all these years actually has little to no predictive value in older women. Triglyceride levels, however, take on a new significance. "

According to the U.S. Centers for Disease Control and Prevention, nearly 800,000 Americans suffer a stroke each year. Ischemic strokes, the type assessed in this study, account for more than eight out of every ten strokes. They occur when blood clots, developing from high levels of a waxy substance in the blood called cholesterol, obstruct blood vessels to the brain. Cholesterol is made up of several lipids, or lipoproteins. Triglycerides are one type of such a lipoprotein, while others include low-density lipoproteins (LDL) and high-density lipoproteins (HDL)."

"We've always believed that total cholesterol and LDL cholesterol levels were the most important biomarkers for identifying stroke risk, but this study gives us strong evidence to question that approach," Dr. Berger said.

The researchers analyzed data from the Hormones and Biomarkers Predicting Stroke (HaBPS) study, consisting of women enrolled in the Women's Health Initiative (WHI), a landmark National Institutes of Health-sponsored study that has monitored the health of more than 90,000 postmenopausal women nationwide for more than 15 years. HaBPS is composed of the first 972 women who experienced an ischemic stroke while participating in the WHI. These women were matched with a control group of 972 participants who had not had strokes. All the women had donated blood samples when they first enrolled in the WHI, and these samples were then analyzed for differences in lipid biomarkers.

The most compelling finding, according to Dr. Berger, was that high triglyceride levels were significantly associated with the development of stroke. In fact, women in the highest quarter of baseline triglyceride levels were nearly twice as likely to have suffered an ischemic stroke as women in the lowest quarter of triglyceride levels during the course of the study. Surprisingly, LDL cholesterol and total cholesterol, however, were not associated with stroke risk in this population, despite their perceived value in the medical community.

Whether the strong association between triglycerides and stroke would also be seen in other populations is still unknown. "This is only the first step. It's a really important step, but it's not the end of the story," Dr. Berger said. "While this study identifies subjects at increased risk of ischemic stroke, the long term goal is to reduce that risk. Future studies aimed at lowering triglyceride levels for reducing the risk of stroke are warranted."