High levels of triglycerides - a type of fat - in the bloodstream can bump up a person's risk of stroke even when cholesterol levels are normal, researchers report.
Dr. David Tanne, lead author of the study, noted that high triglycerides are associated both with strokes caused by blocked arteries and with mini-strokes caused by temporary blockages.
The study is reported in Tuesday's issue of Circulation: Journal of the American Heart Association.
For up to eight years, Tanne, director of the stroke unit at Sheba Medical Center in Tel Hashomer, Israel, and colleagues followed nearly 11,200 patients, mostly men aged 40 to 78, with heart disease but no history of stroke.
Out of that group, 941 were found to have arterial disease in their brains, and 487 suffered a stroke or mini-stroke during the study.
About a fourth of the individuals in the study had triglyceride levels of 200 milligrams per deciliter of blood, a level that increased their risk for stroke by nearly 30 percent, after taking into account other risk factors like high blood pressure, cigarette smoking and diabetes.
Individuals with high triglycerides also tend to have high blood pressure, insulin resistance and obesity, a cluster of abnormalities called the metabolic syndrome, or syndrome X.
Excess levels of triglycerides increase concentrations of two types of fat particles in the bloodstream, which may contribute to the fatty deposits along arterial walls that can obstruct blood flow.
The researchers noted that the fats also seem to be markers for other changes that might worsen hardening of the arteries or cause blood clots. "High triglycerides are associated with several abnormalities of the body's clotting systems, which may contribute further to their association with cardiovascular disease," Tanne said.
He said the study is believed to be the first to independently link triglyceride levels to stroke risk distinct from cholesterol levels, and stressed that more effective screening and treatment of blood fat buildups "could further reduce the health burdens of stroke."
A secondary finding from the study was that people with higher levels of "good cholesterol" - high-density lipoproteins - are less likely to have a stroke.
Stroke is the third-biggest cause of death in the United States, behind heart disease and all forms of cancer, and is the leading cause of serious, long-term disability. Strokes caused by blocked arteries account for about 80 percent of all the brain attacks.
The Heart Association has set these guidelines for triglycerides: normal range is less than 150 milligrams per deciliter of blood; borderline high is 150 to 199; high is 200 to 499 and very high is 500 and above.
Following a low-fat diet, exercising and losing weight can all lower triglyceride levels.
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