High levels of a blood fat called triglycerides greatly increase the risk of stroke, researchers say. They used data from a 31-year study of 14,000 Danish men and women. Triglycerides were measured several times through the years. People with the highest levels were 3 to 4 times as likely to have a stroke as those with the lowest levels. The increase was for ischemic stroke. This type is caused by blockage of a blood vessel in the brain. Researchers also found that triglycerides don't need to be measured after 8 to 12 hours without food. Tests in the study were done at random times of day. HealthDay News wrote about the study November 11. It was in the Journal of the American Medical Association.

What Is the Doctor's Reaction?

Chances are good that you know your cholesterol level. You may even know your HDL ("good" cholesterol) and LDL ("bad" cholesterol). But what about your triglyceride level?

Many have never heard of it. Yet triglyceride measurement is one of the routine tests that measure lipids (fats) in the blood. The tests are used to assess the risk of heart and artery disease, including stroke. Besides triglycerides, the tests include total, HDL and LDL cholesterol levels.

Up to 25% of women and 35% of men have high triglycerides, but you rarely hear much about it. I think of triglycerides as the forgotten lipid.

That may soon change. We already know that triglycerides can be important. For example:

• People with high triglycerides have a higher risk of heart disease, including heart attack.

• High triglycerides are one part of the metabolic syndrome, a condition that also increases heart and artery disease risk. People with the syndrome have at least three of the following:

  • Large waist (for men, more than 40 inches, for women more than 35 inches)

  • Triglyceride level of at least 150 milligrams per deciliter of blood (mg/dL)

  • Low HDL cholesterol (for men, less than 40 mg/dL, for women less than 50 mg/dL)

  • High blood pressure (at least 130/85)

  • Increased blood sugar (with a fasting blood sugar of at least 110 mg/dL)

• A very high triglyceride level (more than 1,000 mg/dL) increases the risk of pancreatitis. This inflammation of the pancreas can be dangerous. Doctors usually treat very high triglyceride levels to lower this risk.

People usually get blood drawn for lipid tests after fasting (no food) for 8 to 12 hours. A high-fat meal can temporarily increase total cholesterol and triglyceride levels. For this reason, a nonfasting test may not be accurate.

Then again, we spend much of our time in the nonfasting state. Recent studies also suggest that nonfasting cholesterol levels may predict heart attack better than fasting levels.

A new study explores the effect of nonfasting triglyceride levels on stroke risk. Researchers in Denmark enrolled nearly 14,000 people with an average age of 54. They measured the subjects' nonfasting triglyceride levels. In the next 31 years, about 11% of the people had an ischemic stroke. This is the most common type of stroke. A blood vessel in the brain is blocked and brain tissue dies.

Here's what the study found:

• People with high nonfasting triglyceride levels had an increased stroke risk. This was true even after researchers accounted for other things that can increase stroke risk. These factors include high blood pressure, diabetes and high total cholesterol.

• For men with triglyceride levels of more than 442 mg/dL, stroke risk was 2.2 times as high as for men with levels of less than 89. Stroke risk was increased nearly 4 times for women with the highest triglyceride levels.

• Age and triglycerides had a powerful effect on stroke risk. The 10-year stroke risk was less than 3% for men and women under age 55. But it rose to nearly 12% for women over 55 and 17% for men over 55 with the highest triglyceride levels.