DALLAS, March 24 -- Major changeable risk factors for heart attack include smoking, high blood cholesterol, high blood pressure and physical inactivity. According to a study published in today's Circulation: Journal of the American Heart Association, high blood levels of the fat triglyceride may need to be added to the list.
Researchers in Denmark say that in middle-aged and older white men, a high level of triglycerides -- the chemical form in which most fat exists in food as well as in the body -- may mean a higher risk for heart attack. Therefore, the scientists say, high blood levels of triglycerides should be considered an independent risk factor for heart attack.
In the study, men with the highest levels of triglycerides were more than twice as likely to have a heart attack when compared to those with the lowest triglyceride levels.
An excess amount of triglycerides in blood is called hypertriglyceridemia, which is linked to the occurrence of heart disease in some people. Elevated triglycerides may be a consequence of other diseases, such as diabetes. Like cholesterol, triglyceride levels can be detected with a blood test.
High levels of triglycerides can influence the size, density distribution and composition of LDL (low-density lipoprotein) cholesterol -- the "bad" cholesterol -- leading to smaller, denser LDL particles, which are more likely to promote the obstructions in the blood vessels that trigger heart attack.
"So far our study appears to provide the strongest evidence that higher triglyceride levels are related to increased risk of ischemic heart disease in men independent of other major risk factors such as total cholesterol and HDL (high-density lipoprotein) cholesterol," says Jorgen Jeppesen, M.D., of the Epidemiological Research Unit, Copenhagen University Hospital, Copenhagen, Denmark.
In an editorial, former American Heart Association President Antonio Gotto, M.D. says that while additional research is necessary to determine whether lowering triglyceride levels can reduce heart attack deaths, the findings make a compelling argument for measuring triglyceride levels as part of an evaluation to determine an individual's risk for heart disease.
"The growing attention to high levels of triglycerides and increased coronary heart disease risk is encouraging to veterans of the 'triglyceride wars,'" says Gotto, dean of the Cornell University Medical School, New York City. "It's also in agreement with another trend in heart attack risk management, namely, the concept of global risk assessment."
Triglycerides are the form in which fat exists in meats, cheese, fish, nuts, vegetable oils, and the greasy layer on the surface of soup stocks or in a pan in which bacon has been fried. In a healthy person, triglycerides and other fatty substances are normally moved into the liver and into storage cells to provide energy for later use.
People with less than 200 milligrams of triglycerides per deciliter (mg/dL) of blood are considered to have normal triglyceride levels. Between 200 and 400 mg/dL is borderline high; between 400 and 1,000 mg/dL is a high triglyceride level; and greater than 1,000 mg/dL is considered very high triglycerides.
"A very interesting finding in our study was that people with triglyceride levels as low as 142 mg/dL were clearly at a higher risk of heart disease," says Jeppesen. "We believe this is of substantial clinical interest since a triglyceride level of below 200 mg/dL is usually considered 'safe.'"
In the study of 2,906 white men who were initially free of any heart disease, researchers found that during an eight-year follow-up period, 229 men had a heart attack. By examining that group of men, the scientists found that heart attack risk increased in those with the highest levels of fasting triglycerides -- measurements taken after 12 hours of fasting prior to the test.
"When the triglyceride levels were measured by the amounts of HDL cholesterol in the blood, a clearer picture emerged," says Jeppesen. "Even those who had high HDL levels, which are thought to protect against heart attack, were still found to be at higher risk for heart disease because of their triglyceride levels."
The American Heart Association says that changes in life habits -- cutting down on calories, reducing saturated fat and cholesterol in the diet, reduce alcohol intake and begin a regular exercise program -- can help in the treatment of hypertriglyceridemia.
Co-authors are Hans Ole Hein, M.D.; Poul Suadicani, D.D. and Finn Gyntelberg, M.D.
NR 98-4877 (Circ/Jeppesen)
Media advisory: Dr. Jeppesen can be reached by phone at 011 45 35 31 60 66 or 011 45 43 71 80 10 or by fax at 011 45 35 31 60 70. (Please do not publish numbers.)