DALLAS, June 20 -- In the first study of its kind in families, researchers have shown that elevated triglycerides -- a blood fat -- sharply increase a person's risk of dying from a heart attack, even if a person's blood cholesterol is normal.
According to Melissa A. Austin, Ph.D., of the department of epidemiology at the University of Washington School of Public Health and Community Medicine in Seattle, who reported the study in today's Circulation: Journal of the American Heart Association, "The findings offer more evidence of the need to measure levels of both cholesterol and triglycerides when patients undergo lipid profile testing."
Triglycerides are a common type of blood fat in the human body, and have long been associated with heart disease. However, the latest study is the first to provide strong evidence that elevated blood triglyceride levels in families, independent of cholesterol levels, can predict heart attack deaths years in advance.
"Because there is an increased risk for individuals who have a family history of high lipids compared to their spouses, there is a need to collect data on close relatives of patients diagnosed with hyperlipidemia and cardiovascular disease," Austin says. Hyperlipidemia is a condition in which a person's blood cholesterol and/or triglyceride levels are elevated.
"Our primary reason for doing the study was to shed light on ways to treat and prevent a potentially deadly condition that affects many families," she says. "Lowering triglyceride levels with medications may also lower the risk in these families, but that still has to be determined by further research."
The landmark 20-year study used medical history data collected in the early 1970s from 101 families in which cardiovascular disease was prevalent and levels of triglycerides were high. Researchers then traced the health status and cause of death for 685 family members over the next two decades.
It was the first study of its kind in several respects, according to Austin. "It is the first to follow families without high cholesterol levels and only high triglycerides," she says. "Some of our families did have high cholesterol, some had only high triglycerides, and others had both."
She says another unique aspect of this study was that most of the family members were relatives of individuals who had a heart attack and also had elevated triglycerides.
The study compared the risk of heart disease death between siblings and offspring versus spouses of individuals with one of two common lipid disorders -- familial combined hyperlipidemia (FCHL) or familial hypertrigleridemia (FHTG). FCHL refers to high triglyceride levels in combination with elevated levels cholesterol in families; FHTG only is elevated triglyceride levels in families.
The two disorders examined in the study represent the most common forms of a condition called "familial hyperlipidemia." The total number of American families affected by these apparently genetic disorders is currently unknown, but they probably account for a large number of heart attack deaths nationwide, says Austin.
The risk of death from cardiovascular disease among siblings and offspring of families with FCHL was 70 percent higher compared to spouses. In families with FHTG, increased triglycerides predicted a 2-3 fold increased risk of cardiovascular death. The risk in FHTG was not changed significantly when researchers took into account the person's cholesterol levels.
Austin also called for more study aimed at pinpointing and understanding the underlying genetic mechanisms that cause high triglyceride levels to run in families. "Only then will we be able to say which treatments and preventive steps are most effective and what can be done to reduce the risk," Austin says.
Triglycerides can be obtained from food and are also secreted by the liver. Excess levels of triglyerides can increase concentrations of two types of fat particles, chylomicrons, and very-low-density lipoproteins. These fat particles may contribute to the fatty deposits that obstruct blood flow, increasing the risk for a heart attack.
Co-authors were Barbara McKnight, Ph.D.; Karen L. Edwards, Ph.D.; Cynthia M. Bradley, M.P.H.; Marguerite J. McNeely, M.D.; Bruce M. Psaty, M.D., Ph.D.; John D. Brunzell, M.D. and Arno G. Motulsky, M.D.
NR00-1145 (Circ/Austin) Media advisory: Dr. Austin can be reached at 206-543-0709 or by Email at maustin@u.washington.edu. (Please do not publish numbers.)
For more information about triglycerides, visit our Website at http://www.americanheart.org.
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