Scientists report they have identified an illness that may be the primary cause of heart attacks in people under 65, and that treating that disease could be a more effective way of preventing heart attacks than treatment for high blood pressure.

A study shows that 2 percent of the population has the newly found syndrome, which may be more responsible for early heart attacks than high blood pressure, Dr. Roger Williams, professor of internal medicine and director of the Cardiovascular Genetics Research Clinic at the University of Utah, said Thursday.Williams found 69 of his 131 subjects - brothers and sisters under age 60 with mild hypertension - had abnormal levels of various types of blood fats, called lipids, that have been linked to heart attacks in previous studies.

"To our surprise, that pointed out they probably have an inherited metabolic abnormality that leads to abnormal blood lipids and high blood pressure," Williams said in an interview. "We have called this newly discovered illness familial dyslipidemic hypertension or FDH.

"Lipid abnormalities are a much stronger predictor of early heart attack than blood pressure elevations, and may account for most heart attacks previously blamed on high blood pressure" alone, Williams concluded from his eight-month study, reported in the Journal of the American Medical Association.

As many as 1.5 million people in the United States will suffer a heart attack this year, and about 540,000 of them will die, making heart disease the leading killer in this country, according to the American Heart Association. About 675,000 of the attacks will be so-called early heart attacks among people under 65.

"It may be more important to treat lipid abnormalities in these patients than the hypertension as prevention of early heart attack," Williams said. "In fact, antihypertensive medication may worsen the condition and actually lead to heart attack in these cases."

Lipid abnormalities usually can be corrected with diet and medication, he said.

An estimated 30 percent of Americans suffer from hypertension. Of those, 75 percent have mild high blood pressure, defined as 160 over 110 or lower. High blood pressure increases the chances of heart attack.

Williams recommends that all hypertensive men under 55 and women under 65 undergo blood tests to determine total cholesterol, triglyceride, HDL and LDL levels.