Study Reexamines Effects of Cholesterol

Healthy nonsmokers with low blood pressure have little to gain by reducing the level of cholesterol in their diets, according to a study recently-published by Harvard Medical School researchers.

While people in high-risk categories--those who smoke or who have elevated blood pressure or high cholesterol level--can add as much as a year to their lives by lowering the cholesterol level in their diets, people in low-risk categories will gain only days or weeks from a diet change, according to the study.

These findings were reported in this month's issue of the Annals of Internal Medicine, a medical journal. Med School researchers who are members of the Institute for Health Research, a joint program of the Harvard Community Health Plan and the University, wrote the report.

"We're trying to move the discussion about cholesterol beyond the question, does low cholesterol improve health? We think it does," said Dr. William C. Taylor, an instructor at the Med School and one of the researchers. "Now we're starting to ask how much it improves health."

Although they found that low cholesterol does not greatly change the life expectancy for low-risk people, the Harvard researchers said that lower cholesterol levels are healthful. "We hope this information isn't misused, that people don't say, 'Oh, cholesterol doesn't matter' and eat recklessly," Taylor said.

In their research, doctors focused on calculating the increase in life expectancy for individuals in different categories, including males and females of different ages, smokers and non-smokers, and people with high and low blood pressure.

Lowering blood pressure and quitting smoking, however, can have greater impact on a person's life expectancy than decreasing cholesterol levels,said Taylor.

"People have focused on the important idea thatblood pressure, smoking, and cholesterol level arethe three major risk factors that predict thelikelihood of developing heart disease," saidTaylor. "If you quit smoking or lower bloodpressure, you change from a high-risk to alow-risk category. But lowering cholesterol doesnot produce as much change."

The Med School researchers did not conducttheir own study--instead they analyzed twoprevious studies to formulate their results. "Wetook other people's findings and tried to use themto make a calculation of how life expectancy mightchange for different individuals," said Taylor.

From death rate statistics which are gatheredin Vital Statistics of the United States, anannual compilation of demographic data,researchers calculated how a change in risk levelwould improve life expectancy.

Taylor said that the doctors needed a figurefor the average difference in blood cholesterollevel when a high-risk person goes on acarefully-monitored diet.

Using the results of the Multiple Risk FactorIntervention Trial, previous research on heartdisease conducted by the National Heart, Blood andLung Institute, the Harvard doctors found that theaverage decrease over a seven-year period was 6.7%.

Another piece of research which contributed tothe recent Harvard findings was the 39-year-oldFramingham Study, which provided the researcherswith an equation describing how much more likelyit is that someione with risk factors will developheart disease