A large number of Americans who have normal cholesterol levels but are at high-risk for a heart attack may be able to spot the danger with a simple blood test and protect their hearts by taking drugs already used widely for heart disease, researchers say.
The conclusion, which scientists called intriguing but tentative, could help doctors address one of the most puzzling aspects of heart disease: About half the people who have heart attacks have normal cholesterol levels.
Researchers looking for other risk factors have focused in recent years on a substance called C-reactive protein, a sign of inflammation in the body. Evidence suggests that heart disease is at least partly a disease of inflammation and that activity of the immune system around the buildup of cholesterol-related plaque can cause the plaque to rupture, leading to a heart attack or stroke.
So scientists examined data that had been collected between 1990 and 1998 in a study of 6,605 men and women at two Texas sites. That study had found that a class of drugs called statins reduced the risk of a first heart attack or stroke. Researchers reanalyzed the data to find out whether statin drugs had an effect specifically on people with below-average cholesterol but higher-than-normal C-reactive protein levels.
In such people, statin drugs seemed to lower C-reactive protein levels by almost 15% in a year and reduced the risk of suffering or dying from a heart attack or stroke, the researchers said in last week's New England Journal of Medicine.
"Everyone interpreted the previous data to say statins are effective against high cholesterol," said Paul Ridker of Brigham and Women's Hospital in Boston, the lead author of the paper. "We show that is partially true. What we also show is that for people with low [cholesterol] but a high C-reactive protein level, the risk of having a heart attack ... is just as high as the people who have high cholesterol levels."
An estimated 25 million Americans have high C-reactive protein levels but are not told to take statins, Ridker said. Based on the findings, at least some may benefit, he said. Though the new study offers the strongest evidence yet that C-reactive protein level may be an independent risk factor for a heart attack, experts said it is too early to recommend widespread testing, even though a simple, inexpensive test is available.
"If you treat those 25 million people, you are going to be treating a large number of people who will never develop a heart attack," said Valentin Fuster of Mount Sinai School of Medicine in New York and past president of the American Heart Assn. "We would end up treating many individuals who do not need to be treated, and these drugs are not free of side effects."
Fuster and others said the new results improve their understanding of heart disease.
Recent guidelines recommend that people should have overall cholesterol levels of less than 200 milligrams per deciliter of blood, and LDL-cholesterol or "bad" cholesterol levels less than 100. People with LDL levels over 160 are now candidates for statins.