The inflammation comes from many sources and triggers heart attacks by weakening the walls of blood vessels, making fatty buildups burst. A large study published Thursday concludes it is twice as likely as high cholesterol to trigger heart attacks.
Over the past five years, research by Dr. Paul Ridker of Boston's Brigham and Women's Hospital has built the case for the "inflammation hypothesis." With his latest study, many believe the evidence is overwhelming that inflammation is a central factor in cardiovascular disease, by far the world's biggest killer.
"I don't think it's a hypothesis anymore. It's proven," said Dr. Eric Topol, chief of cardiology at the Cleveland Clinic.
Inflammation can be measured with a test that checks for C-reactive protein, or CRP, a chemical necessary for fighting injury and infection. The test typically costs between $25 and $50.
Diet and exercise can lower CRP dramatically. Cholesterol-lowering drugs called statins also reduce CRP, as do aspirin and some other medicines.
Doctors believe the condition often begins when the fatty buildups that line the blood vessels become inflamed as white blood cells invade in a misguided defense attempt. Fat cells are also known to turn out these inflammatory proteins. Other possible triggers include high blood pressure, smoking and lingering infections, such as chronic gum disease.
Ridker's study says for the first time what level of CRP should be considered worrisome, so doctors can make sense of patients' readings. However, experts are still divided over which patients to test and how to treat them if their CRP readings are high.
Some, such as Dr. Richard Milani of the Ochsner Clinic in New Orleans, recommend a CRP check for almost anyone getting a cholesterol test. "If I have enough concern to check a patient's cholesterol, it seems naive not to include an inexpensive test that would give me even more information," he said.
Others are reluctant to test people at low outward risk. Dr. Sidney Smith, research director of the American Heart Association, said CRP testing is likely to be most helpful in guiding the care of the 40 percent of U.S. adults already considered at intermediate risk of heart attacks because of other conditions, such as age, obesity and high blood pressure.
"In certain patients the use of this test could be very helpful in motivating them to change their lifestyle," Smith, a professor of medicine at the University of North Carolina, told CBS Radio News — but he doesn't support making blood tests for inflammation part of standard physical exams.
"This test can help predict risk (of heart attack) but we still need to learn more about what to do with it," he said. "(It's) another piece in a puzzle which is very important to solve because heart disease and stroke are the leading cause of death and disability."
In March, the heart association and the Centers for Disease Control and Prevention held a meeting of 50 experts to review the evidence and make recommendations on CRP testing. Although it hoped to be finished this month, the committee went back to the drawing board after learning last week of Ridker's latest results, which are being published in the New England Journal of Medicine.
Though the study involved only women, Ridker said he is confident the findings apply to men as well, because earlier, small studies in men reached similar conclusions.
A skeptical editorial in the journal by Dr. Lori Mosca of Columbia University questioned the need for widespread testing, at least until more studies are done to show that lowering CRP actually saves lives.
Such studies are planned. Until then, Ridker said he believes a high CRP reading can help doctors persuade people with low cholesterol that they still need to diet and exercise.
"The CRP test can predict risk 15 to 25 years in the future," Ridker said. "We have a long time to get our patients to change their lifestyles, and the change does not have to be huge — modest exercise, modest weight loss and stop smoking."
However, Mosca said telling people they have low CRP may falsely reassure them they can continue slothful habits. "Why do we need a test to help us motivate patients to improve their lifestyles?" she said.
She also worried that doctors will immediately put patients on drugs to lower CRP before there is proof it saves lives.
Ridker's latest study is based on an eight-year follow-up of 27,939 volunteers in the Women's Health Study. About half of heart attacks and strokes occurred in those with seemingly safe levels of LDL, the bad cholesterol.
The lowest risk was in women whose CRP readings were below one-half milligram per liter of blood. It more than doubled when readings went over about three.
Dr. Wayne Alexander of Emory University in Atlanta said he already uses CRP testing to help make treatment decisions, such as whether to prescribe statins for people with borderline high cholesterol.
"It changes your threshold about whether to initiate therapy or actually to withhold therapy," he said.