BOSTON – A landmark study offers the strongest evidence yet that simmering, painless inflammation deep within the body is the single most powerful trigger of heart attacks, worse even than high cholesterol.

The latest research is likely to encourage many doctors to make blood tests for inflammation part of standard physical exams for middle-aged people, especially those with other conditions that increase their risk of heart trouble.

The study, based on nearly 28,000 women, is by far the largest to look at inflammation’s role, and it shows that those with high levels are twice as likely as those with high cholesterol to die from heart attacks and strokes.

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 inflammation has many possible sources. Often, 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 low-level infections, such as chronic gum disease.

Doctors theorize that a chronic infection anywhere in the body can produce these inflammatory proteins, which then make their way into the bloodstream and do their damage in the blood vessels.

The proteins are thought to weaken the fatty buildups, or plaques, making them more likely to burst. A piece of plaque can then lead to a clot that can choke off the blood flow and cause a heart attack.

For the first time, Ridker’s study establishes 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.

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 today’s 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.