When it comes to predicting heart trouble, doctors essentially play a guessing game. So among all the factors they consider–such as a person’s age, weight, family medical history and cholesterol levels–it turns out that one of the most reliable indicators may also be a bit unexpected: calcium.
According to the latest research, led by scientists from Baptist Health South Florida medical center in Miami, at least 35% of people who have calcium buildup in their blood vessels but no other heart-disease risk factors are almost four times as likely to have a heart event in seven years, compared with those who have zero calcium and some risk factors. Although the correlation was known before, as studies like Baptist’s gain traction, doctors are taking it more seriously.
There’s no evidence connecting these calcium deposits with the calcium you ingest from dairy products, so it’s still important to get the recommended amounts to maintain strong bones.
But for reasons experts can’t explain, after age 50, bits of calcium can find their way into blood vessels. Once there, they attract immune cells and form dangerous plaques that may stiffen arteries and generate clots that can block blood flow to the heart, even causing a heart attack. “Our data show that the status quo is unacceptable,” says Dr. Khurram Nasir, senior author of the Baptist Health study.
In the past, doctors were reluctant to test for calcium deposits using a coronary-calcium scan because it exposes patients to a small amount of radiation. They believed the risk wasn’t worth the benefit, since other heart-trouble indicators were reliable enough.
But studies like Nasir’s are chipping away at that theory. And now that new cholesterol guidelines have dropped the threshold for starting cholesterol-lowering drugs, or statins–meaning 31 million adults could face a lifelong prescription–more doctors are starting to add tests like calcium screening to determine who really needs medication. “If I see no calcium, I’m inclined to try to get that patient off medicines,” says Dr. Vincent Bufalino, a heart specialist in Chicago.
In the coming weeks, expect more studies to build momentum for the idea that people in their 50s or 60s should know not just their cholesterol numbers but their coronary-calcium score too.
This appears in the March 10, 2014 issue of TIME.