Many middle-age adults with apparently healthy hearts have a buildup of fatty deposits in their arteries, a study shows.

Researchers found that of more than 25,000 50- to 64-year-olds, about 42 percent had signs of atherosclerosis — a buildup of plaque in the arteries that can lead to a heart attack or stroke — despite the fact that none had any history of heart trouble.

They underwent two types of imaging tests: coronary calcium scan (heart scan) and CT angiography. Currently, calcium screening is the standard test. During calcium screening, a CT scan is used to detect calcium deposits in the heart arteries, because calcium is a component of plaques.

A calcium score of zero means there is no detectable calcium in the arteries. Those people are considered to be low-risk for a heart attack.

CT angiography involves injecting a contrast dye into blood vessels, allowing the CT scan to spot plaques. Based on that test, the researchers found 42 percent of study participants had some degree of atherosclerosis.

Even among people with calcium scores of zero, 5.5 percent actually had some degree of atherosclerosis based on angiography.

The findings suggest that CT angiography offers additional information beyond coronary artery calcium scoring.