Here’s a lifesaving question to ask yourself: Are you suffering from heart disease? You may think you’re fine because you’re young or in great shape. But a new study found that a record number of seemingly-healthy people, as young as 18, have early signs of cardiovascular disease, putting them at risk for deadly strokes and heart attacks.

Researchers at Quebec Heart Institute scanned the blood vessels of thin, young people who appeared healthy, meaning none of them had diabetes, high blood pressure, or high cholesterol.

The result? Scans showed that almost half of the volunteers, no matter their ages, had thickening blood vessel walls, which is an early sign of cardiovascular disease, the number one killer of North Americans.

So, why are so many healthy-looking people suffering from deadly heart disease? Lead researcher Dr. Eric Larose says scans showed that a lot of volunteers had hidden fat stuffed around their organs, causing plaque to build up in their arteries, and eventually cutting off blood flow to their heart. And that’s especially dangerous because a lot of doctors don’t even think to test young, thin people for heart disease.

The good news is that heart disease is completely manageable if you catch it early, and stick to a heart-healthy diet, and commit to exercise.

So, no matter how old you are, or how many sit-ups you can do, see your doctor ASAP to get tested for cardiovascular disease.