The 1950s submarine movie "Run Silent, Run Deep" is the story of a World War II submarine captain, played by Clarke Gable, who stalks the Japanese destroyer that blew up his former sub. It's all about running undetected until you're ready to strike.

That's the same thing that happens with silent heart attacks — and the results are potentially as deadly.

Two recent studies reveal that silent heart attacks are two to three times more common than previously thought, and one of those studies found that they may occur almost twice as often as more conventional heart attacks.

To protect yourself from this health risk, here's what you need to know:

1. Silent heart attacks aren't completely silent, but they don't trigger the usual symptoms such as pressure, tightness, or pain in your chest or arms, shortness of breath, and cold sweat. So you may ignore what feels like bad heartburn, achy arms, and fatigue.

2. They triple your risk of dying from heart-related problems.

3. Anyone with a family history of heart problems, who's overweight, has high LDL cholesterol, high blood pressure, or diabetes is at risk.

4. An electrocardiogram or MRI can show if you have had a silent heart attack.

5. If you've had one, or to prevent one, start walking 30 minutes a day and eat 5 to 9 servings of produce a day, as well as 100 percent whole grains and good fats (including DHA omega-3s), and ask your doctor about taking two 81 mg aspirins daily (always with a glass of warm water before and after).