Silent strokes do real damage

(CNN) -- Every year, millions of people have a stroke -- and don't even know it.

The condition is called a silent stroke, because the patient exhibits no outward symptoms typically associated with stroke, such as vision changes, speech problems and paralysis or weakness in one side. A silent stroke is detected only when a patient undergoes a brain scan.

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But real damage is done inside the brain, and it can add up over time. Silent strokes can lead to cognitive impairments, failing memory, difficulty walking and, eventually, dementia.

Researchers admit they still have much to learn about silent strokes. But, doctors do know the same factors that put people at risk for a symptomatic stroke -- family history of the disease, diabetes, high blood pressure -- put people at risk of a silent stroke.

Watch For Your Health to find out what you can do to reduce your risk.