(WebMD) It's possible to have a stroke and not realize it immediately. So it's wise to know the signs. But what if a stroke occurred and you didn't even notice?

A new study found that nearly 11% of people who thought they were healthy actually had some brain damage from a "silent" stroke. Silent strokes are true strokes but don't result in any noticeable symptoms. People who have had a silent stroke are at higher risk for subsequent strokes and for an accelerated loss of mental skills.

Researchers, led by Rohit Das, MD, from Boston University's School of Medicine, reviewed MRI (magnetic resonance imaging) scans from 2,040 people participating in the Framingham Study, an ongoing study examining the relationship between risk factors and subsequent cardiovascular events. The MRI scans were reviewed for evidence of stroke. The average age of the participants was 62; most were of European ancestry. None of the participants had a history of stroke or stroke-type symptoms.

The study also examined whether people who had silent strokes had more concentrated levels of cholesterol in their blood and more extensive thickening in the carotid arteries, the main arteries that supply the head and neck with blood.

Here are the main results from routine MRI scans:

• Nearly 11% of participants who showed no overt sign of stroke had suffered some brain damage from a silent stroke.


• People who had an irregular heartbeat, also known as atrial fibrillation, were morelikely to have had a silent stroke.


• Having high blood pressure (hypertension) was associated with a greater chance of having a silent stroke.


• Elevated levels of the amino acid homocysteine in the blood "significantly" increased participants' chances of having a silent
  stroke.

Researchers say people need to be aware of the risk factors for a silent stroke, which are the same as for a full-blown stroke.

Stroke Risk Factors

• Older age


• Having diabetes


• Having high blood pressure


• Being a smoker


• Having heart disease

In a news release, study co-author Sudha Seshadri says "the findings reinforce the need for early detection and treatment of cardiovascular risk factors in midlife."

"This is especially true since (silent strokes) have been associated with an increased risk of incident stroke and cognitive impairment," Seshadri says.

Stroke Facts

A stroke is brain damage that is caused by a blocked blood vessel or bleeding in the brain.

Here are the most common stroke symptoms, according to the CDC:

• Sudden weakness or numbness of the arms, legs, or face, especially on one side.


• Quick onset of blurred vision in one or both eyes.


• Difficulty walking, dizziness, or loss of balance or coordination.


• Sudden confusion or trouble speaking.


• Sudden severe headache with no known cause.

The study appears in Stroke: Journal of the American Heart Association.

By Kelley Colihan
Reviewed by Elizabeth Klodas
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