MONDAY, Oct. 9 (HealthDay News) -- Many Americans suffer a stroke and don't know it or don't do anything about it, a new study finds.

Researchers say that as many 18 percent of adults with no history of stroke had experienced at least one stroke symptom in the past.

A team at the University of Alabama, Birmingham, interviewed and conducted brief physical examinations of over 18,000 people (average age 66) who had never been diagnosed with stroke. The participants were asked if they had ever suffered certain stroke symptoms and nearly 3,300 (17.8 percent) said they had.

The study found that sudden numbness on one side of the body was reported by 8.5 percent of the participants; sudden weakness on one side of the body was noted by 5.8 percent; sudden vision loss in one or both eyes, 4.6 percent; sudden loss of the ability to express themselves in speech or writing, 3.8 percent; sudden loss of the ability to understand what others were saying, 2.7 percent.

These stroke symptoms were more likely to occur in black Americans and in people with lower incomes, less education, poorer health status and higher stroke-risk scores.

"The last finding suggests that at least some of these symptoms may represent stroke events that reach the threshold required for clinical diagnosis," the study authors wrote. "These undiagnosed or unrecognized events could have a substantial impact on cognitive functioning or personality and could also be powerful harbingers of subsequent major strokes."

The study is published in the Oct. 9 issue of the journal Archives of Internal Medicine.

According to the researchers, prior studies have revealed that many people do not seek medical care for stroke symptoms and, if they do, they don't seek it immediately after experiencing the symptoms.

"Targeted education on the warning signs of stroke and risk factor reduction efforts for individuals who report stroke symptoms may be helpful in improving early recognition and in the prevention of stroke," they concluded.