A U.S. Centers for Disease Control and Prevention study found that only 44 percent of Americans know all five symptoms of stroke and only 38 percent know to call 911 if they think someone is having a stroke.

The analysis of 2005 data from 13 states and the District of Columbia showed that there was no improvement in the public's awareness of stroke symptoms since a similar study in 2001.

It also found significant disparities in awareness of stroke symptoms by race/ethnicity, sex, education level, and state. Blacks, Hispanics and people with lower levels of education were less aware of all five stroke symptoms and the need to call 911 than whites, women, and people with higher levels of education.

The findings appear in this week's issue of the Morbidity and Mortality Weekly Report, published by the CDC.

The five signs and symptoms of stroke include: sudden numbness or weakness in the face, arm, or legs; sudden confusion or trouble speaking or understanding others; sudden trouble seeing in one or both eyes; sudden trouble walking, dizziness, or loss of balance and coordination; and sudden severe headache with no known cause.

Early recognition of these signs and symptoms and knowing to immediately call 911 can make the difference between life and death. May is National Stroke Awareness Month.