WASHINGTON (Reuters) - About 30 percent of Americans have high blood pressure — unchanged from 10 years ago — but many more know about it and are being treated for it, US government researchers reported.

About 30 percent of Americans have high blood pressure, defined as systolic blood pressure or the "top" number of 140 or more and diastolic blood pressure or the "bottom" number of a reading of 90 or more, according to statistics compiled by Sung Sug (Sarah) Yoon, Yechiam Ostchega and Tatiana Louis of the National Center for Health Statistics.

That number has not changed since 1999 and percentages have stayed stable among men and women, all age groups, and for non-Hispanic white, non-Hispanic black, and Mexican-American adults.

Other findings from the survey:

¦ In 1999-2000, 69.6 percent of U.S. adults with high blood pressure knew it but by 2008 more than 80 percent knew.

¦ In 2008 nearly 74 percent of high blood pressure patients took drugs to treat it, up from 60 percent in 1999-2000.

¦ More than 48 percent of adults with high blood pressure have it under control, compared to 30 percent in 1999-2000.

The statistics are taken from the National Health and Nutrition Examination Survey, an extensive questionnaire and physical examination of more than 9,000 people.