BEIJING, -- Even a slightly high blood pressure is considered dangerous to largely increase the stroke risk, a new study found.

The finding was published Wednesday on the online edition of U.S. medical journal Neurology.

In the study, researchers found people who have pre-hypertension, whose blood pressure measured between normal and high, are 55 percent more likely to suffer a stroke compared with normal people.

The study involved data from 12 previous studies on blood pressure and stroke occurrence of some 500,000 adults.

About one in three U.S. adults suffer from pre-hypertension, which is defined at a systolic blood pressure between 120 and 139 or a diastolic blood pressure between 80 and 89, according to the U.S. Joint National Committee on Prevention, Detection, Evaluation and Treatment of High Blood Pressure.

"People who do fall into the higher range of pre-hypertension should modify their lifestyle as much as possible," suggested Dr. Bruce Ovbiagele, director of the Olive View-UCLA Stroke Program and leading author of the study.

Stroke is the number three cause of death, killing more than 130,000 in the U.S. a year, according to a CBS report.