Giving a blood pressure drug to people with measurements above normal but not yet considered too high might delay the development of hypertension, according to preliminary research released on Tuesday.

Patients in a study took either AstraZeneca Plc’s blood pressure drug Atacand for two years or a placebo pill. For the next two years, all patients received a placebo so that researchers could evaluate blood pressure changes.

The 772 people in the study, aged 30 to 65, had what researchers called “pre-hypertension,” meaning blood pressure readings were above normal but did not meet the definition of hypertension, or high blood pressure.

Hypertension increases the risk of having a heart attack or stroke.

The study found people who took Atacand had a 15.6 percent lower risk of developing hypertension than the ones who took a placebo for the entire four years. At the end of the study period, 240 patients in the placebo group and 208 in the Atacand group had high blood pressure.

There were no major differences in reports of side effects between the two groups.

The study’s authors said the findings were promising but needed to be confirmed in future research. They said about 59 million Americans have “pre-hypertension.”

“This study, which is the first of its kind, shows that postponement of hypertension onset through medical treatment is feasible, and without side effects,” said Dr. Stevo Julius, a University of Michigan researcher.

“However, the effect is moderate, and further studies in younger people and over longer periods of time are needed in order to demonstrate clinical usefulness,” he said.

AstraZeneca funded the study, which was released at a meeting of the American College of Cardiology and published by the New England Journal of Medicine.

Atacand also is known by the generic name candesartan.

A blood pressure reading of about 120/80 is considered optimal. High blood pressure was defined in the study as 140/90.

Hypertension was listed as a primary or contributing cause in about 277,000 American deaths in 2003, according to the American Heart Association.