The study, called Sprint, enrolled patients ages 50 and older with high blood pressure. The patients also had at least one other risk factor for heart disease like smoking or a high cholesterol level, or they had kidney disease, or they were simply over the age of 75. Half were assigned to a systolic pressure target below 140, in keeping with today’s medical practice. The rest were assigned a target pressure of less than 120. The study was supposed to continue until 2017, but ended abruptly last summer when researchers announced they already had “potentially lifesaving” results.

Doctors have long wrestled with how low blood pressure should go. Bringing it too far down, particularly in elderly people, can result in complications like dizziness and fainting. According to the results released Monday, about 5 percent of the study’s patients, or 220 people, with the 120 blood pressure target had serious complications over the course of the study — blood pressure so low it caused severe dizziness or fainting, or a reversible injury to the kidneys. Among those with the 140 target, 118 had serious complications.

A complication the investigators worried about with blood pressures of 120 or lower — an abrupt drop in blood pressure when people stood up — actually occurred more often in those with the higher systolic pressure target.

“When we put those complications in the context of a 27 percent reduction in total mortality, it seems that the benefits outweigh the risks,” said David M. Reboussin, a biostatistician at Wake Forest Baptist Medical Center and a principal investigator for the study.

What is most remarkable, researchers said, is that the improvements in death rates and rates of heart attacks occurred on top of improvements these patients already experienced as their blood pressures fell to 140.

To get their systolic pressures to 120, patients took an average of one additional blood pressure drug — 2.8 pills instead of 1.8. Almost all blood pressure pills are inexpensive and available as generics.