Certain patients who undergo intensive treatment to get their blood pressure down to a safer range are at a much lower risk of having a heart attack or stroke, researchers report.

An estimated 7.5 million Canadian have high blood pressure, or hypertension, a condition that slowly damages blood vessels and puts patients at risk of stroke, heart attacks, kidney disease and more.

Normal blood pressure is considered 120 over 80, or lower. A systolic pressure -- that first, top number -- between 120 and 139 is considered above normal, but not quite full hypertension. A reading above 140 meets the definition for high blood pressure.

Guidelines have long recommended getting systolic pressure to under 140 in otherwise healthy adults. But this new study finds that for many patients, lower is better.

The study, called SPRINT, or Systolic Blood Pressure Intervention Trial, looked at more than 9,300 adults over the age of 50 who did not have diabetes but already had at least a risk factor for heart disease and a systolic blood pressure above 130. 

Half the group were given medications to reduce their blood pressure to 120 or below, while the rest were urged to simply keep their blood pressure below 140.  

Those in the intensive treatment group took an average of 2.8 medications while the other group took an average of 1.8. All the participants were encouraged to eat a healthy diet, exercise, and quit smoking.

The results became clear quickly. Those who got their blood pressure down to 120 saw their risk for heart attack, stroke or heart failure reduced by 25 per cent compared to the other group, and their risk for early death decreased by 27 per cent.

After one year, 1.65 per cent of the lower pressure group had suffered a major heart problem or heart-related death, compared to 2.2 per cent of the others. Of the 365 participants who died during the study, 155 were in the intensive treatment group, compared to 210 in the control group.

The benefits were so clear that the U.S. National Institutes of Health ended the study early, in September, after just three years. The full results were presented at the American Heart Association meeting Monday and published online in the New England Journal of Medicine.

The study’s lead investigator, Dr. Jackson Wright, said many types of patients benefited from intensive treatment.

“Regardless of whether they were black or white, whether they were male or female, whether they had kidney  disease or not, whether they had cardiovascular disease, or whether they were over 70 or not, the benefits of the lower blood pressure targets seem to hold,” he told CTV News, speaking from Orlando, Fla.

But the researchers also noted that some patients experienced serious side effects from aggressive management of their blood pressure. Those included hypotension (dangerously low blood pressure), fainting, and falls. Some patients in the intensive treatment also had a higher risk of potentially fatal kidney failure. 

The study looked only at those over 50 who were otherwise healthy, so the findings may not apply to others being treated for high blood pressure. 

As well, many with high blood pressure already have trouble managing their condition, with many not adhering to the medications their doctors already prescribe. 

Still, the study’s findings are likely to prompt discussions among heart groups about whether current blood pressure guidelines go far enough.

Dr. Ernesto Schiffrin, president of Hypertension Canada, told CTV News Channel that his organization will have to look at the results "very carefully" over the next few weeks before making any recommendations.

"(The results) are associated with some side effects that are a trade-off in a way that should inspire us with caution," he said.

"It may be once we examine this in detail, indeed (it is) a game-changer in the sense that it will help reduce cardiovascular events further than we have already achieved."

With a report from CTV medical specialist Avis Favaro and producer Elizabeth St. Philip