Blood pressure treatment guidelines in Canada could change, say experts, after a major U.S. trial was stopped early when aggressive controls cut the risk of death and heart disease in people aged 50 and older.

The trial, called Systolic Blood Pressure Intervention Trial or SPRINT, was designed to investigate whether lower blood pressure reduces health risks. 

Health Overhaul Native Americans

It's premature to lower for patients to demand that their blood pressure be normalized, U.S. researchers say. (Eric Risberg/Associated Press)

When a person's blood pressure is elevated for an extended period of time, it increases the risk of heart attacks, stroke, kidney failure, and other health consequences. It is a leading cause of death and disability in the U.S., Canada and worldwide.

The U.S. National Institutes of Health's clinical trial included more than 9,300 participants aged 50 and older.

"More intensive management of high blood pressure in people 50 years and older can save lives and reduce cardiovascular complications such as heart attacks," said Dr. Gary Gibbons, director of the NIH's National Heart, Lung and Blood Institute, which sponsored the trial. 

Half of participants received an average of two blood pressure-reducing medications with the goal of lowering their systolic or top blood pressure when the heart contracts to below 140. The others received an average of three medications in the hopes of reaching below 120.

Those in the lower target group of 120 cut their risk of heart attacks, strokes and heart failure by almost a third and the risk of death by nearly a quarter, researchers said Friday.

Dr. Jacob Udell, a cardiologist at Peter Munk Cardiac Centre in Toronto, called the findings a gamechanger.

"This will have a huge impact on my clinical practice and I believe the practice of Canadian physicians," Udell said.

But first physicians will need to take a step back, wade through all of the data when it is published to assess which patients are candidates and what the potential risks are, Udell said.

Trial stopped early 

Doctors also need to look at an individual patient's risk factors, diet and exercise patterns, sleep habits and stress levels.

It's only when all the best lifestyle efforts have been made that doctors consider using medications to lower blood pressure.

Most blood pressure medicines are available as inexpensive generics. Common classes of the drugs include angiotensin receptor blockers, or ARBs, calcium channel blockers, ACE inhibitors and diruetics.

Important clinical trials such as SPRINT aren't stopped prematurely unless investigators have an important reason, namely to give participants who weren't in the aggressive blood pressure-lowering group the information, said Dr. Sheldon Tobe,  a hypertension specialist and spokesman for the Heart and Stroke Foundation of Canada.

Tobe said emails are flying among hypertension and heart and stroke experts in Canada as they organize a teleconference to decide what to do with the new U.S. information, critically assess in and make plans to disseminate the information.

Asked to speculate on whether Canadian treatment targets for managing hypertension might change, Tobe said yes, if the findings in the press release hold.

He said the benefits in the trial were similar to the what's seen when blood pressure is lowered in high-risk individuals such as the elderly with drug therapy compared to no medications.

About 7 million Canadians have high blood pressure. The current recommendation is less than 140 over 90 mm Hg, or 130 over 80 mm Hg for those with diabetes, said Tobe, who is also a professor of medicine at the University of Toronto and a research char at the Northern Ontario School of Medicine.

Investigators are still analyzing findings on adverse side-effects in the aggressive management group of reaching a systolic below 120. The trial was originally scheduled to run until December 2018.

Tobe suggested everyone should know their blood pressure and to get checked if they have concerns. 

Blood pressure is a vital sign. The potential risks of lowering blood pressure below 120 include fainting, dizziness and kidney damage, Udell said. 

Researchers plan to continue to track the SPRINT participants to see if kidney disease, cognitive function and dementia also were affected by more aggressive care.

With files from CBC News, Reuters and Associated Press