Blood pressure-lowering medication may prevent serious conditions such as strokes, heart failure and heart attacks even in adults with normal blood pressure, new research suggests.

The benefits of treatment were similar regardless of the starting blood pressure level, in both people who had previously had a heart attack or stroke and in those who had never had heart disease, the study found.

Researchers say the findings have immediate and important implications for global clinical guidelines that typically limit blood pressure-lowering treatment to individuals with high blood pressure.

Lead author Professor Kazem Rahimi, University of Oxford, said: “Our findings are of great importance to the debate concerning blood pressure treatment.

“This new and best available evidence tells us that decisions to prescribe blood pressure medication should not be based simply on a prior diagnosis of cardiovascular disease or an individual’s blood pressure level.

“Instead, medication should be viewed as an effective tool for preventing cardiovascular disease in people at increased risk of developing heart disease or stroke.

“Clinical guidelines should be changed to reflect these findings.”

But he added: “We are not saying that everyone must begin treatment.

“The decision will depend on an individual’s risk factors for developing cardiovascular disease, the potential for side effects and patient choice.”

Researchers say heart disease and stroke, linked to high blood pressure, are the leading cause of death across most of the western world.

Blood pressure is measured in units of millimetres of mercury (mmHg).

So far, studies analysing whether blood pressure-lowering medication is equally beneficial in people with and without a history of cardiovascular disease, and at lower blood pressure levels than currently considered for treatment (typically 140/90 mmHg or higher) have reported conflicting findings.

This has led to contradictory treatment recommendations around the world, the researchers say.

For the research published in The Lancet, the Blood Pressure Lowering Treatment Triallists’ Collaborators pooled data from 344,716 adults (average age 65 years) in 48 randomised trials to explore the effects of blood pressure-lowering medications.

Participants were separated into two groups – those with a prior diagnosis of cardiovascular disease, and those without.

The groups were then divided into seven subgroups based on levels of systolic blood pressure (the top number which measures the force your heart exerts on the walls of your arteries each time it beats) at study entry – less than 120, 120-129, 130-139, 140-149, 150-159, 160-169, 170 and above mmHg.

Around 20% (31,239) of participants with prior cardiovascular disease and 8% (14,928) of those who had never had cardiovascular disease had normal or high-normal systolic blood pressure at the start of the trial.

Over an average of four years follow-up, 42,324 participants had at least one major cardiovascular event – a heart attack, stroke, heart failure, or death from cardiovascular disease.

For every 5 mmHg reduction in systolic blood pressure, the risk of developing major cardiovascular disease fell by around 10%, stroke by 13%, heart failure by 13%, ischaemic heart disease by 8%, and death from cardiovascular disease by 5%.

Researchers found the beneficial effects of the treatment did not differ based on a history of having had cardiovascular disease or the level of blood pressure at study entry.

Co-author Zeinab Bidel, from the University of Oxford, said: “It is important that people are considered for blood pressure-lowering treatment based on their cardiovascular risk, rather than focusing on blood pressure itself as a qualifying factor for or target of treatment.

“We must provide well-rounded guidelines to lower risks for cardiovascular disease that include exercise, nutrition, smoking cessation, and – where appropriate – medication.”

The researcher note some limitations including that the study only investigated the impact of starting blood pressure and prior cardiovascular disease on treatment effects, so the findings cannot be generalised to other patient characteristics that we have not included in our analysis.

Additionally, the effects on diseases other than major cardiovascular disease, including potential side effects of treatment,  were not specifically examined.