The study, led by Professor Kazem Rahimi and his team at the University of Oxford, found a 10 per cent reduction in the risk of heart disease and strokes in the next four years for every 5mmHg decrease in systolic blood pressure (the top, higher number in a blood pressure reading).
A standard dose of blood pressure medication can reduce systolic blood pressure by around 10mmHg, suggesting that the benefits of treatment could be even greater than seen in the study.
Crucially, the researchers found the same relative reduction in people at all levels of cardiovascular risk, from those with an average five-year risk of just three per cent up to nearly 42 per cent. However, the largest reduction in absolute risk was seen in people with the highest five-year risk.
The team behind the analysis – the largest of its kind – suggest that NICE guidelines should be updated in light of their findings and that that selecting people for treatment should be based on their calculated cardiovascular risk, rather than whether their blood pressure is above a certain threshold.
A risk-first approach, they say, would allow for more targeted and effective therapy and could bring some people with high overall risk but only mildly raised blood pressure into consideration for treatment for the first time, while sparing others whose blood pressure is raised but whose overall risk is low.
"Fills important gap"
Professor Kazem Rahimi, Professor of Cardiovascular Medicine and Population Health at the University of Oxford and consultant cardiologist, said: "The benefits of reducing blood pressure to prevent heart attacks and strokes in people at high-risk are well established, but uncertainty has remained about whether this extends to those at lower risk. Our study provides the answers to fill this important gap in our knowledge and suggests that risk-based selection offers a much sharper patient selection than a strategy that is dominated by blood pressure values."Currently, recommendations in UK clinical guidelines start with blood pressure values for patient selection and adopt risk assessment in a second stage. This, combined with earlier evidence from our group that these benefits are consistent even at blood pressure levels well below that threshold, could mean we are missing some patients in the UK whose blood pressure is only mildly elevated but who are at high risk of heart disease and stroke.”
Blood pressure-lowering drugs are among the most widely prescribed medications in the UK, with at least seven to eight million people prescribed them.
But a lack of strong evidence supporting blood pressure-lowering treatment in people at lower-risk of heart attacks and strokes has led to differing recommendations between clinical guidelines around the world.
The team behind the study say that there is a focus on blood pressure levels in the UK, rather than overall cardiovascular risk, and that people may not get their overall cardiovascular risk assessed if their blood pressure is below the threshold for hypertension (140/90mmHg).
Researchers analysed data from 357,440 people, involved in 51 previous studies, to explore the effects of blood pressure-lowering treatment in people with different levels of cardiovascular risk.
Participants were split into 10 groups of around 35,744 according to their predicted risk of developing cardiovascular disease in the next five years. This was calculated using risk factors including age, sex, cholesterol levels, body mass index (BMI), and whether they smoked.
Groups ranged from those with a less than four per cent risk (average three per cent) to more than 27 per cent (average 41.6 per cent).Study volunteers were followed up for an average of 4.2 years for any episode of major cardiovascular disease – a stroke, coronary heart disease, heart attack, and heart failure causing death or hospital admission.
Effective treatment
The relative risk of experiencing a major cardiovascular event fell by 10 per cent for every 5mmHg decrease in systolic blood pressure, researchers found. This was seen consistently across all groups regardless of their predicted risk, suggesting that treatment was effective even in the lowest risk groups.
This translated into progressively larger absolute risk reductions across groups as risk increased. There was a 2.6 per cent decrease in the highest risk group with just 38 people needing treatment over five years to prevent one episode of major cardiovascular disease. In the lowest risk group, there was a 0.4 per cent decreased risk with 255 people requiring, over five years, treatment to prevent one event.
Researchers found that those taking blood pressure-lowering drugs experienced more side effects. As with effects on major cardiovascular disease, increases in side effects were seen to a similar degree across the risk groups. This, Professor Rahimi said, “could narrow the balance of benefits and harms, as predicted risk falls, and this must be taken into account when prescribing medicines.
"Any decision to start treatment should be shared between doctors and patients and guided by an individual's overall cardiovascular risk, balancing the potential for preventing serious events against the possibility of side effects."
There was a 66 per cent increase in the risk of heart palpitations, low blood pressure or a slow heart rate and a 49 per cent increase in the risk of kidney problems such as acute kidney injury. The risk of dizziness and fainting was nine per cent higher with medication, but the risk of falls and bone fractures didn't increase.
Our chief scientific and medical officer, Professor Bryan Williams, said:
"It’s far easier to stop heart disease in the first place than to try to treat it once it has developed. With people in the UK spending more of their lives in ill-health, it's clear that we need to shift our focus and get better at preventing disease to make sure that fewer people ever have a heart attack or stroke.
“This important study suggests that we should be less conversative in our approach to managing cardiovascular risk. Blood pressure is a major factor contributing to lifetime risk of premature heart disease, stroke and death. The study suggests the levels at which we start treating blood pressure are too high and that many more patients could benefit from treatment of their blood pressure to better prevent premature disease and death, even at blood pressure levels lower than those currently recommended for treatment.”