Know Your Numbers! Week: Rising to the Challenge of Hypertension

Professor of Clinical Pharmacology & Therapeutics, Peter Sever, discusses the importance of blood pressure self-management and the latest research.

It’s well-known that high blood pressure, or hypertension, increases the risk of heart attacks and strokes, two leading causes of death and disability worldwide. Despite the importance of managing blood pressure, many people in the UK remain unaware of their numbers or do not receive necessary treatment. 

"When patients take over control of the management of their blood pressure, the result is that blood pressure is much better managed"

To tackle this, ‘Know your Numbers! Week’ runs between 2 and 8 September, aiming to encourage individuals to get their blood pressure checked. 

We sat down with Professor Peter Sever, Professor of Clinical Pharmacology & Therapeutics at Imperial's National Heart and Lung Institute (NHLI), to shed light on the risks associated with high blood pressure and what the latest research reveals. 

What causes blood pressure to rise, and what are the associated risks?

The heart pumps blood through a system that consists of various tubes or blood vessels. When the pressure in the system increases, it’s usually due to disease of the blood vessels, and that is associated with an increased long-term risk, mainly of heart attacks and strokes. That’s why we’re particularly concerned about high blood pressure – heart attacks and strokes collectively constitute one of the greatest causes of death and disability worldwide. 

Conventionally, high systolic blood pressure, the upper reading of 140mm Hg or above, increases your risk and should be treated. A diastolic blood pressure, the lower reading, above 90mm Hg is also abnormal. In recent years, evidence has mounted that we should consider intervention at somewhat lower levels of pressure, around 130 mm Hg for systolic pressure in some higher risk patients. 

What factors influence an individual’s blood pressure levels, and what steps can people take to manage these factors?

Blood pressure levels result from a complex interaction between genetic and environmental factors. We know blood pressure runs in families, and genetic studies have shown that around 50% of your blood pressure is likely to be inherited. However, unlike traditional inherited diseases, there are probably over 100 genes contributing to it, each with a small effect, making it difficult to pinpoint specific genetic causes except in a very small number of cases. 

Environmental factors play a significant role in how those genes express themselves. Despite having "bad" genes, if you eliminate environmental influences, your blood pressure might not rise. Key environmental factors include diet, especially salt intake, which is much higher than necessary in Western diets. Being overweight, consuming too much alcohol, lack of exercise, and environmental stress all contribute to higher blood pressure. 

If you're faced with a patient whose systolic blood pressure is 160, apart from considering drug treatment, you must also develop a lifestyle plan. This includes diet, regular exercise, reducing alcohol and salt intake, and addressing environmental stress – though from a practical point of view, that’s often quite difficult! 

How often should individuals be checking their blood pressure?

It depends on their blood pressure level. If you’re 50 years old and your blood pressure is 120/80, you probably don’t need to check it again for a year. But if your blood pressure is 150, regardless of age, you need to confirm whether that’s a real value by checking it again in a few weeks. If it remains elevated, treatment is necessary. Once on treatment, you should check your blood pressure at least every month or two at home. Depending on how well it’s controlled, you might extend the interval between checks to two to three months or even longer.  

While traditional blood pressure measurements are crucial for assessing cardiovascular health, blood pressure variability is also emerging as an important factor. Can you explain what blood pressure variability is and why it matters?

Traditionally, blood pressure concerns have been based on measurements taken in the clinic or, more recently, at home using one-off measurements of systolic and diastolic pressures. Decisions are made by your physician as to whether you have high, normal or low blood pressure based on that reading. 

However, we've been studying blood pressure variability, which comes in two types. The first is short-term variability, where blood pressure fluctuates throughout 24 hours. The higher this variability, the greater the long-term risk of heart attacks and strokes. The second type is long-term variability, measured over weeks, months, or even years. Again, the higher the variability, the greater the risk of heart attacks and strokes. Long-term variability is prognostically more important, but it has not yet been fully incorporated into guidelines for assessment or treatment.  

In our recent ASCOT Trial paper, published in the European Heart Journal, we found that patients with high blood pressure who are on treatment and whose blood pressure seems well-controlled but have high blood pressure variability remain at very high risk. This hasn’t been demonstrated before, and our data, based on 20 years of follow-up and 3,000 cardiovascular events, is quite powerful. These patients are currently being ignored, and that needs to change. We hope to highlight this in the next set of guidelines. 

We also have evidence suggesting that certain drugs are much better at reducing blood pressure variability than others. We’re now in the process of producing recommendations based on this evidence. 

How can individuals track and manage their blood pressure variability?

That's a great question, and it’s something we’re currently investigating. Most published data on blood pressure variability are based on measurements taken in the clinic over weeks or months. From a practical point of view, if a patient asks about their blood pressure variability, or a doctor says it needs to be measured, they can’t wait weeks or months for an answer. 

We’re exploring alternative ways to assess blood pressure variability. One ongoing study at the NHLI is looking at home blood pressure recording where we have been asking patients to measure their blood pressure morning and evening every day for a week and we can calculate the variability of blood pressure from these readings. When comparing these home readings with variability derived from a series of traditional clinic measurements, so far there’s been a remarkable correlation. This suggests that home monitoring might be a viable way to assess blood pressure variability. 

Why do you think there needs to be a campaign about blood pressure awareness? 

We’ve known for a long time that high blood pressure is a common cause of premature death and disability. In most cases, high blood pressure is easy to treat. We must make sure that everybody has their blood pressure taken. If it’s high, they should be rechecked and reviewed by their GP. People with known high blood pressure must receive treatment, and if their blood pressure isn’t well controlled, their treatment needs to be adjusted. 

When patients take over control of the management of their blood pressure, the result is that blood pressure is much better managed. There is a major need for an educational programme that takes blood pressure management away from the doctor and into the hands of the patient.