High blood pressure: the ‘largest epidemic known to mankind’

High blood pressure, also known as hypertension, has been dubbed the "largest epidemic ever known to mankind" by the medical and scientific journal, The Lancet, and with good reason. It is estimated that nearly a billion people have high blood pressure worldwide. Globally, cardiovascular disease accounts for about 17 million deaths a year, with high blood pressure being the major cause, largely by causing heart disease and stroke.

It is estimated that the cost of stroke in Ireland is in excess of €1 billion per year, with some 10,000 people being affected.

A major cause of stroke is high blood pressure, which makes the latest data from Trinity College Dublin’s longitudinal study on ageing (Tilda) worrying – in people aged over 50 years, almost 65 per cent have high blood pressure but nearly half of these are unaware they have the condition and fewer than 60 per cent are on blood pressure lowering drugs.

Most worrying is the fact that of those on drug treatment, barely half had their blood pressure controlled.

High blood pressure often occurs on its own, especially when there is a family history. However, it may be just one of a number of other risk factors, such as diabetes or high blood cholesterol, that may collectively attack the cardiovascular system. High blood pressure may also be a component of the “metabolic syndrome”, a condition in which a person is obese and has type 2 diabetes.

In elderly people with high blood pressure, atrial fibrillation – when the heart beats irregularly – is very common and, when present, adds greatly to the risk of stroke. Another common association with high blood pressure, especially when nighttime blood pressure is elevated, is sleep apnoea. This condition is characterised by snoring, periods of cessation of breathing during sleep and daytime sleepiness.

High blood pressure, if undiagnosed or badly controlled, will lead in time to reduction in the blood supply to a number of important organs, often called “target organs”. This can result in heart attack, atrial fibrillation and eventually heart failure. In the brain, stroke, brief strokes, cognitive impairment and dementia are all attributable to high blood pressure.

In the kidneys, kidney failure may lead to dialysis. The arteries of the legs and the abdominal aorta may also be affected, with serious consequences. All these conditions can be prevented, or their effects much reduced, by achieving 24-hour control of blood pressure.

What can we do to control the epidemic?

Recently published studies in the world’s leading scientific journals give some clear pointers as to what we can do to halt the epidemic of high blood pressure. The following is a summary of some of the pointers:

Use 24-hour ambulatory blood pressure measurement (ABPM)

Before we can say that a person has hypertension, blood pressure has to be measured. The assumption among the public, and unfortunately also among many doctors, is that blood pressure can be measured as easily as estimating the level of cholesterol in the blood. However, the reality is that the measurement of blood pressure in a doctor’s surgery, with which we are all familiar, is not only inaccurate, but, more often than not, it is also misleading.

This measurement over-diagnoses high blood pressure in at least 20 per cent of people who, in fact, have normal blood pressure away from the medical environment. This is known as “white coat hypertension”. The technique also fails to detect hypertension in at least 10 per cent of the population, known as “masked hypertension”.

Ambulatory blood pressure measurement, or ABPM, which provides a profile of blood pressure behaviour both during the day and the night, away from the stress of the medical environment, overcomes these difficulties.

The government authorities in the US and Europe having carefully examined the evidence as to which method of blood pressure measurement is best – office, home or ambulatory blood pressure monitoring – have concluded that ABPM is the method of choice for clinical practice. In this regard, the HSE has at last recognised the need to reimburse ABPM in general practice. Take medication Of course all doctors will, and should, tell patients with high blood pressure to lead sensible, healthy lives. Unfortunately, however, lifestyle measures, although often lessening the amount of medication required, are rarely enough to avoid the need for drugs.

People with high blood pressure often do not realise that the medication prescribed to lower blood pressure cannot be discontinued. Of course, we would all prefer not to have to take tablets, but put into the context of having a stroke or heart attack, medication is the obvious choice.

If concomitant disease is present, such as diabetes, atrial fibrillation or sleep apnoea, these will have to be treated also. In most patients over the age of 50, treatment with a statin will be prescribed, regardless of the level of cholesterol because it has been clearly demonstrated that statins can reduce the occurrence of stroke by more than 40 per cent.

There are now several drugs available to treat blood pressure, and usually more than one drug is required. One of the major pharmacological advances has been the combination of two or three drugs in differing doses in one tablet, so called “single pill combinations” or SPCs.

This means that instead of having to take two or three separate tablets, one, two or three ingredients are combined and the dosage can be altered to achieve effective blood pressure control by taking just one tablet.

Procedures cannot cure hypertension

There has been much discussion on the possibility that high blood pressure might be lowered by a procedure known as renal denervation, which would remove the need to take drugs.

However, unfortunately, many of the trials showing apparent benefit were flawed scientifically and the technique is now being reappraised in a few expert centres. Whatever the outcome of these studies, it is unlikely that interventional techniques will provide an alternative to drug treatment except, perhaps, in a small number of carefully selected patients.

The need for patients to understand and act

Despite the consequences of high blood pressure, there is remarkable ambivalence among the million or so Irish people with hypertension as to the seriousness of the condition. Indeed, conversations may refer flippantly to a “touch of hypertension” or “of course, I have white coat hypertension”.

The medical profession and Government providers of healthcare have failed badly in halting the epidemic of high blood pressure and its consequences. So what can we, the people – who by living longer are almost certain to develop high blood pressure – do to ensure that our increased longevity is not marred by disability?

First, we need to acquaint ourselves with the dangers of high blood pressure and the ways we can prevent its complications. Second, we need to have our blood pressure properly assessed by having a 24-hour measurement that tells us about the levels of blood pressure during the day and night.

Next, try to adjust our lifestyle – cease smoking; don’t add salt to food; if we are overweight, lose weight; and take regular exercise.

If you need drugs, ask your doctor to consider prescribing a SPC combination drug and stick to your treatment plan. If drugs are causing side effects that are adversely affecting your life, discuss this with your doctor; there are many other drugs.

*Eoin O’Brien is adjunct professor of molecular pharmacology, The Conway Institute, University College Dublin.