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Blood pressure testing: keep your finger on the pulse

From The Times, March 16th 2010

Dr. Mark Porter

A new study on blood pressure indicates that it should be monitored even if you only occasionally get high readings

New research suggests that stable control is more important than previously thought when managing high blood pressure. The news may well change the way doctors approach the problem, but we must make sure that polishing the diamond for the well-treated minority does not detract from the real threat.

Namely that the health of the vast majority of the 12 million adults in the UK with high blood pressure is being put at risk because half of them don't know they have a problem, and a similar proportion of those who do are not being treated in accordance with the latest guidelines.

High blood pressure (hypertension) matters because it prematurely ages the lining of arteries, increasing the risk of problems including heart disease, stroke, kidney damage, and erectile dysfunction. The World Health Organisation estimates that it is now responsible for half of cases of coronary heart disease and three quarters of strokes in the UK.

Most hypertension is due to a combination of ageing and lifestyle factors (particularly a high salt intake) but the underlying mechanisms remain poorly understood. Identifiable causes, such as kidney disease, are found in fewer than 5 per cent of people. High blood pressure is relatively unusual in people under 35 and checks done during pregnancy, contraception consultations and during medicals will pick up the lion's share of cases, but after 35 it becomes common enough to warrant screening. I follow a simple rule - if you are over this age and don't know what your blood pressure is, you should find out, and have it rechecked at least every three years.

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A normal reading in the surgery is generally regarded as anything below 140/90 millimetres of mercury (mmHg), where the lower figure (diastolic) is the constant pressure within the arteries, and the higher (systolic) one the peak reached during each beat of the heart.

It's unclear what constitutes a normal reading done on a machine in the comfort of your home, because most of the evidence linking high blood pressure to complications such as stroke are based on measurements taken in the relatively stressful environments of the surgery or hospital, but I knock off 10/5 mmHg, giving an upper limit of 135/85.

And it's not just where it's taken that matters. Other factors influence it too, ranging from the time of day - it normally peaks in the evening and drops by as much 20 per cent during the early hours of the morning - to how bad the traffic was on the way to the surgery, which is why it's standard practice to recheck high readings.

But that may change in light of a review published in The Lancet suggesting that we shouldn't dismiss occasionally high readings because they may be a sign of trouble ahead. The researchers found that people with fluctuating readings were among the groups most at risk of having a stroke, even if their blood pressure was within the ideal range most of the time.

Whatever the eventual conclusion about this discovery, dealing with high blood pressure effectively requires a partnership between doctor and patient. Therapy is likely to be lifelong, with around a third of patients needing one drug, another third requiring two, and the remainder needing three drugs to get their pressures to target. The current upper limit for good control is set at 140/90 for most people, but studies suggest that the lower the better, with optimum level for long-term health likely to be closer to 120 for the upper figure.

The patient's role in the partnership is to try to reduce his or her blood pressure naturally (by cutting out salt, losing weight and doing more exercise) and to take steps to minimise additional hazards that may compound the problem - giving up smoking, for instance, won't lower blood pressure, but will slash the odds of someone with hypertension going to an early grave because of a heart attack. And that is what the management of high blood pressure is all about.

Blood pressure facts

• A third of men and a quarter of women in the UK have high blood pressure - at least half are receiving no treatment.

• Eating more fruit and veg, exercising and losing weight may be all that is required in milder cases. Cutting out salt is particularly important.
• The equivalent of two glasses of wine a day may be beneficial, but heavier drinking raises blood pressure.
• Home blood pressure machines are a good idea but only buy one that is approved by the British Hypertension Society.

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