High blood pressure: How to beat the invisible killer

High blood pressure can happen at any age – yet many sufferers don't even know they have it. What are the risks and how can we prevent it? By Jeremy Laurance

(Getty)

High blood pressure is common, mostly symptomless, and potentially lethal. Known as the silent killer, it is a direct cause of more than 100,000 strokes each year (two thirds of the total). It also increases the risk of heart disease, kidney problems and blindness. A quarter of adults have high blood pressure, and among those over 60 the proportion rises to half. But many people don't know they have it. An estimated 18 per cent of men and 13 per cent of women with high blood pressure are not receiving treatment that could protect them from an early death.

High blood pressure is not just a problem for older people. Blood pressure can rise at any age. One in 10 men aged 25-34 years have high blood pressure compared with approximately two in five men aged 35-44 years, according to the Blood Pressure Association. Fewer women are affected at a young age, but one in 10 women in their twenties are affected.

Has thinking about blood pressure changed?

Dramatically. The old view was that high blood pressure was necessary in older people in order to pump the blood through furred arteries, which had been narrowed by fatty deposits. In the 1930s there was huge controversy over whether it would be safe to attempt to lower blood pressure. When the first trials of blood pressure- lowering medicines were carried out in the 1960s, only patients with extreme raised pressure were entered into them, because of what were perceived to be the risks. The results showed rapidly and unequivocally that lowering the pressure saved lives.

Is the problem getting worse?

Yes – because we are an ageing population and our arteries get stiffer as we get older. Modern Western lifestyles are also making high blood pressure increasingly common. It is almost unknown in parts of the world such as rural Africa, where factors such as poor diet, lack of exercise, excess salt and too little fruit and vegetables don't apply. This is so even though Africans have an underlying genetic propensity to high blood pressure. The problem is now so widespread in the West, with half the over- sixties affected, that high blood pressure has come to represent normality.

What is high blood pressure?

As the heart pumps the blood around the body it exerts pressure on the artery walls. If you have high blood pressure, it means your heart is having to work harder to pump the blood. This can weaken the heart or damage the artery walls, resulting in a blockage or a rupture of the walls (haemorrhage). High blood pressure is defined as a sustained pressure of 140/90mm Hg or over.

What does that mean?

Blood pressure is measured in millimetres of mercury (Hg). Two measures are used, to record the maximum and minimum pressures during a single beat of the heart. The first figure – 140 – is called the systolic pressure, which is the maximum pressure as the heart contracts, pumping the blood round the body. The second figure – 90 – is the diastolic pressure, or the minimum pressure as the heart relaxes while the ventricles (chambers) of the heart fill with blood before it pumps again.

What is normal blood pressure?

A consistent reading below 120/80mm Hg is regarded as ideal. Any reading in the range 90/60 to 140/90 would be considered good in most people. However, a blood pressure level of 135 over 85 (135/85) may be "normal", but someone with this reading is twice as likely to have a heart attack or stroke as someone with a reading of 115 over 75 (115/75). As a general rule, the lower your blood pressure the better, though it should not be so low that you experience symptoms such as passing out when you stand up because the heart is having difficulty pumping blood to your brain.

What causes high blood pressure?

In most cases there is no single cause. But lifestyle plays a part. Poor diet, lack of exercise, being overweight, drinking to excess and stress all increase the likelihood of high blood pressure. Many people can lower their blood pressure by tackling these issues. For example too much salt increases blood pressure, so it is best to eat as little as possible. Some people may be able to avoid taking blood pressure-lowering drugs by cutting down on salt. But genetics, too, plays a part – high blood pressure runs in families. People from Afro-Caribbean and South Asian communities are at greater risk – and blood pressure rises with age.

Can it cause symptoms?

Yes, but rarely – when a person has very high blood pressure. Symptoms can include headache, blurred vision, nosebleeds and shortness of breath. Get an appointment with your GP as soon as possible if you experience these. Adults over 40 should have their blood pressure checked at least once every five years, and more frequently if there are risk factors such as a family history of heart disease.

What happens when high blood pressure is diagnosed?

Your doctor will first explore if there are changes you can make to your lifestyle that might reduce the pressure. The most important are keeping to a healthy weight, eating more fruit and vegetables, cutting down on salt, taking more exercise and drinking less alcohol. You could also try yoga or meditation to reduce stress. If these fail, or if your lifestyle is already healthy, then your doctor may recommend drug treatment.

What is the "white coat effect"?

High blood pressure cannot be diagnosed from a single reading because it can vary – a series of readings is required. Many people find their blood pressure rises when it is being measured in the presence of a doctor (with or without white coat) and this has cast doubt on the accuracy of these readings. The best measure is a 24-hour reading, which can be obtained by wearing a monitor that automatically records blood pressure every half hour throughout the day.

Can occasional high blood pressure be a risk too?

Conventional thinking has been that sustained high blood pressure is what does the damage and needs to be controlled. But three studies published in The Lancet in March have cast doubt on this view. They found patients with the highest variation in blood pressure were up to 12 times more likely to have a stroke than those with the least variation. About half of all patients with high blood pressure have variable readings between visits for measurement. Leaders of the British Hypertension Society and the National Institute for Clinical Excellence are considering what impact, if any, this should have on guidance for the management of high blood pressure.

What should you do if pregnant?

Have your blood pressure checked regularly, even if it is not high, because pregnancy can raise blood pressure in some women. That way you will get early warning if you are developing pregnancy-induced hypertension, which can lead to pre-eclampsia, a serious condition which affects the placenta and can threaten the life of both mother and baby. About 6 to 8 per cent of pregnancies are affected by high blood pressure problems. Older mothers and those carrying twins or triplets are at higher risk.

Which is the best blood pressure- lowering medicine?

Everyone is different – there is no "best" drug. If you cannot reduce your blood pressure by other means, then drug treatment may be necessary. High blood pressure cannot be "cured" so it will probably mean taking pills for the rest of your life. Which ones you take is partly a matter of trial and error. What works well for one person may not work for another. For many people, one medicine alone will not lower their pressure enough – two drugs together can work in synergy, giving a greater effect than the sum of their effects when given alone.

How do I choose which drugs to take?

Each type of medicine works in a different way. People under 55 tend to respond better to drugs called ACE inhibitors, which relax and widen the arteries, making it easier for the heart to pump the blood. Those over 55 tend to do better on calcium channel blockers, which lower pressure by blocking the effect of calcium, used by the body to narrow blood vessels. Like ACE inhibitors, they relax and widen the arteries, but through a different mechanism. Many patients require both types of medicine.

What about side effects?

These are very safe drugs that have been used for decades – so long that they are out of patent (and hence relatively cheap for the NHS). The commonest side effect of ACE inhibitors is a dry cough. If this becomes bothersome, an angiotensin receptor blocker (ARB), which works in a similar way but appears to lack the side effect may be prescribed. Calcium channel blockers can cause swollen ankles. Diuretics, which are sometimes called water tablets, are also widely prescribed for blood pressure. They act on the kidneys to increase the amount of salt and water that they extract from the blood, increasing the amount of urine. Too much salt can cause extra fluid to build up in the blood vessels, raising blood pressure. Diuretics can mean you need to urinate more, so they are best taken in the morning, to avoid having to get up in the night to go to the toilet.

Can blood pressure be too low?

Usually, the lower your blood pressure the healthier you are. But if it is too low (less than 90/60) you may experience symptoms such as dizziness, fainting, blurred vision, palpitations, nausea and general weakness. Some people feel dizzy on standing up and this is known as postural hypotension, when your blood pressure falls as a result of a sudden change of movement. It usually lasts only a few minutes. Some medicines, such as beta-blockers, alpha blockers and antidepressants can cause this. In general, you only need treatment for low blood pressure if you have symptoms which worry you. Your GP will then try to find the underlying cause of your low blood pressure.