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(5) High Blood Pressure


Does anybody know what really causes high BP?

There is still a lot of uncertainty about the causes of high BP. For the vast majority of people, over 95%, an underlying cause is not found.

These are the individuals who have ‘essential’ hypertension. It is likely that several interrelated factors contribute to high BP in most people. The chief suspects include:

• An overactive hormone system that relates to the kidney (the ‘renin–angiotensin system’);

• An overactive autonomic nervous system (the part of the nervous system that is responsible for our unconscious nervous responses);

• a fault in the cells of the smaller blood vessels that produce substances leading to blood vessel narrowing and increased BP (‘endothelial cell dysfunction’);

• Genetic predisposition (when you have inherited a tendency to high BP);

•Factors occurring at birth, particularly birth weight, possibly reflecting undernourishment in the fetus, which ‘programme’ our body to develop high BP in later life.

I have always thought that physical or psychological stress and tension raises BP. Is that right?

Yes, and this is where confusion arises. Both real and imagined stress cause a large rise in BP, lasting minutes or even hours. Such rises are normal and occur in everyone. They are brief additions to their usual average pressure, high or low. As a cause of eventual organ damage, however, ‘high BP’ refers not to these peaks, but to the steady average level over weeks, months or years, to which BP returns when stress is removed.

My father had high blood pressure. Is high BP inherited?

Although genetic factors have been linked to the development of essential hypertension, multiple genes are most likely to contribute to the development of the disorder in a particular individual. Therefore, in any one individual, high BP is hardly ever simply an inherited disease like muscular dystrophy, Huntington’s disease or haemophilia. A rare exception is polycystic disease of the kidney, mostly determined by a single ‘dominant’ gene, and therefore occurring in 50% of offspring of a single affected parent. In terms of inheritance, high BP is about twice as common in people who have one or two hypertensive parents. When populations are studied, at least a third of the variance in BP within large populations can be predicted from knowledge of BP in parents and brothers and sisters.

In all other cases, BP depends on interaction between many different inherited factors, many of which operate only if certain environmental conditions exist. The most important of these are probably birth weight, adolescent and early adult growth, salt and alcohol intake.

If I have high BP myself, are my children more likely to develop high BP? If so, is there anything I can do about it?

Children of parents with high BP are more likely to develop high BP themselves. In terms of prevention, the general recommendations of taking regular exercise, maintaining a healthy diet and avoiding becoming overweight are particularly relevant. However, there are no unique or different recommendations for individuals with a family history of high BP than there are for those without such a history.

I take quite a few drugs altogether. Would any of the drugs I am taking cause high BP?

Yes. Four groups of medicines or drugs might cause high blood pressure: home remedies bought across the counter at the chemist, herbal medicines, drugs of addiction and abuse, and prescribed medication.

• Home remedies bought over the counter. Many different preparations available for shrinking up the air passages in your nose during colds, hay fever (‘allergic rhinitis’) or ‘chronic catarrh’ (usually unrecognized hay fever) can raise BP, because they contain chemicals closely related to naturally occurring chemicals in the body that influence BP.

If you are using any kind of nasal decongestant, make sure you mention this to anyone who may be measuring your BP.

Despite their popularity, nasal decongestants containing these drugs (sympathomimetic amines) only work for a short time, and cause rebound swelling as soon as they are stopped.

This leads many people to go on using them for days, months or even years on end, in which case they develop severe chronic obstruction in the nose, and catarrh, caused by the very drug that they are using to treat it.

This dependence is reinforced by the fact that these drugs tend to wake people up and give them a bit of a lift, in the same way as dexamphetamine (Dexedrine, ‘speed’) does, so that  (often unconsciously) they become addicted to them.

The moral is, don’t use them unless you have to, and never use them for more than a couple of hours. Traditional remedies such as menthol and eucalyptus are safer and just as effective, but check with your chemist that they don’t contain amine supplements.

• Drugs of addiction and abuse. Dexamphetamine and its more potent and even more dangerous relation ‘Ecstasy’, causes a high mood, wakefulness, indifference to food, and very high BP. Both drugs can cause hallucinations, which may be dangerous if people drive, and, combined with vigorous activity at high room temperature, ‘Ecstasy’ may raise BP high enough to cause death from acute heart failure. Cocaine may also cause prolonged rises in BP, and so, of course, may alcohol.

• Herbal medicines. Herbal remedies that can cause high BP or interact with BP-lowering medication may make BP-lowering drugs less effective. If you suffer from atrial fibrillation and take blood-thinning medication (warfarin or aspirin), herbal products are known to interact and prolong the action of blood-thinning medication. Before you take any herbal remedy, it is always better to discuss with a pharmacist whether it is likely to have any unwanted side effects.

• Prescribed medication. Prescribed drugs include nonsteroidal anti-inflammatory drugs (NSAIDs), drugs derived from liquorice, which were at one time used commonly to treat gastric ulcer but are now rarely prescribed, and some steroid hormones. NSAIDs are commonly used for joint pain. They can increase BP by 5–6 mmHg diastolic pressure, about the same amount as many BP-lowering drugs bring it down. Many of these are now available from chemists over the counter, of which the most widely consumed is ibuprofen (Brufen). Because of this effect, it is important that you remind your doctor or pharmacist that you have high BP if you ever need painkillers, as they will be able to suggest more suitable alternatives for you.

Corticosteroid hormones include cortisone, hydrocortisone, prednisone, prednisolone, and adrenocorticotrophic hormone (ACTH). All of them raise BP by causing sodium and water retention and thus increasing blood volume, if given in high dosage. This normally happens only if steroids are taken into the body as tablets or injections, but heavy use of some strong steroid ointments may penetrate sufficiently through the skin to have the same effect. These big doses should never be used other than for serious, usually life-threatening disease, which will be treated by hospital specialists. The only conditions in which steroid treatment is at all likely to interfere with management of high BP are severe asthma and rheumatoid arthritis.

I’m 30, I don’t smoke and, although I do enjoy an occasional glass of wine, I’m not a heavy drinker – but I’ve got high BP, which I’d always thought only affected people who were much older than me. Are the causes of high BP in people of my age just the same as for people who are middle-aged or older?

Generally yes, bearing in mind that we don’t know most of the causes of much of the high BP in middle-aged and elderly people. The main difference is that, in younger adults like you, there are other rare secondary causes (usually relating to the kidney or adrenal glands). Younger people who developed high BP used to be referred to hospital, but this situation has now changed and investigation of high BP can be carried out by your doctor, usually by means of checking your urine for protein and performing simple blood tests.

Is getting older or just being old in itself a cause of high BP? In other words, is high BP normal in old age?

Blood pressure, particularly systolic BP, rises with age. It is now accepted that, although high BP in the elderly is common, it should not be accepted as normal. In fact the consequences of high BP, particularly stroke and heart attacks, are far more common in the elderly. Clinical trials of BP-lowering drugs have shown that treatment of elderly people with high BP is highly effective and cost effective. The consequence is that elderly people are now commonly treated for high BP, with up to one fifth of people aged over 65 in the UK taking BP-lowering drugs.



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