High blood pressure, or hypertension, affects around 20 per cent of the adult male population. It is known as the silent killer as it creeps up without symptoms to cause a sudden heart attack or stroke. Even if your blood pressure is dangerously high, you may feel relatively well.
Blood pressure (BP) is gauged according to how much mercury (measured in a column length) it can support. Blood pressure is therefore expressed in milli-metres of mercury (mmHg). BP is highest as blood surges through the system when the heart pumps. It is lowest as the heart relaxes between beats. BP is recorded as the higher (systolic) pressure over the lower (diastolic) reading. A typical 20-year-old might have a BP of 120/70 mmHg. A fit 50-year-old might have a BP of around 150/85 mmHg.
The World Health Organization defines hypertension as a blood pressure that is consistently greater than 160 mmHg (systolic) and 95 mmHg (diastolic). Systolic blood pressures of 140160 mmHg and diastolic values of 9095 mmHg are referred to as mild, or borderline hypertension. A 50-year-old man with untreated hypertension might have a BP of 180/100 mmHg or higher.
The best analogy to explain how hypertension develops is to compare circulating blood with water running through a hose pipe. Water pressure within a hose pipe can be raised by increasing the power of the pump (tap) or by squeezing the pipe and reducing its diameter. In exactly the same way, blood pressure can be increased within the circulation by increasing the work of the heart or by reducing the diameter of the vessels through which the blood flows.
BP varies enormously by as much as 70 mmHg throughout the day. Lowest values are recorded during sleep, around three to four hours after the person has fallen to sleep. Highest levels naturally occur at around midday, or whenever the person in question has been awake for about four hours. Physical exercise such as climbing stairs or riding a bicycle temporarily increase BP, but this is an entirely normal physiological response.
Two male activities in particular can produce phenomenally high BPs. These are weight lifting and sexual intercourse. Since these are transient effects, they do not seem to cause any harm.
Emotions such as anger also raise BP. This is because adrenaline and other stress hormones stimulate constriction of the blood vessels and also get the heart pumping faster.
WHAT CAUSES HIGH BP?
High BP results from interactions between inherited, developmental and lifestyle factors. There are probably several abnormal genes involved in high BP, which alone or in combination can cause high BP in later life.
Events that occur during foetal development prior to birth can also programme in a tendency to develop hypertension, stroke or a heart attack. This is probably due to impaired maternal nutrition affecting arterial development. Research shows that low birth weight babies are more likely to develop high BP as adults. Average adult systolic BP increases by 11 mmHg as birth weight goes down from 7.5 lb to 5.5 lb. The size of the placenta at birth is also important. Average systolic BP rises by 15 mmHg as placental weight increases from 1 lb to 1.5 lb in weight. The highest BPs therefore occur in men who were born small babies with large placentas. This may be due to abnormal arterial and blood circulatory patterns being laid down as a result of imbalances between the placenta and the baby.
This is borne out by research that links fingerprint patterns with the risk of developing high BP in later life. Fingerprints are laid down in the womb in the first few weeks following conception. Their patterns are linked to the degree of bumpiness and swelling of the developing fingertips, which in turn is related to irregular blood circulation.
Fingerprint patterns take the form of arches, loops or whorls (see Figure 18, below). The more whorls you have, the more likely you are to become hypertensive. Researchers have found that people with at least one whorl have a BP that is 6 per cent higher than people with no whorls. BP then generally increases as the number of whorls increases. The maximum number of whorls is 10 (two per digit). The average number tends to be two or three.
Figure 18: Fingertip whorls and hypertension
On top of these genetic and developmental predispositions, environmental factors interact to produce hypertension.
It is now thought that the rise in BP with increasing age that is commonly seen in Western countries is linked with our lifetime intake of salt. The chemical name for salt is sodium chloride. It is the sodium that is linked with high BP the average male sodium consumption in the UK is around 3.5 g per day, which is far too high (see Chapter 20). Some men eat twice this amount and are sitting ducks for hypertension.
Obesity is also linked with hypertension in some people, possibly because the heart has to pump harder to get blood around a larger body. Fat people are also more likely to have a high saturated fat diet, high blood cholesterol levels and a greater amount of furring up and narrowing of the arteries (see Chapters 11 and 17).
Another important environmental factor is alcohol intake. Men who regularly drink more than three units of alcohol per day (see alcohol) tend to have higher BPs. Many men drink more than this and have normal BP it depends upon your underlying genes.
The other major environmental factor linked with high BP is stress. Exposure to stress seems to make part of the nervous system overactive in some people, leading to hypertension. Stress leads to increased circulating levels of adrenaline and overactivity of the sympathetic nervous system. This triggers arterial spasm and hypertension.
More than one environmental factor may be operative at any one time. It seems that a man exposed to excess salt at the same time he is feeling stressed is more likely to develop high BP than a man who is just exposed to too much salt, or who is just under stress (see Chapter 17).
Hypertension needs to be taken seriously. It is a powerful predictor of a number of diseases that are common causes of ill health and death in males from middle age onwards. The two commonest consequences of high BP are heart attacks and strokes.
As hypertension makes it more difficult for the heart to pump blood out against the pressure resistance, it also leads to thickening of heart muscle and dilation of the heart chambers. The heart may become a floppy, dilated bag of muscle which is unable to pump efficiently. This leads to heart failure, with fluid accumulating within the body. Thickened heart muscle will also outgrow its blood supply, to result in angina pain.
High BP damages the inside lining of arteries throughout the body. This damage triggers the accumulation of fatty plaques and thrombosis (clots) which may eventually completely block blood flow. Tissues that are cut off from blood and oxygen rapidly die and this can lead to a heart attack (myocardial infarction) or a stroke. It is estimated that, for a man in his forties, each rise of 10 mm Hg in systolic BP increases the risk of heart disease by a massive 20 per cent.
High BP can also cause the equivalent of a blow-out in delicate blood vessels in the brain. This leads to another type of stroke in which haemorrhaging occurs, rather than death of brain cells due to blockage of blood vessels with a clot.
Small blood vessels within the body are even more vulner-able to the effects of high BP than larger arteries. Damage to small blood vessels at the back of the eye leads to retinal haemorrhages and visual disturbances. The eye acts like a window onto the brain, and any small vessel damage seen here mimics the changes happening inside the brain that might lead to a stroke.
Damage to small blood vessels in the kidney interferes with the production of urine, so fluid starts to accumulate in the body. This form of kidney failure is now relatively uncommon because drug treatment to control hypertension prevents it.
HOW TO PREVENT OR REDUCE HIGH BP
You cannot do much to alter your genes (yet) or reprogramme your foetal development. What you can do is alter your lifestyle to minimize the risk of developing hypertension in later life. If you already have high BP, whether it is raised severely, slightly or only moderately, you must reduce your exposure to environmental factors that will inevitably make it worse.
Lifestyle changes that can help prevent or treat high BP include:
cutting right back on salt intake: do not add salt at the table or during cooking; avoid salty foods such as crisps; bacon; tinned, cured, smoked, or pickled fish/meats; meat paste; paté; ready prepared meals; tinned vegetables or tuna in brine; tinned or packet soups, sauces, stock cubes and yeast extracts.
By not adding salt at the table, by reducing the amount of salt used during cooking and by avoiding salty foods you can cut systolic BP by at least 5 mmHg. If everyone did this, it is estimated that the incidence of stroke in the population would be reduced by 26 per cent, and that of coronary heart disease by 15 per cent.
Salt is easily replaceable with spices. It does not take long to retrain your taste buds. Ensuring you eat plenty of potassium-rich foods will also help. Potassium ions are linked with sodium ions in the body. The kidney swaps potassium for sodium in the urine, so the more potassium you eat the more sodium you excrete. Too much potassium can, unfortunately, be harmful as well, so the best way to ensure adequate but safe supplies is to eat potassium-rich foods. These include all fruit, especially bananas, dried apricots, fruit juices and fruit yoghurts; all vegetables, especially pulses, mushrooms, potatoes and spinach; wholegrain breakfast cereals and, surprisingly, coffee.
Small amounts of potassium salts (Ruthmol, Selora) are also useful as sodium replacements but they can be a little bitter. Go easy on them as too much potassium causes problems of its own.
• Cut back on alcohol intake if this is excessive. Keep within the 21 units per week maximum for males. If you can, drop back to 14 units per week or less. (Click here for definitions of units of alcohol.)
• Lose any excess weight through a combination of diet and exercise. Exercise lasting for at least 20 minutes three times per week can in itself lower high BP. You need to increase your pulse rate to around 110120 per minute and work up a light sweat.
• At the same time, men who smoke should stop. High BP and smoking together damage blood vessels even faster than would be expected from either alone. This will almost certainly lead to coronary heart disease in the future.
• If your cholesterol levels are harmfully raised, you should also cut back on your intake of saturated (animal) fat. This contributes to furring up and narrowing of arteries and will lead inexorably to coronary heart disease (see Chapter 11).
If despite these lifestyle changes your BP consistently remains high, you will need treatment with drugs. These are essential to control your BP and minimize your risk of a heart attack, stroke, heart failure, kidney failure and other problems related to vascular damage.
The aim of anti-hypertensive treatment is to reduce diastolic BP to below 90 mmHg and/or to reduce systolic BP to below 160 mmHg.
The main drugs now used to treat hypertension are:
Diuretics (Water Tablets)
Diuretics lower BP by decreasing the amount of fluid within the circulation. They also cause mild dilation of small arteries.
Beta-Blockers
These drugs damp down nerve pathways that cause blood vessel constriction. They slow the heart rate and reduce the force of contraction of the heart.
Calcium Channel Antagonists
These drugs block the movement of calcium ions through cell membranes. This lowers BP by relaxing muscles in arterial walls, and by reducing the force of contraction of the heart.
Ace Inhibitors
These block formation of Angiotensin Converting Enzyme (ACE). Ace is a powerful constrictor of blood vessels, so blocking it leads to blood vessel dilation. ACE inhibitors also increase blood flow to the kidneys, so more fluid is lost as urine.
Alpha Antagonists
These drugs lower BP by dilating arteries and veins.
Angiotensin II Antagonists
This new class of drug has only recently become available. They dilate blood vessels, stimulate kidney function and may also have a direct action on the brain to reduce drinking and increase urine output.
As hypertension is common, it is worth having your BP checked on a regular basis. Early diagnosis, lifestyle changes and the prescription of necessary drugs can control BP and save many lives.
Every male should have his BP checked at least once before the age of 30 years. Over the age of 30, BP should be checked at least once every five years preferably every one to two years.
