– as a baby’s birth length decreases
– as the ratio of a baby’s head circumference to the length of the baby increases from less than 0.65 to 0.7 or more.
– if the mother’s blood haemoglobin level was low during pregnancy
– if maternal nutrition was known to be poor.
Lack of important nutrients – including vitamins, minerals and essential fatty acids – during the first few weeks of embryonic life is thought to trigger the development of abnormal arterial and blood circulatory patterns. These probably result from an imbalance between the placenta and baby. This is supported by research linking fingerprint patterns with the risk of developing high blood pressure 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 is related in turn to irregular blood circulation.
Fingerprint patterns take the form of arches, loops or whorls, and the more whorls you have, the more likely you are to become hypertensive in later life. People with at least one whorl may have a blood pressure that is 6 per cent higher (8mmHg) than people with no whorls. BP then generally increases as the number of whorls increases, up to the maximum number possible, which is ten (two per digit). The average number tends to be two or three. Long, narrow hands are also associated with higher blood pressure, and both effects are more marked on the right hand.
Inherited and developmental factors are not the sole causes of high blood pressure, however. Something else has to happen in any individual before blood pressure goes up, and this is where environmental factors come in. These interact with inherited factors in individuals whose genes predispose them to hypertension to produce high blood pressure in later life. If several environmental factors linked with high blood pressure interact together, your risk of high blood pressure will be even greater.
ATHEROSCLEROSIS
One of the main causes of high blood pressure – especially a raised systolic BP – is hardening, furring up and narrowing of the arteries (atherosclerosis – see Chapter 3). This occurs naturally with increasing age and comes on more quickly if you smoke, eat an excessively fatty diet or are overweight. High blood pressure in turn puts excessive strain on the arterial wall lining and triggers damage that hastens atherosclerosis. Because atherosclerosis in turn causes hardening of arterial walls, a vicious cycle is set up in which blood vessels become even less elastic and less able to distend to even out pressure surges, so BP rises further. High blood pressure is therefore both a cause, and a consequence, of atherosclerosis, with each factor making the other worse.
DIABETES
Diabetes mellitus is a condition in which blood sugar (glucose) levels are raised due to insufficient production of insulin hormone by the pancreas. Some people also have an impaired tolerance to glucose tolerance due to an inability of their cells to respond properly to relatively normal levels of insulin (insulin resistance). Having poorly controlled diabetes significantly increases the risk of developing atherosclerosis, high blood pressure, coronary heart disease (CHD) and stroke – especially in women. The reason is not fully understood, but high blood sugar levels may trigger abnormal blood clotting, damage blood vessel linings to trigger hardening and furring up, affect nerves controlling heart and blood vessel function or weaken muscles in the heart or artery walls.
The risk of severe CHD is two to three times higher in men with diabetes and three to seven times higher in women with diabetes. Therefore, if you have both high blood pressure and are also diabetic, it is vitally important that you keep your blood sugar levels under tight control.
SMOKING
Smoking cigarettes greatly increases the risks associated with hypertension – people with high blood pressure, who also smoke, are two or three times more likely to develop coronary heart disease than hypertensive non-smokers, and life-insurance companies load their premiums accordingly.
Smoking cigarettes triggers hardening and furring up of the arteries (atherosclerosis), which is one of the most important causes of high blood pressure, coronary heart disease and stroke. It is also linked with at least 90 per cent of all cancers. The reason that cigarette smoke is so toxic is that it contains chemicals that:
For more information, see Chapter 21.
OBESITY
People who are overweight or obese are more likely to have high blood pressure than thin people, as there is a larger body tissue mass through which the heart has to pump blood. Overweight people are also more likely to eat an unhealthy diet with a high intake of saturated fat. This raises blood fat levels, which in turn hastens the onset of atherosclerosis. Another factor is that overweight people tend to be inactive.
Although not everyone who is overweight has high blood pressure, however, there seems to be an interaction between obesity and some underlying, predisposing mechanism that is inherited by some people. This may be linked to where excess fat is stored. Overweight people who carry excess weight around their middle (apple-shaped) rather than around their hips (pear-shaped) seem to be at greater risk of a number of health conditions, including high blood pressure, atherosclerosis, raised cholesterol levels, diabetes, CHD and stroke. The reasons are not fully understood but may be linked to the way the body metabolizes dietary fats.
For more information, see Chapter 21.
ALCOHOL
A high alcohol intake is also linked with an increased risk of hypertension. People who regularly consume excessive amounts (more than 3 units of alcohol per day, or 21 units per week) tend to have higher blood pressures. However, many people drink more than this and have a normal blood pressure – it depends on whether you have inherited predisposing factors that make you sensitive to these effects of alcohol.
For more information, see Chapters 11 and 21.
LACK OF EXERCISE
Lack of exercise is an important cause of high blood pressure. Inactivity means the heart is unfit, despite having to work extra hard to pump blood around the increased bulk of the body. People who exercise for at least 20–30 minutes, three times per week, have a lower risk of high