Although it is normal for blood pressure to rise and fall during the course of each day, when it stays abnormally high for long periods of time (usually for around 4 months or longer) it is called high blood pressure, also known as hypertension, which can damage arteries and eventually lead to serious disease.
With over 60% of strokes and around 50% of heart attacks believed to be caused by high blood pressure, the World Health Organisation estimates that, each year, hypertension results in the deaths of more than 7 million people worldwide. In the US alone, around 1 in 4 adults are thought to have high blood pressure, according to estimates.
The cause, or causes, of hypertension are unknown or non-specific in around 9 out of every 10 people who have been diagnosed with the disorder – this is called primary, or essential hypertension. In a minority of individuals, high blood pressure has a known underlying cause, such as kidney disease or adrenal gland problems – these glands produce hormones that are important in controlling blood pressure. In such cases this is known as secondary hypertension.
However, there are a wide range of factors that are known to increase the risk of high blood pressure development. These include:
- Family history – people from families in which high blood pressure is common, have an increased hereditary risk of developing the condition.
- Smoking – nicotine in tobacco smoke is known to cause blood vessels to constrict, and carbon monoxide in tobacco smoke can damage the blood vessels thereby reducing the blood’s ability to carry oxygen.
- Excessive alcohol consumption – men who drink more than 4 units of alcohol per day and women who drink more than 3 units are at an increased risk of developing high blood pressure. (In the UK, 1 unit equals 10 ml of pure alcohol)
- Obesity – being overweight or obese significantly increases the risk of high blood pressure.
- Diet – a poor diet that is high in saturated fats and salt is known to contribute to high blood pressure development .
- Age – as people get older their blood pressure and risk of hypertension increases.
- Diabetes and kidney disease – people with these disorders are known to be at a high risk of hypertension.
- Ethnicity –Black people are more likely to develop high blood pressure than other ethnic groups.
- Stress – It is thought that stress, especially when experienced on an ongoing daily basis, such as occupational stress, contributes to the development of high blood pressure.
Contrary to popular belief, high blood pressure rarely causes any signs or symptoms until damage caused by the condition – to the arteries for example – starts to affect physical health. For this reason, people can live with high blood pressure for many years without realising it until complications start to affect their lives.
However, although hypertension in itself rarely leads to symptoms, it causes damage to blood vessels which significantly increases the risk of heart disease, stroke and kidney disease and for this reason it is often called the “silent killer”. There is also some evidence to suggest that high blood pressure may increase the risk of dementia.
High blood pressure causes strain on the blood vessels in the body. This strain causes the larger blood vessels in the body to lose their elasticity and become more rigid, and the smaller vessels to constrict, forcing the heart to work harder – a similar effect is achieved when squeezing a hosepipe between a finger and thumb.
The resulting damage and constriction of blood vessels can increase the risk of blood clot formation, which, in turn, can cause damage to the heart and brain. Furthermore, high blood pressure can also increase the risk of heart failure, in which the heart is not able to pump blood efficiently around the body, resulting in shortness of breath, fatigue and ankle swelling.
Because high blood pressure can affect anyone and rarely causes any symptoms, it is important that everyone gets their blood pressure checked regularly. Doctors recommend that adults get their blood pressure checked at least once every five years, but preferably more often. This is particularly important as we get older, because blood pressure goes up with age.
Doctors usually measure blood pressure when a patient is relaxed and comfortable using an inflatable rubber strap that is placed around the upper arm and attached to a pressure gauge. The strap is inflated and, using a stethoscope, the doctor listens to the artery just below the strap as the air is released. When the doctor can hear the heart beat, he/she will record the systolic pressure – the blood pressure while the heart is beating. When there is no sound the doctor will record the diastolic pressure – the blood pressure while the heart is relaxing between beats.
Blood pressure readings, which are measured in millimetres (mm) of mercury (Hg) with the systolic reading foremost, can vary due to many individual factors. However, a reading of 140/90 mmHg or above is used to diagnose hypertension.
The doctor may need to record blood pressure on several separate occasions before a diagnosis is made. However, if the blood pressure reading is different on each occasion then he/she may suggest that it is measured continually over 24 hours – this is called ambulatory blood pressure monitoring.
If you are diagnosed with high blood pressure, or identified as being at high risk of the condition, the doctor may recommend one, or a number of lifestyle changes to lower blood pressure or reduce the risk of hypertension developing. These may include:
- Eating a healthy diet that is low in salt, saturated fats, and processed foods, and high in vegetables, fruits and unprocessed cereals.
- Starting a regular exercise program.
- Stopping smoking.
- Losing weight.
- Cutting down on alcohol consumption.
- Reducing stress levels.
However, although lifestyle changes can be very effective for lowering blood pressure to normal levels in some people, other people, especially those with severe hypertension, may require drug treatment, in conjunction with lifestyle changes, to achieve this goal. The main types of antihypertensive medicines include:
- ACE inhibitors: Block the production of a hormone (a natural chemical carried in the blood) in the body called angiotensin II that causes the narrowing of blood vessels. The arteries therefore stay wider and blood pressure is lowered.
- Diuretics: Act on the kidneys to cause them to expel more salt and water from the body in urine and reduce the amount of circulating blood, thus causing blood pressure to drop.
- Beta-blockers: Work by blocking the action of hormones that are involved in controlling the heart, thus slowing the heart beat and reducing blood pressure.
- Calcium channel blockers: Block the movement of calcium into the cells of the heart and blood vessels, causing arteries to relax and widen, thus reducing blood pressure.
- Angiotensin II receptor blockers: Block the binding of angiotensin II to receptors on the walls of blood vessels, allowing arteries to widen and easing the blood flow.
If the underlying cause of high blood pressure is a medical condition, such as a hormonal disorder, treatment of the disorder will often result in blood pressure returning to normal.
However, it must be stressed that taking any medication should only be done with the guidance and advice of a qualified health care professional.
Because high blood pressure itself rarely causes any noticeable symptoms, it is important to remember to have regular check-ups to get your blood pressure measured. However, the good news is that high blood pressure and its effects usually take many years to develop and, if you are identified as being at risk of developing high blood pressure, taking simple steps, such as regular exercise and healthy eating, will significantly reduce this risk.
Furthermore, if you are diagnosed with high blood pressure, making changes to your lifestyle, and/or taking antihypertensive medications, will usually lower it.
UK Blood Pressure Association
http://www.bpassoc.org.uk/
British Heart Foundation
http://www.bhf.org.uk/
US National Heart, Lung and Blood Institute
www.nhlbi.nih.gov
American Heart Association
http://www.americanheart.org
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