What is high blood pressure?
High blood pressure (HBP) or hypertension means high pressure (tension) in the arteries. Arteries are vessels that carry blood from the pumping heart to all the tissues and organs of the body. High blood pressure does not mean excessive emotional tension, although emotional tension and stress can temporarily increase blood pressure. Normal blood pressure is below 120/80; blood pressure between 120/80 and 139/89 is called “pre-hypertension”, and a blood pressure of 140/90 or above is considered high.
The top number, the systolic blood pressure, corresponds to the pressure in the arteries as the heart contracts and pumps blood forward into the arteries. The bottom number, the diastolic pressure, represents the pressure in the arteries as the heart relaxes after the contraction. The diastolic pressure reflects the lowest pressure to which the arteries are exposed.
An elevation of the systolic and/or diastolic blood pressure increases the risk of developing heart (cardiac) disease, kidney (renal) disease, hardening of the arteries (atherosclerosis or arteriosclerosis), eye damage, and stroke (brain damage). These complications of hypertension are often referred to as end-organ damage because damage to these organs is the end result of chronic (long duration) high blood pressure. For that reason, the diagnosis of high blood pressure is important so efforts can be made to normalize blood pressure and prevent complications.
It was previously thought that rises in diastolic blood pressure were a more important risk factor than systolic elevations, but it is now known that in people 50 years or older systolic hypertension represents a greater risk.
Although high blood pressure can cause headaches, dizziness and problems with vision, the majority of people suffer no symptoms at all. As a result many people with hypertension remain undiagnosed because they have no symptoms to motivate them to see a doctor or get their blood pressure checked. However, despite the lack of symptoms hypertension can lead to heart attack, stroke, kidney damage, and many other medical problems.
Causes and risk factors
In over 90 per cent of cases, the cause is unknown. In the remaining cases, high blood pressure is a symptom of a recognizable underlying problem such as a kidney abnormality, tumor of the adrenal gland or congenital defect of the aorta (in these cases when the root cause is corrected, blood pressure usually returns to normal). This type of high blood pressure is called secondary hypertension. If high blood pressure isn’t treated and is combined with obesity, smoking, high blood cholesterol levels or diabetes, the risk of heart attack is several times higher.
Arteries also suffer the effects of high blood pressure, becoming scarred, hardened and less elastic. Though this hardening of the arteries often occurs with age, high blood pressure accelerates the process. The hardened or narrowed arteries are
unable to supply the amount of blood the body’s organs need, preventing them working effectively.
Another risk is that a blood clot may lodge in an artery narrowed by atherosclerosis, blocking blood supply.
Treatment and recovery
The only way to find out if you have high blood pressure is to have your blood pressure checked. A doctor or other qualified health professional should check a patient’s blood pressure at least once every two years. It’s measured in millimeters of mercury (mm Hg) and is defined in an adult by the recording of two readings:
- The first is called the systolic pressure and represents the force of the blood as the heart contracts (beats) to pump it around the body. This is the higher of the two readings and records blood pressure at or above 140mm Hg.
- The second, called the diastolic, is the pressure while the heart is relaxed and filling with blood again in preparation for the next contraction or heart beat. This value is lower than the systolic pressure and records blood pressure at or above 90mm Hg.
When high blood pressure is first diagnosed, tests may be done for an underlying cause (i.e. secondary hypertension) especially if the person is young or has very high blood pressure. If an underlying cause is found it should be treated.
There’s no cure as such for essential hypertension, but following a healthy lifestyle can be enough to bring blood pressure down to a normal level. This is one reason why drug treatment may not be offered for healthy individuals with only mild hypertension (above 140/90 mmHg but below 160/100 mmHg). Medication is used if lifestyle changes alone fail to lower blood pressure sufficiently. Its generally recommend that drug treatment is offered to:
- Those with a blood pressure above 160/100 mmHg.
- Those with isolated systolic hypertension of more than 160 mmHg.
- Those with a blood pressure of more than 140/90 mmHg (i.e. mild hypertension) but who also have cardiovascular disease or significant risk of developing cardiovascular disease, diabetes, or damage to the heart, kidney or eyes as a result of high blood pressure.