High blood pressure or hypertension is a common condition that increases the risk of various illnesses such as stroke, heart attacks and kidney damage. Blood pressure rises with age and even persons who have normal blood pressure at age 55 are estimated to have a 90% chance of developing hypertension in their lifetime.
A common misconception is that high blood pressure results in symptoms such as headaches and giddiness. The majority of people who have high blood pressure in fact have no symptoms and are only discovered incidentally when their doctor measures their blood pressure.
There are two components to a blood pressure reading. The higher reading taken when the heart is pumping at its maximum is called systolic and the lower reading taken when the heart is relaxing is called the diastolic. Both readings are important but with increasing age, the systolic number rises and the diastolic number fall.
A systolic level of below 140 and a diastolic level of 90 is considered the cut-off for hypertension and this applies to all age groups. For persons at high risk such as those who have diabetes, a lower cut-off of 130 systolic and 80 diastolic is recommended. This is due to the severe problems that a combination of both diabetes and high blood pressure has on various organs. Even lower blood pressure cut-offs are recommended in certain person groups.
Studies have also shown that risk of illnesses such as strokes, kidney disease and heart disease rises continuously with increasing blood pressure. In fact, a 20 point rise in the systolic blood pressure translates to a 2 times increase risk of these illnesses. Compared to a person with a systolic blood pressure of 115, a person with a level of 135 would be at 2 times, a person with 155 would be 4 times and a person with a level of 175 would be at 8 times higher risk.
Blood pressure is measured in units of mercury. The short form symbol is mmHg.
There are numerous problems with these simple guides on blood pressure levels.
Different people may have different tolerance to blood pressure. Some individuals may be more susceptible to organ damage than others, translating to a need for lower blood pressure. It is therefore important in people with high blood pressure to assess certain organs for the bad effects of an elevated blood pressure. This includes evaluation of the kidneys, heart, blood vessels and eyes.
Blood pressure also varies with activity, stress and the time of day. Some people suffer from white-coat hypertension. These people have normal blood pressure at home but in a doctor’s office they have elevated blood pressure. Conversely, some people have elevated blood pressure at home but borderline or normal blood pressure when seeing their doctors.
Blood pressure should therefore be ideally measured at home as well as during doctor visits. The availability of home blood pressure monitoring sets has now made this possible. We encourage our patients with high blood pressure to purchase these sets and measure at home on a regular basis.
It is important to ensure blood pressure is controlled round the clock.
Among persons with high blood pressure, there are variations in blood pressure during sleep and during the day. People whose blood pressure drop by more than 10% during sleep, often referred to as “dippers” are considered to have a normal response. “Non-dippers” whose blood pressure drops less than 10% during sleep are at higher risk of stroke and heart disease. Some individuals also exhibit a marked change from sleep to waking. Persons whose blood pressure rises more than 55 points on waking are in fact at the highest risk of stroke.
Ideally, 24 hour blood pressure should be considered in the majority of persons who have high blood pressure. Machines that can monitor 24 hour blood pressure are presently available.
Alternatively, home blood pressure sets could be used and blood pressure on waking, prior to the morning medication should be measured. This can be compared to blood pressure taken at other times of the day.
Persons, who have borderline blood pressure, defined as a level of 120 to 139 systolic or 80 to 89 diastolic have a higher risk of developing hypertension as they get older. These persons are often referred to as having “pre-hypertension”.
Women who develop high blood pressure during pregnancy also appear to have increased risk of hypertension later in life. Persons with a strong family history of hypertension are also more pre-disposed to high blood pressure.
We recommend that people who have a pre-disposition to developing hypertension embark on lifestyle changes to lower their blood pressure. This may prevent hypertension or at least delay the onset to hypertension.
Modern medications are effective at controlling blood pressure. The majority of high blood pressure medicines today provide a good 24 hour control of pressure. However, the majority of individuals with hypertension require two or more pills to adequately control their blood pressure. The use of combination medications at lower doses results in good control without adverse side effects.
Lifestyle is also very important in controlling blood pressure. This includes regular exercise, a low salt diet and lots of fruits and fibres. People who are overweight should also aim to lose weight and smokers should stop smoking. Lifestyle alone can sometimes reduce blood pressure by 10 points or more.
Persons with hypertension should be evaluated for the presence of other risk factors. This includes obesity, high cholesterol and diabetes. The combination of hypertension with other risk factors greatly elevates the potential for strokes and heart disease. All risk factors should also be well controlled in people with hypertension.