Abnormally elevated blood pressure (hypertension) should not be taken lightly. Sustained hypertension (HT) in both children and adults can cause significant injuries to numerous organs, among which are the cardiovascular system (heart and major arteries), brain, and kidneys. Life span with hypertension is also reduced. Since HT does not usually cause symptoms, it may remain unrecognized until a blood pressure is taken. This is why HT has been called the “silent killer.” Decades of research show that hypertension, alone, can underlie many serious conditions. There also are more complex interactions of hypertension with heart disease, high cholesterol, obesity, smoking, genetics, thyroid disease, and diabetes, among others.
The measurement of blood pressure
Blood pressure (BP) levels are determined in several ways. By far, most are measured with a BPcuff (sphygmomanometer). You are doubtlessly familiar with the common BP cuff placed around the upper arm along with a stethoscope or other listening device used to detect blood flow sounds below the cuff. The cuff is first inflated and then deflated slowly.
First described in the early 1900s, several sounds can be detected from blood flowing through underlying arteries. The point at which blood flow can first be heard estimates the maximum pressure from the heart during contraction and is called the systolic BP.
When the heart is at rest and refilling between beats, the sounds become muffled or disappear. This is the diastolic BP.
Most people are familiar with the recording of two numbers separated by a slash in their medical records (e.g. 128/85). The first number is the systolic pressure and the second the diastolic pressure. Both of these pressures play important roles in health and disease.
What blood pressures are abnormal?
Numerous large research studies have measured the blood pressures of healthy individuals in order to define normal BP levels. Further, abnormal BP ranges have been developed and correlated to risk.
These ranges of BPs in adults are:
Table 1: Ranges for normal and abnormal blood pressure in adults.
|Category||Systolic BP*||Diastolic BP*|
|Elevated (a.k.a. pre-hypertension)||120-129||and||<80|
|Stage 1||130-139||or||80 to 89|
*Blood pressure values are expressed as millimeters of mercury (mmHg), the conventional measurement standard.
Despite these guidelines, it is important to realize that there is no clear BP threshold for risk.
Those individuals with elevated but not hypertensive blood pressures have an increased chance of stroke and cardiovascular disease compared to those with normal blood pressure.
Also, long-term studies have shown that stroke risk incrementally increases as blood pressure increases, even within the normal range. This is a strong argument for optimizing blood pressure control, when possible, as opposed to just “making it better.”
What can cause hypertension?
Conditions that increase the likelihood of HT are numerous. Well-recognized risk factors may be “non-modifiable” or “modifiable” conditions. Non-modifiable factors are those that cannot be changed. These include age, gender, race, and a family history of elevated blood pressures.
- Age. Normal blood pressure ranges for children are lower than those in adults. As we become older, HT develops more frequently. As arteries stiffen with aging, the heart must generate higher pressures to overcome the increased resistance to blood flow.
- Gender. Men before age 55, and post-menopausal women have a greater chance of developing HT.
- Family history. HT in family members increases the risk of developing HT.
- Race. Baseline BP in African Americans is significantly higher than in Whites. Should normal blood pressure guidelines be higher in African Americans? No. Given the significant incidence of heart disease and stroke in this population, elevated BP should be managed with the goal of reducing baseline blood pressures to well within normal ranges.
By contrast, measures that can reduce blood pressure are called “modifiable” risks. Even modest BP reductions show measurable effects on the risks of stroke and cardiovascular disease.
Frequently prescribed measures to manage blood pressure include:
- Weight loss. Overweight and obesity are highly associated with hypertension, and weight loss can lead to substantial BP reduction. The heart must raise blood pressure in order to circulate oxygenated blood to a larger volume of blood vessels. However, the underlying processes for this relationship are complex, and include alterations in the functions of certain hormones, the nervous system, and metabolic disturbances.
- Healthy dietary changes. Dietary changes to directly reduce blood pressure have been advocated for many years. For those with HT, diet, alone, may not sufficiently lower blood pressure into normal ranges. It often is more effective when combined with other treatments. For instance, there is evidence showing that by combining diet and exercise, BP reduction is greater than either, separately. More frequently prescribed diets include the DASH (Dietary Approaches to Stop Hypertension) and Mediterranean diets. While there are some differences, both diets emphasize fruits and vegetables, whole grains, nuts, and unsaturated oils. In both diets, eating red and processed meats is discouraged and alcohol consumption should be minimized or eliminated. Decreased dietary salt (sodium) and increased potassium both are shown to favorably affect BP.
- Exercise programs. While it may seem odd that cardio exercise can reduce rather than increase BP, it is a fact that regular aerobic exercises can result in a sustained improvement of HT. Examples of aerobic exercises include walking, jogging, and stationary bicycles. Around two to two-and-a-half hours per week is an initial goal unless other health conditions limit activity. In controlled studies, the BP reduction was significant for both systolic and diastolic pressures.
- Smoking cessation. Most studies demonstrate that hypertensive individuals will have a reduction in BP after quitting. Smoking independently increases the risk of cardiovascular disease and stroke. Around 50% of hypertensive individuals have a small but significant decrease in both systolic and diastolic BP after smoking cessation.
- Treatment of sleep apnea. Obstructive sleep apnea is seen in 30% to 40% of patients with hypertension while in the general population the frequency is 4% to 7%. Multiple mechanisms are likely the source of this association, with an important role played by the characteristic nighttime decreases of blood oxygen when sleep apnea is treated.
Medications. If BP cannot be controlled with the lifestyle changes described above, medications are usually prescribed. There are numerous classes of anti-hypertensive drugs that provide flexibility in treatment. The general classes of the more commonly prescribed medications include:
- Diuretics. These drugs cause your kidneys to remove excess water and salt, thereby reducing the volume and hence pressure of blood in your blood vessels.
- Angiotensin-converting enzyme inhibitors (ACE inhibitors) and angiotensin II receptor blockers (ARBs). Both of these types of medications impair the actions of angiotensin II which constricts arteries. As a result, blood vesselsrelax, thereby reducing BP.
- Calcium channel blockers. This group medications also cause BPs to relax by altering the amount of calcium entering cells that line the inside of arteries.
- Beta-blockers. These medications act on BPprincipally by reducing heart rate and the force of blood ejected from the heart during contraction.
A systolic BP of <120 and diastolic pressure of <80 are healthy target ranges.
Hypertension is a serious condition that can increase the risks of heart disease, stroke, kidney injury and shortened lifespan.
The presence of hypertension is often asymptomatic, emphasizing the need for periodic blood pressure measurements, especially when there are associated risk factors.
The success of HT management depends heavily on an individual’s commitment to a partnership with the medical team.
Health providers can evaluate and recommend weight loss, lifestyle, diet modifications, medications, and home monitoring, but without diligently following the treatment program, effectiveness is not guaranteed.
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