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Hypertension: Causes, Symptoms and Treatments

by on June 25, 2016
 



Hypertension: Causes, Symptoms and Treatments

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MNT Knowledge Center


The number of people living with hypertension (high blood pressure) is predicted to be 1.56 billion worldwide by the year 2025.1

In the US, around 75 million people have hypertension, with more people dying of hypertension-related cardiovascular disease than from the next three deadliest diseases combined.10

In 2011-2012 in the US, about a third of all people over the age of 20 years had hypertension, based on high blood pressure assessments and the number of people taking antihypertensive medications.2

Control of hypertension has become a key national priority in the US as part of the Million Hearts initiative from the Department of Health and Human Services, which aims to prevent 1 million heart attacks
and strokes in the US by 2017.3

The increasing prevalence of the condition is blamed on lifestyle and dietary factors, such as physical inactivity, alcohol and tobacco use, and a diet high in sodium (usually from processed and fatty foods).1

This page offers detailed but easy-to-follow information about hypertension. Should you be interested in the latest scientific research on hypertension, please see our hypertension news section.

Contents of this article:

  1. What is hypertension (high blood pressure)?
  2. Causes and symptoms
  3. Treatments and prevention

You will also see introductions at the end of some sections to any recent developments that have been covered by MNT‘s news stories. Also look out for links to information about related conditions.

Fast facts on hypertension

Here are some key points about hypertension. More detail and supporting information is in the body of this article.

  • Hypertension is defined as blood pressure higher than 140 over 90 mmHg (millimeters of mercury).
  • A diagnosis of hypertension may be made when one or both readings are high: systolic (the pressure as the heart pumps blood around the body), given first; or diastolic (pressure as the heart relaxes and refills with blood), given second.
  • Modern lifestyle factors are responsible for a growing burden of hypertension: physical inactivity, salt-rich diets with processed and fatty foods, and alcohol and tobacco use.
  • High blood pressure can also be secondary to other conditions – kidney disease, for example – and can be associated with some medications.
  • Hypertension itself does not cause symptoms but in the long-term leads to complications caused by narrowing of blood vessels.
  • Doctors diagnose high blood pressure over a number of visits using a sphygmomanometer, which involves applying an inflatable cuff to the upper arm.
  • Lifestyle measures are used first to treat high blood pressure, including salt restriction and other dietary changes, moderation of alcohol, and stress reduction.
  • One or more drugs from a number of different classes may be used for treatment.

What is hypertension (high blood pressure)?

Blood pressure is the force exerted by the blood against the walls of blood vessels, and the magnitude of this force depends on the cardiac output and the resistance of the blood vessels.4

[inside a blood vessel]
The blood flowing inside vessels exerts a force against the walls – this is blood pressure.

More information on the biology and physics of normal blood pressure is available, along with details of how blood pressure is measured, what normal measurements look like, and how they change with age and exercise.

Hypertension is defined as having a blood pressure higher than 140 over 90 mmHg, with a consensus across medical guidelines.1,5

This means the systolic reading (the pressure as the heart pumps blood around the body) is over 140 mmHg (millimeters of mercury) and/or the diastolic reading (as the heart relaxes and refills with blood) is over 90 mmHg.

This threshold has been set to define hypertension for clinical convenience as patients experience benefits once they bring their blood pressure below this level.6

However, medical experts consider high blood pressure as having a continuous relationship to cardiovascular health.1,6 They believe that, to a point, the lower the blood pressure the better (down to levels of 115-110 mmHg systolic, and 75-70 mmHg diastolic).1

They believe that, to a point (down to levels of 115-110 mmHg systolic, and 75-70 mmHg diastolic) the lower the blood pressure the better.1

This view has led the American Heart Association (AHA), for example, to define the following ranges of blood pressure (in mmHg):

  • Normal blood pressure is below 120 systolic and below 80 diastolic
  • Prehypertension is 120-139 systolic or 80-89 diastolic
  • Stage 1 high blood pressure (hypertension) is 140-159 systolic or 90-99 diastolic
  • Stage 2 high blood pressure (hypertension) is 160 or higher systolic or 100 or higher diastolic
  • Hypertensive crisis (a medical emergency) is when blood pressure is above 180 systolic or above 110 diastolic.

On the next page, we look at the causes and symptoms of hypertension and how it is diagnosed. On the final page, we discuss the available treatments for hypertension and how it can be prevented.

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MNT Knowledge Center

(Continued from page 1…)

Causes of hypertension

As acute stress, intense exercise and other factors can briefly elevate blood pressure even in people whose blood pressure is normal, a diagnosis of hypertension requires several readings showing high blood pressure over time. 7

Having high blood pressure for a short amount of time is a normal physiological response to many situations. However, a systolic reading of 180 mmHg or higher OR a diastolic reading of 110 mmHG or higher could be a sign of a hypertensive crisis that warrants immediate medical attention.

Anyone who gets such a reading when testing their own blood pressure should wait a couple of minutes and repeat the test. If the reading remains at that level or increases, seek emergency medical treatment (call an ambulance or have someone drive you to the hospital immediately.

Blood pressure does vary throughout the day, lowering during sleep and rising on awakening. It also rises in response to excitement, anxiety and physical activity.7

Blood pressure also increases steadily with age as arteries become stiffer and narrower due to plaque build-up. Vascular and heart disease also contribute to rising blood pressure in older adults, and a high systolic reading is a major risk factor for cardiovascular disease in adults over 50 years old.

The disease burden of high blood pressure is a growing problem worldwide, in part because of a rapidly aging population. Other key contributors include lifestyle factors, such as:1

  • Physical inactivity
  • A salt-rich diet associated with processed and fatty foods
  • Alcohol and tobacco use.

Certain diseases and medications (as described below) can cause high blood pressure, and there are a number of general risk factors for hypertension, including:7

[abdominal obesity]
Obesity is a risk factor for high blood pressure and other cardiovascular conditions.

  • Age – everyone is at greater risk of high blood pressure as they get older. Prevalence of hypertension is higher in people over 60 years of age
  • Race – African-American adults are at higher risk than white or Hispanic American adults
  • Size – being overweight or obese is a key risk factor for hypertension
  • Sex – males and females have different risk profiles. While lifetime risk is the same for everybody, men are more prone to hypertension at a younger age and women have a higher rate of hypertension at older ages
  • Lifestyle – greater intake of dietary salt, excessive alcohol, low dietary potassium, and physical inactivity all contribute to an increased risk of hypertension.

Other risk factors include a family history of the disease, and chronic, poorly managed stress.7

Specific causes of hypertension

High blood pressure that is not caused by another condition or disease is termed primary hypertension (or essential hypertension). This is more common than secondary hypertension, which has an identified cause such as chronic kidney disease.4

Primary hypertension is unlikely to have a specific cause but is instead usually a result of multiple factors, including blood plasma volume and activity of the renin-angiotensin system, the hormonal regulator of blood volume and pressure. Primary hypertension is also influenced by environmental factors, including lifestyle-related issues as outlined above.4

Secondary hypertension has specific causes – that is, it is secondary to another problem. One example, now thought to be one of the most common causes of treatment-resistant hypertension, is primary aldosteronism, a hormone disorder causing an imbalance between potassium and sodium levels, thus leading to high blood pressure.4

Primary aldosteronism may account for some 5-15% of cases of hypertension. It is important that physicians determine if the condition is caused by hyperplasia of the adrenal gland(s) or an adrenal gland tumor as treatments differ between the two.9

Common reversible causes are excessive intake of alcohol and use of oral contraceptives, which can cause a slight rise in blood pressure; hormone therapy for menopause is also a culprit.7 Secondary hypertension can also result from:4,7

  • Diabetes (both due to kidney problems and nerve damage)
  • Kidney disease
  • Pheochromocytoma (a cancer)
  • Cushing syndrome (which can be caused by use of corticosteroid drugs)
  • Congenital adrenal hyperplasia (disorder of the adrenal glands, which secrete the hormone cortisol)
  • Hyperthyroidism (overactive thyroid gland).
  • Hyperparathyroidism (which affects calcium and phosphorous levels)
  • Pregnancy
  • Sleep apnea
  • Obesity.

Recent developments on causes of hypertension from MNT news

Food container plastics linked to hypertension

Chemicals supposed to be safe replacements for harmful chemicals in plastics are linked to hypertension and insulin resistance, a precursor to diabetes, find scientists from NYU Langone Medical Center in New York City.

Gradual increase in salt intake linked to high blood pressure

Even a small difference in dietary salt consumption among people who do not have hypertension “may result in critical differences in individual blood pressure after several years,” conclude the authors of a Japanese study.

Easily stressed teens have increased hypertension risk later in life

A new study that followed 1.5 million teens through to adulthood investigates the role of early psychological parameters on the likelihood of developing hypertension.

Symptoms of hypertension

High blood pressure itself is usually asymptomatic, meaning that patients do not experience any direct symptoms of the condition. This is why hypertension is often referred to as “the silent killer,” as it can quietly causes damage to the cardiovascular system.4,7

Hypertension can also lead to problems in the organs affected by high blood pressure. Long-term hypertension can cause complications through arteriosclerosis, where the formation of plaques results in narrowing of blood vessels.

The complications associated with hypertension-related arteriosclerosis can include:4,7

  • An enlarged or weakened heart, to a point where it may fail to pump enough blood (heart failure)
  • Aneurysm – an abnormal bulge in the wall of an artery (which can burst, causing severe bleeding and, in some cases, death)
  • Blood vessel narrowing – in the kidneys this can lead to possible kidney failure; in the heart, brain and legs, this can lead to heart attack, stroke or the need for amputation, respectively
  • Blood vessels in the eyes my rupture or bleed, leading to vision problems or blindness (hypertensive retinopathies – classified by worsening grades one through four).

Diagnosis and tests for hypertension

Diagnosis of hypertension is made by measuring blood pressure over a number of clinic visits, using a sphygmomamometer – the familiar upper-arm cuff device. An isolated high reading is not taken as proof of hypertension. Rather, diagnosis can be made after elevated readings are taken on at least three separate days.4

Measurements may be taken at the doctor’s office while a patient is seated and after standing; this helps the doctor to look for orthostatic or postural hypotension.6

[blood pressure reading with sphygmomanometer]
Blood pressure is measured by sphygmomanometry.

The reliability of blood pressure readings may be improved by having a patient or someone else take a series of measurements outside the doctor’s office using standardized devices.6

We have more detailed information about measuring blood pressure.

In addition to measuring blood pressure using sphygmomanometry, a doctor will take a history (ask questions, such as about cardiovascular problems) and do a physical examination before diagnosing hypertension.4

These questions and additional tests can help to identify the cause of high blood pressure and determine whether there have been any complications. Such tests may include urine tests, kidney ultrasound imaging, blood tests, an electrocardiogram (ECG) and/or an echocardiograph.4

On the final page, we look at the available treatments for hypertension and how it can be prevented.

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(Continued from page 2…)

Treatments for hypertension

Lifestyle changes are important for both treatment and prevention of high blood pressure, and they can be as effective as a drug treatment. These lifestyle changes can also have wider benefits for heart health and overall health.6

The lifestyle measures shown to reduce blood pressure and recommended by experts include:6

  • Salt restriction – typical salt intake is between 9 and 12 g a day and modest blood pressure reductions can be achieved even in people with normal levels by lowering salt to around 5 g a day – the greatest effects are seen in people with hypertension
  • Moderation of alcohol consumption – expert guidelines say moving from moderate to excessive drinking is “associated both with raised blood pressure and with an increased risk of stroke”
  • High consumption of vegetables and fruits and low-fat – people with, or at risk of, high blood pressure are advised to minimize intake of saturated fat and total fat and to eat whole-grain, high-fibre foods, at least 300 g of fruit and vegetables a day, beans, pulses, and nuts, and omega-3-rich fish twice a week
  • Reducing weight and maintaining it – hypertension is closely correlated with excess body weight, and weight reduction is followed by a fall in blood pressure
  • Regular physical exercise – guidelines say “hypertensive patients should participate in at least 30 min of moderate-intensity dynamic aerobic exercise (walking, jogging, cycling or swimming) on 5 to 7 days a week”
  • Stress reduction – avoiding sources of stress, where possible, and developing healthy coping strategies for managing unavoidable stress can help with blood pressure control, especially as many people turn to alcohol, drugs, smoking and unhealthy foods or overeating to cope with stress.

Smoking can also raise blood pressure, and because of its wider effects on heart health and the rest of the body, giving up smoking is highly recommended for people with high blood pressure.6

The DASH diet

The US National Heart Lung and Blood Institute recommends the DASH diet for people with high blood pressure.4,8

Standing for Dietary Approaches to Stop Hypertension, DASH has been specially formulated to help people lower blood pressure. It is a flexible and balanced eating plan based on research studies sponsored by the institute, which says the diet:8

  • Lowers high blood pressure
  • Improves levels of blood lipids (fats in the bloodstream)
  • Reduces the risk of developing cardiovascular disease.

There is a National Institute cookbook called Keep the Beat Recipes with cooking ideas to help achieve these results.

There is some evidence that probiotic supplements may be beneficial for people with hypertension. A review of studies found that people taking a multistrain probiotic formula containing at least 10 billion colony-forming units every day for at least 8 weeks had significant decreases in systolic and diastolic blood pressure, with the greatest effects seen in people with hypertension at the beginning of the study.

No significant effects were seen when people took probiotics for less than 8 weeks, however.11

Drug treatments for hypertension

Lifestyle measures are standard first-line treatment for hypertension, although doctors will prescribe medication alongside lifestyle measures to lower blood pressure in people with a level above 140 over 90.4

Drugs are usually started as monotherapy (just one drug) and at a low dose.4 Side-effects associated with antihypertensive drugs are usually minor.7

A number of different classes of drug are available to help lower blood pressure:4,6,7

  • Diuretics (including thiazides, chlorthalidone and indapamide) – a cornerstone of treatment since 1977
  • Beta-blockers (and alpha-blockers)
  • Calcium-channel blockers
  • Central agonists
  • Peripheral adrenergic inhibitors
  • Vasodilators
  • Angiotensin-converting enzyme (ACE) inhibitors
  • Angiotensin receptor blockers.

The choice of drug depends on the individual and any other conditions they may have. While a single drug is usually tried in monotherapy first, a combination of at least two antihypertensive drugs is usually required.6

Anyone taking antihypertensive medications should be sure to carefully read labels before taking any over-the-counter medications such as decongestants as these may interact with medications used to lower blood pressure.

Recent developments on hypertension from MNT news

Folic acid may reduce risk of first stroke in people with hypertension

Folic acid supplementation and hypertension medication combined reduced the risk of a first stroke among adults with high blood pressure.

Acupuncture may reduce high blood pressure

A new study suggests that a form of acupuncture may benefit patients with high blood pressure and lower their risk of stroke and heart disease.

Coffee may harm cardiovascular health for young adults with mild hypertension

Young adults with mild cases of high blood pressure may want to steer clear of coffee, as new research suggests drinking the beverage could increase the risk of cardiovascular events such as heart attacks in this population.

Could yogurt help lower high blood pressure?

Yogurt may have a beneficial effect on women’s blood pressure, especially when part of a healthy diet. This was the conclusion of a study recently presented at the American Heart Association’s (AHA’s) Epidemiology/Lifestyle 2016 Scientific Sessions in Phoenix, AZ.


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