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What Causes High Blood Pressure

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What causes high blood pressure (hypertension)?  This is a common question, especially by patients who are affected by high blood pressure. Unfortunately, the answer is not always definitive.

A doctor can diagnose someone with hypertension, by testing their blood pressure, but determining the exact cause is not always straight forward.

In fact, there are no definite or known causes of high blood pressure in approximately 90% of patients who have been diagnosed with this condition.  This is known as essential hypertension.

In the other 10% of patients, the cause can be directly linked to some other medical condition such as kidney disease, obesity and blockage of arteries of the kidneys.  Hypertension that can be directly linked to some other condition is known as secondary hypertension.

Although in the majority of cases the exact hypertension causes are unknown, there are steps that can be taken to avoid and/ or minimize the risk of secondary hypertension.  Many causes can be treated and are, in fact, avoidable.  Simple dietary and lifestyle adjustments can go a long way in helping to keep blood pressure within normal ranges.


The dangers of hypertension can be easily overlooked, since it exhibits little to no symptoms.  With this condition, the heart is often or always working harder than normal and the arteries are narrowed and constricted.

Not only is hypertension one of the major underlying causes of kidney failure, but it is also a symptom of kidney failure.  High blood pressure causes enormous stress on the kidneys, which can eventually lead to kidney failure.  Since one of the crucial functions of the kidneys is to regulate blood pressure, high blood pressure can be a sign that the kidneys are not functioning as they should.

Common Causes High Blood Pressure

Hypertension is considered to be a chronic resting blood pressure that is consistently high (above 140/90 mmHg).  Many factors contribute to hypertension.  Although the exact causes of essential hypertension are unknown, there appears to be a genetic link, since it tends to run in families.  Some known and common causes of hypertension include the following:

  • Narrowed arteries. Arteries may become narrow for a number of reasons. These include plaque build-up, fibrosis (formation of thickened connective tissue or scar tissue), endothelial dysfunction (dysfunction of the inner walls of the arteries), or in response to your endocrine or nervous systems. When your arteries are narrow, your heart has to work harder to push the blood through them.


  • Obesity or being overweight causes high blood pressure. Within the last decade or so, obesity has become a major health issue, plaguing developed western societies.

    Excess fat is a major risk factor and one of the prime causes of high blood pressure. Fat is tissue, just like muscles or organs. Tissue requires a constant blood supply and therefore, has a lot of blood vessels. It is estimated that one pound of fat contains about one mile of capillaries. That requires a lot of extra blood and a lot of extra pipes to pump the blood through. This increases the load on the heart, requiring it to work much harder to pump blood around the body, and causes high blood pressure. In many cases, just losing ten to twenty pounds can bring blood pressure down to normal levels.


  • High cholesterol and sodium diet. With the fast pace and demands of modern society, many people turn to fast foods and microwave dishes as their main sources of meals. Although these dishes are convenient and tasty, they are not always the most healthy or nutritious. They are loaded with cholesterols and sodium. This is a major contributor to obesity and possibly one of the leading hypertension causes.

    Cholesterols contribute to the buildup of plaque in the arteries... causing them to become narrow. As outlined above, narrowed arteries cause the heart to work harder to pump the blood through them and are considered among the leading causes of high blood pressure and heart failure.

    Sodium draws water from the kidneys back into the body, causing fluid retention. Excess sodium can also lead to increases in blood pressure by increasing blood volume... leading to enlargement of the heart, protein in the urine, kidney disease, and strokes.


  • Smoking. The dangers of smoking have been highlighted in the media and many other forums. Apart from the risk of cancer and other diseases that can be caused by smoking, it also causes high blood pressure.

    Smoking cigarettes causes high blood pressure by increasing tension in the walls of the heart muscle and speeding the rate of muscular contraction. It crowds out oxygen with carbon dioxide... decreasing oxygen per unit of blood. This means that someone who smokes will need more blood to deliver the same amount of oxygen around the body. This forces the heart to work harder to deliver enough oxygen to the tissues... leading to high blood pressure.


  • Constant emotional stress (and psychological factors) also causes high blood pressure. Anxiety, excitement, fear, anger, and other forms of stress require your body to respond with the "fight or flight" mechanism. The burst of adrenaline races to your major organs, increasing your heart rate, blood cholesterol, and blood pressure.

    Occasional emotional responses to stress, fear, anger... may not have a long-term effect on blood pressure. However, regular and consistent emotional and psychological stress can adversely affect blood pressure and health. People who display aggressive, hostile, or cynical behaviors tend to have increased heart rates and higher cardiac output, resulting in high blood pressure.


  • Hormonal dysfunction also causes high blood pressure. Several substances such as renin, angiotensin, endothelin, and many others play important roles in complex systems that regulate the cardiac output. When these regulators are not working properly, the blood volume increases, creating more work for the heart, and increases blood pressure.


  • Blood clot and thick blood. While blood clots are probably not considered as one of the leading causes of high blood pressure, they should be noted. Plaque build-up in some arteries can sometimes cause blood platelets to get stuck on protruding pieces of plaque, forming a blood clot (thrombus). Or the plaque itself can rupture, releasing clotting substances that instantly cause formation of a blood clot. Blood clots can severely limit the flow of blood through an artery or even block it completely... resulting in high blood pressure, heart attack and stroke.

    Similarly, having thick blood also causes hypertension. The thickness of the blood is an important factor that determines resistance and blood pressure. Thick blood, like sludge, moves more slowly through blood vessels, requiring more force to send it along.

There are other causes of hypertension, such as pregnancy and physical stress, but these are usually temporary.  Additionally, there are medical conditions that can cause secondary hypertension.  Examples of such conditions include Cushing's syndrome (a metabolic disorder resulting in excessive production of the steroid hormone cortisol), Hyperparathyroidism (too much parathyroid hormone), Thyroid disease, Sleep apnea (temporary stoppage of breathing during sleep), and Kidney disease.

Fortunately, most causes of high blood pressure can be treated either naturally or with medication.  Once the underlying causes are corrected and a healthy lifestyle is adopted, blood pressure tends to return to normal levels.  Whether a secondary or a hereditary condition causes high blood pressure, early diagnosis and treatment supervised by a competent medical practitioner are essential for effectively minimizing the damages and risks of hypertension.

Blood pressure is determined by three main factors - "blood volume" or cardiac output, the "resistance offered by the blood vessels", and the "thickness (viscosity) of the blood".

The cardiac output or blood volume is known as the systolic blood pressure, or the force (pressure) exerted when the heart contracts.  The resistance of the blood vessels as blood is pumped through them is known as the diastolic blood pressure.  This is the pressures exerted when the heart is resting between beats.

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