Arteries & circulation
Hypertension
What is hypertension?
Hypertension, also known as high blood pressure, is a very common condition. Globally, an average of one-third of all adults are affected by it.
If you have hypertension, the pressure of the blood being pumped out from the left side of your heart, through your arteries and into your body, is consistently too high. This puts a strain on your heart and your blood vessels, and long-term it can increase your risk of heart and kidney disease, stroke, and even dementia.
Hypertension is famously referred to as a “silent killer” because it usually has no symptoms, and you probably won’t know you have it unless you have a medical check-up.
Normal blood pressure and hypertension
How is hypertension defined?
When your healthcare provider checks your blood pressure, the reading is shown as two numbers:
- The first (higher) number is your systolic pressure. This is the pressure of your blood against your artery walls when your heart contracts to pump blood out into your body. Normal systolic pressure is 120 mmHg or less.
- The second (lower) number is your diastolic pressure. This is the pressure on your artery walls when your heart is relaxed and refilling. Normal diastolic pressure is 80 mmHg or less. Ideally, it should be around 70 mmHg.
Your blood pressure reading is expressed as systolic pressure/diastolic pressure, and a normal level is 120/80 mmHg or less. (“mmHg” stands for “millimeters of mercury” and is a standard unit of measurement for pressure.)
Definitions of normal and high blood pressure have changed in recent years, but most experts now agree that a systolic reading that is consistently above 130 mmHg paired with a diastolic reading that is consistently above 80 mmHg is problematic.
Blood pressure levels
Normal
Systolic: less than 120 mmHg
Diastolic: less than 80 mmHg
Elevated
Systolic: 120-129 mmHg
Diastolic: less than 80 mmHg
High
Systolic: 130 mmHg or higher
Diastolic: 80 mmHg or higher
The chart above shows how normal blood pressure, elevated blood pressure, and high blood pressure are defined.
Your risk of developing hypertension increases with age, although children and teenagers in developed nations like the US, which also have high rates of obesity and other lifestyle challenges, have been increasing for the past 20 years.
Why is hypertension a problem?
Hypertension is a serious health problem even though you can have it and experience no symptoms.
Long-term hypertension can damage your heart, your eyes, and your kidneys, and it can put you at risk of having a stroke or developing vascular dementia (this is a kind of dementia caused by multiple small broken blood vessels in your brain). All of these things are bad news.
The increased pressure of blood in your arteries can directly damage the artery walls, causing scarring and weakness. It is this weakening of the artery walls that increases your risk of having a stroke or developing vascular dementia. It also increases your risk of having an aneurysm.
Finally, artery-wall scarring can cause atherosclerosis by encouraging the build-up of plaque, a substance made of cholesterol, fat, and calcium that can coat the inside of your arteries.
Plaque deposits restrict the flow of blood in your arteries and, if they rupture, the fragments can cause a blockage that might result in a heart attack or a stroke.
For more information about atherosclerosis and plaque, take a look at our Atherosclerosis section.
Atherosclerotic plaque in an artery
A study published in 2010 estimated that hypertension had contributed to nearly 20% of all deaths that year. Globally, that equated to a total of 9.4 million people.
What causes hypertension?
Some people are genetically predisposed to developing hypertension – it can run in families, and race can be a factor.
In the US, Black Americans are more likely to have high blood pressure than White Americans, and Hispanic and East Asian Americans are less likely.
Globally, people of South Asian origin (Indians, Pakistanis, and Bangladeshis) have a higher than average risk of developing hypertension.
No one is quite sure what genetic factors cause these racial differences.
Most of the time, however, hypertension develops as the result of lifestyle choices. Diet and exercise habits play a big part; if you are overweight, you drink too much, and you don’t exercise, you are likely to have high blood pressure. Smoking and vaping can also be a factor.
Hypertension that is caused by lifestyle or genetic predisposition is called primary hypertension. Ninety percent or more of all cases of hypertension are primary.
Hypertension caused by other health disorders or by medications is called secondary hypertension.
Primary hypertension
Hypertension that develops as a result of age, weight, family history, or lifestyle is called primary hypertension.
Often, if you have primary hypertension, there will be more than one cause. You may smoke and also be overweight, or drink too much and not get any exercise. Risks like these stack up, and once you add age into the mix, high blood pressure becomes more and more likely.
Common causes of primary hypertension include:
- Age: Being over 60 years old is a risk factor
- Being overweight
- Diabetes or prediabetes (metabolic syndrome)
- Smoking
- Lack of exercise
- Drinking too much alcohol
- Excessive stress
- Sleep apnea
- Genetic predisposition
- Illicit drugs like cocaine and methamphetamine
Secondary hypertension
Hypertension can also be caused by certain medications, including birth control pills and anti-inflammatory drugs, and by other diseases, especially kidney diseases. This kind of hypertension is known as secondary hypertension.
Common causes of secondary hypertension include:
- Certain medications, such as birth control pills
- Kidney and renal artery diseases
- Sleep apnea
- Adrenal gland disorders
- Thyroid disorders
- Rarely, a kind of tumor that secretes adrenaline
What are the symptoms of hypertension?
Hypertension, famously, has no symptoms until it reaches crisis levels (above about 180/100 mmHg). If you have hypertension, you almost certainly won’t know it unless your doctor checks your blood pressure and tells you.
Disorders like hypertension illustrate the importance of having regular medical check-ups. Caught early and managed effectively, your hypertension can be brought under control and you can avoid the unpleasant long-term health effects of untreated disease.
How is hypertension treated?
Treatment options for high blood pressure depend on its severity and on whether you have primary or secondary hypertension.
If you have primary hypertension, your doctor will recommend lifestyle changes and will probably also prescribe medication for you. If you have secondary hypertension, he or she will first want to treat the underlying cause.
Treatment options for primary hypertension:
- Lifestyle changes: Your doctor may recommend that you lose weight, exercise more, eat less salt, and drink less alcohol
- Medication: If lifestyle changes don’t bring your blood pressure down to the normal range again, your doctor will prescribe medication
Treatment options for secondary hypertension:
- Treating the disorder that is causing your hypertension (for example kidney disease or hyperthyroidism)
- Switching or stopping any medications that may raising your blood pressure
What are the aims of treatment?
The aims of treatment for both primary and secondary hypertension are to lower your blood pressure and bring it as close as possible to normal (120/80 mmHg or less).
If this can be achieved, it will significantly lower your risk of stroke, atherosclerosis, hypertension-related heart, kidney, and eye diseases, and vascular dementia.