Causes of High Blood Pressure
What causes high
blood pressure?
Blood pressure is the measure of the
force of blood pushing against blood vessel walls. The heart pumps blood into
the arteries (blood vessels), which carry the blood throughout the body. High
blood pressure, also called hypertension, is dangerous because it makes the
heart work harder to pump blood to the body and contributes to hardening of the
arteries, or atherosclerosis, and to the development of heart failure.
What Is
"Normal" Blood Pressure?
A blood pressure reading has a top
number (systolic) and bottom number (diastolic). The ranges are:
·
Normal: Less than 120 over 80 (120/80)
·
Prehypertension: 120-139 over 80-89
·
Stage 1 high blood pressure: 140-159 over
90-99
·
Stage 2 high blood pressure: 160 and above
over 100 and above
·
High blood pressure in people over age 60: 150 and above over
90 and above
People whose blood pressure is above
the normal range should consult their doctor about steps to take to lower it.
What Causes High
Blood Pressure?
The exact causes of high blood
pressure are not known, but several factors and conditions may play a role in
its development, including:
·
Smoking
·
Being overweight or obese
·
Lack of physical activity
·
Too much salt in the diet
·
Too much alcohol consumption (more than 1 to 2 drinks per day)
·
Stress
·
Older age
·
Genetics
·
Family history of high blood pressure
·
Chronic kidney disease
·
Adrenal and thyroid disorders
Types of high blood pressure
Essential Hypertension
In as many as 95% of reported high
blood pressure cases in the U.S., the underlying cause cannot be determined.
This type of high blood pressure is called essential hypertension.
Though essential hypertension remains
somewhat mysterious, it has been linked to certain risk factors. High blood
pressure tends to run in families and is more likely to affect men than women.
Age and race also play a role. In the United States, blacks are twice as likely
as whites to have high blood pressure, although the gap begins to narrow around
age 44. After age 65, black women have the highest incidence of high blood
pressure.
Essential hypertension is also
greatly influenced by diet and lifestyle. The link between salt and high blood
pressure is especially compelling. People living on the northern islands of
Japan eat more salt per capita than anyone else in the world and have the
highest incidence of essential hypertension. By contrast, people who add no
salt to their food show virtually no traces of essential hypertension.
The majority of all people with high
blood pressure are "salt sensitive," meaning that anything more than
the minimal bodily need for salt is too much for them and increases their blood
pressure. Other factors that can raise the risk of having essential
hypertension include obesity; diabetes; stress; insufficient intake of
potassium, calcium, and magnesium; lack of physical activity; and chronic
alcohol consumption.
Secondary Hypertension
When a direct cause for high blood
pressure can be identified, the condition is described as secondary
hypertension. Among the known causes of secondary hypertension, kidney disease
ranks highest. Hypertension can also be triggered by tumors or other
abnormalities that cause the adrenal glands (small glands that sit atop the
kidneys) to secrete excess amounts of the hormones that elevate blood pressure.
Birth control pills -- specifically those containing estrogen -- and pregnancy
can boost blood pressure, as can medications that constrict blood vessels.
Who Is More Likely to Develop High Blood Pressure?
·
People with family members who have high blood pressure
·
Smokers
·
African-Americans
·
Pregnant women
·
Women who take birth control pills
·
People over the age of 35
·
People who are overweight or obese
·
People who are not active
·
People who drink alcohol excessively
·
People who eat too many fatty foods or foods with too much salt
·
People who have sleep apnea
Symptoms of high blood pressure
Most people with high blood pressure don't have any
symptoms, so you may only find out you have high blood pressure by having it
checked.
If you have very high blood pressure, or your blood pressure
rises quickly, you may have headaches, problems with your vision, fits or
black-outs – but this is very uncommon.
Complications of high blood pressure
If you have high blood pressure, you have an increased risk
of major illnesses including:
·
cardiovascular disease, such as
angina (chest pain caused by reduced blood flow),stroke, heart attack, heart failure or atrial fibrillation (irregular heart beat)
·
kidney damage
·
damaged sight
Causes of high blood pressure
Depending on the cause, high blood pressure can be diagnosed as
primary or secondary hypertension.
Primary hypertension
About 95 in 100 people with high blood pressure have primary
hypertension. This means there is no single cause, but various lifestyle
factors can contribute, including:
·
smoking
·
obesity (being very overweight)
·
drinking alcohol excessively – especially if you binge drink
·
lack of exercise
·
your diet, particularly salt intake
If someone else in your family has high blood pressure, you also
have a higher risk of developing it.
Secondary
hypertension
About five in 100 people with high blood pressure have secondary
hypertension. This means there is a known underlying cause – examples include:
·
kidney disease
·
endocrine disease (hormone disorders)
·
a narrowing of part of your aorta (the largest artery leading from
your heart) or the arteries leading to your kidneys
Secondary hypertension can also be caused by:
·
steroid medicines
·
the contraceptive pill
·
pregnancy, which can lead to pre-eclampsia – this can be serious and
harm your baby
Diagnosis of high blood pressure
Your GP may diagnose you with high blood pressure when he
or she measures it as part of a medical examination. This is a good reason to
have regular check-ups with your GP, especially if you're over 40.
Your GP or nurse will measure your blood pressure with a
sphygmomanometer. He or she will place a cuff around your upper arm, inflate it
to a certain level and then deflate it slowly. Your blood pressure is measured
in mmHg, or millimeters of mercury. The blood pressure monitor will provide a
reading as two numbers, one number on top of the other, such as 120/80mmHg (one
hundred and twenty over eighty millimeters of mercury).
·
The first figure is called systolic
blood pressure. This is a measure of the pressure when your heart muscle is
contracted and pumping blood out of your heart. This is the highest pressure in
your blood vessels.
·
The second figure is called
diastolic blood pressure. This is the pressure between heart beats when your
heart is resting and filling with blood. This is the lowest pressure in your
blood vessels.
Generally speaking, the lower your blood pressure, the
better it is for your health. For people under the age of 80, doctors recommend
your blood pressure is kept below 140/90 measured in the clinic, or 135/85
measured at home. A slightly higher level is acceptable for people over 80. If
you have diabetes, kidney disease or cardiovascular disease, your blood
pressure should be lower than this – ideally less than 130/80.
Your GP may ask you to come back for repeat measurements
over a number of weeks and arrange a 24-hour blood pressure recording before
suggesting you have treatment. This is so he or she can check that the high
reading is an ongoing problem and not a one-off.
You may also need some tests to see if high blood pressure
is affecting the rest of your body. These may include:
·
a urine test – protein in your
urine may be the first sign of damage to your kidneys
·
a blood test to check your
cholesterol and blood sugar levels, as well as the condition of your kidneys
·
an electrocardiogram (ECG) – a test that measures
the electrical activity of your heart to check for signs of heart enlargement
or other damage
Monitoring
If you have a high blood pressure reading, you may be given
24-hour ambulatory blood pressure monitoring (ABPM). This is because some
people have a high reading when they see a doctor, but normal blood pressure at
other times (so-called ‘white coat hypertension’). A monitoring device is
strapped around your waist and attached to a cuff, which is wrapped around your
upper arm. The cuff inflates and deflates automatically and takes recordings of
your blood pressure throughout the 24 hours. You can carry on with your usual
activities whilst wearing the monitor, except for having a bath or shower. Your
GP will use the measurements to find out your average blood pressure.
In some cases, another form of home blood pressure monitoring
(HBPM) may be used to confirm your diagnosis. Your GP may provide a blood
pressure monitor for you to record your blood pressure twice a day at home, in
the morning and evening, for four to seven days.
You might also
consider getting a blood pressure monitor to use yourself at home on a regular
basis. This can help you identify situations or activities in your daily life
that cause your blood pressure to rise. And if you’re having treatment for
blood pressure, it may also help you to see how your treatment is working. Even
if you use a blood pressure monitor at home, you should continue to have your
blood pressure tested regularly by your GP.
Treatment of high
blood pressure
If you need treatment, it’s likely to be long-term as high blood
pressure can’t usually be cured. You may need to go to hospital for treatment
if you have very high blood pressure, but it's more likely that your GP and/or
a nurse will look after you.
Self-help
Your GP or nurse will talk to you about lifestyle changes that
might help, such as:
·
stopping smoking
·
changing your diet to be low-fat, low-salt and that includes fruit
and vegetables
·
cutting down on alcohol
·
cutting down on coffee and high-caffeine drinks, such as cola
·
taking regular, aerobic exercise
·
losing any excess weight
It may also help, where possible, to reduce stress in your life
to prevent short-term rises in blood pressure – you could try relaxation
techniques or meditation.
Medicines
If your blood pressure stays high, your GP may prescribe you one
or more of the following antihypertensive medicines.
·
ACE inhibitors (eg ramipril) or angiotensin-II receptor antagonists (eg
candesartan) – these relax and widen the walls of your blood vessels by
reducing the production of hormones that cause your blood vessels to constrict
(narrow).
·
Calcium-channel blockers (eg amlodipine) – these
help to widen your blood vessels by relaxing the muscles in your blood vessel
walls.
·
Diuretics (eg indapamide) – these increase the amount of water and
salt removed from your blood by your kidneys, lowering the volume of your
blood, which reduces blood pressure.
If your symptoms don’t improve, then your GP may prescribe one
of the following.
·
Beta-blockers (eg atenolol) – these reduce the work your heart has to do
by reducing your pulse rate and the force of contraction of your heart at rest
and when you exercise.
·
Alpha-blockers (eg doxazosin) – these help to widen your blood
vessels by relaxing the muscles in your blood vessel walls.
The medicines your GP prescribes will depend on a number of
factors, including your age and ethnicity. It may take time to find the best
treatment for you; one that balances the benefits against any side-effects.
It's important to
take your medicines every day, even if you don't have any symptoms.
Special
considerations
Pregnancy
If you're pregnant, your blood pressure will be monitored
regularly, regardless of whether you have high blood pressure or not. Long-term
high blood pressure may be picked up at an antenatal appointment. It's also
possible that you may develop high blood pressure during your pregnancy
(gestational hypertension). High blood pressure that develops after 20 weeks of
pregnancy can mean you have pre-eclampsia.
If you have high blood pressure and think you may be, or are
trying to become pregnant, it's important to speak to your GP. Certain
medicines for treating high blood pressure aren't suitable for pregnant women.
Ethnic groups
If you're of African-Caribbean origin, you're at a higher risk
of high blood pressure and should visit your GP to discuss how often you need
to have your blood pressure checked.
You should also be
monitored regularly if you're of South-Asian origin because you have a higher
risk of developing heart disease and diabetes.
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