What is high blood pressure?
In a bicycle tire, air pressing against the inner wall of the tire keeps it inflated. Depending on how much air is in the tire, it is either full of air and ready to roll, or too low and looking “flat.” In the body, blood pressure works the same way. Blood pressure is the force of blood pressing against the inner walls of blood vessels. Just like air in a bike tire, the force of the blood inside a blood vessel determines the blood pressure.
To measure a person’s blood pressure, doctors take several readings using a blood pressure cuff (also called a sphygmomanometer). Blood pressure is expressed as 2 numbers and is often read as one number “over” another (e.g., “120 over 70”). These 2 numbers represent the pressure inside the blood vessels when the heart contracts (systolic – top number) and when the heart is relaxed (diastolic – bottom number).
Blood pressure is measured in millimetres of mercury (mm Hg). A person’s blood pressure varies throughout the day. It changes depending on the time of day and the person’s activity and may increase in stressful situations.
What is high blood pressure?
When blood exerts too much pressure on the inner walls of the blood vessels (the arteries and veins), this is known as high blood pressure or hypertension. Even though the word hypertension contains “tension,” this is not strictly a disease of anxious people, although high stress levels over a prolonged period of time can influence the level of blood pressure. A person who does not have certain conditions such as diabetes is said to have high blood pressure if they have a number of consecutive readings with a systolic pressure equal to or above 140 mm Hg or a diastolic pressure equal to or above 90 mm Hg (i.e., 140/90 mm Hg) as measured by a doctor (or higher than 135/85 mm Hg when measured at home). Normal blood pressure is between 120 mmHg and 129 mm Hg for systolic blood pressure and between 80 mmHg and 84 mm Hg for diastolic blood pressure. If you have diabetes with or without kidney disease, high blood pressure is anything at or above 130/80 mm Hg.
About 20% of Canadians who have hypertension are not aware of their condition. Many people with high blood pressure discover their condition during a routine yearly examination with their doctor.
Risk factors and causes of high blood pressure
For 85% to 95% of people with high blood pressure, the exact cause is unknown and there are usually multiple factors contributing; this is called essential hypertension or primary hypertension. For the other 5% to 10% of people, the cause can be linked to an underlying medical condition or medication. This is called secondary hypertension.
Reviewing medical and family histories often helps determine the underlying medical problem that led to high blood pressure. Some of causes of secondary high blood pressure include:
- Cushing’s disease
- hormonal disorders
- kidney disease
- medications such as hormonal contraceptives or corticosteroids
If you have secondary hypertension, the underlying cause will be managed first.
For essential hypertension, several factors increase the risk of high blood pressure. Some of the factors that you cannot control and that increase your risk are:
- Age: The risk of developing hypertension increases with age. If you’re over 55 years of age, you have a 90% chance of developing hypertension sometime in your life.
- Ethnicity: People of South Asian, First Nations, or African heritage have greater rates of high blood pressure.
- Family history: There is a higher chance of developing high blood pressure if your parents had the condition.
Other risk factors for high blood pressure are things that you can change and include:
- Unhealthy eating: Eating a high-fat or high-salt diet can increase the risk of getting high blood pressure.
- Alcohol intake: Drinking too much alcohol increases blood pressure.
- Inactive lifestyle: Lack of physical activity decreases the rate at which the body burns calories. This type of lifestyle can lead to weight gain which is a risk factor for high blood pressure as well as other medical conditions such as diabetes.
- Obesity: Excess fat, especially around the midsection, can increase your risk of developing high blood pressure. It is also a risk factor for developing type 2 diabetes and other conditions.
- Smoking: This habit can lead to an increase in blood pressure in some people. Smoking is associated with atherosclerosis, which narrows the arteries and forces the heart to pump harder to move blood.
High blood pressure symptoms and diagnosis
Most often, people with high blood pressure have no symptoms. This is why high blood pressure is often called a “silent killer.” Complications related to untreated hypertension can have serious effects such as stroke and heart attack, and could possibly lead to death.
Headaches, dizziness, and nosebleeds can sometimes be reported if the blood pressure is very high, but are very rare symptoms.
When measuring blood pressure, it is recommended that at least 2 readings separated by a few minutes be taken. If a raised blood pressure reading is discovered at a check-up, your doctor will usually ask for you to come back for a follow-up in a month to confirm whether you should take medication to treat it. It is very important to keep these follow-up appointments.
If you have a systolic pressure equal to or above 140 mm Hg or a diastolic pressure equal to or above 90 mm Hg as measured by a doctor (or higher than 135/85 when measured at home) on a number of consecutive readings, you have high blood pressure. Normal blood pressure is between 120 mm Hg and 129 mm Hg for systolic blood pressure and between 80 mm Hg and 84 mm Hg for diastolic blood pressure. If you have diabetes, high blood pressure is anything at or above 130/80 mm Hg.
How can I prevent high blood pressure?
You can help prevent high blood pressure by having a healthy lifestyle. This means
- Eating a healthy diet. To help manage your blood pressure, you should limit the amount of sodium (salt) that you eat, and increase the amount of potassium in your diet. It is also important to eat foods that are lower in fat, as well as plenty of fruits, vegetables, and whole grains. The DASH diet is an example of an eating plan that can help you to lower your blood pressure.
- Getting regular exercise. Exercise can help you maintain a healthy weight and lower your blood pressure. You should try to get moderate-intensity aerobic exercise at least 2 and a half hours per week, or vigorous-intensity aerobic exercise for 1 hour and 15 minutes per week. Aerobic exercise, such as brisk walking, is any exercise in which your heart beats harder and you use more oxygen than usual.
- Being at a healthy weight. Being overweight or having obesity increases your risk for high blood pressure. Maintaining a healthy weight can help you control high blood pressure and reduce your risk for other health problems.
- Limiting alcohol. Drinking too much alcohol can raise your blood pressure. It also adds extra calories, which may cause weight gain. Men should have no more than two drinks per day, and women only one.
- Not smoking. Cigarette smoking raises your blood pressure and puts you at higher risk for heart attack and stroke. If you do not smoke, do not start. If you do smoke, talk to your health care provider for help in finding the best way for you to quit.
- Managing stress. Learning how to relax and manage stress can improve your emotional and physical health and lower high blood pressure. Stress management techniques include exercising, listening to music, focusing on something calm or peaceful, and meditating.
If you already have high blood pressure, it is important to prevent it from getting worse or causing complications. You should get regular medical care and follow your prescribed treatment plan. Your plan will include healthy lifestyle habit recommendations and possibly medicines.