Blood pressure is often mentioned when talking about maintaining our overall health and to prevent the development of diseases, but what is blood pressure?
It refers to the amount of force applied to the walls of our blood vessel which each beat of our heart. Typically, a healthy blood pressure should be close to 120/80 mmHG but it varies from person to person depending on a variety of factors including:
- Age
- Fitness levels (e.g. professional athletes)
- Existing medial conditions
Therefore, it is important to know what your usual blood pressure is so you can recognise when it is too high or too low for you.
How does our blood pressure change?
The amount of pressure in your blood changes frequently throughout the day depending on your position (laying down or standing up), hydration, stress levels (both emotional stress and physical stress including exercise), some medications and consuming stimulants such as caffeine.
Our body has a number of natural processes which aim to keep our blood pressure as close to normal throughout the day when our environment changes. These are:
- Vasoconstriction and vasodilation: if our body detects that our BP is too high it sends signals to our blood vessels to relax (vasodilation), causing them to widen and reducing the pressure. Similarly, when our BP is too low our blood vessels narrow (vasoconstriction) to increase the pressure inside the vessels.
- Our kidneys influence blood pressure by managing our salt and water levels. When our BP is too high, our kidneys filter out more salt into the urine. Due to a process called osmosis, water will follow the salt and is excreted from the body through urination. This reduces the amount of blood inside our vessels (blood volume) which reduces our BP. If our BP is too low, the kidneys hold onto more salt and water than normal, increasing our volume of blood which increases our blood pressure.
In addition, fainting can occur when you’re experiencing low blood pressure. This occurs when there is a lack of oxygen supply to the brain as the pressure is not strong enough for adequate circulation around the body. Fainting enable to body to increase BP by reducing the effects of gravity – making it easier for blood to flow towards your brain.
What is abnormal?
High BP is called hypertension – it usually refers to BP above 130/90 or a reading above your normal levels.
When this happens you may have severe headaches or feel dizzy and as it progresses you may experience chest pain, vision changes, and shortness of breath.
Low BP is called hypotension – it usually refers to BP below 110/70 or a reading below your normal levels.
When this happens you may feel light-headed, dizziness, weakness, blurred vision and you may faint.
What happens when your BP is consistently too high?
When there is high pressure in our arteries over a long period of time it can cause stress to our heart and blood vessels as they work twice as hard and less blood is being circulated.
This can lead to:
- Heart failure
- Heart attack
- Stroke
- Kidney disease or failure
- Vision loss
- Sexual dysfunction
Are more people at risk of hypertension than others?
You are more likely to experience high BP if you:
- Are over 64 years old
- Smoke or drink alcohol
- Sit for long periods of time
- Are dehydrated
- Have depression, anxiety or emotional stress
- Are overweight
- Eat poorly (including a high sugar diet)
- Have other health conditions such as type 2 diabetes or high cholesterol levels
- Have a family history of hypertension or cardiovascular disease
How can we maintain a healthy blood pressure?
- Avoiding smoking and limit drinking
- Minimise your salt intake
- Stay hydrated
- Eat a balanced diet with a variety of vegetables, fruits, wholegrain and protein
- Get regular physical activity – aim for at least 30 minutes a day
- Visit your GP for regular check ups
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Sources:
American Heart Association. What is high blood pressure? https://www.heart.org/en/health-topics/high-blood-pressure/the-facts-about-high-blood-pressure/what-is-high-blood-pressure
Better Health Channel. Blood pressure. https://www.betterhealth.vic.gov.au/health/conditionsandtreatments/blood-pressure
Better Health Channel. Fainting. https://www.betterhealth.vic.gov.au/health/conditionsandtreatments/fainting#
Shahoud, J.S., Sanvictores, T., & Aeddula, N.R. 2023. Physiology, arterial pressure regulation. StatPearls.