Blood pressure is the force exerted by the blood against the walls of blood vessels, and the magnitude of this force depends on the cardiac output and the resistance of the blood vessels.
Hypertension is defined as having a blood pressure higher than 140 over 90 mmHg, with a consensus across medical guidelines.This means the systolic reading (the pressure as the heart pumps blood around the body) is over 140 mmHg (millimeters of mercury) and/or the diastolic reading (as the heart relaxes and refills with blood) is over 90 mmHg.
- Normal blood pressure is below 120 systolic and below 80 diastolic
- Prehypertension is 120-139 systolic or 80-89 diastolic
- Stage 1 high blood pressure (hypertension) is 140-159 systolic or 90-99 diastolic
- Stage 2 high blood pressure (hypertension) is 160 or higher systolic or 100 or higher diastolic
- Hypertensive crisis (a medical emergency) is when blood pressure is above 180 systolic or above 110 diastolic.
Causes of hypertension
Blood pressure does vary throughout the day, lowering during sleep and rising on awakening. It also rises in response to excitement, anxiety and physical activity.Blood pressure also increases steadily with age as arteries become stiffer and narrower due to plaque build-up. Vascular and heart disease also contribute to rising blood pressure in older adults, and a high systolic reading is a major risk factor for cardiovascular disease in adults over 50 years old.High blood pressure that is not caused by another condition or disease is termed primary hypertension (or essential hypertension). This is more common than secondary hypertension, which has an identified cause such as chronic kidney disease.The disease burden of high blood pressure is a growing problem worldwide, in part because of a rapidly aging population. Other key contributors include lifestyle factors, such as:- Physical inactivity
- A salt-rich diet associated with processed and fatty foods
- Alcohol and tobacco use.
- Lifestyle - greater intake of dietary salt, excessive alcohol, low dietary potassium, and physical inactivity all contribute to an increased risk of hypertension.
Other risk factors include a family history of the disease, and chronic, poorly managed stress.
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