Hypertension and its causes

What is blood pressure?



Blood pressure is measured in millimeters of mercury (mm Hg). A person's blood pressure varies throughout the day. It changes depending on the time of day and a person's activity and may increase in stressful situations.

What is hypertension?

When blood exerts too much pressure on the inner walls of the blood vessels, this is known as hypertension. Even though the word 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 has a systolic pressure equal to or above 140 mm Hg or a diastolic pressure equal to or above 90 mm Hg on a number of consecutive readings is said to have high blood pressure. Normal blood pressure is less than 120 mm Hg for systolic blood pressure and less than 80 mm Hg for diastolic blood pressure.

Many people who have hypertension are not aware of their condition, and many discover their condition during a routine yearly examination with their doctor.

Causes and classes

In the 95% of cases where the exact cause of hypertension is unknown, it is called essential hypertension or primary hypertension. Lifestyle, environment, and family history of the condition all play a role in these cases.

In the other 5% of cases, the cause can be linked to a medical condition. Reviewing medical and family histories often helps determine the underlying medical problem that led to high blood pressure. Some of the medical conditions that may increase a person's blood pressure include:

  • a previous heart attack
  • a previous stroke
  • hormonal disorders
  • kidney disease

If you have secondary hypertension, the underlying medical condition will be treated first.


Doctors divide hypertension into classes based on the blood pressure reading:

  • pre-hypertension: systolic blood pressure from 120 to 139, diastolic from 80 to 89
  • stage 1: systolic 140 to 159, diastolic 90 to 99
  • stage 2: systolic ≥ 160, diastolic ≥ 100

A diagnosis may be made if either of the numbers, systolic or diastolic, is out of the normal range.


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