In most people, no cause can be identified.
But in about 5% of people with hypertension, the condition can be traced back to underlying diseases such as kidney disorders or conditions that cause narrowing of the arteries of the kidney.
Hypertension is classified based on causes and characteristics. There are two major types of hypertension and five subtypes.
The two major types are:
- Primary or essential hypertension. This has no known cause and is diagnosed in about 95% of people. It has a strong genetic predisposition and is associated with poor lifestyle.
- Secondary hypertension. This is often caused by specific diseases or factors (e.g. kidney damage), and is sometimes curable.
The subtypes include:
- Malignant hypertension. Unless properly treated, this type of hypertension is fatal within five years for the majority of individuals. It occurs particularly in young black men.
- Isolated systolic hypertension. This may occur in older people, and results from the age-related stiffening of the arteries. Treatment is of the utmost importance.
- White coat hypertension. This refers to blood pressure (BP) that is only high when tested by a health professional. Persistent hypertension may develop in time.
- Resistant hypertension. If BP cannot be reduced to below 140/90mmHg, despite a triple-drug regime, resistant hypertension is considered.
- Masked hypertension. This is the opposite of white coat hypertension (i.e. normal BP in the doctor’s office, but an elevated BP elsewhere), and is present in 10% of people with hypertension. Masked hypertension will damage the heart and blood vessels in exactly the same way as in untreated individuals.
Reviewed by Prof Brian Rayner, nephrologist and Director of the Hypertension Clinic, Groote Schuur Hospital. MBChB, FCP, MMed, PhD. May 2018.