Hypertension, or high blood pressure, is a long-term condition where blood pressure in the arteries remains persistently elevated. Blood pressure is the force of blood pushing against artery walls. It depends on heart function and the resistance of blood vessels.
Normal resting BP is around 100–120 mmHg systolic and 70–80 mmHg diastolic. If the pressure stays high over time, it increases the risk of heart attack, stroke, kidney failure and other serious disorders.
AHA 2017 Blood Pressure Classification
| Category | Systolic | Diastolic |
|---|---|---|
| Normal | <120 | <80 |
| Elevated | 120–129 | <80 |
| Stage 1 Hypertension | 130–139 | 80–89 |
| Stage 2 Hypertension | ≥140 | ≥90 |
| Hypertensive Crisis | >180 | >120 |
Types of Hypertension
a) Primary (Essential) Hypertension
This is the most common type (90–95% of cases). It has no single identifiable cause. It develops gradually due to a combination of factors such as:
- High salt intake
- Obesity
- Alcohol use
- Smoking
- Genetic susceptibility
b) Secondary Hypertension
Occurs due to an identifiable underlying disorder and usually appears suddenly. Causes include:
- Kidney disease
- Obstructive sleep apnea
- Adrenal gland tumours
- Thyroid disorders
- Congenital blood vessel abnormalities
- Medications like birth-control pills
Symptoms
Hypertension is often called the “silent killer” because many people have no symptoms. When symptoms occur, they may include:
- Headache
- Dizziness
- Shortness of breath
- Blurred vision
- Pounding sensation in head or neck
- Nausea
Causes
Hypertension is multifactorial. Several combined factors lead to high pressure:
- High salt intake: common in elderly, obese or kidney patients.
- Genetics: having hypertensive parents doubles the risk.
- Increased resistance in small arteries: due to stiffness or narrowing.
Risk Factors
- Age: risk increases as people grow older.
- Race: more common and severe in people of African origin.
- Overweight: more body mass → more blood supply needed → increased pressure.
- Physical inactivity: increases heart workload and promotes weight gain.
- Tobacco use: damages artery walls and raises BP temporarily.
- High sodium intake: causes fluid retention.
- Low potassium intake: leads to sodium accumulation.
- Alcohol: heavy drinking weakens the heart.
- Stress: triggers temporary BP rise and unhealthy coping habits.
- Chronic diseases: kidney disease, diabetes, sleep apnea, etc.
Pathophysiology
Most essential hypertension is due to increased peripheral resistance while cardiac output stays normal.
- Early hypertension: some younger patients show high cardiac output with normal resistance (hyperkinetic state). Over time, cardiac output falls and resistance rises.
- Established hypertension: small arteries and arterioles become narrowed due to structural changes.
- Elderly patients: isolated systolic hypertension is due to stiffened arteries, causing wide pulse pressure.
Key contributing mechanisms:
- Kidney dysfunction: abnormal handling of salt and water.
- Overactive sympathetic nervous system.
- Endothelial dysfunction and inflammation: involving cytokines like IL-17, TNF-α, IL-1, IL-6 and IL-8.
- High sodium / low potassium intake: increases intracellular sodium, causing vascular smooth muscle contraction.
Complications
Long-standing hypertension damages blood vessels and major organs.
- Heart attack and stroke: due to atherosclerosis.
- Aneurysm: vessel wall weakening and bulging.
- Heart failure: from thickened heart muscle (left ventricular hypertrophy).
- Kidney damage: reduced filtration and chronic kidney disease.
- Eye damage: retinopathy causing vision impairment.
- Metabolic syndrome: cluster of obesity, high insulin, high triglycerides and low HDL.
- Cognitive decline: memory and learning difficulties.
- Dementia: reduced blood flow to the brain.
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