What are the primary causes of hypertension?

Primary Causes of Hypertension

Hypertension is primarily caused by a complex interaction of genetic predisposition and environmental/lifestyle factors, with approximately 90-95% of cases being primary (essential) hypertension and 5-10% being secondary hypertension with identifiable causes. 1, 2

Primary (Essential) Hypertension

Genetic Factors

• Hypertension is a complex polygenic disorder where many genes or gene combinations influence blood pressure 1
• Family history of hypertension is a strong predictor 1
• Genetic variants account for approximately 3.5% of blood pressure variability 1
• High number of small-effect alleles associated with higher blood pressure results in more rapid increase in blood pressure with age 1

Environmental and Lifestyle Factors

Overweight and Obesity

• Strong and almost linear relationship between body mass index and blood pressure with no evidence of threshold 1
• Obesity at a young age increases future risk of hypertension (relative risk of 2.7) 1
• Weight loss can significantly reduce blood pressure in overweight/obese individuals 1

Dietary Factors

• Excess sodium intake: Positively associated with blood pressure in multiple studies 1
• Salt sensitivity: More common in blacks, older adults, and those with comorbidities like CKD, diabetes, or metabolic syndrome 1
• Insufficient potassium intake: Dietary potassium supplementation is recommended unless contraindicated 1
• Poor diet: Insufficient intake of calcium, magnesium, protein (especially from vegetables), fiber, and fish fats 1

Physical Activity

• Sedentary lifestyle contributes to hypertension 2
• Increased physical activity with structured exercise programs can reduce blood pressure 1

Alcohol Consumption

• Strong direct relationship between alcohol consumption and blood pressure, especially above 3 standard drinks per day 1
• Reduction in alcohol intake can significantly lower blood pressure in those consuming ≥3 drinks/day 1

Other Lifestyle Factors

• Psychosocial stress 2
• Smoking 1
• Poor sleep quality 2

Secondary Hypertension (5-10% of cases)

Common Causes

1. Renal Parenchymal Disease

   • Chronic kidney disease
   • Polycystic kidney disease

2. Renovascular Disease

   • Atherosclerotic renal artery stenosis
   • Fibromuscular dysplasia

3. Endocrine Disorders

   • Primary aldosteronism
   • Pheochromocytoma
   • Cushing's syndrome
   • Thyroid disorders (hyperthyroidism)
   • Hyperparathyroidism

4. Obstructive Sleep Apnea

   • Characterized by snoring and hypersomnolence 1

5. Medication-Induced

   • NSAIDs
   • Oral contraceptives
   • Steroids
   • Decongestants
   • Erythropoietin
   • Cyclosporine
   • Cocaine and amphetamines 1, 2

6. Coarctation of the Aorta

   • Congenital narrowing of the aorta 1

Clinical Clues for Secondary Hypertension

• BP lability, episodic pallor and dizziness (pheochromocytoma)
• Snoring, hypersomnolence (obstructive sleep apnea)
• Muscle cramps, weakness (hypokalemia from primary aldosteronism)
• Weight loss, palpitations, heat intolerance (hyperthyroidism)
• Edema, fatigue, frequent urination (kidney disease)
• Central obesity, facial rounding, easy bruisability (Cushing's syndrome)
• Absence of family history of hypertension 1

Pathophysiological Mechanisms

Hypertension results from dysregulation of multiple systems:

1. Renal mechanisms:

   • Impaired sodium excretion
   • Altered pressure natriuresis

2. Vascular mechanisms:

   • Endothelial dysfunction
   • Increased peripheral vascular resistance
   • Vascular remodeling and fibrosis 1

3. Neurohormonal mechanisms:

   • Overactivity of sympathetic nervous system
   • Dysregulation of renin-angiotensin-aldosterone system

4. Immune mechanisms:

   • Inflammation
   • Oxidative stress 1

Clinical Implications

Understanding the primary causes of hypertension helps guide appropriate management:

• For primary hypertension: Lifestyle modifications (weight reduction, DASH diet, sodium restriction, physical activity, alcohol moderation) and appropriate pharmacotherapy
• For secondary hypertension: Treating the underlying cause while maintaining blood pressure control

Early detection and treatment are crucial to prevent hypertension-mediated organ damage and reduce cardiovascular risk 2.