Causes of High Blood Pressure
Hypertension results from two main categories: primary (essential) hypertension accounting for approximately 90% of cases with multifactorial origins, and secondary hypertension representing 10% with identifiable underlying causes. 1, 2
Primary (Essential) Hypertension
Primary hypertension develops through complex interactions between genetic predisposition, environmental factors, and behavioral influences, though the exact cause remains unknown. 1, 2
Modifiable Lifestyle Factors
Obesity is the single most important modifiable cause, responsible for 40% of all hypertension cases and up to 78% in men and 65% in women. 1, 2 The relationship between body mass index and blood pressure is continuous and almost linear with no threshold. 1, 2
Dietary sodium excess is positively associated with blood pressure and accounts for much of the age-related increase in blood pressure. 1, 2 Excessive sodium consumption is independently associated with increased risk of stroke and cardiovascular disease beyond its blood pressure effects. 1, 2
Additional dietary factors include insufficient intake of potassium, calcium, magnesium, protein, fiber, and fish fats. 1, 2
Excessive alcohol intake (≥3 standard drinks per day) shows a strong, direct relationship with blood pressure elevation. 2 Current guidelines recommend men limit consumption to no more than 2 standard drinks per day and women to 1 standard drink per day. 3
Physical inactivity and prolonged sedentary lifestyles combined with caloric intake exceeding energy expenditure lead to steep rises in blood pressure, particularly systolic, with advancing age. 4
Genetic Factors
Genetic variants collectively account for only about 3.5% of blood pressure variability, despite hypertension being a complex polygenic disorder. 1, 2 Family history of hypertension is a characteristic feature suggesting primary hypertension. 3, 1
Pathophysiological Mechanisms
- Overactivation of the renin-angiotensin-aldosterone system (RAAS) contributes to development and maintenance of hypertension 2
- Endothelial dysfunction impairs normal vascular regulation 2
- Dysregulation of renal sodium handling and pressure natriuresis plays a fundamental role 2
- Increased peripheral vascular resistance, vascular remodeling, and fibrosis with inflammation perpetuate elevated blood pressure 2
Secondary Hypertension
Secondary hypertension accounts for approximately 10% of cases overall, but increases to 10-35% in resistant hypertension populations and up to 20-40% in patients presenting with malignant hypertension. 2, 4
Renal Causes
Chronic kidney disease and renal parenchymal disease are the most common secondary causes of hypertension. 1, 2 The most common parenchymal kidney diseases include chronic glomerulonephritis, polycystic kidney disease, and hypertensive nephrosclerosis. 2
Renal artery stenosis should be suspected with onset of hypertension before age 30 or after age 55, presence of abdominal bruit, accelerated hypertension, and recurrent flash pulmonary edema. 2
Endocrine Causes
Primary aldosteronism presents with unprovoked hypokalemia, muscle cramps, and weakness. 3, 1, 2
Pheochromocytoma causes blood pressure lability, episodic pallor, dizziness, headache, palpitations, and perspiration. 3, 1, 2
Cushing's syndrome presents with central obesity, facial rounding, easy bruisability, truncal obesity, glucose intolerance, and purple striae. 3, 1, 2
Hyperthyroidism causes weight loss, palpitations, and heat intolerance. 3, 1, 2
Obstructive Sleep Apnea
Obstructive sleep apnea presents with snoring and hypersomnolence and requires continuous positive airway pressure therapy to improve blood pressure control. 1, 2
Drug-Induced Hypertension
Medications and substances that elevate blood pressure include: 3, 1, 2
- Nonsteroidal anti-inflammatory drugs (NSAIDs)
- Cocaine
- Amphetamines
- Corticosteroids
- Calcineurin inhibitors
- Alcohol
Vascular Causes
Aortic coarctation is characterized by decreased pressure in lower extremities or delayed/absent femoral arterial pulses. 2
Clinical Approach to Identifying the Cause
Features Suggesting Primary Hypertension
- Gradual increase in blood pressure with slow rate of rise 3, 1, 2
- Lifestyle factors favoring higher blood pressure (weight gain, high-sodium diet, decreased physical activity, excessive alcohol consumption) 3, 1
- Strong family history of hypertension 3, 1
Features Suggesting Secondary Hypertension
- Absence of family history of hypertension 3, 1
- Sudden onset or worsening of hypertension 3, 1
- Young age (any hypertension <20 years; needing treatment <30 years) 3
- Resistant to multidrug regimen (≥3 drugs) 3
- Elevated serum creatinine 3
- Proteinuria or hematuria 3
- Hypokalaemia with increased or high normal plasma sodium 3
Common pitfall: Poor compliance or adherence to drug treatment or lifestyle changes is the most common cause of resistant hypertension and should be evaluated before extensive workup for secondary causes. 4