What is the epidemiology of secondary hypertension?

Epidemiology of Secondary Hypertension

Secondary hypertension accounts for approximately 5-10% of all hypertension cases in adults, with renovascular hypertension being the most common type, affecting between 0.5% and 5% of the general hypertensive population and up to 25% in elderly dialysis patients. 1, 2

Prevalence of Secondary Hypertension by Cause

• Renovascular hypertension: 0.5-5% of general hypertensive population, up to 25% in elderly dialysis patients 1

  • Atherosclerotic disease (90% of renovascular cases)
  • Fibromuscular dysplasia (10% of renovascular cases)

• Obstructive sleep apnea: Most prevalent secondary cause, present in up to 83% of patients with resistant hypertension 2

• Primary aldosteronism: Approximately 20% of resistant hypertension cases 2

• Other causes (collectively less common):

  • Renal parenchymal disease
  • Pheochromocytoma/paraganglioma
  • Cushing's syndrome
  • Thyroid disorders (hyperthyroidism and hypothyroidism)
  • Hyperparathyroidism
  • Coarctation of the aorta
  • Medication/substance-induced hypertension

Age Distribution

• Young patients (<35 years): Higher likelihood of secondary causes, particularly:

  • Fibromuscular dysplasia
  • Coarctation of the aorta
  • Endocrine disorders 3

• Older patients (>50 years): New-onset hypertension suggests:

  • Atherosclerotic renovascular disease
  • Renal parenchymal disease 3

Clinical Features Associated with Secondary Hypertension

Secondary hypertension should be suspected in patients with:

• Abdominal bruit
• Malignant or accelerated hypertension
• Significant hypertension (diastolic >110 mmHg) in young adults (<35 years)
• New onset after 50 years of age
• Sudden development or worsening of hypertension
• Refractory hypertension requiring multiple medications
• Deterioration of renal function with ACE inhibitors
• Generalized arteriosclerotic occlusive disease 1

Special Populations

• Children: Secondary causes are more common, especially in those younger than 6 years 2
• Resistant hypertension: Higher prevalence of secondary causes, particularly:
  • Obstructive sleep apnea (up to 83%)
  • Primary aldosteronism (approximately 20%) 2
• End-stage renal disease: Renovascular hypertension approaches 25% prevalence in elderly dialysis patients 1

Diagnostic Considerations

The diagnosis of secondary hypertension is important as these forms:

• Require specific treatments based on the underlying pathophysiology
• Are potentially curable or significantly improvable
• May prevent irreversible vascular remodeling if detected early 4, 5

However, despite appropriate therapy or removal of the secondary cause, blood pressure rarely returns to completely normal with long-term follow-up, suggesting either concomitant essential hypertension or irreversible vascular remodeling 4.

Pitfalls and Caveats

• Universal screening for secondary causes is not cost-effective; evaluation should be targeted based on clinical suspicion 5, 6
• Even after successful treatment of the secondary cause, some patients may require ongoing antihypertensive therapy due to residual hypertension 4
• The definition of significant renovascular stenosis varies, with most investigators considering 50-60% stenosis significant, though perfusion pressure generally isn't reduced until stenosis exceeds 70-75% 1

Understanding the epidemiology of secondary hypertension is crucial for appropriate clinical suspicion, targeted evaluation, and effective management of these potentially curable forms of hypertension.