Can Hypertension (HTN) cause Sleep Apnea?

Can Hypertension Cause Sleep Apnea?

No, hypertension does not cause sleep apnea, but rather obstructive sleep apnea (OSA) is a recognized cause of secondary hypertension. 1 The relationship between these conditions is primarily in the opposite direction, with OSA being a risk factor for developing hypertension and contributing to treatment resistance in hypertensive patients.

Relationship Between Hypertension and Sleep Apnea

Directionality of the Relationship

• OSA is a common secondary cause of hypertension, particularly resistant hypertension 1
• OSA is highly prevalent (≥80%) in adults with resistant hypertension 1
• Observational studies have shown that the presence of OSA is associated with increased risk of incident hypertension 1
• The Sleep Heart Health Study and Wisconsin Sleep Cohort Study found that OSA is a risk factor for hypertension 1

Mechanisms by Which OSA Causes Hypertension

1. Sympathetic Nervous System Activation:

   • Intermittent hypoxemia and increased upper airway resistance in OSA induce sustained increases in sympathetic nervous system activity 1
   • Frequent intermittent sympathetic stimulation may lead to resistant hypertension 2

2. Renin-Angiotensin-Aldosterone System (RAAS) Activation:

   • OSA activates the RAAS, which contributes to hypertension development 1
   • Angiotensin II promotes fibrosis and inflammation, contributing to vascular remodeling 1

3. Oxidative Stress and Inflammation:

   • OSA has been associated with increases in reactive oxygen species and reductions in nitric oxide bioavailability 1
   • Pro-inflammatory cytokines contribute to atherosclerotic consequences 3

Clinical Implications

Prevalence and Recognition

• OSA is listed as a common secondary cause of resistant hypertension in guidelines 1
• About 50% of sleep apnea patients are hypertensive 1
• About 30% of hypertensive patients also have sleep apnea 1
• Hypertensive patients with untreated OSA are more likely to have uncontrolled blood pressure despite medication 2

Blood Pressure Patterns in OSA

• Patients with OSA often show a non-dipping blood pressure profile (lack of normal nocturnal BP reduction) 3
• Higher diastolic blood pressure is common in these patients 3
• OSA episodes produce surges in systolic and diastolic pressure that keep mean blood pressure levels elevated at night 4

Treatment Effects

• Treatment of OSA with continuous positive airway pressure (CPAP) may lower pulmonary artery pressures when the degree of pulmonary hypertension is mild 1
• CPAP treatment has modest beneficial effects on daytime blood pressure (2-3 mmHg reductions) 1
• CPAP treatment for six months can reduce blood pressure and improve cardiovascular risk markers in patients with resistant hypertension and OSA 5
• The effectiveness of CPAP to reduce blood pressure is not well established according to current guidelines (Class IIb recommendation) 1

Clinical Approach to Patients with Hypertension

Screening for OSA

• Screening for OSA is an essential element of evaluating patients with hypertension, particularly resistant hypertension 4
• Clinical findings suggesting OSA include:
  • History of loud snoring
  • Poor quality or restless sleep
  • Excessive daytime sleepiness 1
  • Obesity and recent weight gain (though not necessary for OSA to be present) 1

Management Considerations

• For patients with both hypertension and OSA:
  • The optimal way of controlling hypertension is to treat the underlying OSA and associated obesity 3
  • CPAP is the primary treatment for OSA, though its effects on BP reduction are modest 1
  • Antihypertensive therapy alone is less effective in patients with untreated OSA 3

Conclusion

The evidence clearly shows that OSA contributes to the development and maintenance of hypertension, rather than hypertension causing OSA. Clinicians should consider screening for OSA in patients with hypertension, especially those with resistant hypertension, as treating the underlying sleep disorder may improve blood pressure control and reduce cardiovascular risk.