Can Untreated Sleep Apnea Lead to Hypertension?
Yes, untreated obstructive sleep apnea is an established independent risk factor for developing hypertension, with observational studies demonstrating increased risk of incident hypertension in patients with OSA. 1
Evidence for the Causal Relationship
The 2017 ACC/AHA Hypertension Guidelines explicitly recognize that obstructive sleep apnea is a risk factor for hypertension, along with other cardiovascular diseases including coronary and cerebrovascular diseases, heart failure, and atrial fibrillation. 1
The American Academy of Sleep Medicine recognizes sleep apnea as an independent risk factor for hypertension, which is associated with difficult-to-control blood pressure. 2
Key Epidemiologic Findings:
Observational studies have shown that the presence of obstructive sleep apnea is associated with increased risk of incident hypertension. 1
Obstructive sleep apnea is highly prevalent in adults with resistant hypertension (≥80%). 1
The American Journal of Respiratory and Critical Care Medicine reports that uncontrolled sleep apnea can cause hypertension, often difficult to control and resistant to treatment. 3
Pathophysiologic Mechanisms
OSA induces sustained increases in sympathetic nervous system activity through intermittent hypoxemia and increased upper airway resistance, which raises blood pressure through increased cardiac output, peripheral resistance, and fluid retention. 4
The distinctive pattern of intermittent hypoxia seen in OSA increases sympathetic tone, oxidative stress, inflammation, and endothelial dysfunction—all of which can lead to persistent elevation of blood pressure beyond the obstructive events themselves. 5
Clinical Characteristics of OSA-Related Hypertension
OSA-related hypertension is characterized by resistant hypertension, nocturnal hypertension, abnormal blood pressure variability, and vascular remodeling. 6
The American College of Cardiology recommends considering OSA as a common secondary cause of resistant hypertension, with more severe sleep apnea correlating with worse blood pressure control. 4
Cardiovascular Consequences Beyond Hypertension
Severe untreated sleep apnea is associated with a 3-fold increased risk of fatal cardiovascular events (adjusted OR 2.87; 95% CI, 1.17-7.51). 2
Additional cardiovascular risks include:
- Increased risk of coronary artery disease 2, 3
- Development and worsening of congestive heart failure 3
- Cardiac arrhythmias including atrial fibrillation 3
- Stroke risk with an odds ratio of 2.24 (95% CI, 1.57-3.19) 2, 3
Clinical Implications for Screening
The American Academy of Sleep Medicine recommends considering sleep apnea in patients with difficult-to-control hypertension, coronary artery disease, heart failure, arrhythmias, history of stroke or TIA, and type 2 diabetes. 2
OSA should be considered as part of the workup of patients with hypertension, particularly those with resistant hypertension where the prevalence approaches 80%. 5, 6
Treatment Effects on Blood Pressure
While CPAP is the primary treatment for OSA, studies of the effects of CPAP on BP have demonstrated only small effects on BP (e.g., 2-3 mm Hg reductions), with results dependent on patient compliance with CPAP use, severity of obstructive sleep apnea, and presence of daytime sleepiness. 1
However, CPAP treatment significantly reduces cardiovascular risk in sleep apnea patients, with a reduced risk of vascular events (adjusted HR of 0.34; 95% CI, 0.20-0.58). 2
Important Caveat:
The effectiveness of continuous positive airway pressure (CPAP) to reduce BP in adults with hypertension and obstructive sleep apnea is not well established (Class IIb recommendation, Level of Evidence B-R). 1 A well-designed RCT demonstrated that CPAP plus usual care, compared with usual care alone, did not prevent cardiovascular events in patients with moderate-severe obstructive sleep apnea and established CVD. 1
Pharmacological Management
Pharmacological treatment remains important for achieving optimal BP control in OSA patients, as CPAP alone provides only modest BP reduction. 7
Antihypertensive medications targeting sympathetic pathways or the renin-angiotensin-aldosterone system have theoretical potential:
- Beta-blockers are effective due to the acute and chronic increase in sympathetic nerve activity in OSA patients 7
- ACE inhibitors and ARBs are generally effective for lowering BP in hypertensive patients with OSA 7
- Spironolactone produces good antihypertensive response in patients with OSA and resistant hypertension 7