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Increased Dietary Sodium Is Related to Severity of Obstructive Sleep Apnea in Patients With Resistant Hypertension and Hyperaldosteronism
Study Questions:
Can urinary sodium levels predict severity of obstructive sleep apnea (OSA) in patients with resistant hypertension?
Methods:
Patients with resistant hypertension were prospectively evaluated by overnight polysomnography and 24-hour urinary sodium and aldosterone levels while maintaining their usual diet. Mild, moderate, and severe OSA were defined as an apnea-hypopnea index (AHI) of 5-14, 15-29, and ≥30 events/hour, respectively. Resistant hypertension was defined as uncontrolled hypertension (>140/90 mm Hg) determined at two or more clinic visits despite the use of three or more antihypertensive medications at pharmacologically effective doses. Hyperaldosteronism was defined as a plasma renin activity of <1 ng/ml/h and urinary aldosterone level of ≥12 µg/24 h. Secondary causes of hypertension other than hyperaldosteronism, such as renovascular hypertension, pheochromocytoma, or Cushing syndrome, were excluded by laboratory analysis and radiologic imaging as clinically indicated. Patients with a history of atherosclerotic disease (myocardial infarction or stroke in <6 months), congestive heart failure, current smoking, or diabetes treated with insulin were excluded from study participation.
Results:
In total, 97 patients with resistant hypertension were evaluated. Overall, 47.4% were men, 48.5% were black, the mean age was 55.2 ± 9.0 years, and the mean office blood pressure was 156.3 ± 22.4/88.9 ± 13.3 mm Hg. Patients took an average of 4.3 ± 1.1 antihypertensive medications, which included angiotensin-converting enzyme inhibitors (61.2%), angiotensin-receptor blockers (57.3%), calcium channel blockers (76.7%), beta-blockers (77.7%), and diuretics (91.3%). Overall, the prevalence of OSA was 77.3%. Prevalence of mild, moderate, and severe OSA was 37.1%, 24.7%, and 15.5%, respectively. Twenty-eight patients (28.9%) had hyperaldosteronism. Body mass index (BMI) showed no correlation among patients with or without hyperaldosteronism. Age, sex, BMI, neck circumference, urinary sodium level, and systolic and diastolic blood pressure were similar between patients with and patients without hyperaldosteronism. Multiple regression analysis showed no significant relationship between AHI and any of the covariates among the entire population. Urinary sodium level was an independent predictor of severity of OSA only in patients with hyperaldosteronism.
Conclusions:
The authors concluded that dietary salt is related to the severity of OSA in patients with resistant hypertension and hyperaldosteronism. The results support dietary salt restriction as a treatment strategy for reduction of OSA severity in these patients.
Perspective:
Before concluding that high dietary sodium causes more severe OSA, further studies restricting sodium in patients with resistant hypertension and hyperaldosteronism are needed.
Keywords: Angiotensin Receptor Antagonists, Hyperaldosteronism, Sodium, Dietary, Renin, Diuretics, Blood Pressure, Hypertension, Calcium Channel Blockers, Sleep Apnea, Obstructive
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