By Barbara Phillips, MD, MSPH
Professor of Medicine, University of Kentucky; Director, Sleep Disorders Center, Samaritan Hospital, Lexington
Dr. Phillips reports no financial relationships relevant to this field of study.
SYNOPSIS: In patients with obstructive sleep apnea and hypertension, continuous positive airway pressure use was associated with clinically and statistically significant reductions in blood pressure for both resistant and non-resistant hypertension.
SOURCE: Walia HK, Griffith SD, Foldvary-Schaefer N, et al. Longitudinal effect of CPAP on BP in resistant and nonresistant hypertension in a large clinic-based cohort. Chest 2016;146:747-755.
Over the past decade, the prevalence of drug-resistant hypertension has risen sharply, while the prevalence of hypertension has remained stable.1 Drug-resistant hypertension is defined as blood pressure that remains above 140/90 mmHg despite simultaneous use of three classes of antihypertensive agents, or blood pressure that requires at least four medications to control. Walia et al speculated that the increased prevalence of sleep-disordered breathing could be contributing to the rising prevalence of drug-resistant hypertension. The authors decided to leverage their large clinical sleep apnea population and electronic records to test the hypotheses that continuous positive airway pressure (CPAP) use in obstructive sleep apnea (OSA) will reduce blood pressure significantly both in resistant and non-resistant hypertension, but the effect will be more pronounced in resistant hypertension. They also speculated that neck circumference will more accurately predict the risk of resistant hypertension than body mass index (BMI).
Researchers undertook electronic medical record data extraction for adult outpatients in the Cleveland Clinic Sleep center over three and a half-year period. Hypertension and OSA diagnoses were based on physician diagnoses. CPAP use was self-reported. Patients with the most common causes of secondary hypertension (chronic renal disease, primary hyperaldosteronism, Cushing syndrome, renal artery stenosis) were excluded. Authors collected baseline demographic and clinical data as well as sleep study data and data on antihypertensive use.
They analyzed data from 894 patients with hypertension and OSA, 15% of whom had resistant hypertension. The mean age and BMI were significantly higher in the resistant hypertension group (P = 0.02 and P = 0.007, respectively). There were no statistically significant differences between resistant and non-resistant groups in terms of sex or race. The mean arterial pressure and systolic pressure at baseline were higher in the resistant group, but there was no difference in diastolic blood pressure between groups.
In the year following CPAP initiation, there were significant decreases in systolic (3.08 mmHg), diastolic (2.28 mmHg), and mean (2.54 mmHg) arterial pressures. Patients with resistant hypertension exhibited higher blood pressures overall, both before and after CPAP initiation There was no differential effect of CPAP on blood pressure between the resistant and nonresistant groups.
In secondary analyses, Walia et al found that neck circumference predicted blood pressure fall with CPAP better than did BMI, and that Apnea plus Hypopnea Index (AHI) predicted blood pressure; each one-unit increase in AHI was associated with incremental increases in blood pressure. Patients who reported CPAP adherence had greater improvement in blood pressure than the entire cohort.
COMMENTARY
This paper should lead to changes in the management of hypertension, especially drug-resistant hypertension, which is notoriously difficult to control. In this large “real-world” clinical sample, Walia et al found statistically and clinically significant improvements in blood pressure within a year of CPAP initiation, regardless of whether the hypertension was resistant, in an intention-to-treat model.
These blood pressure changes are enough to affect important outcomes. Even modest reductions in blood pressure of 2-3 mmHg can reduce coronary artery disease by 4-5% and stroke by 6-8%.2
CPAP adherence is somewhat predictable and is actually no worse than adherence to most treatments for chronic diseases. For example, as many as one-third of patients presenting with “drug-resistant hypertension” are actually nonadherent with antihypertensive medications.3 Sicker, symptomatic (e.g., sleepy) OSA patients are more likely to adhere to CPAP.4 Additionally, patients suffering from more severe sleep apnea exhibit higher blood pressure. This leads to speculation that patients with drug-resistant hypertension and severe OSA may be more likely to adhere to CPAP than to their medication, since CPAP makes them feel better (CPAP reliably reduces sleepiness) and the medications may not. Consider the possibility of OSA as part of the workup of hypertension, especially drug-resistant hypertension.
REFERENCES
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Calhoun DA, Jones D, Textor S, et al. American Heart Association Professional Education Committee. Resistant hypertension: Diagnosis, evaluation, and treatment: A scientific statement from the American Heart Association Professional Education Committee of the Council for High Blood Pressure Research. Circulation 2008;117:e510-e526.
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Chobanian AV, Bakris GL, Black HR, et al; Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure. National Heart, Lung, and Blood Institute; National High Blood Pressure Education Program Coordinating Committee. Seventh report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure. Hypertension 2003;42:1206-1252.
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Calhoun DA. Apparent and true resistant hypertension: Why not the same? J Am Soc Hypertens 2013;7:509-511.
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Sawyer AM, Gooneratne NS, Marcus CL, et al. A systematic review of CPAP adherence across age groups: Clinical and empiric insights for developing CPAP adherence interventions. Sleep Med Rev 2011;15:343-356.
