Chest
Volume 132, Issue 6, December 2007, Pages 1858-1862
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Original Research
Sleep Medicine
Obstructive Sleep Apnea and Resistant Hypertension: A Case-Control Study

https://doi.org/10.1378/chest.07-1170Get rights and content

Background

Obstructive sleep apnea syndrome (OSAS) has been linked to resistant hypertension, but the magnitude of this association and its independence of confounding have not been established.

Methods

Case patients were 63 patients with resistant hypertension (BP ≥ 140/90 mm Hg using at least three BP-lowering drugs, including a diuretic), and control subjects were 63 patients with controlled BP receiving drug treatment. The primary outcome was the frequency of OSAS (apnea-hypopnea index [AHI] ≥ 10 episodes per hour) determined with a portable home monitor. The comparison of AHI episodes in patients truly normotensive, truly hypertensive, and in patients with white coat or masked hypertension, based on BP determined at office and by ambulatory BP monitoring (ABPM) was a secondary outcome.

Results

Case patients and control subjects were well matched for confounding factors. OSAS was present in 45 case patients (71%) and in 24 control subjects (38%) [p < 0.001]. In a logistic regression model, OSAS was strongly and independently associated with resistant hypertension (odds ratio, 4.8; 95% confidence interval, 2.0 to 11.7). The AHI of case patients with normal BP in ABPM (white coat hypertension) and control subjects with abnormal BP in ABPM (masked hypertension) was intermediate between the AHI of individuals with normal and abnormal BP measures in both settings (p < 0.001).

Conclusions

The magnitude and independence of the risk of OSAS for resistant hypertension strengthen the concept that OSAS is a risk factor for resistant hypertension. Comorbid OSAS should be considered in patients with resistant hypertension.

Section snippets

Materials and Methods

This case-control study was performed in the hypertension clinic of the Hospital de Clínicas de Porto Alegre (Porto Alegre, RS, Brazil), where a cohort study of patients with hypertension is underway.101112 Case patients and control subjects were consecutively enrolled between March 2004 and June 2006. Adult patients of both genders who were 40 to 70 years of age and had body mass index (BMI) values ranging from 25 to 40 kg/m2 were invited to participate. The Institutional Review Board approved

Results

In total, 143 consecutive patients who fulfilled the criteria for enrollment were invited to participate. Ten patients refused to participate. Of the 133 patients who signed the inform consent form, 7 patients had polysomnography or ABPM measures inadequate for analysis, leaving 126 patients for effective analysis. Characteristics of case patients and control subjects are displayed in Table 1. Gender, age, and BMI were comparable in the two groups. BP measured at office and by ABPM was

Discussion

This is the first controlled study to show an independent association between OSAS and resistant hypertension. The odds ratio close to 5.0 is impressive and strengthens the concept that OSAS is a major risk factor of resistant hypertension.

The risk of OSAS for hypertension has been demonstrated in several studies.151617 The association of OSAS with resistant hypertension, however, was less investigated to date. In a case series,9 OSAS was diagnosed in 83% of patients with resistant

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  • Cited by (0)

    This study was funded by Conselho Nacional de Pesquisa, Fundação de Amparo î Pesquisa do Estado do Rio Grande do Sul, and Fundo de Incentivo î Pesquisa do Hospital de Clínicas de Porto Alegre.

    This article is not under consideration elsewhere, and the authors have no potential conflicts of interest regarding this article.

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