Elsevier

Sleep Medicine Reviews

Volume 17, Issue 1, February 2013, Pages 19-28
Sleep Medicine Reviews

Clinical Review
Effects of continuous positive airway pressure (CPAP) treatment for obstructive sleep apnea in arterial stiffness: A meta-analysis

https://doi.org/10.1016/j.smrv.2012.01.002Get rights and content

Summary

Obstructive sleep apnea (OSA) is associated with increased arterial stiffness, a cumulative indicator of arterial health. Continuous positive airway pressure (CPAP) is the gold standard treatment for OSA. We conducted a meta-analysis of the available literature investigating the effect of CPAP on arterial stiffness in patients with OSA. Fifteen articles (n = 615 patients) assessing indices of arterial stiffness were identified. Five different meta-analyses were performed assessing: a) all indices of arterial stiffness, b) augmentation index (AIx), c) all pulse wave velocities (PWV), d) brachial-ankle PWV and e) carotid-femoral PWV. Pooled standardized mean differences (SMDs) and weighted mean differences (WMDs) were appropriately calculated through fixed or random effects models after assessing between-study heterogeneity. A significant improvement of all indices of arterial stiffness was observed after CPAP treatment (SMD = −0.74; 95%CI: −1.08 to −0.41). AIx and PWVs were also significantly improved (WMD = −4.86; 95%CI: −7.31 to −2.41 and WMD = −0.87; 95%CI: −0.98 to −0.77, respectively), as well as brachial-ankle PWV and carotid-femoral PWV (WMD = −0.86; 95%CI: −0.97 to −0.75 and WMD = −1.21; 95%CI:−1.92 to −0.50, respectively). Neither the proportion of compliant patients nor the duration of CPAP use altered the effect of arterial stiffness reduction after CPAP treatment. In conclusion, our meta-analyses showed significant improvements in all indices of arterial stiffness after CPAP treatment in patients with OSA. As clinical use of arterial stiffness is growing in popularity, the efficacy of this useful tool in assessing cardiovascular risk reduction among patients with OSA treated with CPAP needs to be further explored.

Introduction

Obstructive sleep apnea (OSA) is a clinical disorder, which is characterized by recurrent episodes of partial or complete obstruction of the upper airway during sleep, resulting in oxygen desaturation and arousals from sleep. The syndrome is known to affect a substantial number of middle-aged, obese men, whereas, recently, an increasing prevalence among women has been also reported.1 Continuous positive airway pressure (CPAP) is worldwide accepted as the ‘gold standard’ treatment in current management of OSA, as it reduces symptoms and improves quality of life.2

The strong association between OSA and cardiovascular disease (CVD) has attracted considerable interest in recent years. Apnea and hypopnea cause temporary elevations in blood pressure in association with blood oxygen desaturation, arousal and sympathetic activation and may cause elevated blood pressure during the daytime and, ultimately, sustained hypertension.3, 4 Moreover, OSA exposes the cardiovascular (CV) system to intermittent hypoxia, oxidative stress and systemic inflammation which may impair myocardial contractility and cause development and progression of heart failure.5 Moreover, previous evidence suggests that OSA itself is an independent risk factor for cardiovascular morbidity and mortality.6, 7

Arterial stiffness is a composite indicator of arterial health and it is strongly associated with atherosclerosis at various sites in the arterial tree.8, 9 It is caused by structural changes in the vascular wall, including fibrosis, medial smooth muscle cell necrosis, breaks in elastin fibers, calcifications and diffusion of macromolecules into the arterial wall.8, 10, 11 Numerous epidemiological studies have demonstrated that higher arterial stiffness is also associated with increased risk of CVD and cardiovascular events.10, 11, 12

Recent studies have suggested that patients with OSA have increased arterial stiffness, endothelial dysfunction and early signs of atherosclerosis.6 Chung et al.13 found carotid-femoral pulse wave velocity (cfPWV), the ‘gold standard’ measurement of arterial stiffness, to be significantly higher in patients with severe OSA in comparison with patients with mild to moderate OSA and normal controls. Likewise, several studies have also shown a favorable effect of CPAP treatment on arterial stiffness. The role of potential confounding factors, such as obesity, insulin resistance and metabolic syndrome, however, should also be taken into account when exploring this association. The aim of the present meta-analysis is to summarize existing evidence and quantify the potential contribution of CPAP treatment in the improvement of arterial stiffness among patients with OSA.

Section snippets

Data collection

The present meta-analysis was conducted in accordance with the ‘preferred reporting items for systematic reviews and meta-analyses’ (PRISMA) guidelines.14 A combined computerized and manual systematic literature search was performed and the respective publications were identified through Medline, Embase, Scopus, Google Scholar, Ovid and the Cochrane Library. Reference lists were also manually searched for relevant articles.

Types of studies, search terms, eligibility and exclusion criteria

Publications of interest included randomized and non-randomized clinical

Results

As shown in the flow diagram (Fig. 1) 15 articles presenting 17 studies19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33 were deemed eligible out of 101 potentially relevant articles, including a total of 615 patients. Of these studies, none was performed on mutually overlapping populations. A careful review of the included studies was performed in order to ensure that no individual participating in one eligible study participated in any other study included in the meta-analysis, thus

Discussion

The findings of the present meta-analyses, comprising of 615 OSA patients, suggested that CPAP may be an effective intervention for the reduction of arterial stiffness in patients with OSA. In particular, a significant improvement of arterial stiffness was found when all outcome measures of arterial stiffness were pooled together. Moreover, in the subsequent meta-analyses among studies using the same arterial stiffness measure we found that CPAP treatment was associated with a 4.86% improvement

Conflict of interest

None declared.

Acknowledgments

This study was supported in part by the Medical School of the National and Kapodistrian University of Athens.

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