Effects of long-term treatment for obstructive sleep apnea on pulse wave velocity

Obstructive sleep apnea and non-dipper: epiphenomena or risks of Alzheimer's disease?: a review from the HOPE Asia Network

Obstructive sleep apnea (OSA) and associated nocturnal blood pressure (BP) surges is associated with non-dipper. On the other hand, the relationship between neurodegenerative diseases and non-dipper hypertension has been reported. To date, few studies have evaluated the relationships of nocturnal BP dipping patterns and OSA in relation to neurodegenerative diseases, particularly Alzheimer's disease (AD). This review examines the etiology of the association between OSA and the non-dipper pattern of hypertension and how both are involved in the development of AD. To set the stage for this review, we first focus on the pathophysiology of AD, which is interrelated with sleep apnea and non-dipper through dysregulation of central autonomic network.

Arterial Stiffness Assessment Using the Arteriograph in Patients with Moderate-Severe OSA and Metabolic Syndrome-A Pilot Study

BACKGROUND

Both obstructive sleep apnea (OSA) and metabolic syndrome (MS) promote arterial stiffening. As a basis for this study, we presumed that arterial stiffness could be assessed using the Arteriograph (TensioMed, Budapest, Hungary) to detect early modifications induced by continuous positive airway therapy (CPAP) in reversing this detrimental vascular remodeling. Arterial stiffness is increasingly acknowledged as a major cardiovascular risk factor and a marker of subclinical hypertension-mediated organ damage. The aim of this pilot study was to evaluate the arterial stiffness changes in patients with moderate-severe OSA and MS after short-term CPAP use.

METHODS

We performed a prospective study that included patients with moderate-severe OSA and MS who had not undergone previous CPAP therapy. All subjects underwent clinical examination and arterial stiffness assessment using the oscillometric technique with Arteriograph (TensioMed, Budapest, Hungary) detection before and after 8-week CPAP therapy.

RESULTS

39 patients with moderate-severe OSA were included. Eight weeks of CPAP therapy significantly improved central systolic blood pressure (Δ = -11.4 mmHg, p = 0.009), aortic pulse wave velocity (aoPWV: Δ = -0.66 m/s, p = 0.03), and aortic augmentation index (aoAix: Δ = -8.25%, p = 0.01) only in patients who used the device for a minimum of 4 h/night (n = 20).

CONCLUSIONS

Arterial stiffness was improved only among CPAP adherent patients and could be detected using the Arteriograph (TensioMed, Budapest, Hungary), which involves a noninvasive procedure that is easy to implement for the clinical evaluation of arterial stiffness.

Long-term variations of arterial stiffness in patients with obesity and obstructive sleep apnea treated with continuous positive airway pressure

BACKGROUND

Obstructive sleep apnea (OSA) is associated with cardiovascular co-morbidities and mortality. Arterial stiffness is an independent predictor of cardiovascular risk and mortality, and is influenced by the presence of OSA and related comorbidities. There is a paucity of data regarding long-term evolution of arterial stiffness in CPAP-treated OSA patients. We aimed to prospectively study long term PWV variations and determinants of PWV deterioration.

METHODS

In a prospective obese OSA cohort, at time of diagnosis and after several years of follow-up we collected arterial stiffness measured by carotid-femoral pulse wave velocity (PWV), clinical and metabolic parameters, and CPAP adherence. Univariate and multivariate analyses were performed in order to determine contributing factors.

RESULTS

Seventy two OSA patients (men: 52.8%, median age: 55.8 years and median BMI of 38.5 kg/m2) with a prevalence of hypertension: 58.3%, type 2 diabetes: 20.8%, hypercholesterolemia: 33.3%, current or past smoking: 59.7%, were evaluated after a median follow-up of 7.4 [5.8; 8.3] years. Over the period of follow-up, the median increase in PWV was 1.34 [0.10; 2.37] m/s. In multivariate analysis, the increase in PWV was associated with older age (10 extra years was associated with a 5.24 [1.35; 9.12] % increase in PWV) and hypertension (a significant increase in PWV of 8.24 [1.02; 15.57] %). No impact of CPAP adherence on PWV evolution was found.

CONCLUSION

PWV progression in CPAP-treated OSA patients is mainly related to pre-existing cardio-metabolic comorbidities and not influenced by CPAP adherence. In this high cardiovascular risk population, it is crucial to associated weight management and exercise with CPAP treatment.

State of the Art Review: Brachial-Ankle PWV

The brachial-ankle pulse wave velocity (brachial-ankle PWV), which is measured simply by wrapping pressure cuffs around the four extremities, is a simple marker to assess the stiffness of the medium- to large- sized arteries. The accuracy and reproducibility of its measurement have been confirmed to be acceptable. Risk factors for cardiovascular disease, especially advanced age and high blood pressure, are reported to be associated with an increase of the arterial stiffness. Furthermore, arterial stiffness might be involved in a vicious cycle with the development/progression of hypertension, diabetes mellitus and chronic kidney disease. Increase in the arterial stiffness is thought to contribute to the development of cardiovascular disease via pathophysiological abnormalities induced in the heart, brain, kidney, and also the arteries themselves. A recent independent participant data meta-analysis conducted in Japan demonstrated that the brachial-ankle PWV is a useful marker to predict future cardiovascular events in Japanese subjects without a previous history of cardiovascular disease, independent of the conventional model for the risk assessment. The cutoff point may be 16.0 m/s in individuals with a low risk of cardiovascular disease (CVD), and 18.0 m/s in individuals with a high risk of CVD and subjects with hypertension. In addition, the method of measurement of the brachial-ankle PWV can also be used to calculate the inter-arm systolic blood pressure difference and ankle-brachial pressure index, which are also useful markers for cardiovascular risk assessment.

Association between sleep-disordered breathing and arterial stiffness in heart failure patients with reduced or preserved ejection fraction

AIMS

Sleep-disordered breathing (SDB) is associated with arterial stiffness, which may be one of the factors that lead to heart failure (HF). We examined the relationship between pulse wave velocity (PWV) and SDB in patients who have HF with reduced ejection fraction (HFrEF) and HF with preserved ejection fraction (HFpEF).

METHODS AND RESULTS

We measured the apnoea-hypopnoea index (AHI) by polysomnography, echocardiographic parameters, and PWV in 221 HF patients. Age, blood pressure, and PWV were higher in HFpEF (ejection fraction > 50%, n = 70) patients than in HFrEF (ejection fraction < 50%, n = 151) patients. All HF patients were divided into three groups according to AHI: none-to-mild SDB group (AHI < 15 times/h, n = 77), moderate SDB group (15 < AHI < 30 times/h, n = 59), and severe SDB group (AHI > 30 times/h, n = 85). Although blood pressure and echocardiographic parameters did not differ among the three groups, PWV was significantly higher in the severe SDB group than in the none-to-mild and moderate SDB groups (P = 0.002). When the HFrEF and HFpEF patients were analysed separately, PWV was significantly higher in the severe SDB group than in the none-to-mild and moderate SDB groups in patients with HFpEF (P = 0.002), but not in those with HFrEF (P = 0.068). In the multiple regression analysis to determine PWV, the presence of severe SDB was found to be an independent predictor of high PWV in HFpEF (β = 0.234, P = 0.005), but not in HFrEF patients.

CONCLUSIONS

Severe SDB is associated with elevated arterial stiffness and may be related to the pathophysiology of HF, especially in HFpEF patients.

Cardiorespiratory interaction with continuous positive airway pressure

The treatment of choice for obstructive sleep apnoea (OSA) is continuous positive airway pressure therapy (CPAP). Since its introduction in clinical practice, CPAP has been used in various clinical conditions with variable and heterogeneous outcomes. In addition to the well-known effects on the upper airway CPAP impacts on intrathoracic pressures, haemodynamics and blood pressure (BP) control. However, short- and long-term effects of CPAP therapy depend on multiple variables which include symptoms, underlying condition, pressure used, treatment acceptance, compliance and usage. CPAP can alter long-term cardiovascular risk in patients with cardiorespiratory conditions. Furthermore, the effect of CPAP on the awake patient differs from the effect on the patients while asleep, and this might contribute to discomfort and removal of the use interface. The purpose of this review is to highlight the physiological impact of CPAP on the cardiorespiratory system, including short-term benefits and long-term outcomes.

CPAP therapy induces favorable short-term changes in epicardial fat thickness and vascular and metabolic markers in apparently healthy subjects with obstructive sleep apnea-hypopnea syndrome (OSAHS)

BACKGROUND

Obstructive sleep apnea-hypopnea syndrome (OSAHS) is an independent risk factor for hypertension, coronary artery disease, and diabetes mellitus. Epicardial fat has been recently recognized as a new risk factor and active participant on cardiometabolic risk. The aim of this study was to assess an independent relationship between sleep apnea severity, metabolic and vascular markers, and epicardial fat, at baseline and after 3 months of continuous positive airway pressure (CPAP) therapy.

MATERIALS AND METHOD

Our study group consisted of 48 patients with suspected OSAHS and no prior history of cardiovascular disease or diabetes mellitus. All patients underwent full overnight polysomnography. Thickness of epicardial and visceral adipose tissue, brachial artery flow-mediated dilation (FMD), carotid intima media thickness (cIMT), pulse wave velocity (PWV), plasma C-reactive protein (CRP) levels, fasting glucose levels, HbA1c, homeostatic model assessment of insulin resistance index (HOMA), and lipid profile were measured at baseline and after 3 months of CPAP use in patients with moderate to severe OSAHS.

RESULTS

In OSAHS patients (Apnea-hypopnea index (AHI) ≥15/h, N = 28), epicardial fat correlated with fasting glucose (rho = 0.406, p = 0.04) and HOMA (rho = 0.525, p = 0.049) but was not associated with visceral fat (rho = 0.126, p = 0.595). Epicardial adipose tissue (EAT) (p = 0.022) increased across AHI severity along with PWV (p = 0.045) and carotid intima media thickness (IMT) (p = 0.034) while FMD (p = 0.017) decreased. Therapy with CPAP reduced both epicardial (p < 0.001) and visceral fat (p = 0.001). Alterations in epicardial fat across the follow-up were associated with changes in PWV (p = 0.026) and HOMA (p = 0.037) independently of major confounders.

CONCLUSIONS

Epicardial fat thickness was associated with OSA severity and may be an additional marker of cardiovascular risk as well as of future diabetes in these patients. CPAP therapy reduced epicardial fat, suggesting its potentially beneficial role in reducing cardiometabolic risk in OSA patients.

Sleep, obesity, and weight loss in adults: is there a rationale for providing sleep interventions in the treatment of obesity?

Rates of obesity and sleep disturbances are substantial in adults. A number of cross-sectional, longitudinal, and experimental studies have found that insufficient sleep and possibly longer sleep are associated with obesity and related eating patterns. Methodological discrepancies and limitations in the literature create ambiguity about the nature and potential mechanisms underlying these relationships. Insomnia and circadian patterns in eating and sleeping have also been examined in relation to weight. Although these studies are not as extensive as those examining sleep duration, the extant literature suggests possible associations between obesity and both insomnia (particularly when combined with short sleep duration) and circadian eating behaviours. However, research has only just begun to examine the benefits of combining sleep interventions with obesity treatment. The goal of the current review is to summarize research examining behavioural sleep patterns and disorders in relation to obesity, to discuss methodological considerations, and to provide an overview of studies examining whether addressing sleep disturbances can augment weight loss treatment effects. We conclude that future studies are needed that take into account sleep duration, sleep disorder co-morbidity, and chronobiology to explore the impact of sleep interventions on weight loss.

Impact of adaptive servo-ventilation on cardiovascular function and prognosis in heart failure patients with preserved left ventricular ejection fraction and sleep-disordered breathing

AIMS

Effective pharmacotherapy for heart failure with preserved left ventricular ejection fraction (HFpEF) is still unclear. Sleep-disordered breathing (SDB) causes cardiovascular dysfunction, giving rise to factors involved in HFpEF. However, it remains unclear whether adaptive servo-ventilation (ASV) improves cardiovascular function and long-term prognosis of patients with HFpEF and SDB.

METHODS AND RESULTS

Thirty-six patients with HFpEF (LVEF >50%) and moderate to severe SDB (apnoea-hypopnoea index >15/h) were enrolled. Study subjects (LVEF 56.0%, apnoea-hypopnoea index 36.5/h) were randomly assigned to two groups: 18 patients treated with medications and ASV (ASV group) and 18 patients not treated with ASV (non-ASV group). NYHA class, cardiac function including LVEF, left atrial volume index (LAVI), E/E', vascular function including flow-mediated dilatation (FMD) and cardio-ankle vascular index (CAVI), and levels of BNP and troponin T were determined at baseline and 6 months later. Patients were followed to register cardiac events after enrolment (follow-up 543 days). ASV therapy improved cardiac diastolic function and decreased CAVI and BNP (NYHA class, 2.3 to 1.5; LAVI, 48.6 to 42.6 mL/m(2); E/E', 12.8 to 7.1; CAVI, 9.0 to 7.7; BNP, 121.5 to 58.1 pg/mL, P < 0.0125, respectively). LVEF, FMD, and troponin T did not change significantly in either group. Importantly, the event-free rate was significantly higher in the ASV group than in the non-ASV group (94.4% vs. 61.1%, log-rank P < 0.05).

CONCLUSION

ASV may improve the prognosis of HFpEF patients with SDB, with favourable effects such as improvement of symptoms, cardiac diastolic function, and arterial stiffness. ASV may be a useful therapeutic tool for HFpEF patients with SDB.

Is obstructive sleep apnoea causally related to arterial stiffness? A critical review of the experimental evidence

Large elastic arteries and smaller muscular conduit arteries become stiffer with ageing, a process that is accelerated in the presence of cardiovascular disease (CVD). In recent years, numerous techniques have been developed to measure arterial stiffness, either in single vessels or in entire muscular arterial trees. These techniques have increasingly been shown to improve stratification of cardiovascular risk and risk reduction beyond that provided by conventional risk factors. Obstructive sleep apnoea (OSA) has been increasingly linked with excess cardiovascular morbidity and mortality however the mechanisms are still not well understood. Robustly designed studies have shown that treatment of OSA with nasal continuous positive airway pressure improves important intermediate risk factors for CVD including hypertension and endothelial function. More recently, there has been increased exploration of arterial stiffness in both cross-sectional and interventional studies in OSA patients. This review aims to give the reader a better understanding of the measurement and pathophysiology of arterial stiffness as well as providing an indication of how well a prognostic indicator are the various measures of arterial stiffness for hard cardiovascular endpoints. A critical appraisal is then provided of cross-sectional and interventional studies that have explored these same techniques in OSA populations.

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

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.

Analysis of pulse wave velocity in the thoracic aorta by flow-sensitive four-dimensional MRI: reproducibility and correlation with characteristics in patients with aortic atherosclerosis

PURPOSE

To measure aortic pulse wave velocity (PWV) using flow-sensitive four-dimensional (4D) MRI and to evaluate test-retest reliability, inter- and intra-observer variability in volunteers and correlation with characteristics in patients with aortic atherosclerosis.

MATERIALS AND METHODS

Flow-sensitive 4D MRI was performed in 12 volunteers (24 ± 3 years) and 86 acute stroke patients (68 ± 9 years) with aortic atherosclerosis. Retrospectively positioned 28 ± 4 analysis planes along the entire aorta (inter-slice-distance = 10 mm) and frame wise lumen segmentation yielded flow-time-curves for each plane. Global aortic PWV was calculated from time-shifts and distances between the upslope portions of all available flow-time curves.

RESULTS

Inter- and intra-observer variability of PWV measurements in volunteers (7% and 8%) was low while test-retest reliability (22%) was moderate. PWV in patients was significantly higher compared with volunteers (5.8 ± 2.9 versus 3.8 ± 0.8 m/s; P = 0.02). Among 17 patient characteristics considered, statistical analysis revealed significant (P < 0.05) but low correlation of PWV with age (r = 0.25), aortic valve insufficiency (r = 0.29), and pulse pressure (r = 0.28). Multivariate modeling indicated that aortic valve insufficiency and elevated pulse pressure were significantly associated with higher PWV (adjusted R(2) = 0.13).

CONCLUSION

Flow-sensitive 4D MRI allows for estimating aortic PWV with low observer dependence and moderate test-retest reliability. PWV in patients correlated with age, aortic valve insufficiency, and pulse pressure.

Vascular changes, cardiovascular disease and obstructive sleep apnea

Vascular changes related to obstructive sleep apnea (OSA) can lead to chronic cardiovascular consequences such as hypertension. The cardiovascular consequences are owing to nocturnal perturbations related to intrathoracic pressure changes, intermittent hypoxia, sympathetic neural activation, endothelial dysfunction, oxidative stress and systemic inflammation. Intermittent hypoxia due to sleep-related events in OSA activates the renin-angiotensin system and increases the levels of endothelin-1. Intermittent hypoxia also results in oxidative stress, as evidenced by elevated levels of xanthine oxidoreductase, lipid peroxidation and the presence of reactive oxygen species. There is also evidence for a decrease in antioxidant capacity. Patients with OSA may have endothelial dysfunction that resolves with continuous positive airway pressure. OSA is a state of inflammation as evidenced by elevated levels of C-reactive protein, IL-6, NF-κB, TNF-α, ICAM-1, VCAM-1 and E-selectin. This may suggest that OSA is a predisposing factor for atherogenesis. This article will discuss the role of nocturnal perturbations consequent to OSA resulting in endothelial dysfunction, oxidative stress, and inflammation and how they may subsequently play a causative role in cardiovascular disorders.

Increased arterial stiffness in obstructive sleep apnea: a systematic review

Obstructive sleep apnea is a prevalent disease that is associated with significant morbidity and mortality, particularly due to cardiovascular disease. An emerging cardiovascular risk factor, arterial stiffness, may also be involved in the cardiovascular complications of obstructive sleep apnea. The purpose of this review was to summarize the current literature regarding the effect of obstructive sleep apnea on arterial stiffness. We conducted a systematic literature review using PubMed, Embase and the Cochrane Library. We identified 24 studies that met search criteria investigating the effect of obstructive sleep apnea on arterial stiffness. Arterial stiffness was found to be increased in obstructive sleep apnea patients compared with controls or increased in severe compared with mild sleep apnea. In some studies, a positive correlation was identified between the degree of arterial stiffness and sleep apnea severity. In the two randomized, controlled trials and the two nonrandomized trials identified, treatment of obstructive sleep apnea with continuous positive airway pressure led to significant decreases in arterial stiffness. Obstructive sleep apnea appears to have an independent effect on arterial stiffness, which may be one of the mechanisms accounting for sleep apnea-associated cardiovascular risk.