Obstructive sleep apnea and cardiovascular disease

Obstructive sleep apnea (OSA) is a sleep-disordered breathing condition, which is increasingly being recognized as having wide-ranging pathophysiological effects on multiple organ systems. Although multiple factors affect the incidence and severity of OSA, male sex and obesity seem to play an influential role. The apnea-ventilation cycle, characterized by abnormalities in gas exchange, exaggerated respiratory effort and frequent arousals, has been shown to have deleterious effects on circulatory hemodynamics, the autonomic milieu, hormonal balance, inflammatory and coagulation cascades, endothelial function, and the redox state, with potential cardiovascular significance. Consequently, OSA is being increasingly implicated in a multitude of cardiovascular diseases (CVD) such as hypertension, congestive heart failure, atrial fibrillation, stroke, coronary artery disease, pulmonary hypertension, and metabolic syndrome. The strength of association for individual CVD is varied, and outcomes of clinical studies are conflicting. In addition, obesity, which is closely linked to both OSA and CVD, makes it harder to ascertain the independent role of OSA on CVD. Although available evidence is inconclusive, there is an increasing recognition of the direct role for OSA in CVD. Similarly, although several studies have demonstrated the cardiovascular benefits of OSA treatment, further studies are needed to confirm this.     

Characteristics of hypertension in obstructive sleep apnea: An Asian experience

Obstructive sleep apnea (OSA) is a risk of hypertension and is associated with cardiovascular disease (CVD) incidence. In Asian countries, the prevalence of OSA is high, as in Western countries. When blood pressure (BP) is evaluated in OSA individuals using ambulatory BP monitoring (ABPM), the BP phenotype often indicates abnormal BP variability, such as increased nighttime BP or abnormal diurnal BP variation, that is, non‐dipper pattern, riser pattern, and morning BP surge, and all these conditions have been associated with increased CVD events. Asians have a higher prevalence of increased nighttime BP or morning BP surge than Westerners. Therefore, this review paper focused on OSA and hypertension from an Asian perspective to investigate the importance of the association between OSA and hypertension in the Asian population. Such abnormal BP variability has been shown to be associated with progression of arterial stiffness, and this association could provoke a vicious cycle between abnormal BP phenotypes and arterial stiffness, a phenomenon recognized as systemic hemodynamic atherothrombotic syndrome (SHATS). OSA may be one of the background factors that augment SHATS. An oxygen‐triggered nocturnal oscillometric BP measurement device combined with a pulse oximeter for continuous SpO₂ monitoring could detect BP variability caused by OSA. In addition to treating the OSA, accurate and reliable detection and treatment of any residual BP elevation and BP variability caused by OSA would be necessary to prevent CVD events. However, more detailed detection of BP variability, such as beat‐by‐beat BP monitoring, would further help to reduce CV events.     

Obstructive sleep apnea and hypertension: Mechanisms,evaluation, and management

Obstructive sleep apnea (OSA) is a recognized cause of secondary hypertension. OSA episodes produce surges in systolic and diastolic pressure that keep mean blood pressure levels elevated at night. In many patients, blood pressure remains elevated during the daytime, when breathing is normal. Contributors to this diurnal pattern of hypertension include sympathetic nervous system overactivity and alterations in vascular function and structure caused by oxidant stress and inflammation. Treatment of OSA with nasal continuous positive airway pressure (CPAP) abolishes apneas, thereby preventing intermittent arterial pressure surges and restoring the nocturnal “dipping” pattern. CPAP treatment also has modest beneficial effects on daytime blood pressure. Because even small decreases in arterial pressure can contribute to reducing cardiovascular risk, screening for OSA is an essential element of evaluating patients with hypertension.     

Obstructive sleep apnea and hypertension

There is growing evidence of a causal relationship between obstructive sleep apnea (OSA) and hypertension. Untreated OSA may have direct and deleterious effects on cardiovascular function and structure through several mechanisms, including sympathetic activation, oxidative stress, inflammation, and endothelial dysfunction. OSA may contribute to or augment elevated blood pressure levels in a large proportion of the hypertensive patient population. It is important to consider OSA in the differential diagnosis of hypertensive patients who are obese. OSA should be especially considered in those hypertensive patients who respond poorly to combination therapy with antihypertensive medications.     

Increased incidence of cardiovascular disease in middle-aged men with obstructive sleep apnea: a 7-year follow-up

The incidence of a cardiovascular disease (CVD) was explored in a consecutive sleep clinic cohort of 182 middle-aged men (mean age, 46.8 +/- 9.3; range, 30-69 years in 1991) with or without obstructive sleep apnea (OSA). All subjects were free of hypertension or other CVD, pulmonary disease, diabetes mellitus, psychiatric disorder, alcohol dependency, as well as malignancy at baseline. Data were collected via the Swedish Hospital Discharge Register covering a 7-year period before December 31, 1998, as well as questionnaires. Effectiveness of OSA treatment initiated during the period as well as age, body mass index (BMI), systolic blood pressure (SBP), diastolic blood pressure (DBP) at baseline, and smoking habits were controlled. The incidence of at least one CVD was observed in 22 of 60 (36.7%) cases with OSA (overnight oxygen desaturations of 30 or more) compared with in 8 of 122 (6.6%) subjects without OSA (p < 0.001). In a multiple logistic regression model, significant predictors of CVD incidence were OSA at baseline (odds ratio [OR] 4.9; 95% confidence interval [CI], 1.8-13.6) and age (OR 23.4; 95% CI, 2.7-197.5) after adjustment for BMI, SBP, and DBP at baseline. In the OSA group, CVD incidence was observed in 21 of 37 (56.8%) incompletely treated cases compared with in 1 of 15 (6.7%) efficiently treated subjects (p < 0.001). In a multiple regression analysis, efficient treatment was associated with a significant risk reduction for CVD incidence (OR 0.1; 95% CI, 0.0-0.7) after adjustment for age and SBP at baseline in the OSA subjects. We conclude that the risk of developing CVD is increased in middle-aged OSA subjects independently of age, BMI, SBP, DBP, and smoking. Furthermore, efficient treatment of OSA reduces the excess CVD risk and may be considered also in relatively mild OSA without regard to daytime sleepiness.     

Causes and consequences of blood pressure alterations in obstructive sleep apnea

The obstructive sleep apnea (OSA) syndrome has been considered to be a cause of both transient blood pressure elevations during sleep and sustained hypertension during the awake state. The purpose of this review was to examine critically the existing literature regarding (1) the blood pressure alterations associated with OSA, (2) causal mechanisms relating specific blood pressure alterations to OSA, and (3) potential consequences of the systemic circulatory abnormalities associated with OSA. Particular attention was directed at studies that assessed the prevalence of OSA in patients with hypertension and that examined the effects on blood pressure of treatment of OSA. We conclude that patients with OSA have abnormal sleep blood pressure patterns, manifested most frequently by apnea-associated blood pressure elevations. Confounding factors such as obesity and antihypertensive drug therapy, and conflicting evidence regarding changes in daytime blood pressure after therapy for OSA, make it premature to conclude that OSA and daytime hypertension are directly associated. Circumstantial evidence suggests that the blood pressure alterations that occur during sleep could contribute to the high cardiovascular morbidity in patients with OSA. Further research into the relationship between OSA and hypertension should improve the future care of patients with these conditions and enhance our understanding of cardiopulmonary pathophysiology.     

Obstructive sleep apnea: an update on mechanisms and cardiovascular consequences

Background and aimThere is growing recognition of the widespread incidence and health consequences of obstructive sleep apnea (OSA). This review examines the evidence linking sleep apnea with cardiovascular disease and discusses potential mechanisms underlying this link.Data synthesisThe weight of evidence provides increasing support for a causal relationship between OSA and hypertension. Furthermore, OSA may contribute to the initiation and progression of cardiac ischemia, heart failure and stroke. Chronic sympathetic activation appears to be a key mechanism linking OSA to cardiovascular disease. Other potential mechanisms include inflammation, endothelial dysfunction, increased levels of endothelin, hypercoagulability and stimulation of the renin angiotensin system. OSA, hypertension and obesity often coexist and interact, sharing multiple pathophysiological mechanisms and cardiovascular consequences. Effective treatment of OSA may attenuate neural and humoral abnormalities in circulatory control, improve blood pressure control and conceivably reduce the risk of future cardiovascular events.ConclusionPatients with OSA are at increased risk for cardiovascular disease. OSA should be considered in the differential diagnosis of hypertensive patients who are obese. In particular, OSA should be excluded in patients with hypertension resistant to conventional drug therapy.     

Relationships between cardiometabolic disorders and obstructive sleep apnea: Implications for cardiovascular disease risk

Previous studies have reported the effects of obstructive sleep apnea (OSA) and cardiometabolic disorders on cardiovascular disease (CVD), but associations between cardiometabolic biomarkers and two cardinal features of OSA (chronic intermittent hypoxia and sleep fragmentation) and their interactions on CVD in OSA populations remain unclear. A total of 1727 subjects were included in this observational study. Data on overnight polysomnography parameters, biochemical biomarkers, and anthropometric measurements were collected. Metabolic syndrome (MS), including blood pressure, waist circumference (WC), fasting glucose, triglycerides (TG), and high‐density lipoprotein cholesterol (HDL‐C), was diagnosed based on modified criteria of the Adult Treatment Panel III. WC, mean arterial pressure, TG and low‐density lipoprotein cholesterol (LDL‐C) were independently associated with apnea‐hypopnea index (AHI) after adjustment for confounding factors (β = 0.578, P = 0.000; β = 0.157, P = 0.001; β = 1.003, P = 0.019; and β = 4.067, P = 0.0005, respectively). Furthermore, the interaction analysis revealed joint effects between hypertension, obesity, hyperglycemia, and LDL‐C dyslipidemia and AHI on CVD. The relative excess risks of CVD due to the interactions with OSA were 2.06, 1.02, 0.48, and 1.42, respectively (all P < 0.05). In contrast, we found no independent effect of the microarousal index (MAI) on CVD. However, LDL‐C level and some MS components (WC, TG) were associated with MAI. Our findings indicate that hypoxemia and cardiometabolic disorders in OSA may potentiate their unfavorable effects on CVD. Sleep fragmentation may indirectly predispose patients with OSA to an increased risk of CVD. Thus, cardiometabolic disorders and OSA synergistically influence cardiometabolic risk patterns.     

Obstructive sleep apnea and hypertension

There has long been a recognized link between obstructive sleep apnea (OSA) and the cardiovascular system, no aspect of which has been more studied than blood pressure. Research in OSA has not only demonstrated dysregulation of homeostatic cardiovascular mechanisms but also has furthered our understanding of blood pressure regulatory control. Acute nocturnal blood pressure elevations associated with disordered breathing events have been reproduced from a number of observational studies, the accrual of which has also made an increasing argument for the importance of OSA in the pathogenesis of diurnal hypertension, as suggested by the Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC 7), which implicated OSA as a secondary cause of hypertension. Accumulating data from randomized controlled treatment trials in OSA, particularly with continuous positive airway pressure, though sometimes inconsistent, suggest a potential role in blood pressure reduction. Further research is needed to better clarify indications for OSA treatment as well as its role as an adjunct to other antihypertensive treatments.     

阻塞性睡眠呼吸暂停对肺循环的影响

阻塞性睡眠呼吸暂停（OSA）是一种常见病和多发病,其对心血管系统包括肺循环和体循环有着重要影响。OSA可引起急性肺动脉高压,主要是由于低氧性肺血管收缩以及机械效应和觉醒状态下的反射性血管收缩,在一些OSA患者中发现了一些长期的改变,这可能是由于大多数患者经常因相关的肺疾病导致日间低氧血症,从而发展成持续的肺动脉高压的结果,但也有证据表明OSA是引起日间肺动脉高压的独立危险因素。现将OSA对肺循环与右心室的已知影响,包括急性和慢性影响作一综述。     

Deleterious effects of sleep-disordered breathing on the heart and vascular system

Obstructive sleep apnea (OSA) is the most common form of sleep-disordered breathing, affecting 5-15% of the population. It is characterized by intermittent episodes of partial or complete obstruction of the upper airway during sleep that disrupts normal ventilation and sleep architecture, and is typically associated with excessive daytime sleepiness, snoring, and witnessed apneas. Patients with obstructive sleep apnea present risk to the general public safety by causing 8-fold increase in vehicle accidents, and they may themselves also suffer from the physiologic consequences of OSA; these include hypertension, coronary artery disease, stroke, congestive heart failure, pulmonary hypertension, and cardiac arrhythmias. Of these possible cardiovascular consequences, the association between OSA and hypertension has been found to be the most convincing. Although the exact mechanism has not been understood, there is some evidence that OSA is associated with frequent apneas causing mechanical effects on intrathoracic pressure, cardiac function, and intermittent hypoxemia, which may in turn cause endothelial dysfunction and increase in sympathetic drive. Therapy with continuous positive airway pressure has been demonstrated to improve cardiopulmonary hemodynamics in patients with OSA and may reverse the endothelial cell dysfunction. Despite the availability of diagnostic measures and effective treatment, many patients with sleep-disordered breathing remain undiagnosed. Therefore, OSA continues to be a significant health risk both for affected individuals and for the general public. Awareness and timely initiation of an effective treatment may prevent potential deleterious cardiovascular effects of OSA.     

The association of obstructive sleep apnea and left ventricular hypertrophy in obese and overweight children with history of elevated blood pressure

Obesity is a potent cardiovascular disease (CVD) risk factor and is associated with left ventricular hypertrophy (LVH). Obstructive sleep apnea (OSA) is common among individuals with obesity and is also associated with CVD risk. The authors sought to determine the association of OSA, a modifiable CVD risk factor, with LVH among overweight/obese youth with elevated blood pressure (EBP). This was a cross‐sectional analysis of the baseline visit of 61 consecutive overweight/obese children with history of EBP who were evaluated in a pediatric obesity hypertension clinic. OSA was defined via sleep study or validated questionnaire. Children with and without OSA were compared using Fisher's exact tests, Student's t tests, and Wilcoxon rank sum test. Multivariable logistic regression evaluated the association between OSA and LVH. In this cohort, 71.7% of the children had LVH. Children with OSA were more likely to have LVH (85.7% vs 59.4%, P = 0.047). OSA was associated with 4.11 times greater odds of LVH (95% CI 1.15, 14.65; P = 0.030), remaining significant after adjustment for age, sex, race, and BMI z‐score (after adjustment for hypertension, P = 0.051). A severe obstructive apnea‐hypopnea index (AHI >10) was associated with 14 times greater odds of LVH (95% CI 1.14, 172.64, P = 0.039). OSA was significantly associated with LVH among overweight/obese youth with EBP, even after adjustment for age, sex, race, and BMI z‐score. Those with the most severe OSA (AHI >10) had the greatest risk for LVH. Future studies exploring the impact of OSA treatment on CVD risk in children are needed.     

Carotid Intima Media Thickness in Patients with Obstructive Sleep Apnea: Comparison with a Community-Based Cohort

Background

The impact of obstructive sleep apnea (OSA) on the development of atherosclerotic cardiovascular disease (CVD) in the absence of overt CVD or risk factors is unclear. Our purpose was to assess whether patients with OSA without overt CVD or risk factors have subclinical atherosclerosis as evaluated by carotid intima medial thickness (CIMT) compared to matched controls.

Methods

We measured CIMT in patients >40 years old, who underwent polysomnography for suspected OSA and did not have a history of CVD or risk factors (smoking, hypertension, diabetes, hyperlipidemia). OSA severity was classified according to apnea–hypopnea index. Serum levels of high-sensitivity C-reactive protein, fibrinogen, and lipids were assessed and relationships with OSA severity explored. CIMT measurements from patients with OSA were compared those of to age-, gender-, and BMI-matched controls from a community-based cohort without known CVD or OSA.

Results

Fifty-one patients were studied. Of these, patients with severe OSA had an increased CIMT compared to patients without OSA, but the relationship was not significant after controlling for age (p = 0.10). However, 37 patients had OSA and were matched to 105 controls. CIMT was significantly increased in OSA patients versus controls (0.77 vs. 0.68 mm, p = 0.03). The difference between patients and controls was greater for patients with severe OSA (0.83 vs. 0.71 mm) than for patients with mild-to-moderate OSA (0.71 vs. 0.67 mm).

Conclusions

Patients with OSA but without a history of or risk factors for CVD have increased CIMT compared to a BMI-, age-, and gender-matched cohort. This provides evidence that OSA is an independent risk factor for the development of CVD.     

Pathogenesis and Treatment of Microalbuminuria in Patients With Diabetes: The Road Ahead

The incidence of type 2 diabetes is increasing in the United States, which is expected to result in an increased prevalence of microalbuminuria and higher cardiovascular risk. Microalbuminuria is an indication that a low-level inflammatory process is ongoing. In patients with hypertension, with or without diabetes, increasing urinary albumin excretion (UAE) is associated with elevated levels of inflammatory markers, endothelial dysfunction, and platelet activation. Microalbuminuria is associated with an increased incidence of cardiovascular disease (CVD) morbidity and mortality in patients with hypertension and in those with diabetes with or without hypertension. Antihypertensive agents that modulate the renin-angiotensin-aldosterone system (RAAS) can delay the onset and reduce progression of microalbuminuria and decrease CVD morbidity and mortality in patients with diabetes. Clinical trials provide a spectrum of results regarding the protective effects of RAAS-blocking agents. Consideration of baseline blood pressure (BP), UAE and CVD risk, and the extent of BP lowering with treatment is necessary when interpreting clinical trial results in patients with microalbuminuria. It remains to be determined whether targeting the underlying inflammatory process can retard or prevent microalbuminuria progression or whether treatment of microalbuminuria can prevent end-stage renal disease or death.     

Obstruktive Schlafapnoe und kardiovaskuläre Komorbidität

Obstructive sleep apnea (OSA) is the most common entity of sleep-disordered breathing in Germany. OSA is independently associated with an increased risk of cardiovascular disease. It predisposes to arterial hypertension in particular, but also to coronary artery disease, cardiac arrhythmias and atrial fibrillation. OSA has been established as an independent risk factor for arterial hypertension, and treatment of OSA with continuous positive airway pressure (CPAP) causes a significant and persistent drop in blood pressure. Long-term CPAP treatment reduces the rate of important cardiovascular comorbidities.     

Effect of the renin--angiotensin system on the vessel wall: using ACE inhibition to improve endothelial function

Plasma renin activity and cardiovascular disease (CVD) incidence correlate closely in people with hypertension. The effects of angiotensin II (Ang II) on blood pressure (BP) are important in hypertensive patients; accumulating data suggest that the growth effects of Ang II in the cardiovascular system play a critical role in the development of atherosclerosis. Atherosclerosis development in hypertensive patients requires fundamental changes in endothelial structure and function. Key among the factors that may affect the endothelium is the renin--angiotensin--bradykinin system. Ang II, independent of other environmental and neurohormonal factors, mediates the vessel wall changes critical for the development of atherosclerotic disease. A strong correlation appears to exist between Ang II and CVD. Blockade of the renin-angiotensin system has a major impact on arterial structure and function independent of BP. Certain angiotensin-converting enzyme (ACE) inhibitors produce significant improvements in arterial compliance, which may yield a reduction in cardiovascular events. Blockade of the neurohormonal system may be a critical first-line approach to management of hypertension in an effort to prevent or reverse endothelial dysfunction. Moreover, the effects of ACE inhibition, in addition to its effect on BP, suggest that this therapeutic approach may be appropriate for managing patients at risk of CVD who do not yet have hypertension. The ideal antihypertensive agent should yield smooth, consistent BP control over the entire 24-hour period, both to avoid BP variability that places patients at increased risk of cardiovascular events and to offer protection during the vulnerable early morning hours when patients are well known to be at high risk.     

Obstructive Sleep Apnea and Blood Pressure Elevation: What is the Relationship?

Sleep disordered breathing has increasingly been recognised as a frequent cause of ill-health in the community. Moderate or severe forms of the most common condition, obstructive sleep apnea (OSA), occur in up to 12% of the adult male population. A substantial body of literature has been published on the potential relationship between OSA and cardiovascular disease. In particular, OSA has been associated with cardiac failure, stroke, myocardial infarction and hypertension. Part of this association may be explained by other confounders, mainly obesity, which is common in OSA patients. The present review was prepared following a workshop aimed to critically review available scientific evidence suggesting that hypertension is a direct consequence of OSA. In addition, pathophysiologic mechanisms that may be involved in the relationship between OSA and cardiovascular disease, particularly brief intermittent elevation of blood pressure and sustained systemic hypertension, are discussed.     

快速眼动睡眠期的阻塞型呼吸暂停与高血压

快速眼动(REM)睡眠期阻塞型睡眠呼吸暂停(OSA)是指发生在REM期的阻塞型睡眠呼吸暂停综合征,由于REM期交感神经活性异常增高,因此发生在此期的OSA可以使交感神经活性更高,心血管功能更不稳定。目前认为REM-OSA很可能是OSA相关高血压发生的主要原因,并且也可能是目前OSA相关高血压用持续正压通气(CPAP)治疗效果不明显的重要原因。临床工作中应重视对REM-OSA的诊断和治疗,这对OSA相关高血压的防治具有重要意义。     

Expanding the definition and classification of hypertension

Cardiovascular abnormalities are frequently the cause, as well as the effect, of elevated blood pressure. As such, early cardiovascular disease (CVD) may be established before identifiable blood pressure thresholds are crossed. To identify individuals at risk for CVD at an earlier point in the disease process, as well as to avoid labeling persons as hypertensive who are at low risk for CVD, the Hypertension Writing Group proposes incorporating the presence or absence of cardiovascular risk factors, early disease markers, and target organ damage into the definition and classification scheme of hypertension. To describe both the complexity and progressive nature of hypertension, the following definition is proposed: "Hypertension is a progressive cardiovascular syndrome arising from complex and interrelated etiologies. Early markers of the syndrome are often present before blood pressure elevation is observed; therefore, hypertension cannot be classified solely by discrete blood pressure thresholds. Progression is strongly associated with functional and structural cardiac and vascular abnormalities that damage the heart, kidneys, brain, vasculature, and other organs and lead to premature morbidity and death." Classification of hypertension must involve assessing global cardiovascular risk to situate an individual's risk for CVD and events along a continuum. As knowledge of early CVD continues to evolve, the approach to classifying individuals along that continuum can be expected to evolve accordingly. The four categories currently used to classify hypertension are normal, prehypertension, and stages 1 and 2 hypertension. The population identified with prehypertension includes a subgroup with early CVD. We believe it would be preferable to classify all individuals as either normal or hypertensive, based on their cardiovascular evaluation, using the four categories of normal and stages 1, 2, and 3 hypertension.