Undiagnosed sleep-disordered breathing among male nondippers with essential hypertension

Obesity in Hypertensive Patients Is Characterized by a Dawn Phenomenon in Systolic Blood Pressure Values and Variability

One of the causes of hypertension is excess weight gain, which can also affect the course of this disease. Both the diagnosis and management of hypertension commonly use ambulatory blood pressure monitoring; the results of which correlate more strongly with cardiovascular diseases and cardiovascular death than office blood pressure monitoring. We evaluated blood pressure values and their variability from hour to hour to see if and when they differed between hypertensive patients with and without obesity. The study included 1345 patients who underwent 24 h ambulatory blood pressure monitoring and then were divided into groups according to body mass index and waist circumference. The obtained data were analyzed according to the subjects' wake-up time, and short-term blood pressure variability parameters were calculated as the mean of the absolute values of the differences between consecutive measurements. The systolic blood pressure in obese subjects was significantly higher between 1 and 5 h before waking than in normal-weighted individuals. In turn, the variability in systolic and diastolic blood pressure was higher with increasing body mass index. The difference in systolic blood pressure values and blood pressure variability was most prominent in the last 5 h of sleep in obese patients.

Management of nocturnal hypertension: An expert consensus document from Chinese Hypertension League

Nocturnal hypertension is highly prevalent among Chinese and Asian populations, which is mainly attributed to high salt intake and high salt sensitivity. Nocturnal hypertension increases the risk of cardiovascular and all-cause mortality, independent of daytime blood pressure (BP). However, it can usually be detected by 24-h ambulatory BP monitoring, rather than routine office or home BP measurement, thus is often underdiagnosed in clinical practice. Currently, no specific guidance is available for the management of nocturnal hypertension in China or worldwide. Experts from the Chinese Hypertension League summarized the epidemiologic and pathophysiologic characteristics and clinical phenotype of nocturnal hypertension and provided consensus recommendations on optimal management of nocturnal hypertension, with the goal of maximally reducing the cardiovascular disease risks. In this consensus document, 24-h ABPM is recommended for screening and diagnosis of nocturnal hypertension, especially in the elderly, patients with diabetes, chronic kidney diseases, obstructive sleep apnea and other conditions prone to high nocturnal BP. Lifestyle modifications including salt intake restriction, exercise, weight loss, sleep improvement, and mental stress relief are recommended. Long-acting antihypertensive medications are preferred for nocturnal and 24-h BP control. Some newly developed agents, renal denervation, and other device-based therapy on nocturnal BP reduction are evaluated.

Non-Conventional Risk Factors: "Fact" or "Fake" in Cardiovascular Disease Prevention?

Cardiovascular diseases (CVDs), such as arterial hypertension, myocardial infarction, stroke, heart failure, atrial fibrillation, etc., still represent the main cause of morbidity and mortality worldwide. They significantly modify the patients' quality of life with a tremendous economic impact. It is well established that cardiovascular risk factors increase the probability of fatal and non-fatal cardiac events. These risk factors are classified into modifiable (smoking, arterial hypertension, hypercholesterolemia, low HDL cholesterol, diabetes, excessive alcohol consumption, high-fat and high-calorie diet, reduced physical activity) and non-modifiable (sex, age, family history, of previous cardiovascular disease). Hence, CVD prevention is based on early identification and management of modifiable risk factors whose impact on the CV outcome is now performed by the use of CV risk assessment models, such as the Framingham Risk Score, Pooled Cohort Equations, or the SCORE2. However, in recent years, emerging, non-traditional factors (metabolic and non-metabolic) seem to significantly affect this assessment. In this article, we aim at defining these emerging factors and describe the potential mechanisms by which they might contribute to the development of CVD.

Cardiovascular Disease in Obstructive Sleep Apnea: Putative Contributions of Mineralocorticoid Receptors

Obstructive sleep apnea (OSA) is a chronic and highly prevalent condition that is associated with oxidative stress, inflammation, and fibrosis, leading to endothelial dysfunction, arterial stiffness, and vascular insulin resistance, resulting in increased cardiovascular disease and overall mortality rates. To date, OSA remains vastly underdiagnosed and undertreated, with conventional treatments yielding relatively discouraging results for improving cardiovascular outcomes in OSA patients. As such, a better mechanistic understanding of OSA-associated cardiovascular disease (CVD) and the development of novel adjuvant therapeutic targets are critically needed. It is well-established that inappropriate mineralocorticoid receptor (MR) activation in cardiovascular tissues plays a causal role in a multitude of CVD states. Clinical studies and experimental models of OSA lead to increased secretion of the MR ligand aldosterone and excessive MR activation. Furthermore, MR activation has been associated with worsened OSA prognosis. Despite these documented relationships, there have been no studies exploring the causal involvement of MR signaling in OSA-associated CVD. Further, scarce clinical studies have exclusively assessed the beneficial role of MR antagonists for the treatment of systemic hypertension commonly associated with OSA. Here, we provide a comprehensive overview of overlapping mechanistic pathways recruited in the context of MR activation- and OSA-induced CVD and propose MR-targeted therapy as a potential avenue to abrogate the deleterious cardiovascular consequences of OSA.

Obstructive Sleep Apnea and Cardiovascular Diseases: Sad Realities and Untold Truths regarding Care of Patients in 2022

Obstructive sleep apnea (OSA) is one of the most common and serious sleep-related breathing disorders with a high prevalence among patients with cardiovascular (CV) diseases. Despite its widespread presence, OSA remains severely undiagnosed and untreated. CV mortality and morbidity are significantly increased in the presence of OSA as it is associated with an increased risk of resistant hypertension, heart failure, arrhythmias, and coronary artery disease. Evaluation and treatment of OSA should focus on recognizing patients at risk of developing OSA. The use of screening questionnaires should be routine, but a formal polysomnography sleep study is fundamental in establishing and classifying OSA. Recognition of OSA patients will allow for the institution of appropriate therapy that should alleviate OSA-related symptoms with the intent of decreasing adverse CV risk. In this review, we focus on the impact OSA has on CV disease and evaluate contemporary OSA treatments. Our goal is to heighten awareness among CV practitioners.

Isolated nocturnal hypertension in pediatric kidney transplant recipients

BACKGROUND

Isolated nocturnal hypertension (INH) is defined as nighttime hypertension in the setting of normal daytime blood pressure (BP), diagnosed by ambulatory BP monitoring (ABPM).

METHODS AND RESULTS

Hypertension affects 60%-80% of pediatric kidney transplant recipients, and INH is the most common type of ambulatory hypertension. INH is associated with an increased prevalence of hypertension-mediated target organ damage such as left ventricular hypertrophy in adults and in pediatric kidney transplant recipients.

CONCLUSION

Ambulatory BP monitoring should be performed annually in all pediatric kidney transplant recipients to diagnose hypertension phenotypes that are not detectable by office BP such as masked hypertension, white-coat hypertension, or INH. Isolated nocturnal hypertension in pediatric transplant patients requires study as a treatment target.

Isolated nocturnal hypertension is associated with increased left ventricular mass index in children

BACKGROUND

Isolated nocturnal hypertension (INH) is associated with increased prevalence of left ventricular hypertrophy (LVH) and cardiovascular morbidity and mortality in adult patients. Unlike in adults, data illustrating the possible association between INH and cardiac target organ damage is lacking in children. This study aimed to investigate whether INH is associated with increased left ventricular mass index (LVMI) and LVH in children.

METHODS

Retrospective data from all untreated children with confirmed ambulatory hypertension (HT) in our center was reviewed. Ambulatory blood pressure monitoring (ABPM) and echocardiography were performed concurrently. Ambulatory normotensive children served as controls. LVH was defined as LVMI ≥ 95th percentile.

RESULTS

There were 102 ABPM studies; of these, 79 children had renal HT, and 23 had primary HT. Median age of children was 13.2 years (3.8-18.9). Nineteen children had INH, 9 children had isolated daytime HT, 54 had daytime and nighttime HT, and 20 were normotensive. The LVMI adjusted for age (patient's LVMI/95th percentile of the LVMI) was significantly higher in children with INH than in normotensive children (0.83 ± 0.03 vs. 0.74 ± 0.03, p = 0.03). Left ventricular hypertrophy was present in 11% of children with INH; this was not significantly higher than in normotensive children (0%, p = 0.23).

CONCLUSIONS

This study investigated the association between INH and cardiac structure in children with primary and renal HT and showed children with INH had higher LVMI adjusted for age than normotensive children and children with INH had similar LVMI adjusted for age to children with isolated daytime HT.

Night-time systolic blood pressure and subclinical cerebrovascular disease: the Cardiovascular Abnormalities and Brain Lesions (CABL) study

AIMS

Although ambulatory blood pressure (BP) is a better predictor of cardiovascular outcomes than office BP, its association with subclinical cerebrovascular disease is not clarified. We investigated the associations of office and ambulatory BP values with subclinical cerebrovascular disease in a population based, predominantly elderly cohort without prior stroke.

METHODS AND RESULTS

Eight hundred and twenty-eight participants underwent 24-h ambulatory BP monitoring (ABPM), 2D echocardiography and brain magnetic resonance imaging in the Cardiac Abnormalities and Brain Lesion (CABL) study. Daytime, night-time, and 24-h BPs, nocturnal dipping pattern, morning surge (MS), and 24-h variability were assessed. Subclinical cerebrovascular disease was defined as silent brain infarcts (SBIs) and white matter hyperintensity volume (WMHV). The association of BP measures with the presence of SBI and upper quartile of log-WMHV (log-WMHV4) was analysed. SBIs were detected in 111 patients (13.4%). Mean log-WMHV was -0.99 ± 0.94. In multivariable analysis, only night-time systolic BP (SBP) was significantly associated with SBI [odds ratio (OR) 1.15 per 10 mmHg, P = 0.042], independent of cardiovascular risk factors, and pertinent echocardiographic parameters. Although daytime, night-time, 24-h BPs, and non-dipping pattern were all significantly associated with log-WMHV4 (all P < 0.05), night-time SBP showed the strongest association (OR 1.21 per 10 mmHg, P = 0.003) and was the sole independent predictor when tested against the other BP parameters. Office BP measures, MS, and BP variability were not associated with subclinical cerebrovascular disease in adjusted analyses.

CONCLUSION

Elevated night-time SBP is strongly associated with subclinical cerebrovascular disease. Night-time SBP by ABPM allows to identify individuals at higher risk of hypertensive brain injury.

Nondipping Nocturnal Blood Pressure Predicts Sleep Apnea in Patients With Hypertension

STUDY OBJECTIVES

Systemic hypertension is highly prevalent in obstructive sleep apnea (OSA) but there are limited data on OSA prevalence in cohorts with hypertension comparing dippers and nondippers. We investigated this relationship in a clinic-based cohort of patients with hypertension who were not screened for any pretest possibility of OSA.

METHODS

A total of 100 patients with hypertension aged (mean ± SD) 58 ± 10 years, body mass index 30.5 ± 6.1 kg/m2, and Epworth Sleepiness Scale score 6 ± 4 were included. All underwent overnight attended sleep studies and 24-hour ambulatory blood pressure monitoring. The primary study end-point was OSA prevalence based on the standard criteria of apnea-hypopnea index (AHI) ≥ 15 events/h in patients with dipping and nondipping nocturnal blood pressure.

RESULTS

Results showed 10.5% of dippers and 43.5% of nondippers had an AHI ≥ 15 (chi-square P = .001). In univariate analysis, AHI correlated significantly with blood pressure dip (r = -.26, P < .05), as did ESS (r = -.28, P < .05). In linear regression, AHI predicted the magnitude of blood pressure dip (standardised β = -.288, P = .03), whereas age, body mass index, systolic blood pressure and diastolic blood pressure did not.

CONCLUSIONS

Patients with nondipping nocturnal blood pressure are at high risk of OSA, regardless of symptom profile, which supports the recommendation that such patients should be assessed for co-existing OSA.

Severity of obstructive sleep apnea is associated with the nocturnal fluctuation of pulse rate, but not with that of blood pressure, in older hypertensive patients receiving calcium channel blockers

AIM

Obstructive sleep apnea (OSA) is associated with increased variability in nocturnal blood pressure (BP). Calcium channel blockers (CCB) are superior to other classes of antihypertensives in decreasing BP variability. We investigated whether OSA severity is associated with nocturnal BP variability in older hypertensive patients treated with CCB.

METHODS

We measured home systolic and diastolic BP and pulse rate (PR) automatically during sleep at an interval of an hour once a week using an electronic sphygmomanometer in 29 hypertensive patients (aged ≥65 years) receiving CCB. We calculated the coefficient of variation (CV) from four consecutive measurements. All patients underwent a home-based portable sleep study.

RESULTS

We found no difference in PR, BP or CV of BP between the patients with no-to-mild OSA and with moderate-to-severe OSA, categorized by the respiratory disturbance index (RDI) and 3% oxygen desaturation index (ODI). The CV of PR in patients with moderate-to-severe OSA was higher than the patients with no-to-mild OSA categorized by 3% ODI (P = 0.01). Body mass index was correlated with RDI and 3% ODI (r = 0.56 and 0.43, respectively). The CV of BP did not correlate to RDI or 3% ODI. The CV of PR was positively correlated both with RDI and with 3% ODI (r = 0.41 and 0.42, respectively).

CONCLUSIONS

The severity of OSA was associated with PR variability, but not with BP variability, in older patients receiving CCB. Our results suggest the need for future studies to determine whether CCB can suppress the influence of OSA on BP fluctuation during sleep. Geriatr Gerontol Int 2019; 19: 604-610.

The additive effects of OSA and nondipping status on early markers of subclinical atherosclerosis in normotensive patients: a cross-sectional study

The additive effect of hypertension on carotid atherosclerosis in patients with obstructive sleep apnea (OSA) is well-established; however, the effect of the nondipping pattern has not yet been evaluated. In this study, we aim to assess the effect of the nondipping pattern on carotid atherosclerosis, which is quantified as carotid intima-media thickness (CIMT), and on the high-risk carotid profile in normotensive patients with OSA. We included 189 patients with OSA in this cross-sectional study. We followed a 2 × 2 factorial design to create groups according to the presence of OSA and nondipping pattern. All patients underwent carotid ultrasonography to quantify their CIMT and presence of plaques. Patients who had CIMT ≥ 0.9 mm and/or carotid plaques were classified as having a high-risk carotid profile. Patients in the OSA/nondipper group had a 26% higher CIMT and five times the prevalence of a high-risk carotid profile compared to patients in the non-OSA/dipper group. CIMT was correlated with age, the apnea-hypopnea index (AHI), minimum oxygen saturation, and nighttime systolic blood pressure (SBP). Independent of age, diabetes, and AHI, a one mmHg increase in nighttime SBP was associated with a 0.22 mm increase in CIMT and a 4% increase in odds for the high-risk carotid profile. Similarly, independent of age and diabetes, being in the OSA/nondipper group was associated with 6.7 times increased odds for a high-risk carotid profile than being in the non-OSA/dipper group. Modeling with both the nondipping status and presence of OSA produced an 8% higher discriminative value than modeling with neither of these parameters. We found an additive effect of the nondipping pattern on carotid atherosclerosis in normotensive patients with OSA. Our findings suggested that in addition to having established hypertension, a nondipping pattern in normotensive patients with OSA may aggravate atherosclerosis.

Chronotherapy for Hypertension

PURPOSE OF REVIEW

Given the emerging knowledge that circadian rhythmicity exists in every cell and all organ systems, there is increasing interest in the possible benefits of chronotherapy for many diseases. There is a well-documented 24-h pattern of blood pressure with a morning surge that may contribute to the observed morning increase in adverse cardiovascular events. Historically, antihypertensive therapy involves morning doses, usually aimed at reducing daytime blood pressure surges, but an absence of nocturnal dipping blood pressure is also associated with increased cardiovascular risk.

RECENT FINDINGS

To more effectively reduce nocturnal blood pressure and still counteract the morning surge in blood pressure, a number of studies have examined moving one or more antihypertensives from morning to bedtime dosing. More recently, such studies of chronotherapy have studied comorbid populations including obstructive sleep apnea, chronic kidney disease, or diabetes. Here, we summarize major findings from recent research in this area (2013-2017). In general, nighttime administration of antihypertensives improved overall 24-h blood pressure profiles regardless of disease comorbidity. However, inconsistencies between studies suggest a need for more prospective randomized controlled trials with sufficient statistical power. In addition, experimental studies to ascertain mechanisms by which chronotherapy is beneficial could aid drug design and guidelines for timed administration.

Obstructive sleep apnoea and Type 2 diabetes mellitus: are they connected?

Obstructive sleep apnoea (OSA), a sleep-related breathing condition, is diagnosed based on a patient's apnoea-hypopnea index from a sleep study, and the presence or absence of symptoms. Diabetes mellitus (DM) and OSA share a significant common risk factor, obesity, with all three conditions contributing to the risk of developing cardiovascular diseases. The pathophysiological links between OSA and DM are still unclear, but intermittent hypoxia may be an important mechanism. More awareness of the possible link between OSA and DM is needed, given their increasing prevalence locally and worldwide. Continuous positive airway pressure is the standard treatment for OSA, while weight loss through dietary and lifestyle modifications is important to holistically manage patients with either condition. There is currently insufficient evidence to support the benefits of screening every diabetic patient for OSA. However, diabetic patients with symptoms suggestive of OSA should be referred to a sleep specialist for further evaluation.

The association between different features of sleep-disordered breathing and blood pressure: A cross-sectional study

Sleep disordered breathing (SDB) is highly prevalent in patients with high blood pressure (BP). Severity of SDB can be evaluated by the number of apneas and hypopneas per hour (AHI) or by measures of hypoxia. The objective of this study was to assess the association between different measures of SDB and BP. In 134 consecutive patients, polygraphy was performed to determine the AHI. Pulse oximetry was used to determine hypoxemic burden (time below 90% oxygen saturation [T90] and hypoxia load [HL], representing the integrated area above the curve of desaturation). AHI did not correlate with systolic and diastolic BP or pulse pressure. In contrast, HL correlated with pulse pressure during the day (P = .01) and night (P = .0034) before and after adjustment for body mass index. The correlation between systolic BP and HL at night disappeared following adjustment for body mass index. This study generates the hypothesis that nocturnal hypoxemic burden may represent a suitable marker of BP pattern and a potential treatment target in hypertensive patients.

Obstructive sleep apnoea-hypopnoea and arrhythmias: new updates

AIMS

Obstructive sleep apnoea-hypopnoea (OSAH) is a prevalent condition characterized by repetitive pharyngeal collapse during sleep, leading to hypoxemia, hypercapnia, and persistent inspiratory efforts against an occluded airway until arousal. Several studies demonstrated that OSAH exerts acute and chronic effects on the cardiovascular system. Thus, although being a respiratory problem, the most important consequences of OSAH are cardiovascular, among which there are arrhythmias. The purpose of this review is to systematically analyse what has been recently published about the relationship between OSAH and every cardiac arrhythmia separately.

METHODS

We searched Pubmed, Scopus, Web of Science and Cochrane Collaboration databases for 'OSAHS arrhythmias', 'OSAH arrhythmias' and 'OSA arrhythmias'. We analyse 1298 articles and meta-analyses, excluding already edited reviews.

RESULTS

Arrhythmias, especially of ventricular origin, are frequent in OSAH. Ventricular premature beats, couplets and ventricular tachycardia runs are even more frequent in patients suffering from heart failure. They may be due to left heart remodelling, overwork and ischaemia and can explain at least some sudden deaths occurring between midnight and 6 a.m. Sinus pauses and atrioventricular blocks are increased according to the severity of the disturbance and may be reduced by continuous positive airway pressure therapy, preventing pace-maker implantation. Finally, atrial fibrillation, resistance against antiarrhythmic drugs and recurrences after surgical procedures are strongly related to OSAH.

CONCLUSION

Arrhythmias are frequent in OSAH. Treatment of OSAH may reduce some of them. An implantable cardioverter-defibrillator and continuous positive airway pressure should be considered in some patients.

Repercusiones cardiovasculares del síndrome de apnea-hipopnea obstructiva del sueño (SAHOS)

En la población de sujetos con síndrome de apnea-hipopnea obstructiva del sueño se describen entidades clínicas cardiovasculares asociadas con esta entidad y que afectan su curso y pronóstico. Dentro de estas se encuentran hipertensión arterial, arritmias, enfermedad coronaria, insuficiencia cardíaca, hipertensión pulmonar y tromboembolismo venoso. Del mismo modo, se describen los mecanismos fisiopatológicos de estas asociaciones, su prevalencia e impacto. Dado que afectan el curso de la enfermedad y, por tanto, la severidad de la misma, estas entidades juegan un papel muy importante en la toma de decisiones al momento de ofrecer el mejor manejo en cada caso, el cual debe ser abordado de forma multidisciplinaria.

The Relationship Between β-Receptor Sensitivity and Nocturnal Blood Pressure and Heart Rate Recovery in Normotensive People

This study examined the relationship between nocturnal blood pressure (BP) dipping and chronotropic dose25 (CD25) as an indicator of β-adrenergic receptor functioning in normotensive people. In addition, the authors evaluated the influence of β-receptor functioning on heart rate recovery after exercise. The sample consisted of 41 participants (18 men, 23 women). Ambulatory BP monitoring took place in each patient's home. On a separate occasion, β-adrenergic receptor sensitivity was determined by response to isoproterenol infusion. Heart rate (HR) recovery was defined as the change from peak HR to that measured after 1 and 2 minutes of recovery. Relationships between dipping and CD25 were found such that participants with higher CD25 values had less nocturnal decline in systolic BP, diastolic BP, and mean arterial pressure ( r =–0.445, –0.533, –0.510, respectively; p<0.004, 0.001, 0.001, respectively). Heart rate recovery at 1 and 2 minutes after exercise was 28.8 ±5 and 49.9 ±6 beats/minute, respectively. Participants with higher CD25 values had more heart rate decline during the first 2 minutes of recovery ( r =0.407, p<0.008). In addition, heart rate recovery was inversely related to systolic, diastolic, and mean nocturnal blood pressure dipping ( r =–0.348, –0.432, –0.408, respectively, p<0.028, 0.005, 0.009, respectively). Normotensive people with an abnormal circadian pattern of blood pressure may have desensitized β-adrenergic receptors. This desensitization may contribute to blunted nocturnal blood pressure and increased heart rate recovery as measured at 2 minutes following exercise testing.

Association of Serum Uric Acid Level With Blood Pressure Variability in Newly Diagnosed Essential Hypertension

Serum uric acid (UA) is independently associated with hypertension and blood pressure (BP) variability (BPV) is associated with cardiovascular events and mortality in hypertensive patients. The aim of the present study was to assess the association of serum UA with BPV in 300 untreated essential hypertension patients (mean age 57.3±13.6 years). BPV was quantified as the standard deviation (SD) of the 24-hour, daytime, and nighttime mean values obtained by using ambulatory BP monitoring. In correlation analysis, log UA values were found to be positively correlated with 24-hour systolic BPV and nighttime systolic and diastolic BPV (Pearson coefficients of 0.246, 0.280, and 0.353, respectively; P<.001 for all). In multivariate analysis, log UA had an independent association with 24-hour systolic BPV and nighttime systolic and diastolic BPV. This study show for the first time that increased serum UA is independently associated with BPV in untreated essential hypertension patients.

Sleep, death, and the heart

Obstructive and central sleep apnea have been associated with increased risk of adverse cardiovascular events and mortality. Sympathetic dysregulation occurring as a result of the respiratory disturbance is thought to play a role in this increased risk. Sleep apnea increases the risk of arrhythmias, myocardial ischemia/infarction, stroke, and heart failure, all of which may increase mortality risk. A higher incidence of nocturnal arrhythmias, cardiac ischemia, and sudden death has been noted in subjects with sleep-disordered breathing (SDB). In this review, the association between SDB and each of these conditions is discussed, as well as the potential mechanisms underlying these risks and the effects of treatment of SDB. Particular emphasis is placed on the relationship between SDB and nocturnal atrial and ventricular arrhythmias, myocardial ischemia/infarction and sudden death.

High trait rumination is associated with blunted nighttime diastolic blood pressure dipping

Background

Blunted blood pressure (BP) dipping during nighttime sleep has been associated with an increased risk of cardiovascular events. Psychological traits have been associated with prolonged cardiovascular activation and a lack of cardiovascular recovery. This activation may extend into nighttime sleep and reduce BP dipping.

Purpose

This study aims to evaluate the association between trait rumination and nighttime BP dipping.

Methods

Sixty women scoring either high or low on trait rumination underwent one 24-h ambulatory BP monitoring session. Self-reported wake and sleep times were used to calculate nighttime BP.

Results

High trait rumination was associated with less diastolic blood pressure (DBP) dipping relative to low trait rumination. Awake ambulatory BP, asleep systolic blood pressure (SBP) and DBP, and asleep SBP dipping were not associated with trait rumination.

Conclusions

In a sample of young women, high trait rumination was associated with less DBP dipping, suggesting that it may be associated with prolonged cardiovascular activation that extends into nighttime sleep, blunting BP dipping.

Obstructive sleep apnoea syndrome

Obstructive sleep apnoea syndrome (OSAS) is a common clinical condition in which the throat narrows or collapses repeatedly during sleep, causing obstructive sleep apnoea events. The syndrome is particularly prevalent in middle-aged and older adults. The mechanism by which the upper airway collapses is not fully understood but is multifactorial and includes obesity, craniofacial changes, alteration in upper airway muscle function, pharyngeal neuropathy and fluid shift towards the neck. The direct consequences of the collapse are intermittent hypoxia and hypercapnia, recurrent arousals and increase in respiratory efforts, leading to secondary sympathetic activation, oxidative stress and systemic inflammation. Excessive daytime sleepiness is a burden for the majority of patients. OSAS is also associated with cardiovascular co-morbidities, including hypertension, arrhythmias, stroke, coronary heart disease, atherosclerosis and overall increased cardiovascular mortality, as well as metabolic dysfunction. Whether treating sleep apnoea can fully reverse its chronic consequences remains to be established in adequately designed studies. Continuous positive airway pressure (CPAP) is the primary treatment modality in patients with severe OSAS, whereas oral appliances are also widely used in mild to moderate forms. Finally, combining different treatment modalities such as CPAP and weight control is beneficial, but need to be evaluated in randomized controlled trials. For an illustrated summary of this Primer, visit: http://go.nature.com/Lwc6te.

Chemoreflexes, sleep apnea, and sympathetic dysregulation

Obstructive sleep apnea (OSA) and hypertension are closely linked conditions. Disordered breathing events in OSA are characterized by increasing efforts against an occluded airway while asleep, resulting in a marked sympathetic response. This is predominantly due to hypoxemia activating the chemoreflexes, resulting in reflex increases in sympathetic neural outflow. In addition, apnea - and the consequent lack of inhibition of the sympathetic system that occurs with lung inflation during normal breathing - potentiates central sympathetic outflow. Sympathetic activation persists into the daytime, and is thought to contribute to hypertension and other adverse cardiovascular outcomes. This review discusses chemoreflex physiology and sympathetic modulation during normal sleep, as well as the sympathetic dysregulation seen in OSA, its extension into wakefulness, and changes after treatment. Evidence supporting the role of the peripheral chemoreflex in the sympathetic dysregulation seen in OSA, including in the context of comorbid obesity, metabolic syndrome, and systemic hypertension, is reviewed. Finally, alterations in cardiovascular variability and other potential mechanisms that may play a role in the autonomic imbalance in OSA are also discussed.

[Beneficial effect of continuous positive airway pressure therapy in obstructive sleep apnea syndrome]

Continuous positive airway pressure therapy is an evidence based therapy of obstructive sleep apnea syndrome. The effective treatment of obstructive sleep apnea can decrease sympaticotonia and, consequently, blood pressure. Furthermore, it can improve inflammatory and metabolic parameters resulting in a decreased cardiovascular risk. This article summarizes the positive effects of continuous positive airway pressure therapy on cardiovascular risk factors in obstructive sleep apnea syndrome.

Relationship of circadian pattern of urine sodium excretion to hypertension and obstructive sleep apnoea

OBJECTIVES

Obstructive sleep apnoea (OSA) and hypertension frequently coexist, and both are associated with higher night-time than daytime urine sodium excretion rate (UNaV). However, the relative contribution of each condition is unknown. We compared the circadian pattern of UNaV in hypertensive and normotensive patients with and without OSA.

METHODS

Hypertensive [blood pressure (BP) >140/90 or on antihypertensive medications, excluding diuretics] and normotensive (BP <135/85) patients underwent overnight polysomnography to determine the presence or absence of OSA (apnoea-hypopnoea index ≥10 or <10, respectively), same-day 24-h urine collection divided into day and night-time samples and automated evening BP measurement.

RESULTS

Twenty-six hypertensive (9 without and 17 with OSA) and 26 normotensive (15 without and 11 with OSA) patients were studied. Night-time UNaV was higher in the hypertensive than the normotensive patients. Whereas in the normotensive patients night-time UNaV was unaffected by OSA, in the hypertensive patients, it was higher in those with than without OSA (P = 0.009 for OSA × hypertension interaction). Night : day UNaV ratio was higher in hypertensive than normotensive patients, but was not significantly affected by OSA in either group. On multivariate analysis, SBP and apnoea-hypopnoea index were independent predictors of night-time UNaV (model r = 0.574, P < 0.001) and night : day UNaV ratio (model r = 0.397, P < 0.001). However, SBP was the strongest independent predictor.

CONCLUSIONS

In hypertensive patients, OSA exacerbates the reversal of the normal circadian sodium excretion pattern by elevating nocturnal UNaV, possibly via its BP-elevating effects. However, OSA does not affect nocturnal UNaV in normotensive patients.

Nocturnal intermittent hypoxia predicts prevalent hypertension in the European Sleep Apnoea Database cohort study

Systemic hypertension is associated with obstructive sleep apnoea syndrome (OSAS) but the pathophysiological mechanisms are incompletely understood. A collaborative European network of 24 sleep centres established a European Sleep Apnoea Database to evaluate cardiovascular morbidity associated with OSAS. 11 911 adults referred with suspected OSAS between March 2007 and September 2013 underwent overnight sleep studies, either cardiorespiratory polygraphy or polysomnography. We compared the predictive value of the apnoea-hypopnoea index (AHI) and 4% oxygen desaturation index (ODI) for prevalent hypertension, adjusting for relevant covariates including age, smoking, obesity, dyslipidaemia and diabetes. Among patients (70% male, mean±sd age 52±12 years), 78% had AHI>5 events·h(-1) and 41% systemic hypertension. Both AHI and ODI independently related to prevalent hypertension after adjustment for relevant covariates (p<0.0001 for linear trend across quartiles (Q) of severity for both variables). However, in multiple regression analysis with both ODI and AHI in the model, ODI was, whereas AHI was not, independently associated with prevalent hypertension: odds ratios (95% CI) for Q4 versus Q1 regarding ODI were 2.01 (1.61-2.51) and regarding AHI were 0.92 (0.74-1.15) (p<0.0001 and p=0.3054, respectively). This cross sectional study suggests that chronic intermittent hypoxia plays an important role in OSAS-related hypertension.

Cardiac workload in patients with sleep-disordered breathing early after acute myocardial infarction

BACKGROUND

Sleep-disordered breathing (SDB) may promote an increase in cardiac workload early after acute myocardial infarction (AMI). We tested the hypothesis that in the early phase after AMI, SDB is associated with increased 24-h arterial BP, heart rate (HR), and, thus, cardiac workload.

METHODS

In this prospective study, 55 consecutive patients with AMI and subsequent percutaneous coronary intervention (78% men; mean age, 54 ± 10 y; mean BMI, 28.3 ± 3.6 kg/m²; mean left ventricular ejection fraction [LVEF], 47% ± 8%) underwent polysomnography and 24-h ambulatory BP and heart rate monitoring within 5 days after MI. Cardiac workload was calculated as systolic BP multiplied by HR. The presence of SDB was defined as ≥ 10 apneas and hypopneas per hour of sleep.

RESULTS

Fifty-five percent of the patients had SDB, of which 40% was predominantly central in nature. Patients with SDB had higher 24-h HR and systolic and diastolic BP compared with those without SDB (115 vs 108 mm Hg, P = .029; 71 vs 67 mm Hg, P = .034; 69 vs 64 beats/min, P = .050, respectively). Use of antihypertensive medication and β-receptor blockers was similar in both groups. In a multivariate linear regression analysis, SDB was significantly associated with an increased 24-h cardiac workload (β-coefficient, 0.364; 95% CI, 0.071-0.657; P = .016), independently of age, sex, BMI, LVEF, and antihypertensive medication.

CONCLUSION

Patients with AMI and SDB have significantly increased 24-h BP, HR, and cardiac workload. Treatment of SDB may be a valuable nonpharmacologic approach to lower cardiac workload in these patients.

2013 ambulatory blood pressure monitoring recommendations for the diagnosis of adult hypertension, assessment of cardiovascular and other hypertension-associated risk, and attainment of therapeutic goals

Correlation between systolic (SBP) and diastolic (DBP) blood pressure (BP) level and target organ damage, cardiovascular disease (CVD) risk, and long-term prognosis is much greater for ambulatory BP monitoring (ABPM) than daytime office measurements. The 2013 ABPM guidelines specified herein are based on ABPM patient outcomes studies and constitute a substantial revision of current knowledge. The asleep SBP mean and sleep-time relative SBP decline are the most significant predictors of CVD events, both individually as well as jointly when combined with other ABPM-derived prognostic markers. Thus, they should be preferably used to diagnose hypertension and assess CVD and other associated risks. Progressive decrease by therapeutic intervention of the asleep BP mean is the most significant predictor of CVD event-free interval. The 24-h BP mean is not recommended to diagnose hypertension because it disregards the more valuable clinical information pertaining to the features of the 24-h BP pattern. Persons with the same 24-h BP mean may display radically different 24-h BP patterns, ranging from extreme-dipper to riser types, representative of markedly different risk states. Classification of individuals by comparing office with either the 24-h or awake BP mean as "masked normotensives" (elevated clinic BP but normal ABPM), which should replace the terms of "isolated office" or "white-coat hypertension", and "masked hypertensives" (normal clinic BP but elevated ABPM) is misleading and should be avoided because it disregards the clinical significance of the asleep BP mean. Outcome-based ABPM reference thresholds for men, which in the absence of compelling clinical conditions are 135/85 mmHg for the awake and 120/70 mmHg for the asleep SBP/DBP means, are lower by 10/5 mmHg for SBP/DBP in uncomplicated, low-CVD risk, women and lower by 15/10 mmHg for SBP/DBP in male and female high-risk patients, e.g., with diabetes, chronic kidney disease (CKD), and/or past CVD events. In the adult population, the combined prevalence of masked normotension and masked hypertension is >35%. Moreover, >20% of "normotensive" adults have a non-dipper BP profile and, thus, are at relatively high CVD risk. Clinic BP measurements, even if supplemented with home self-measurements, are unable to quantify 24-h BP patterning and asleep BP level, resulting in potential misclassification of up to 50% of all evaluated adults. ABPM should be viewed as the new gold standard to diagnose true hypertension, accurately assess consequent tissue/organ, maternal/fetal, and CVD risk, and individualize hypertension chronotherapy. ABPM should be a priority for persons likely to have a blunted nighttime BP decline and elevated CVD risk, i.e., those who are elderly and obese, those with secondary or resistant hypertension, and those diagnosed with diabetes, CKD, metabolic syndrome, and sleep disorders.

Dipper and non-dipper blood pressure 24-hour patterns: circadian rhythm-dependent physiologic and pathophysiologic mechanisms

Neuroendocrine mechanisms are major determinants of the normal 24-h blood pressure (BP) pattern. At the central level, integration of the major driving factors of this temporal variability is mediated by circadian rhythms of monoaminergic systems in conjunction with those of the hypothalamic-pituitary-adrenal, hypothalamic-pituitary-thyroid, opioid, renin-angiotensin-aldosterone, plus endothelial systems and specific vasoactive peptides. Humoral secretions are typically episodic, coupled either to sleep and/or the circadian endogenous (suprachiasmatic nucleus) central pacemaker clock, but exhibiting also weekly, monthly, seasonal, and annual periodicities. Sleep induction and arousal are influenced also by many hormones and chemical substances that exhibit 24-h variation, e.g., arginine vasopressin, vasoactive intestinal peptide, melatonin, somatotropin, insulin, steroids, serotonin, corticotropin-releasing factor, adrenocorticotropic hormone, thyrotropin-releasing hormone, endogenous opioids, and prostaglandin E2, all with established effects on the cardiovascular system. As a consequence, physical, mental, and pathologic stimuli that activate or inhibit neuroendocrine effectors of biological rhythmicity may also interfere with, or modify, the temporal BP structure. Moreover, immediate adjustment to exogenous components/environment demands by BP rhythms is modulated by the circadian-time-dependent responsiveness of biological oscillators and their neuroendocrine effectors. This knowledge contributes to a better understanding of the pathophysiology of abnormalities of the 24-h BP pattern and level and their correction through circadian rhythm-based chronotherapeutic strategies.

Nocturnal medications dosing: does it really make a difference in blood pressure control among patients with chronic kidney disease?

Ambulatory blood pressure (BP) monitoring is superior to clinic BP monitoring in predicting long-term consequences of hypertension. This has raised interest in diurnal variation in BP and elevation in nighttime BP as a prognostic and therapeutic target. Several studies have identified prevalence of nocturnal hypertension in patients with accelerated progression of chronic kidney disease and target organ damage. Some studies suggest that nocturnal BP can be lowered by changing administration of antihypertensive medication to bed time; whether that results in retarding kidney disease progression is not very clear. Further research is needed to determine if certain classes of medications or interventions are superior in controlling nocturnal hypertension, and protocols need to be developed to screen patients for monitoring nocturnal BP. Further studies are needed to evaluate long-term renal outcomes of evening dosing in patients with nocturnal hypertension and chronic kidney disease.

Obstructive sleep apnea syndrome (OSAS) and hypertension: pathogenic mechanisms and possible therapeutic approaches

Obstructive sleep apnea syndrome (OSAS), a chronic condition characterized by collapse of the pharynx during sleep, has been increasingly recognized as a health issue of growing importance over the last decade. Recently emerging evidence suggests that there is a causal link between OSAS and hypertension, and hypertension represents an independent risk factor in OSAS patients. However, the pathophysiological basis for patients with OSAS having an increased risk for hypertension remains to be elucidated. The main acute physiological outcomes of OSAS are intermittent hypoxia, intrapleural pressure changes, and arousal from sleep, which might induce endothelial dysfunction, sympathetic activation, renin-angiotensin-aldosterone system activation, lipid metabolism dysfunction, and increased oxidative stress. This brief review focuses on the current understanding of the complex association between OSAS and hypertension.

Circadian rhythms and cardiovascular health

The functional organization of the cardiovascular system shows clear circadian rhythmicity. These and other circadian rhythms at all levels of organization are orchestrated by a central biological clock, the suprachiasmatic nuclei of the hypothalamus. Preservation of the normal circadian time structure from the level of the cardiomyocyte to the organ system appears to be essential for cardiovascular health and cardiovascular disease prevention. Myocardial ischemia, acute myocardial infarct, and sudden cardiac death are much greater in incidence than expected in the morning. Moreover, supraventricular and ventricular cardiac arrhythmias of various types show specific day-night patterns, with atrial arrhythmias--premature beats, tachycardias, atrial fibrillation, and flutter - generally being of higher frequency during the day than night--and ventricular fibrillation and ventricular premature beats more common, respectively, in the morning and during the daytime activity than sleep span. Furthermore, different circadian patterns of blood pressure are found in arterial hypertension, in relation to different cardiovascular morbidity and mortality risk. Such temporal patterns result from circadian periodicity in pathophysiological mechanisms that give rise to predictable-in-time differences in susceptibility-resistance to cyclic environmental stressors that trigger these clinical events. Circadian rhythms also may affect the pharmacokinetics and pharmacodynamics of cardiovascular and other medications. Knowledge of 24-h patterns in the risk of cardiac arrhythmias and cardiovascular disease morbidity and mortality plus circadian rhythm-dependencies of underlying pathophysiologic mechanisms suggests the requirement for preventive and therapeutic interventions is not the same throughout the day and night, and should be tailored accordingly to improve outcomes.

Hypertension and catecholamine levels in sleep apnoea

BACKGROUND

Sleep-disordered breathing has been strongly associated with systemic hypertension. Increased sympathetic activity in sleep-disordered breathing may be responsible for this association.

METHOD

In this sleep clinic-based study, 82 newly diagnosed patients of sleep-disordered breathing were evaluated for hypertension, and their plasma and urinary levels of catecholamines were measured. Catecholamine levels were then compared separately with the severity of sleep apnoea and blood pressure (BP).

RESULTS

The prevalence of hypertension in the study population was 46.3%. The BP showed a strong and statistically significant correlation with apnoea-hypopnoea index (diastolic, r = 0.65, P < 0.001 and systolic, r = 0.60, P < 0.001) which was maintained even after the results were analysed separately for obese and non-obese subjects. Both plasma and urinary levels of catecholamines were greater in patients with severe sleep apnoea (compared to nonsevere cases) and in those with hypertension compared to normotensives. However, statistical significance was achieved only for urine catecholamines and not for plasma catechol-amines in both the cases.

CONCLUSION

Hypertension is highly prevalent among Indian subjects with obstructive sleep apnoea. Catecholamine levels are significantly higher in hypertensive than in normotensive apnoeics and are also directly related to the severity of obstructive sleep apnoea. Twenty-four hour urinary catecholamine levels are more valid measures of sympathetic activity than spot plasma samples.

Obstructive sleep apnea: the most common secondary cause of hypertension associated with resistant hypertension

Recognition and treatment of secondary causes of hypertension among patients with resistant hypertension may help to control blood pressure and reduce cardiovascular risk. However, there are no studies systematically evaluating secondary causes of hypertension according to the Seventh Joint National Committee. Consecutive patients with resistant hypertension were investigated for known causes of hypertension irrespective of symptoms and signs, including aortic coarctation, Cushing syndrome, obstructive sleep apnea, drugs, pheochromocytoma, primary aldosteronism, renal parenchymal disease, renovascular hypertension, and thyroid disorders. Among 125 patients (age: 52±1 years, 43% males, systolic and diastolic blood pressure: 176±31 and 107±19 mm Hg, respectively), obstructive sleep apnea (apnea-hypopnea index: >15 events per hour) was the most common condition associated with resistant hypertension (64.0%), followed by primary aldosteronism (5.6%), renal artery stenosis (2.4%), renal parenchymal disease (1.6%), oral contraceptives (1.6%), and thyroid disorders (0.8%). In 34.4%, no secondary cause of hypertension was identified (primary hypertension). Two concomitant secondary causes of hypertension were found in 6.4% of patients. Age >50 years (odds ratio: 5.2 [95% CI: 1.9-14.2]; P<0.01), neck circumference ≥41 cm for women and ≥43 cm for men (odds ratio: 4.7 [95% CI: 1.3-16.9]; P=0.02), and presence of snoring (odds ratio: 3.7 [95% CI: 1.3-11]; P=0.02) were predictors of obstructive sleep apnea. In conclusion, obstructive sleep apnea appears to be the most common condition associated with resistant hypertension. Age >50 years, large neck circumference measurement, and snoring are good predictors of obstructive sleep apnea in this population.

Obstructive sleep apnea and heart failure: pathophysiologic and therapeutic implications

Obstructive sleep apnea (OSA) exposes the cardiovascular system to intermittent hypoxia, oxidative stress, systemic inflammation, exaggerated negative intrathoracic pressure, sympathetic overactivation, and elevated blood pressure (BP). These can impair myocardial contractility and cause development and progression of heart failure (HF). Epidemiological studies have shown significant independent associations between OSA and HF. On the other hand, recent prospective observational studies reported a significant association between the presence of moderate to severe OSA and increased risk of mortality in patients with HF. In randomized trials, treating OSA with continuous positive airway pressure suppressed sympathetic activity, lowered BP, and improved myocardial systolic function in patients with HF. These data suggest the potential for treatment of OSA to improve clinical outcomes for patients with HF. However, large-scale randomized trials with sufficient statistical power will be needed to ascertain whether treatment of OSA will prevent development of, or reduce morbidity and mortality from HF.

Managing hypertension in obstructive sleep apnea: the interplay of continuous positive airway pressure, medication and chronotherapy

Hypertension is highly prevalent and usually uncontrolled among patients with obstructive sleep apnea despite multiple interventions, namely lifestyle modifications, use of antihypertensive drugs and continuous positive airway pressure application. Main prognosticators of the blood pressure (BP) reduction with continuous positive airway pressure therapy are high levels of BP, severity of apnea and daytime sleepiness. The long-term effect of continuous positive airway pressure on BP is still inconclusive, and compliance issues constitute a major limitation. There is no clear evidence for preference for a specific type of antihypertensive drug, and selection should primarily be guided by the patient's cardiometabolic profile and associated clinical conditions. Furthermore, as hypertensive patients with obstructive sleep apnea frequently exhibit a disturbed circadian BP pattern, chronotherapy emerges as a possible therapeutic supplement.

Do restless legs syndrome (RLS) and periodic limb movements of sleep (PLMS) play a role in nocturnal hypertension and increased cardiovascular risk of renally impaired patients?

Hypertension can cause or promote renal failure and is related to cardiovascular mortality, the major cause of death in patients with renal impairment. Changes in the circadian BP pattern, particularly the blunting or reversal of the nocturnal decline in BP, are common in chronic renal failure. These changes in turn are among the major determinants of left ventricular hypertrophy. Using a chronobiological approach, it is possible to obtain better insight into the reciprocal relationship between hypertension, renal disease, and increased cardiovascular risk of renal patients. Disruption of the normal circadian rhythm of rest/activity may be hypothesized to underlie the high cardiovascular morbidity and mortality of such patients. Epidemiological studies reveal that hemodialysis patients experience poor subjective sleep quality and insomnia and, in comparison to healthy persons, are more likely to show shorter sleep duration and lower sleep efficiency. Sleep apnea may be present and is usually investigated in these patients; however, the prevalence of restless legs syndrome (RLS), which is high in dialysis patients and which has been associated with increased risk for cardiovascular disease in the general population, could also play a role in the pathogenesis of sleep-time hypertension in renal patients. Careful assessment of sleep quality, in particular, diagnostic screening for RLS and periodic limb movements (PLM) in renal patients, is highly recommended. In renal failure, attention to sleep quality and related perturbations of the sleep/wake cycle may help prevent the occurrence and progression of cardiovascular disease.

Nocturnal dosing and chronic kidney disease progression: new insights

PURPOSE OF REVIEW

Several studies have identified the presence of altered diurnal blood pressure patterns, specifically elevated nighttime blood pressure in patients with chronic kidney disease. The lack of nocturnal decline in blood pressure is associated with markers of hypertensive target organ damage and predictive of long-term clinical outcomes. The purpose of this review is to summarize the literature in this area and explore the potential for use of nighttime blood pressure for improving risk stratification and as a therapeutic target.

RECENT FINDINGS

The mechanisms of persistent elevation of blood pressure at night in chronic kidney disease are likely to be multifactorial, including altered sodium handling and sympathetic activation among others. Elevated nocturnal blood pressures have been shown to be associated with increased adverse clinical outcomes. Recent studies demonstrate that it is feasible to lower nocturnal blood pressure by modifying the time of administration of antihypertensive medications.

SUMMARY

Currently, clinical blood pressure measurements are assessed and targeted for drug therapy. This article shows the importance of measuring ambulatory blood pressures, specifically nocturnal blood pressures to improve risk stratification. More research needs to be done to identify interventions that lower nighttime blood pressure, and test their efficacy in improving clinical outcomes.

Can nocturnal hypertension predict cardiovascular risk?

Nocturnal hypertension and non-dipping of blood pressure during sleep are distinct entities that often occur together and are regarded as important harbingers of poor cardiovascular prognosis. This review addresses several aspects related to these blood pressure abnormalities including definitions, diagnostic limitations, pathogenesis and associated patient profiles, prognostic significance, and therapeutic strategies. Taken together, persistent nocturnal hypertension and non-dipping blood pressure pattern, perhaps secondary to abnormal renal sodium handling and/or altered nocturnal sympathovagal balance, are strongly associated with deaths, cardiovascular events, and progressive loss of renal function, independent of daytime and 24-hour blood pressure. Several pharmacological and non-pharmacological approaches may restore nocturnal blood pressure and circadian blood pressure rhythm to normal; however, whether this translates to a clinically meaningful reduction in unfavorable cardiovascular and renal consequences remains to be seen.