Cardiovascular Regulation in Obstructive Sleep Apnea

Impact of beta-blockers on mortality and cardiovascular disease outcomes in patients with obstructive sleep apnoea: a population-based cohort study in target trial emulation framework

Background

There is no real-world evidence regarding the association between beta-blocker use and mortality or cardiovascular outcomes in patients with obstructive sleep apnoea (OSA). We aimed to investigate the impact of beta-blocker use on all-cause mortality and cardiovascular diseases (CVDs) in patients with OSA.

Methods

We conducted a target trial emulation study of 37,581 patients with newly diagnosed OSA from 1st January 2000 to 30th November 2021 using the IMRD-UK database (formerly known as the THIN database). We compared the treatment strategies of initiating beta-blocker treatment within one year versus non-beta-blocker treatment through the method of clone-censor-weight. Covariates, including patients' demographics, lifestyle, comorbidities, and recent medications, were measured and controlled. Patients were followed up for all-cause mortality or composite CVD outcomes (angina, myocardial infarction, stroke/transient ischaemic attack, heart failure, or atrial fibrillation). We estimated the five-year absolute risks, risk differences and risk ratio with 95% confidence intervals (CIs) with standardised, weighted pooled logistic regression, which is a discrete-time hazard model for survival analysis. Several sensitivity analyses were performed, including multiple imputation addressing the missing data.

Findings

The median follow-up time was 4.1 (interquartile range, 1.9-7.8) years. The five-year absolute risk of all-cause mortality and CVD outcomes were 4.9% (95% CI, 3.8-6.0) and 13.0% (95% CI, 11.4-15.0) among beta-blocker users, and 4.0% (95% CI, 3.8-4.2) and 9.4% (95% CI, 9.1-9.7) among non-beta-blocker users, respectively. The five-year absolute risk difference and risk ratio between the two groups for all-cause mortality and CVD outcomes were 0.9% (95% CI, -0.2 to 2.1) and 1.22 (95% CI, 0.96-1.54), and 3.5% (95% CI, 2.1-5.5) and 1.37 (95% CI, 1.22-1.62), respectively. Findings were consistent across the sensitivity analyses.

Interpretation

Beta-blocker treatment was associated with an increased risk of CVD and a trend for an increased risk of mortality among patients with OSA. Further studies are needed to confirm our findings.

Funding

Innovation and Technology Commission of the Hong Kong Special Administration Region Government.

Management of hypertension in obstructive sleep apnea

Obstructive sleep apnea (OSA) plays an important role in the development of hypertension. Thus, this review summarizes pharmacological and non-pharmacological approaches to blood pressure (BP) control in patients with OSA. Current treatments for OSA, such as continuous positive airway pressure, are effective at lowering BP. However, they only provide a modest BP reduction, and pharmacological treatment remains important for achieving optimal BP control. Furthermore, current guidelines for the treatment of hypertension do not make specific recommendations on pharmacological treatment protocols for controlling BP in patients with OSA. Moreover, the BP-lowering effects of various classes of antihypertensives may be different in hypertensive patients with OSA than in those without OSA due to the underlying mechanisms that promote hypertension in OSA. The acute and chronic increase in sympathetic nerve activity in patients with OSA explain the effectiveness of beta blockers in controlling BP in these patients. As activation of the renin-angiotensin-aldosterone system may also promote hypertension in OSA, angiotensin-converting enzyme inhibitors and angiotensin II receptor blockers have generally been found effective for lowering BP in hypertensive patients with OSA. The aldosterone antagonist spironolactone also produces a good antihypertensive response in patients with OSA and resistant hypertension. However, there are limited data available that compare the effects of various classes of antihypertensive medication on BP control in those with OSA, and most data have been obtained from small-scale studies. This demonstrates the need for large-scale randomized controlled trials to evaluate a range of BP-lowering regimens in patients with OSA and hypertension.

The association between sleep deprivation and arterial pressure variations: a systematic literature review

Objectives

Arterial hypertension is a cardiovascular disease defined as a sustained high blood pressure, constituting an important risk factor for the development of heart diseases, such as coronary heart disease and heart failure. At the same time, pathophysiological pathways underlying sleeping deprivation provides biological plausibility for a causation connection between sleep deprivation and acute or chronic blood pressure elevation, such as the mechanism behind blood pressure dipping at night, which strongly relies on reduced sympathetic activity provided by sleep, besides empirical and clinical evidence suggesting that sleep disorders incidence is correlate with posterior development of arterial hypertension. The aim of this study was to systematically review published studies analyzing the possible relationship between sleep deprivation and variations in blood pressure during nighttime and daytime.

Methods

The research was carried out in the second semester of 2020 following the PRISMA model and using the LILACS, MEDLINE and COCHRANE (CENTRAL) databases. The keywords used were associated using the Boolean method. Only trials and studies in humans unrelated to sleep apnea were included, in an attempt to answer the question proposed. Duplications and articles outside the topic were excluded.

Results

After the selection processes, fourteen studies were left, which were classified, depending on the findings, in four categories: 1) blood pressure differences only in sleep deprivation's night; 2) blood pressure differences only in the following day after sleep deprivation's night; 3) blood pressure differences in both nights and 4) those that found no blood pressure differences.

Conclusion

It was found an increase in blood pressure on the night of sleep deprivation, suggesting a possible causality with an acute increase in blood pressure depending on the population studied. In general, sleep deprivation is acutely associated with blood pressure elevation or acute elevation of markers that suggest the role of compensatory mechanisms, such as increased natriuresis and increased parasympathetic activity.

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Sleep deprivation results in increased simpathetic activity.

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Chronic sleep deprivation might lead to systemic arterial hypertension.

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Increased parasympathetic activity in acute sleep deprivation play a role as compensatory mechanism.

Leptin: A Potential Link Between Obstructive Sleep Apnea and Obesity

Chronic intermittent hypoxia (CIH), a pathophysiological manifestation of obstructive sleep apnea (OSA), is strongly correlated with obesity, as patients with the disease experience weight gain while exhibiting elevated plasma levels of leptin. This study was done to determine whether a relationship may exist between CIH and obesity, and body energy balance and leptin signaling during CIH. Sprague-Dawley rats were exposed to 96 days of CIH or normoxic control conditions, and were assessed for measures of body weight, food and water intake, and food conversion efficiency. At the completion of the study leptin sensitivity, locomotor activity, fat pad mass and plasma leptin levels were determined within each group. Additionally, the hypothalamic arcuate nucleus (ARC) was isolated and assessed for changes in the expression of proteins associated with leptin receptor signaling. CIH animals were found to have reduced locomotor activity and food conversion efficiency. Additionally, the CIH group had increased food and water intake over the study period and had a higher body weight compared to normoxic controls at the end of the study. Basal plasma concentrations of leptin were significantly elevated in CIH exposed animals. To test whether a resistance to leptin may have occurred in the CIH animals due to the elevated plasma levels of leptin, an acute exogenous (ip) leptin (0.04 mg/kg carrier-free recombinant rat leptin) injection was administered to the normoxic and CIH exposed animals. Leptin injections into the normoxic controls reduced their food intake, whereas CIH animals did not alter their food intake compared to vehicle injected CIH animals. Within ARC, CIH animals had reduced protein expression of the short form of the obese (leptin) receptor (isoform OBR₁₀₀) and showed a trend toward an elevated protein expression of the long form of obese (leptin) receptor (OBRb). In addition, pro-opiomelanocortin (POMC) protein expression was reduced, but increased expression of the phosphorylated extracellular-signal-regulated kinase 1/2 (pERK1/2) and of the suppressor of cytokine signaling 3 (SOCS3) proteins was observed in the CIH group, with little change in phosphorylated signal transducer and activator of transcription 3 (pSTAT3). Taken together, these data suggest that long-term exposure to CIH, as seen in obstructive sleep apnea, may contribute to a state of leptin resistance promoting an increase in body weight.

Obstructive Sleep Apnea-Induced Neurogenic Nocturnal Hypertension: A Potential Role of Renal Denervation?

There is a bidirectional, causal relationship between obstructive sleep apnea (OSA) and hypertension. OSA-related hypertension is characterized by high rates of masked hypertension, elevated nighttime blood pressure, a nondipper pattern of nocturnal hypertension, and abnormal blood pressure variability. Hypoxia/hypercapnia-related sympathetic activation is a key pathophysiological mechanism linking the 2 conditions. Intermittent hypoxia also stimulates the renin-angiotensin-aldosterone system to promote hypertension development. The negative and additive cardiovascular effects of OSA and hypertension highlight the importance of effectively managing these conditions, especially when they coexist in the same patient. Continuous positive airway pressure is the gold standard therapy for OSA but its effects on blood pressure are relatively modest. Furthermore, this treatment did not reduce the cardiovascular event rate in nonsleepy patients with OSA in randomized controlled trials. Antihypertensive agents targeting sympathetic pathways or the renin-angiotensin-aldosterone system have theoretical potential in comorbid hypertension and OSA, but current evidence is limited and combination strategies are often required in drug resistant or refractory patients. The key role of sympathetic nervous system activation in the development of hypertension in OSA suggests potential for catheter-based renal sympathetic denervation. Although long-term, randomized controlled trials are needed, available data indicate sustained and relevant reductions in blood pressure in patients with hypertension and OSA after renal denervation, with the potential to also improve respiratory parameters. The combination of lifestyle interventions, optimal pharmacological therapy, continuous positive airway pressure therapy, and perhaps also renal denervation might improve cardiovascular risk in patients with OSA.

Effect of laterotrusive occlusal scheme on chewing duration, external intercostal muscular activity, heart rate, and oxygen saturation

Objective: To evaluate the effect of the laterotrusive occlusal scheme on chewing duration, external intercostal (EIC) electromyographic (EMG) activity, heart rate (HR), and oxygen saturation (OS) during different tasks in the upright seated position.Methods: Fifty young participants, 25 with canine guidance and 25 with group function, were included. Chewing duration, bilateral EIC EMG activity, HR, and OS were recorded during the following tasks: 1) chewing until swallowing threshold; 2) laterotrusive teeth grinding.Results: Chewing duration, bilateral EIC EMG activity, HR, and OS showed no significant differences between the two laterotrusive occlusal schemes during the tasks studied.Conclusion: These results suggest that chewing duration, EIC muscle activity, HR, and OS were not significantly influenced by the laterotrusive occlusal scheme. Therefore, when a modification of the laterotrusive occlusal scheme is needed during oral rehabilitation or orthodontic treatment, canine guidance or group function should not significantly change EMG activity of EIC muscles.

Ankylosing Spondylitis Is Associated With Risk of New-Onset Obstructive Sleep Apnea: A Nationwide Population-Based Cohort Study

Objectives: Investigating the risk of obstructive sleep apnea(OSA) among ankylosing spondylitis (AS) patients based on administrative healthcare databases.

Methods: We conducted a nationwide cohort study by using the Taiwan National Health Insurance Research Database with 1997–2013 claim records. The AS cohort included 2,210 patients who were newly diagnosed between 2003 and 2013. Randomly selected non-AS controls were matched at a 1:4 ratio. The endpoint was set as OSA occurrence or the end of 2013. Cumulative incidences, hazard ratios (HRs) and 95% confidence intervals (CIs) were calculated after adjusting for age, gender, comorbidities, and co-medication. Multivariate analyses were performed using the Cox proportional hazards model. Due to the violation of the proportionality assumption, landmark analysis was conducted to explore the risk of OSA during specific follow-up periods.

Results: The adjusted HR (aHR) of OSA in the AS group was 2.826 (95% C.I. = 1.727–4.625) compared to the control group. On landmark analysis, aHR was 7.919 (95% C.I. = 3.169–19.792) for the AS group 0–24 months from the index date and decreased to 1.816 (95% C.I. = 0.944–3.494) at ≥ 24 months from the index date. The increased risks of OSA in the AS group compared to the control group were found for both males and females (aHRs were 4.533 and 2.672). On age-stratified analysis, a significant risk only for the 40–59 age group with aHR of 3.913 (95% C.I. = 1.890–8.102).

Conclusions: A higher risk of developing OSA was found among newly diagnosed AS cohort during the maximum 11-year follow-up period, especially within 2 years after newly diagnosed AS and in the 40–59 age group.

Associations between primary aldosteronism and diabetes, poor bone health, and sleep apnea-what do we know so far?

Primary aldosteronism (PA), the most common cause of secondary hypertension, is a well-recognized condition that can lead to cardiovascular and renal complications. PA is frequently left undiagnosed and untreated, leading to aldosterone-specific morbidity and mortality. In this review we highlight the evidence linking PA with other conditions such as (i) diabetes mellitus, (ii) obstructive sleep apnea, and (iii) bone health, along with clinical implications and proposed underlying mechanisms.

Awake teeth grinding in participants with canine guidance or group function: Effect on diaphragm EMG activity, heart rate, and oxygen saturation

Objective: To compare the effect of canine guidance or group function on diaphragm activity, heart rate, and oxygen saturation during awake teeth grinding at different body positions. Methods: Fifty healthy participants, 25 with canine guidance and 25 with group function, were included. Bilateral electromyographic (EMG) recordings of the diaphragm (DIA) during awake teeth grinding were performed in standing, seated upright, and right lateral decubitus positions. Simultaneously, heart rate and oxygen saturation were measured. Results: EMG activity of the DIA muscle was similar in the working side and non-working side between participants with canine guidance and group function in the different body positions studied. The heart rate and oxygen saturation showed no significant differences between the two groups. Conclusion: EMG activity of the DIA muscle, the heart rate, and oxygen saturation during teeth grinding are not significantly influenced by the type of laterotrusive occlusal scheme.

Review of and Updates on Hypertension in Obstructive Sleep Apnea

Obstructive sleep apnea (OSA) is a prevalent sleep disorder as is hypertension (HTN) in the 21st century with the rising incidence of obesity. Numerous studies have shown a strong association of OSA with cardiovascular morbidity and mortality. There is overwhelming evidence supporting the relationship between OSA and hypertension (HTN). The pathophysiology of HTN in OSA is complex and dependent on various factors such as sympathetic tone, renin-angiotensin-aldosterone system, endothelial dysfunction, and altered baroreceptor reflexes. The treatment of OSA is multifactorial ranging from CPAP to oral appliances to lifestyle modifications to antihypertensive drugs. OSA and HTN both need prompt diagnosis and treatment to help address the growing cardiovascular morbidity and mortality due to these two entities.

Healthcare Service Utilization by Patients with Obstructive Sleep Apnea: A Population-Based Study

OBJECTIVE

Although obstructive sleep apnea (OSA) is not a life-threatening disease, very few studies have compared differences in healthcare service utilization between patients with and those without OSA in an Asian population according to different age groups. This study attempted to investigate differences in healthcare service utilization between patients with and those without OSA in different age groups in Taiwan.

METHODS

Sampled subjects and data on their health service utilization were retrieved from the Taiwan Longitudinal Health Insurance Database 2005. We included 568 patients with OSA and 2840 subjects without OSA. Each subject was followed for a 1-year period to evaluate their healthcare resource utilization. Wilcoxon-Mann-Whitney tests were performed to compare differences in healthcare utilization between patients with and those without OSA during the 1-year follow-up period.

RESULTS

As to all healthcare service utilization, patients with OSA had significantly more outpatient visits (30.3 vs. 18.6), outpatient costs (US$1231.2 vs. US$764.8), inpatient days (1.8 vs. 1.2), inpatient costs (US$563.6 vs. US$276.7), and total costs (US$1794.8 vs. US$1041.5) than comparison subjects during the 1-year follow-up period. Moreover, patients with OSA aged 40~49 and 50~59 years respectively incurred 2.11- and 2.02-fold higher total costs compared to patients without OSA. However, patients with OSA aged over 70 years did not have higher total costs compared to those without OSA.

CONCLUSIONS

This study found that patients with OSA had greater healthcare service utilization than those without OSA. Additionally, patients with OSA in the 40~49- and 50~59-year age groups had about 2-fold higher total costs of healthcare services than those without OSA.

Could transient hypoxia be associated with rhythmic masticatory muscle activity in sleep bruxism in the absence of sleep-disordered breathing? A preliminary report

Sleep bruxism (SB) is a repetitive jaw-muscle activity characterised by clenching or grinding of the teeth during sleep. Sleep bruxism activity is characterised by rhythmic masticatory muscle activity (RMMA). Many but not all RMMA episodes are associated with sleep arousal. The aim of this study was to evaluate whether transient oxygen saturation level change can be temporally associated with genesis of RMMA/SB. Sleep laboratory or home recordings data from 22 SB (tooth grinding history in the absence of reported sleep-disordered breathing) and healthy subjects were analysed. A total of 143 RMMA/SB episodes were classified in four categories: (i) no arousal + no body movement; (ii) arousal + no body movement; (iii) no arousal + body movement; (iv) arousal + body movement. Blood oxygen levels (SaO2 ) were assessed from finger oximetry signal at the baseline (before RMMA), and during RMMA. Significant variation in SaO2 over time (P = 0·001) was found after RMMA onset (+7 to +9 s). No difference between categories (P = 0·91) and no interaction between categories and SaO2 variation over time (P = 0·10) were observed. SaO2 of six of 22 subjects (27%) remained equal or slight increase after the RMMA/SB onset (+8 s) compared to baseline; 10 subjects (45%) slightly decreased (drop 0·01-1%) and the remaining (27%) decreased between 1% and 2%. These preliminary findings suggest that a subgroup of SB subjects had (i) a minor transient hypoxia potentially associated with the onset of RMMA episodes, and this (ii) independently of concomitant sleep arousal or body movements.

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.

The efficacy of antihypertensive drugs in chronic intermittent hypoxia conditions

Sleep apnea/hypopnea disorders include centrally originated diseases and obstructive sleep apnea (OSA). This last condition is renowned as a frequent secondary cause of hypertension (HT). The mechanisms involved in the pathogenesis of HT can be summarized in relation to two main pathways: sympathetic nervous system stimulation mediated mainly by activation of carotid body (CB) chemoreflexes and/or asphyxia, and, by no means the least important, the systemic effects of chronic intermittent hypoxia (CIH). The use of animal models has revealed that CIH is the critical stimulus underlying sympathetic activity and hypertension, and that this effect requires the presence of functional arterial chemoreceptors, which are hyperactive in CIH. These models of CIH mimic the HT observed in humans and allow the study of CIH independently without the mechanical obstruction component. The effect of continuous positive airway pressure (CPAP), the gold standard treatment for OSA patients, to reduce blood pressure seems to be modest and concomitant antihypertensive therapy is still required. We focus this review on the efficacy of pharmacological interventions to revert HT associated with CIH conditions in both animal models and humans. First, we explore the experimental animal models, developed to mimic HT related to CIH, which have been used to investigate the effect of antihypertensive drugs (AHDs). Second, we review what is known about drug efficacy to reverse HT induced by CIH in animals. Moreover, findings in humans with OSA are cited to demonstrate the lack of strong evidence for the establishment of a first-line antihypertensive regimen for these patients. Indeed, specific therapeutic guidelines for the pharmacological treatment of HT in these patients are still lacking. Finally, we discuss the future perspectives concerning the non-pharmacological and pharmacological management of this particular type of HT.

Cardiac structural and functional changes in old elderly patients with obstructive sleep apnoea-hypopnoea syndrome

OBJECTIVE

To investigate cardiac structural changes in elderly patients with obstructive sleep apnoea-hypopnoea syndrome (OSAHS) and the impact on left ventricular systolic and diastolic function.

METHODS

The study enrolled elderly patients with OSAHS and age-matched healthy control subjects. Cardiac structure, left ventricular diastolic function and left ventricular systolic function were measured using a Doppler ultrasound scanner and compared between the two groups.

RESULTS

The study included 136 patients with OSAHS and 50 healthy control subjects. There were significant differences in the echocardiography indicators that reflect cardiac structure, including interventricular septum, left ventricle posterior wall thickness, and left ventricular mass and mass index between the two groups. There were significant differences between the two groups in the ventricular septal early diastolic myocardial peak velocity/late diastolic myocardial peak velocity (Em/Am), mitral annulus Em/Am, and left ventricle posterior wall Em/Am. There were also significant differences in the indicators of interventricular septum, mitral annulus and left ventricular posterior wall systolic peak velocity between the two groups.

CONCLUSION

Elderly patients with OSAHS demonstrated cardiac structural changes and their left ventricular diastolic and systolic functions were significantly diminished.

Stress-triggered changes in peripheral catecholaminergic systems

The sympathetic nervous system not only regulates cardiovascular and metabolic responses to stress but also is altered by stress. The sympathoneural and sympathoadrenomedullary systems are modified by different metabolic pathways and have different responses to short- and to long-term stressors. Stress also induces nonneuronal catecholamine enzymes, primarily through corticosteroids. Catecholamine synthetic enzymes are induced by different pathways in response to short- and long-term acting stressors, like cold exposure or immobilization, and differently in the sympathetic ganglia and the adrenal medulla. However, a long-term exposure to one stressor can increase the response to a second, different stressor. Tyrosine hydroxylase gene transcription increases after only 5min of immobilization through phosphorylation of CREB, but this response is short lived. However, repeated stress gives a longer-lived response utilizing transcription factors such as Egr-1 and Fra-2. Glucocorticoids and ACTH also induce sympathoneural enzymes leading to distinct patterns of short-term and long-lived activation of the sympathetic nervous system. Nonneuronal phenylethanolamine N-methyltransferase (PNMT) develops early in the heart and then diminishes. However, intrinsic cardiac adrenergic cells remain and nonneuronal PNMT is present in many cells of the adult organism and increases in response to glucocorticoids. Both stress-induced and administered glucocorticoids induce fetal PNMT and hypertension. Human stressors such as caring for an ill spouse or sleep apnea cause a persistent increase in blood norepinephrine, increased blood pressure, and downregulated catecholamine receptors. Hypertension is associated with a loss of slow-wave sleep, when sympathetic nerve activity is lowest. These findings indicate that stress-induced alteration of the sympathetic nervous system occurs in man as in experimental animals.