The sleep apnea cardiovascular endpoints (SAVE) trial: Rationale and start-up phase

Cardiovascular correlates of sleep apnea phenotypes: Results from the Hispanic Community Health Study/Study of Latinos (HCHS/SOL)

Background

Identifying Obstructive Sleep Apnea (OSA) phenotypes among middle-aged and older Hispanics/Latinos can facilitate personalized care, better inform treatment decisions, and could lead to improved clinical outcomes.

Methods

We focused on middle-aged and older adults (ages ≥45–74 years at baseline) with an apnea-hypopnea index (AHI) ≥5 from the HCHS/SOL (2008–2011) (unweighted n = 3,545). We used latent class analyses (LCA) to identify empirical and clinically meaningful OSA phenotypes. Sleep variables included AHI, percent sleep time SpO2<90%, Epworth Sleepiness Scale (ESS), Women’s Health Initiative Insomnia Rating Scale (WHIIRS) score, self-reported average sleep duration, restless legs symptoms, napping frequency, and self-reported sleep quality. We used survey logistic and Poisson regression to test the associations between our OSA phenotypes and prevalent and incident cardiovascular measures (cardiovascular disease, heart failure, Stroke/TIA, hypertension, diabetes, and the Framingham Cardiovascular Risk Score).

Results

Average AHI, ESS, WHIIRS, and sleep duration were 18.1±19.5, 6.3±6.1, 7.4±6.6, and 7.8±1.7 hours, respectively, and 2.9% had zero percent time SpO2 <90%. We identified a three-class solution that clustered individuals into (1) insomnia OSA (44.3%), (2) asymptomatic mild OSA, (36.2%) and (3) symptomatic OSA (19.5%). Elevated WHIIRS and AHI scores primarily drove classification into groups one and three, respectively. In covariate adjusted models, OSA phenotypes were differentially associated with prevalence (baseline and seven years later) and incidence of cardiovascular measures.

Conclusions

OSA subtypes in diverse U.S. Hispanic/Latino adults have different cardiovascular complications. More targeted research, that takes these variations into account, could help ameliorate Hispanic/Latino sleep and cardiovascular health disparities.

Low Prognostic Value of Novel Nocturnal Metrics in Patients With OSA and High Cardiovascular Event Risk: Post Hoc Analyses of the SAVE Study

BACKGROUND

Traditional methods for the quantification of OSA severity may not encapsulate potential relationships between hypoxemia in OSA and cardiovascular risk.

RESEARCH QUESTION

Do novel nocturnal oxygen saturation (Spo₂) metrics have prognostic value in patients with OSA and high cardiovascular event risk?

STUDY DESIGN AND METHODS

We conducted post hoc analyses of the Sleep Apnea Cardiovascular Endpoints (SAVE) trial. In 2687 individuals, Cox proportional hazards models that were stratified for treatment allocation were used to determine the associations between clinical characteristics, pulse oximetry-derived metrics that were designed to quantify sustained and episodic features of hypoxemia, and cardiovascular outcomes. Metrics included oxygen desaturation index, time <90% Spo₂, average Spo₂ for the entire recording (mean Spo₂), average Spo₂ during desaturation events (desaturation Spo₂), average baseline Spo₂ interpolated across episodic desaturation events (baseline Spo₂), episodic desaturation event duration and desaturation/resaturation-time ratio, and mean and SD of pulse rate.

RESULTS

Neither apnea-hypopnea index, oxygen desaturation index, nor any of the novel Spo₂ metrics were associated with the primary SAVE composite cardiovascular outcome. Mean and baseline Spo₂ were associated with heart failure (hazard ratio [HR], 0.81; 95% CI, 0.69-0.95; P = .009; and HR, 0.78; 95% CI, 0.67-0.90; P = .001, respectively) and myocardial infarction (HR, 0.86; 95% CI, 0.77-0.95; P = .003; and HR, 0.81; 95% CI, 0.73-0.90; P < .001, respectively). Desaturation duration and desaturation/resaturation time ratio, with established risk factors, predicted future heart failure (area under the curve, 0.86; 95% CI, 0.79-0.93).

INTERPRETATION

Apnea-hypopnea index and oxygen desaturation index were not associated with cardiovascular outcomes. In contrast, the pattern of oxygen desaturation was associated with heart failure and myocardial infarction. However, concomitant risk factors remained the predominant determinants for secondary cardiovascular events and thus deserve the most intensive management.

Agreement in the Scoring of Respiratory Events Among International Sleep Centers for Home Sleep Testing

STUDY OBJECTIVES

Home sleep testing (HST) is used worldwide to confirm the presence of obstructive sleep apnea (OSA). We sought to determine the agreement of HST scoring among international sleep centers.

METHODS

Fifteen HSTs, previously recorded using a type 3 monitor, were deidentified and saved in European Data Format. The studies were scored by nine technologists from the sleep centers of the Sleep Apnea Global Interdisciplinary Consortium (SAGIC) using the locally available software. Each study was scored separately using one of three different airflow signals: nasal pressure (NP), transformed (square root) nasal pressure signal (transformed NP), and uncalibrated respiratory inductive plethysmography (RIP) flow. Only one of the three airflow signals was visible to the scorer at each scoring session. The scoring procedure was repeated to determine the intrarater reliability.

RESULTS

The intraclass correlation coefficients (ICCs) using the NP were: apnea-hypopnea index (AHI) = 0.96 (95% confidence interval [CI]: 0.93-0.99); apnea index = 0.91 (0.83-0.96); and hypopnea index = 0.75 (0.59-0.89). The ICCs using the transformed NP were: AHI = 0.98 (0.96-0.99); apnea index = 0.95 (0.90-0.98); and hypopnea index = 0.90 (0.82-0.96). The ICCs using the RIP flow were: AH I = 0.98 (0.96-0.99); apnea index = 0.66 (0.48-0.84); and hypopnea index = 0.78 (0.63-0.90). The mean difference of first and second scoring sessions of the same respiratory variables ranged from -1.02 to 0.75/h.

CONCLUSION

There is a strong agreement in the scoring of the respiratory events for HST among international sleep centers. Our results suggest that centralized scoring of HSTs may not be necessary in future research collaboration among international sites.

COMMENTARY

A commentary on this article appears in this issue on page 7.

Impact of Randomization, Clinic Visits, and Medical and Psychiatric Cormorbidities on Continuous Positive Airway Pressure Adherence in Obstructive Sleep Apnea

STUDY OBJECTIVES

To evaluate factors associated with continuous positive airway pressure (CPAP) adherence in patients with obstructive sleep apnea (OSA) in the Apnea Positive Pressure Long-term Efficacy Study (APPLES) cohort.

METHODS

The data from a prospective 6-mo multicenter randomized controlled trial with 558 subjects randomized to active CPAP and 547 to sham CPAP were analyzed to assess adherence to CPAP during first 2 mo (early period) and during months 5-6 (late period).

RESULTS

Participants randomized to active CPAP had higher hours of nightly adherence compared to the sham CPAP group at both 2 (4.9 ± 2.0 h versus 4.07 ± 2.14 h, p < 0.001) and 6 mo (4.70 ± 2.08 h versus 3.41 ± 2.19 h, p < 0.001). Those assigned to sham CPAP were more likely to correctly identify their treatment group (70.0% versus 55.2%, p < 0.001). Irrespective of treatment group assignment, those who believed they were receiving active CPAP had higher hours of adherence than those who thought they were in the sham CPAP group at both 2 mo (4.91 ± 2.01 versus 4.17 ± 2.17, p < 0.001) and 6 mo (4.65 ± 2.10 versus 3.65 ± 2.22, p < 0.001). Among those randomized to active CPAP, older age was significantly related to CPAP use > 4 h per night. Presence of cardiovascular disorders was associated with higher hours of CPAP use, whereas presence of anxiety was associated with a trend toward lower hours of CPAP use. Presence of nasal congestion was associated with a decrease in mean daily CPAP use between the early and the late adherence period. The adherence during the week prior to a clinic visit was higher than the average adherence during the 2-mo period prior to the visit.

CONCLUSIONS

Randomization to active therapy, belief that one is in the active treatment group, older age, and possibly presence of cardiovascular disorders are positively linked to CPAP adherence. Nasal congestion and anxiety are negatively associated with CPAP adherence. CPAP nightly usage increases as clinic visits approach.

Meta-analysis of effects of obstructive sleep apnea on the renin-angiotensin-aldosterone system

Background

Obstructive sleep apnea (OSA) is the most common cause of resistant hypertension, which has been proposed to result from activation of the renin–angiotensin–aldosterone system (RAAS). We meta-analyzed the effects of OSA on plasma levels of RAAS components.

Methods

Full-text studies published on MEDLINE and EMBASE analyzing fasting plasma levels of at least one RAAS component in adults with OSA with or without hypertension. OSA was diagnosed as an apnea-hypopnea index or respiratory disturbance index ≥ 5. Study quality was evaluated using the Newcastle-Ottawa Scale, and heterogeneity was assessed using the I² statistic. Results from individual studies were synthesized using inverse variance and pooled using a random-effects model. Subgroup analysis, sensitivity analysis, and meta-regression were performed, and risk of publication bias was assessed.

Results

The meta-analysis included 13 studies, of which 10 reported results on renin (n = 470 cases and controls), 7 on angiotensin II (AngII, n = 384), and 9 on aldosterone (n = 439). AngII levels were significantly higher in OSA than in controls [mean differences = 3.39 ng/L, 95% CI: 2.00–4.79, P < 0.00001], while aldosterone levels were significantly higher in OSA with hypertension than OSA but not with hypertension (mean differences = 1.32 ng/dL, 95% CI: 0.58–2.07, P = 0.0005). Meta-analysis of all studies suggested no significant differences in aldosterone between OSA and controls, but a significant pooled mean difference of 1.35 ng/mL (95% CI: 0.88–1.82, P < 0.00001) emerged after excluding one small-sample study. No significant risk of publication bias was detected among all included studies.

Conclusions

OSA is associated with higher AngII and aldosterone levels, especially in hypertensive patients. OSA may cause hypertension, at least in part, by stimulating RAAS activity.

Translational approaches to understanding metabolic dysfunction and cardiovascular consequences of obstructive sleep apnea

Obstructive sleep apnea (OSA) is known to be independently associated with several cardiovascular diseases including hypertension, myocardial infarction, and stroke. To determine how OSA can increase cardiovascular risk, animal models have been developed to explore the underlying mechanisms and the cellular and end-organ targets of the predominant pathophysiological disturbance in OSA-intermittent hypoxia. Despite several limitations in translating data from animal models to the clinical arena, significant progress has been made in our understanding of how OSA confers increased cardiovascular risk. It is clear now that the hypoxic stress associated with OSA can elicit a broad spectrum of pathological systemic events including sympathetic activation, systemic inflammation, impaired glucose and lipid metabolism, and endothelial dysfunction, among others. This review provides an update of the basic, clinical, and translational advances in our understanding of the metabolic dysfunction and cardiovascular consequences of OSA and highlights the most recent findings and perspectives in the field.

Established vascular effects of continuous positive airway pressure therapy in patients with obstructive sleep apnoea-an update

The aim of this review was to summarize the current data from randomised controlled trials (RCTs) on vascular effects of continuous positive airway pressure (CPAP) therapy in patients with obstructive sleep apnoea (OSA). There is good evidence from RCTs that CPAP lowers blood pressure (BP) to a clinically significant amount. The effect seems to be dependent on the hours of nightly CPAP usage. Data from RCTs have also proven a beneficial effect of CPAP on measures of vascular function such as endothelial function and arterial stiffness. However, there is still a lack of evidence from RCTs proving that CPAP reduces vascular events and mortality.

Obstructive sleep apnea and acute coronary syndromes: etiology, risk, and management

Obstructive sleep apnea (OSA) is characterized by upper airway collapse and airflow reduction despite respiratory effort, resulting in intermittent hypoxia and arousals, leading to a cascade of hemodynamic, autonomic, inflammatory, and metabolic effects, responsible for its adverse cardiovascular effect. OSA is an independent risk factor for cardiovascular disease, and its prevalence in patients presenting with acute coronary syndromes is up to 69%. Furthermore, OSA has been associated with increased risk of adverse events after an acute coronary syndrome. Continuous positive airway pressure is considered the mainstay of treatment of OSA and has been shown to reduce the risk of cardiovascular events. However, the proper time to start treatment in the acute setting is unknown. A prospective randomized clinical trial is currently underway to answer this question.

Predictors of long-term adherence to continuous positive airway pressure therapy in patients with obstructive sleep apnea and cardiovascular disease in the SAVE study

STUDY OBJECTIVES

To determine the clinical variables that best predict long- term continuous positive airway pressure (CPAP) adherence among patients with cardiovascular disease who have obstructive sleep apnea (OSA).

DESIGN

12-mo prospective within-trial observational study.

SETTING

Centers in China, Australia, and New Zealand participating in the Sleep Apnea cardioVascular Endpoints (SAVE) study.

PATIENTS

There were 275 patients age 45-70 y with cardiovascular disease (i.e., previously documented transient ischemic attack, stroke, or coronary artery disease) and OSA (4% oxygen desaturation index (ODI) > 12) who were randomized into the CPAP arm of the SAVE trial prior to July 1, 2010.

METHODS

Age, sex, country of residence, type of cardiovascular disease, baseline ODI, severity of sleepiness, and Hospital Anxiety and Depression Scale (HADS) scores plus CPAP side effects and adherence at 1 mo were entered in univariate analyses in an attempt to identify factors predictive of CPAP adherence at 12 mo. Variables with P < 0.2 were then included in a multivariate analysis using a linear mixed model with sites as a random effect and 12-mo CPAP use as the dependent outcome variable.

MEASUREMENTS AND RESULTS

CPAP adherence at 1, 6, and 12 mo was (mean ± standard deviation) 4.4 ± 2.0, 3.8 ± 2.3, and 3.3 ± 2.4 h/night, respectively. CPAP use at 1 mo (effect estimate ± standard error, 0.65 ± 0.07 per h increase, P < 0.001) and side effects at 1 mo (-0.24 ± 0.092 per additional side effect, P = 0.009) were the only independent predictors of 12- mo CPAP adherence.

CONCLUSION

Continuous positive airway pressure use in patients with coexisting cardiovascular disease and moderate to severe obstructive sleep apnea decreases significantly over 12 months. This decline can be predicted by early patient experiences with continuous positive airway pressure (i.e., adherence and side effects at 1 month), raising the possibility that intensive early interventions could improve long-term continuous positive airway pressure compliance in this patient population.

CLINICAL TRIALS REGISTER

Clinical Trials, http://www.clinicaltrials.gov, NCT00738179.

Sleep apnoea and the heart

Sleep apnoea is associated with significant daytime functioning impairment and marked cardiovascular morbidities, leading to a significant increase in mortality. Sympathetic activation, oxidative stress and systemic inflammation have been shown to be the main intermediary mechanisms associated with sleep apnoea and intermittent hypoxia. There are now convincing data regarding the association between hypertension, arrhythmias, coronary heart disease, heart failure, increased cardiovascular mortality and sleep apnoea. This has been evidenced in sleep apnoea patients and is supported by experimental data obtained in intermittent hypoxia. Whether treating sleep apnoea enables chronic cardiovascular consequences to be reversed is not fully established as regard coronary heart disease, arrhythmias and heart failure. In this late condition, complex bidirectional relationships occur, with obstructive sleep apnoea being a risk factor for heart failure whilst central sleep apnoea mainly appears as a consequence of heart failure. It remains to be established in adequately designed studies, i.e. large randomised controlled trials, whether treating sleep apnoea can improve heart failure morbidity and mortality.

Rationale and methodology of the impact of continuous positive airway pressure on patients with ACS and nonsleepy OSA: the ISAACC Trial

BACKGROUND

Obstructive sleep apnea (OSA) is common in acute coronary syndrome (ACS) and a possible cause of increased morbidity and mortality.

OBJECTIVES

The main objective is to determine in patients with ACS and OSA if CPAP treatment reduces the incidence of cardiovascular events (cardiovascular death, nonfatal myocardial infarction, nonfatal stroke, hospitalization for heart failure, and hospitalization for unstable angina or transient ischemic attack). The secondary objectives are to determine the prevalence of nonsleepy OSA in patients with ACS; assess the effect of CPAP on the incidence of newly diagnosed diabetes mellitus, symptoms, and quality of life; identify biomarkers of risk involved in cardiovascular complications in these patients; and conduct a cost-effectiveness analysis of diagnosis and treatment.

POPULATION AND METHODOLOGY

Multicenter, prospective, randomized and controlled study. Patients are admitted to the coronary care unit with diagnosis of ACS and without daytime sleepiness (Epworth Sleepiness Scale ≤10) at 15 teaching hospitals in Spain. All patients undergo a sleep study by cardiorespiratory polygraphy. Patients with an apnea-hypopnea index ≥15/hour will be randomized to treatment with CPAP (group 1, 632 patients) or conservative treatment (group 2, 632 patients). Patients with an apnea-hypopnea index <15/hour (group 3, 600 patients) will be followed as a reference group. Patients will be monitored at baseline (T0), 1 month (T1), 3 months (T2), 6 months (T3), 12 months (T4), and every 6 months thereafter (where applicable) during the follow-up period.

CONCLUSIONS

The ISAACC trial will contribute to evaluating the effect of CPAP treatment on cardiovascular events in patients with ACS and OSA.

Agreement in the scoring of respiratory events and sleep among international sleep centers

STUDY OBJECTIVES

The American Academy of Sleep Medicine (AASM) guidelines for polysomnography (PSG) scoring are increasingly being adopted worldwide, but the agreement among international centers in scoring respiratory events and sleep stages using these guidelines is unknown. We sought to determine the interrater agreement of PSG scoring among international sleep centers.

DESIGN

Prospective study of interrater agreement of PSG scoring.

SETTING

Nine center-members of the Sleep Apnea Genetics International Consortium (SAGIC).

MEASUREMENTS AND RESULTS

Fifteen previously recorded deidentified PSGs, in European Data Format, were scored by an experienced technologist at each site after they were imported into the locally used analysis software. Each 30-sec epoch was manually scored for sleep stage, arousals, apneas, and hypopneas using the AASM recommended criteria. The computer-derived oxygen desaturation index (ODI) was also recorded. The primary outcome for analysis was the intraclass correlation coefficient (ICC) of the apnea-hypopnea index (AHI). The ICCs of the respiratory variables were: AHI = 0.95 (95% confidence interval: 0.91-0.98), total apneas = 0.77 (0.56-0.87), total hypopneas = 0.80 (0.66-0.91), and ODI = 0.97 (0.93-0.99). The kappa statistics for sleep stages were: wake = 0.78 (0.77-0.79), nonrapid eye movement = 0.77 (0.76-0.78), N1 = 0.31 (0.30-0.32), N2 = 0.60 (0.59-0.61), N3 = 0.67 (0.65-0.69), and rapid eye movement = 0.78 (0.77-0.79). The ICC of the arousal index was 0.68 (0.50-0.85).

CONCLUSION

There is strong agreement in the scoring of respiratory events among the SAGIC centers. There is also substantial epoch-by-epoch agreement in scoring sleep variables. Our results suggest that centralized scoring of PSGs may not be necessary in future research collaboration among international sites where experienced, well-trained scorers are involved.