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Abstract Rationale There is currently no effective pharmacological treatment for obstructive sleep apnea (OSA). Recent investigations indicate that drugs with noradrenergic and antimuscarinic effects improve genioglossus muscle activity and upper airway patency during sleep. Objectives We aimed to determine the effects of the combination of a norepinephrine reuptake inhibitor (atomoxetine) and an antimuscarinic (oxybutynin) on OSA severity (apnea–hypopnea index [AHI]; primary outcome) and genioglossus responsiveness (secondary outcome) in people with OSA. Methods A total of 20 people completed a randomized, placebo-controlled, double-blind, crossover trial comparing 1 night of 80 mg atomoxetine plus 5 mg oxybutynin (ato–oxy) to placebo administered before sleep. The AHI and genioglossus muscle responsiveness to negative esophageal pressure swings were measured via in-laboratory polysomnography. In a subgroup of nine patients, the AHI was also measured when the drugs were administered separately. Measurements and Main Results The participants’ median (interquartile range) age was 53 (46–58) years and body mass index was 34.8 (30.0–40.2) kg/m2. ato–oxy lowered AHI by 63% (34–86%), from 28.5 (10.9–51.6) events/h to 7.5 (2.4–18.6) events/h (P < 0.001). Of the 15/20 patients with OSA on placebo (AHI > 10 events/hr), AHI was lowered by 74% (62–88%) (P < 0.001) and all 15 patients exhibited a ≥50% reduction. Genioglossus responsiveness increased approximately threefold, from 2.2 (1.1–4.7)%/cm H2O on placebo to 6.3 (3.0 to 18.3)%/cm H2O on ato–oxy (P < 0.001). Neither atomoxetine nor oxybutynin reduced the AHI when administered separately. Conclusions A combination of noradrenergic and antimuscarinic agents administered orally before bedtime on 1 night greatly reduced OSA severity. These findings open new possibilities for the pharmacologic treatment of OSA. Clinical trial registered with www.clinicaltrials.gov (NCT02908529).

Abstract Study Objectives The bases for sex disparities in obstructive sleep apnea (OSA), is poorly understood. We quantified the influences of event definitions, sleep-state, and body position on apnea–hypopnea indices (AHIs) in men and women, and evaluated sex differences in pathophysiological endotypes. Methods Polysomnography (PSG) data were analyzed from 2057 participants from the multi-ethnic study of atherosclerosis. Alternative AHIs were compared using various desaturation and arousal criteria. Endotypes (loop gain, airway collapsibility, arousal threshold) were derived using breath-by-breath analysis of PSG signals. Regression models estimated the extent to which endotypes explained sex differences in AHI. Results The sample (mean 68.5 ± 9.2 years) included 54% women. OSA (AHI4P ≥15/h, defined by events with ≥4% desaturations) was found in 41.1% men and 21.8% women. Compared to AHI4P, male/female AHI ratios decreased by 5%–10% when using 3%-desaturation and/or arousal criteria; p < 0.05. REM-OSA (REM-AHI ≥15/h) was similar in men and women regardless of event desaturation criteria. REM-AHI4P ≥15/h was observed in 57% of men and women each. In NREM, AHI4P in men was 2.49 (CI95: 2.25, 2.76) of that in women. Women demonstrated lower loop gain, less airway collapsibility, and lower arousal threshold in NREM (ps < 0.0005). Endotypes explained 30% of the relative sex differences in NREM-AHI4P. Conclusions There are significant sex differences in NREM-AHI levels and in physiological endotypes. Physiological endotypes explained a significant portion of the relative sex differences in NREM-AHI. Definitions that use 4%-desaturation criteria under-estimate AHI in women. Combining NREM and REM events obscures OSA prevalence in REM in women.

Abstract Study Objectives: Arousals from sleep vary in duration and intensity. Accordingly, the physiological consequences of different types of arousals may also vary. Factors that influence arousal intensity are only partly understood. This study aimed to determine if arousal intensity is mediated by the strength of the preceding respiratory stimulus, and investigate other factors mediating arousal intensity and its role on post-arousal ventilatory and pharyngeal muscle responses. Methods: Data were acquired in 71 adults (17 controls, 54 obstructive sleep apnea patients) instrumented with polysomnography equipment plus genioglossus and tensor palatini electromyography (EMG), a nasal mask and pneumotachograph, and an epiglottic pressure sensor. Transient reductions in CPAP were delivered during sleep to induce respiratory-related arousals. Arousal intensity was measured using a validated 10-point scale. Results: Average arousal intensity was not related to the magnitude of the preceding respiratory stimuli but was positively associated with arousal duration, time to arousal, rate of change in epiglottic pressure and negatively with BMI (R2 > 0.10, P ≤ 0.006). High (> 5) intensity arousals caused greater ventilatory responses than low (≤ 5) intensity arousals (10.9 [6.8–14.5] vs. 7.8 [4.7–12.9] L/min; P = 0.036) and greater increases in tensor palatini EMG (10 [3–17] vs. 6 [2–11]%max; P = 0.031), with less pronounced increases in genioglossus EMG. Conclusions: Average arousal intensity is independent of the preceding respiratory stimulus. This is consistent with arousal intensity being a distinct trait. Respiratory and pharyngeal muscle responses increase with arousal intensity. Thus, patients with higher arousal intensities may be more prone to respiratory control instability. These findings are important for sleep apnea pathogenesis.

The magnitude of progressive augmentation (PA) and ventilatory long‐term facilitation (vLTF) are two forms of respiratory plasticity that are enhanced in some humans with obstructive sleep apnoea (OSA). This response might be linked to repeated nocturnal exposure to intermittent hypoxia or other traits connected to OSA. A meta‐analysis was completed using data from 91 OSA participants who completed one of two mild intermittent hypoxia protocols during wakefulness. Two iterations of a subset regression analysis were completed to identify the best model that predicted the magnitude of PA or vLTF. Novel (e.g., arousal and hypoxic burden) or standard indicators of sleep apnoea (e.g., apnoea/hypopnoea index), anthropometric variables, protocol elements and physiological variables measured during wake and sleep were included as independent variables. After model selection, a multiple linear regression analysis was used to identify the most impactful variables in the model. The hypoxic ventilatory response (HVR) alone ( R  = 0.589, P  < 0.001) or in combination with the arousal index ( R  = 0.625, P  < 0.015 for both variables) predicted the magnitude of PA, whilst the HVR in combination with the arousal burden ( R  = 0.602, P  < 0.001) or arousal index ( R  = 0.593, P  < 0.002 for all variables) predicted the magnitude of vLTF. The HVR and markers of arousal are strong predictors of the magnitude of PA and vLTF. In contrast, markers of apnoea severity, including the hypoxic burden, did not add to the ability to predict the magnitude of PA or vLTF. What is the central question of this study? The goal of this meta‐analysis was to provide insight into the mechanisms that impact the magnitude of progressive augmentation (PA) and ventilatory long‐term facilitation (vLTF) in order to predict the response to treatment with mild intermittent hypoxia in patients living with obstructive sleep apnoea. What is the main finding and its importance The findings suggest that peripheral chemoreflex sensitivity to hypoxia influences the magnitude of PA and vLTF. In addition, besides intermittent hypoxia, stimuli that activate neural pathways involved in both the arousal response and the initiation of respiratory plasticity might also contribute to enhancing the magnitude of PA or vLTF.

Abstract Study Objectives Precision medicine for obstructive sleep apnea (OSA) requires noninvasive estimates of each patient’s pathophysiological “traits.” Here, we provide the first automated technique to quantify the respiratory arousal threshold—defined as the level of ventilatory drive triggering arousal from sleep—using diagnostic polysomnographic signals in patients with OSA. Methods Ventilatory drive preceding clinically scored arousals was estimated from polysomnographic studies by fitting a respiratory control model (Terrill et al.) to the pattern of ventilation during spontaneous respiratory events. Conceptually, the magnitude of the airflow signal immediately after arousal onset reveals information on the underlying ventilatory drive that triggered the arousal. Polysomnographic arousal threshold measures were compared with gold standard values taken from esophageal pressure and intraoesophageal diaphragm electromyography recorded simultaneously (N = 29). Comparisons were also made to arousal threshold measures using continuous positive airway pressure (CPAP) dial-downs (N = 28). The validity of using (linearized) nasal pressure rather than pneumotachograph ventilation was also assessed (N = 11). Results Polysomnographic arousal threshold values were correlated with those measured using esophageal pressure and diaphragm EMG (R = 0.79, p < .0001; R = 0.73, p = .0001), as well as CPAP manipulation (R = 0.73, p < .0001). Arousal threshold estimates were similar using nasal pressure and pneumotachograph ventilation (R = 0.96, p < .0001). Conclusions The arousal threshold in patients with OSA can be estimated using polysomnographic signals and may enable more personalized therapeutic interventions for patients with a low arousal threshold.

Sleep-disordered breathing (SDB) is a prevalent disorder characterized by recurrent episodic upper airway obstruction. Using data from the Hispanic Community Health Study/Study of Latinos (HCHS/SOL), we apply principal component analysis (PCA) to seven SDB-related measures. We estimate the associations of the top two SDB PCs with serum levels of 617 metabolites, in both single-metabolite analysis, and a joint penalized regression analysis. The discovery analysis includes 3299 individuals, with validation in a separate dataset of 1522 individuals. Five metabolite associations with SDB PCs are discovered and replicated. SDB PC1, characterized by frequent respiratory events common in older and male adults, is associated with pregnanolone and progesterone-related sulfated metabolites. SDB PC2, characterized by short respiratory event length and self-reported restless sleep, enriched in young adults, is associated with sphingomyelins. Metabolite risk scores (MRSs), representing metabolite signatures associated with the two SDB PCs, are associated with 6-year incident hypertension and diabetes. These MRSs have the potential to serve as biomarkers for SDB, guiding risk stratification and treatment decisions. Sleep-disordered breathing (SDB) is a prevalent disorder linked to higher cardiovascular disease risk. Here, the authors show that summary scores reflecting SDB metabolite signatures are associated with increased risks for incident hypertension and diabetes, potentially useful in guiding risk stratification.

The combination of noradrenergic (reboxetine) plus antimuscarinic (oxybutynin) drugs (reb-oxy) reduced obstructive sleep apnea (OSA) severity but no data are available on its effects on cardiac autonomic modulation. We sought to evaluate the impact of 1-week reb-oxy treatment on cardiovascular autonomic control in OSA patients. OSA patients were randomized to a double-blind, crossover trial comparing 4 mg reboxetine plus 5 mg oxybutynin to a placebo for OSA treatment. Heart rate (HR) variability (HRV), ambulatory blood pressure (BP) monitoring (ABPM) over 24 h baseline and after treatment were performed. Baroreflex sensitivity was tested over beat-to-beat BP recordings. 16 subjects with (median [interquartile range]) age 57 [51–61] years and body mass index 30 [26–36]kg/m 2 completed the study. The median nocturnal HR was 65 [60–69] bpm at baseline and increased to 69 [64–77] bpm on reb-oxy vs 66 [59–70] bpm on placebo ( p  = 0.02). The mean 24 h HR from ABPM was not different among treatment groups. Reb-oxy administration was not associated with any modification in HRV or BP. Reb-oxy increased the baroreflex sensitivity and did not induce orthostatic hypotension. In conclusion , administration of reb-oxy did not induce clinically relevant sympathetic overactivity over 1-week and, together with a reduction in OSA severity, it improved the baroreflex function.

Obstructive sleep apnoea (OSA), characterized by recurrent periods of upper airway obstruction and intermittent hypoxaemia, is prevalent in patients with cardiovascular disease (CVD), and is therefore important to consider in the prevention and management of CVD. Observational studies indicate that OSA is a risk factor for incident hypertension, poorly controlled blood pressure, stroke, myocardial infarction, heart failure, cardiac arrhythmias, sudden cardiac death and all-cause death. However, clinical trials have not provided consistent evidence that treatment with continuous positive airway pressure (CPAP) improves cardiovascular outcomes. These overall null findings might be explained by limitations in trial design and low levels of adherence to CPAP. Studies have also been limited by the failure to consider OSA as a heterogeneous disorder that consists of multiple subtypes resulting from variable contributions from anatomical, physiological, inflammatory and obesity-related risk factors, and resulting in different physiological disturbances. Novel markers of sleep apnoea-associated hypoxic burden and cardiac autonomic response have emerged as predictors of OSA-related susceptibility to adverse health outcomes and treatment response. In this Review, we summarize our understanding of the shared risk factors and causal links between OSA and CVD and emerging knowledge on the heterogeneity of OSA. We discuss the varied mechanistic pathways that result in CVD that also vary across subgroups of OSA, as well as the potential role of new biomarkers for CVD risk stratification.In this Review, Redline and colleagues summarize our understanding of the shared risk factors and causal links between obstructive sleep apnoea (OSA) and cardiovascular disease and emerging knowledge on the heterogeneity of OSA. They also explore the potential role of new biomarkers for cardiovascular risk stratification in patients with OSA.

Surgical interventions, like barbed reposition pharyngoplasty (BRP), are a valuable alternative for patients with obstructive sleep apnea (OSA) who are unable to tolerate continuous positive airway pressure (CPAP). However, predicting surgical success remains challenging, partly due to the contribution of non-anatomical factors. Therefore, combined medical treatment with acetazolamide, known to stabilize respiratory drive, may lead to superior surgical results. This double-blind, parallel-group randomized controlled trial evaluates the efficacy of acetazolamide as an add-on therapy to BRP in OSA. A total of 26 patients with moderate to severe OSA undergoing BRP were randomized to receive either acetazolamide or placebo post-surgery for 16 weeks. The group who was treated with BRP in combination with acetazolamide showed a reduction in AHI of 69.4%, significantly surpassing the 32.7% reduction of the BRP + placebo group (p < 0.01). The sleep apnea-specific hypoxic burden also decreased significantly in the group who was treated with BRP + acetazolamide (p < 0.01), but not in the group receiving BRP + placebo (p = 0.28). Based on these results, acetazolamide as an add-on therapy following BRP surgery shows promise in improving outcomes for OSA patients, addressing both anatomical and non-anatomical factors.

The overlap syndrome (OVS), defined as coexisting chronic obstructive pulmonary disease (COPD) and obstructive sleep apnea (OSA), is linked to worse outcomes than either condition alone. Patients with COPD and OSA may have fewer obstructive events, but underlying mechanisms remain unclear. Using a large clinical cohort, we tested the hypothesis that OSA severity and pathophysiological traits differ in OVS versus OSA‐alone. Data from the SNOOzzzE cohort (3319 adults with in‐laboratory polysomnography 2017–2019) were used. OVS patients were identified through chart review and matched to OSA‐only patients (3:1) by age, sex, and body mass index. OSA severity was assessed using apnea hypopnea index (AHI), hypoxic burden (HB), and T90 (%time with SpO2 < 90%), while OSA traits were quantified from polysomnographic signals via validated algorithms. Mixed model analysis quantified group differences before and after adjustment for covariate differences (Black race, smoking) accounting for matching as a random effect. In our diverse cohort (103 OVS vs. 309 OSA‐only; 38% women, 44% non‐White, 17% Hispanic), OVS patients tended to have a lower AHI and HB (approximately −10%, p < 0.1), but significantly higher T90 (~50%, p = 0.003). OVS patients had less upper airway collapsibility, lower arousal threshold, lower ventilatory response to arousal (p < 0.05) and tended to have higher upper airway dilator muscle compensation (p = 0.09). In adjusted analyses, effect estimates were similar, but significance was attenuated. Hyperinflation and air trapping were inversely associated with AHI/HB. OSA severity and mechanisms differ in OVS versus OSA‐only. Future research should seek to evaluate these differences for their prognostic ability.