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

Sleep Apnea Specific Hypoxic Burden in Children With Down Syndrome and Typically Developing Children

Hypoxic burden (HB) is a measure incorporating frequency, depth and duration of respiratory event-related desaturations. While HB is associated with cardiovascular disease in adults with obstructive sleep apnea (OSA), it has not been assessed in typically developing (TD) children with OSA, nor in children with Down syndrome (DS), who have a higher incidence of OSA with more severe hypoxia. We assessed whether HB in these children was related to heart rate variability (HRV), an indicator of cardiovascular outcomes. Children (3-19 years, n = 44) with DS and TD children matched for OSA severity, age and sex underwent overnight polysomnography and were grouped into primary snoring (PS), Mild or Moderate/Severe (MS) OSA. HRV was analysed using power spectral analysis of the electrocardiograph. Regression analysis determined whether HB was predictive of HRV. Children with MS OSA in both groups had higher HB compared with children with PS (p < 0.001 for both) and Mild OSA (DS, p < 0.001; TD, p < 0.05). Children with DS and PS or Mild OSA had higher HB compared with TD children (PS p < 0.05; Mild OSA p < 0.001). There was no difference between the MS OSA groups. HB predicted dampened sympathetic and parasympathetic activity only in children with DS (R2 = 0.12, β = -10.6, SE = 4.6, p = 0.03). HB was higher in children with DS and PS or Mild OSA compared to TD children and predicted dampened autonomic function in children with DS. The potential contribution of the adverse effects of HB on autonomic function adds weight to the importance of identifying and treating OSA in children with DS.

APOE Polymorphism, Obstructive Sleep Apnea, and Cognitive Function

Objective  Obstructive sleep apnea (OSA) is associated with the apolipoprotein E ε4 polymorphic allele ( APOE ε4 ) and with worse cognitive function. However, the influence of APOE ε4 on cognitive function in patients with moderate-to-severe OSA is controversial. The present study evaluated the influence of APOE ε4 polymorphism and cognitive function in sedentary OSA patients with no other major comorbidities. Materials and Methods  In total, 55 middle-aged patients underwent conventional nocturnal polysomnography, APOE ε4 polymorphism genotyping, cognitive evaluation (attention, inhibitory control, frontal functions, processing speed, and episodic memory), and they filled out the International Physical Activity Questionnaire. Results  Overall, 13 patients had no or mild OSA, and 42 had moderate-to-severe OSA (apnea-hypopnea index [AHI] ≥ 15 events/h of sleep) and APOE ε4 was present in 7.7% and 21.4% of the patients in each group respectively. Among patients with moderate-to-severe OSA, the sleep parameters were similar in the groups of APOE ε4 carriers and noncarriers. Compared with patients with no or mild OSA, the cognitive parameters were worse for processing speed (Digit Symbol Test) and attention (Stroop Color Word Test, SCWT-Part 2) among the patients with moderate-to-severe OSA. The difference was present even after the exclusion of APOE ε4 carriers. Among patients with moderate-to-severe OSA, APOE ε4 carriers presented worse episodic memory, evaluated through the Rey Auditory Verbal Learning Test, than APOE ε4 noncarriers. Conclusion  Moderate-to-severe OSA is associated with poor cognitive function that is further impaired by the presence of APOE ε4 polymorphism.

Exploring phenotypes to improve long-term mortality risk stratification in obstructive sleep apnea through a machine learning approach: an observational cohort study

BACKGROUND

Obstructive sleep apnea (OSA) is a heterogeneous sleep disorder for which the identification of phenotypes might help for risk stratification for long-term mortality. Thus, the aim of the study was to identify distinct phenotypes of OSA and to study the association of phenotypes features with long-term mortality by using machine learning.

METHODS

This retrospective study included patients diagnosed with OSA who completed a 15-year follow-up and were adherent to continuous positive airway pressure (CPAP) therapy. Multidimensional data were collected at baseline and were used to identify OSA phenotypes using the hierarchical approach. Associations between phenotypic features and long-term mortality were assessed using supervised analysis.

RESULTS

A total of 402 patients, predominantly male (70 %), were included. Clustering analysis identified three distinct phenotypes: Cluster 1 (middle-aged, severely obese, very severe OSA with nocturnal hypoxemia), Cluster 2 (young, overweight, moderate OSA with limited nocturnal hypoxemia), and Cluster 3 (elderly, obese, multimorbid, severe OSA with nocturnal hypoxemia). Mortality was significantly higher in Clusters 1 and 3 (p < 0.001). Supervised methods identified eight main features of these clusters, among which nocturnal hypoxemia was found to be the main risk factor for mortality even after confounding factors-adjustment (hazard ratio 2.63, 95 % confidence interval 1.09-6.36, p = 0.032).

CONCLUSIONS

This study demonstrated the interest of attributing OSA patients to distinct phenotypes including precise determination of nocturnal hypoxemia to improve mortality risk stratification.

Efficient Screening in Obstructive Sleep Apnea Using Sequential Machine Learning Models, Questionnaires, and Pulse Oximetry Signals: Mixed Methods Study

BACKGROUND

Obstructive sleep apnea (OSA) is a prevalent sleep disorder characterized by frequent pauses or shallow breathing during sleep. Polysomnography, the gold standard for OSA assessment, is time consuming and labor intensive, thus limiting diagnostic efficiency.

OBJECTIVE

This study aims to develop 2 sequential machine learning models to efficiently screen and differentiate OSA.

METHODS

We used 2 datasets comprising 8444 cases from the Sleep Heart Health Study (SHHS) and 1229 cases from Taipei Veterans General Hospital (TVGH). The Questionnaire Model (Model-Questionnaire) was designed to distinguish OSA from primary insomnia using demographic information and Pittsburgh Sleep Quality Index questionnaires, while the Saturation Model (Model-Saturation) categorized OSA severity based on multiple blood oxygen saturation parameters. The performance of the sequential machine learning models in screening and assessing the severity of OSA was evaluated using an independent test set derived from TVGH.

RESULTS

The Model-Questionnaire achieved an F1-score of 0.86, incorporating demographic data and the Pittsburgh Sleep Quality Index. Model-Saturation training by the SHHS dataset displayed an F1-score of 0.82 when using the power spectrum of blood oxygen saturation signals and reached the highest F1-score of 0.85 when considering all saturation-related parameters. Model-saturation training by the TVGH dataset displayed an F1-score of 0.82. The independent test set showed stable results for Model-Questionnaire and Model-Saturation training by the TVGH dataset, but with a slightly decreased F1-score (0.78) in Model-Saturation training by the SHHS dataset. Despite reduced model accuracy across different datasets, precision remained at 0.89 for screening moderate to severe OSA.

CONCLUSIONS

Although a composite model using multiple saturation parameters exhibits higher accuracy, optimizing this model by identifying key factors is essential. Both models demonstrated adequate at-home screening capabilities for sleep disorders, particularly for patients unsuitable for in-laboratory sleep studies.

Long-term mortality risk in obstructive sleep apnea: the critical role of oxygen desaturation index

BACKGROUND

Mortality predictors in obstructive sleep apnea (OSA) patients yet to be comprehensively understood, especially within large cohorts undergoing long-term follow-up. We aimed to determine the independent predictors of mortality in OSA patients.

METHODS

In our retrospective cohort study, 3,541 patients were included and survival data was obtained from electronic medical records. Demographic characteristics, anthropometric measurements, comorbidities, laboratory tests, and polysomnography parameters were analyzed for the survived and deceased patient groups. Univariate and multivariate Cox regression analyses were performed to determine independent predictors of all-cause mortality in patients followed for at least 5 years.

RESULTS

Among all patients, 2,551 (72%) patients were male, with a mean age of 49.7 years. 231 (6.5%) patients had died. Deceased patients were significantly older and had higher waist-to-hip ratio and Epworth Sleepiness Scale (p < 0.001, p < 0.001, p = 0.003). OSA (nonpositional and not-rapid eye movement-related), periodic limb movements in sleep and Comorbidities of Sleep Apnea Score ≥ 1 were found to be associated with increased mortality (p < 0.001). Systemic immune-inflammation index was also significantly higher in the deceased group (p < 0.001). Higher oxygen desaturation index (ODI) and apnea-hypopnea index (AHI) were associated with increased mortality (p < 0.001). Due to the high correlation between ODI and AHI, two separate multivariate Cox regression models were created. While AHI lost its significance in the multivariate analysis, ODI remained significantly higher in the deceased patient group (HR = 1.007, 1.001-1.013, p = 0.01).

CONCLUSION

ODI, as the only polysomnography parameter, emerged as an independent predictor of mortality in OSA patients.

Association Between the Weight-Adjusted Waist Index and OSA Risk: Insights from the NHANES 2017-2020 and Mendelian Randomization Analyses

Background

Obesity is a significant risk factor for obstructive sleep apnea (OSA). The weight-adjusted-waist index (WWI) reflects weight-independent centripetal obesity. Our study aims to evaluate the relationship between WWI and OSA.

Methods

The data used in the current cross-sectional investigation are from the National Health and Nutrition Examination Survey (NHANES), which was carried out between 2017 and 2020. We utilized weighted multivariable-adjusted logistic regression to evaluate the relationship between WWI and the risk of OSA. In addition, we applied various analytical methods, including subgroup analysis, smoothing curve fitting, threshold effect analysis and the receiver operating characteristic (ROC) curve. To further explore the relationship, we conducted a MR study using genome-wide association study (GWAS) summary statistics. We performed the main inverse variance weighting (IVW) method along with other supplementary MR methods. In addition, a meta-analysis was conducted to provide an overall evaluation.

Results

WWI was positively related to OSA with the full adjustment [odds ratio (OR)=1.14, 95% confidence interval (95% CI): 1.06-1.23, P<0.001]. After converting WWI to a categorical variable by quartiles (Q1-Q4), compared to Q1 the highest WWI quartile was linked to an obviously increased likelihood of OSA (OR=1.26, 95% CI: 1.06-1.50. P=0.01). Subgroup analysis revealed the stability of the independent positive relationship between WWI and OSA. Smoothing curve fitting identified a saturation effect of WWI and OSA, with an inflection point of 11.62. In addition, WWI had the strongest prediction for OSA (AUC=0.745). Sensitivity analysis was performed to verify the significantly positive connection between WWI and stricter OSA (OR=1.18, 95% CI: 1.05-1.32, P=0.005). MR meta-analysis further supported our results (OR=2.11, 95% CI: 1.94-2.30, P<0.001). Sensitivity analysis confirmed the robustness and reliability of these findings.

Conclusion

WWI was significantly associated with the risk of OSA, suggesting that WWI could potentially serve as a predictor for OSA.

Rostral fluid shifts and other mechanisms of interaction between obstructive sleep apnea and heart failure - a systematic review

<b>Introduction:</b> Obstructive sleep apnea (OSA) is a chronic inflammatory disorder characterized by episodes of total or partial upper airway obstruction during sleep. Untreated OSA leads to various cardiovascular complications, including heart failure (HF), both involving complex and detrimental pathophysiological processes.<b>Aim:</b> The aim of this study is to describe the role of rostral fluid shifts and other mechanisms responsible for the co-existence of OSA and HF, providing insight into potential diagnostic and therapeutic strategies.<b>Materials and methods:</b> Two authors independently searched the literature and assessed articles following PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analytics) guidelines.<b>Results:</b> Rostral fluid shifts, characterized by nocturnal redistribution from the lower limbs to the neck tissues, exacerbate upper airway obstruction by increasing neck circumference and predisposing individuals to respiratory events. This phenomenon is particularly significant in patients with HF due to impaired cardiovascular function leading to fluid retention. The repetitive collapse of the upper airway during sleep triggers abrupt changes in intrathoracic pressure negatively impacting cardiac tissue remodeling by promoting inflammation and fibrosis. Moreover, sleep fragmentation and arousals activate the sympathetic nervous system (SNS), imposing additional strain on the cardiovascular system. Accumulated data suggest that rostral fluid shifts are a clinically significant pathomechanism in the coexistence of OSA and HF. Therapeutic strategies, including the benefits of continuous positive airway pressure (CPAP) therapy and lifestyle modifications, have been discussed. This systematic review highlights the need for integrated treatment approaches to manage both OSA and HF effectively.<b>Conclusions:</b> Understanding and addressing these interconnected mechanisms is essential to offer an integrated diagnostic and therapeutic management of patients, highlighting the importance of multidisciplinary care to optimize patient health and quality of life.

A new perspective on OSAS cases with the Baveno classification

OBJECTIVE/BACKGROUND

Since the apnea-hypopnea index (AHI), which is used in the diagnosis and grading of OSAS, does not adequately reflect the clinical perspective of the disease, the Baveno classification of OSA was developed, which allows multicomponent evaluation of OSAS patients. The aim of our study was to evaluate the application of the Baveno classification in clinical practice.

PATIENTS/METHODS

A prospective study was performed on patients diagnosed with OSAS between January 2021 and June 2022. Patients were divided into 4 groups according to Baveno classification (Groups A-D) and three groups as mild, moderate, and severe OSAS according to AHI.

RESULTS

A total of 378 patients (70% male, mean age 48.68 ± 11.81 years) were included in the study. The patients had mild (n: 75; 20%), moderate (n: 88; 23%), and severe (n: 215; 57%) OSAS. According to Baveno classification, patients were included in Groups A (n: 90; 24%), B (n: 105 (28%), C (n: 65; 17%), and D (n: 118; 31%). The mean AHIs of the Baveno groups were similar (p = 0.116). Oxygen desaturation index (ODI) was higher in Groups B and D compared to Group A. The duration of T90 desaturation was longer in Groups C and D compared to Groups A and B (p < 0.05).

CONCLUSIONS

The Baveno classification divided our OSAS cases into equivalent groups. One out of every four patients with mild OSAS was in Group D. This data was noteworthy in that the Baveno classification allows for the identification of symptomatic and comorbid patients with mild OSAS according to AHI and for the application of more effective treatments to these patients. Patients with comorbidities experienced oxygen desaturation for a longer period of time at night, and oxygenation deteriorated in patients with prominent symptoms. Baveno classification was found to be a more reasonable and easily applicable approach in clinical practice.

The clinical and hemodynamic characteristics of pulmonary hypertension in patients with OSA-COPD overlap syndrome

BACKGROUND

Our study aimed to assess the clinical and hemodynamic characteristics of pulmonary hypertension (PH) in patients with overlapping obstructive sleep apnea (OSA) and chronic obstructive pulmonary disease (COPD), referred to OSA-COPD overlap syndrome (OS).

METHODS

We enrolled a total of 116 patients with OS, COPD, or OSA who underwent right heart catheterization (RHC) due to suspected PH. We conducted a retrospective analysis of the clinical and hemodynamic characteristics of these patients.

RESULTS

Among the three groups (OS group, n = 26; COPD group, n = 36; OSA group, n = 54), the prevalence of PH was higher in the OS group (n = 17, 65.4%)compared to OSA group (n = 26,48.1%) and COPD group (n = 20,55.6 %). Among three groups with PH, the superior vena cava pressure (CVP) and right ventricular pressure (RAP) were higher in the OS group than in the OSA group (P < 0.05). Patients in the OS and COPD groups had higher pulmonary artery wedge pressure (PAWP) than in the OSA group (14.88 ± 4.79 mmHg, 13.45 ± 3.68 mmHg vs. 11.00 ± 3.51 mmHg, respectively, P < 0.05). OS patients with PH exhibited higher respiratory event index (REI), time spent with SpO2 <90%, oxygen desaturation index (ODI), minimal SpO2 (MinSpO2) and mean SpO2 (MSpO2) compared to OS patients without PH. After adjusting for potential covariates, we found that MinSpO2 (OR 0.937, 95 % CI 0.882-0.994, P = 0.032), MSpO2 (OR 0.805, 95% CI 0.682-0.949, P = 0.010), time spent with SpO2 <90% (OR 1.422, 95% CI 1.137-1.780, P = 0.002), and FEV1 % pred (OR 0.977, 95 % CI 0.962-0.993, P = 0.005) were related to the development of PH.

CONCLUSIONS

Patients with OS showed higher prevalence of PH, along with higher PAWP, CVP and RAP. Worse nocturnal hypoxemia was found in OS patients with PH.

The impact of study type and sleep measurement on oxygen desaturation index calculation

STUDY OBJECTIVES

The oxygen desaturation index (ODI) is an important measure of sleep-disordered breathing during polysomnography (PSG); however, the AASM Manual (V3) does not specify whether to include oxygen desaturations occurring during wake epochs. Additionally, an ODI obtained from PSG can differ from an ODI using home sleep apnea tests (HSATs) that do not measure sleep, hampering diagnostic and treatment decision reliability. This study aimed to (1) compare an ODI that included all desaturations with an ODI that excluded desaturations occurring during wake epochs in PSG and (2) compare ODIs obtained from PSG with HSAT.

METHODS

100 consecutive PSGs for investigation of obstructive sleep apnea were compared. ODIs were calculated including all desaturations (ODIall) and by excluding desaturations entirely during wake epochs (ODIsleep). Additionally, we compared ODIall with an ODI calculated using monitoring time as the denominator (ODIHSAT).

RESULTS

The median (interquartile range) 3% ODI for ODIall was 22.8 (13.1, 44.1) events/h and ODIsleep was 17.6 (11.5, 35.2) events/h (median difference: -3.9 events/h [-8.2, -0.9]; 21.0% [8.7%, 33.2%]). This discrepancy was larger with increasing ODI and decreasing sleep efficiency. The ODIHSAT was 17.4 (11.3, 35.2) events/h and the median reduction in ODIHSAT vs ODIall was -4.5 (-10.9, -2.0) events/h (21.6%; 11.1%, 33.8).

CONCLUSIONS

ODI was significantly reduced when desaturations in wake epochs were excluded, and when ODI was based on monitoring time rather than sleep time, with the potential for underestimation of disease severity. Results suggest that ODI can differ substantially depending on the calculation and study type used, and that there is a need for standardization to ensure consistent diagnosis and treatment outcomes.

CITATION

Whenn CB, Wilson DL, Ruehland WR, Churchward TJ, Worsnop C, Tolson J. The impact of study type and sleep measurement on oxygen desaturation index calculation. J Clin Sleep Med. 2024;20(5):709-717.

Comparing efficacy of the mandibular advancement device after drug-induced sleep endoscopy and continuous positive airway pressure in patients with obstructive sleep apnea

PURPOSE

The purpose of this study was to compare objective and self-reported outcomes of two treatments for managing mild, moderate, and severe obstructive sleep apnea (OSA) in adults: a mandibular advancement device (MAD) and continuous positive airway pressure (CPAP).

METHODS

Patients diagnosed with OSA by means of polysomnography (PSG) included one group treated with a custom-made, two-piece, adjustable MAD and a second group treated with CPAP for 8 weeks. Before the initiation of the treatment, all patients assigned to MAD underwent drug-induced sleep endoscopy (DISE), and all CPAP group patients underwent manual titration of CPAP after PSG. Objective (PSG) and self-reported (Epworth Sleepiness Scale [ESS] and Short Form Health Survey [SF-36]) data were used to assess outcomes. Collected data included apnea-hypopnea index (AHI), mean capillary oxygen saturation (SpO2), oxygen desaturation index (ODI), arousal index (AI), degree of daytime sleepiness, and quality of life. A PSG follow-up after 8 weeks with MAD in situ, and data from the CPAP data card were used to assess the effect of the two treatments.

RESULTS

A total of 59 patients included 30 treated with MAD and 29 treated with CPAP. Between baseline and the 8-week follow-up, the mean AHI score decreased significantly from 35.1 to 6.8 episodes/h (p < 0.001) in patients treated with MAD and from 35.2 to 3.0 episodes/h (p < 0.001) in patients treated with CPAP. The mean AHI score at the 8-week follow-up was significantly lower in CPAP group than in MAD group (p = 0.003). The two groups did not differ significantly at follow-up regarding SpO2 (p = 0.571), ODI (p = 0.273), AI (p = 0.100), ESS score (p = 0.648), and SF-36 score (p = 0.237).

CONCLUSION

In the short term, patients on CPAP attained better PSG outcomes in terms of AHI reduction. Both MAD after DISE evaluation and CPAP resulted in similar improvements in clinical symptoms and health-related quality of life, even in patients with severe OSA.

Analysis of QRS complex morphology in children and adolescents with obstructive sleep apnea syndrome

Obstructive sleep apnea syndrome (OSAS) leads to many cardiovascular, neurologic, metabolic, and neurocognitive consequences. Conduction deficits, deviations in electrical axis, and changes in QRS morphology reflect the impairments in cardiac muscle activity and underlie the cardiovascular complications of OSAS. Here we aimed to determine the relationship between OSAS and changes in the cardiac conduction system in children and adolescents. During the 6-month duration of the study, all children having the diagnosis of OSAS in Sleep and Disorders Unit following a full-night polysomnography (PSG) were consecutively evaluated. ECGs were performed and analyzed in the Division of Pediatric Cardiology, Department of Pediatrics. The maximum spatial vector size (QRSmax), QRS electrical axis (EA), left and right ventricular hypertrophy, and the presence of fragmented QRS (fQRS) or prolonged R or S wave were examined in detail. A total of 17 boys with OSAS and 13 healthy boys participated in the study. The mean QRSmax and the QRSmax on V5 derivative were significantly lower in the patient group compared to those in the control group (p = 0.011 and p = 0.017, respectively). EA was similar between the two groups. While none of the patients with OSAS nor the control group had left ventricular hypertrophy, only one boy with OSAS had right ventricular hypertrophy according to ECG-derived analysis. The percentage of fQRS or notched R or S waves was significantly higher in patients with OSAS compared to healthy controls (p = 0.035), especially in children below the age of 5 years (p = 0.036).  Conclusion: This study demonstrated that male children and adolescents with OSAS have a combination of QRS complex changes characterized by low QRS voltages, and increased frequency of fragmented QRS. These findings reflect that the electrical remodeling and structural remodeling of the myocardium are considerably affected by OSAS in children and adolescents, leading to ventricular changes and intraventricular conduction problems. What is Known: • Pediatric obstructive sleep apnea syndrome (OSAS) characterized by recurrent intermittent hypoxemia, hypercapnia, and sleep fragmentation results in sympathetic nervous system activation, increased inflammation, and hypoxic endothelial dysfunction. When left untreated, OSAS leads to many cardiovascular, neurologic, metabolic and neurocognitive consequences, and also to sudden infant death syndrome in young children, probably due to the involvement of the cardiac conduction system. What is New: • This study demonstrated that mean QRSmax was significantly lower in male children and adolescents with OSAS, reflecting the structural and electrical remodeling of the myocardium, and one boy with OSAS had RVH according to ECG-derived analysis. The percentage of fQRS or notched R or S waves was much higher in boys with OSAS, especially in children below the age of five years. These finding showed that myocardium was considerably affected to impair the intraventricular conduction in younger children with OSAS.

Obstructive sleep apnoea-hypopnoea syndrome

Obstructive sleep apnoea-hypopnoea syndrome (OSAHS) is a common disorder characterised by repetitive episodes of the complete or partial collapse of the pharyngeal airway during sleep. This results in cessation (apnoea) or reduction (hypopnoea) of airflow, leading to oxygen desaturation and sleep fragmentation. An individual's disposition to develop OSAHS depends on the collapsibility of a segment of the upper airway. The degree of collapsibility can be quantified by the balance between occluding or extraluminal pressures of the surrounding tissues. Patients can experience snoring, unrefreshing sleep, witnessed apnoeas, waking with a choking sensation and excessive daytime sleepiness. OSAHS has a broad range of consequences, including cardiovascular, metabolic, and neurocognitive sequelae. Treatment options include lifestyle measures, in particular weight loss, and strategies to maintain upper airway patency overnight, including continuous positive airway pressure, mandibular advancement devices and positional modifiers.

Adaptive responses to chronic intermittent hypoxia: contributions from the European Sleep Apnoea Database (ESADA) Cohort

Obstructive sleep apnoea (OSA) is a common disease in the general population, and is associated with increased cardiovascular risk and several comorbidities. Obesity favours upper airway collapsibility, but other pathophysiological traits have been identified, i.e. upper airway muscle activity, modulation of the respiratory drive, and the arousal threshold. OSA causes chronic intermittent hypoxia, inflammatory activation and autonomic imbalance with diurnal and nocturnal sympathetic hyperactivity. Disentangling so many components to investigate the pathogenesis of OSA's consequences is very hard clinically. However, albeit imperfect, clinical medicine constitutes a major source of inspiration for basic research, and a mutual exchange of information is essential between clinicians and physiologists to improve our understanding of disease states. OSA is no exception, and this narrative review will summarize the results of clinical studies performed over the years by the European Sleep Apnoea Database (ESADA) Study Group, to explore the variables linked to markers of intermittent hypoxia as opposed to the traditional assessment of OSA severity based on the frequency of respiratory events during sleep (the Apnoea Hypopnoea Index). The results of the clinical studies indicate that intermittent hypoxia variables are associated with several comorbidities, although evidence of a cause-effect relationship is still missing in many cases. It is also possible that adaptive rather than maladaptive responses could be evoked by intermittent hypoxia. The intensity, duration and frequency of intermittent hypoxia episodes causing adaptive rather than maladaptive responses, and their clinical implications, deserve further investigation.

Blood pressure control in hypertensive sleep apnoea patients of the European Sleep Apnea Database cohort - effects of positive airway pressure and antihypertensive medication

Aims

We analysed longitudinal blood pressure (BP) data from hypertensive obstructive sleep apnoea (OSA) patients in the European Sleep Apnea Database cohort. The study investigated the interaction between positive airway pressure (PAP)-induced BP change and antihypertensive treatment (AHT).

Methods and results

Hypertensive patients with AHT [monotherapy/dual therapy n = 1283/652, mean age 59.6 ± 10.7/60.6 ± 10.3 years, body mass index (BMI) 34.2 ± 6.5/34.8 ± 7.0 kg/m2, apnoea-hypopnoea index 46 ± 25/46 ± 24 n/h, proportion female 29/26%, respectively] started PAP treatment. Office BP at baseline and 2- to 36-month follow-up were assessed. The interaction between AHT drug classes and PAP on BP was quantified and the influences of age, gender, BMI, co-morbidities, BP at baseline, and study site were evaluated. Following PAP treatment (daily usage, 5.6 ± 1.6/5.7 ± 1.9 h/day), systolic BP was reduced by -3.9 ± 15.5/-2.8 ± 17.7 mmHg in mono/dual AHT and diastolic BP by -3.0 ± 9.8/-2.7 ± 10.8 mmHg, respectively, all P < 0.0001. Systolic and diastolic BP control was improved following PAP treatment (38/35% to 54/46% and 67/67% to 79/74%, mono/dual AHT, respectively). PAP treatment duration predicted a larger BP improvement in the monotherapy group. Intake of renin-angiotensin blockers [angiotensin converting enzyme inhibitor (ACEI)/angiotensin receptor blocker (ARB)] alone or in any AHT combination was associated with better BP control. The AHT-dependent BP improvement was independent of confounders.

Conclusion

In this pan-European OSA patient cohort, BP control improved following initiation of PAP. Longer PAP treatment duration, was associated with a favourable effect on BP. Our study suggests that ACEI/ARB, alone or in combination with other drug classes, provides a particularly strong reduction of BP and better BP control when combined with PAP in OSA.

Risk-prediction model for incident hypertension in patients with obstructive sleep apnea based on SpO2 signals

This work proposes a method utilizing oxygen saturation (SpO2) for predicting incident hypertension in patients with obstructive sleep apnea (OSA). We extracted time domain features and frequency domain features from the SpO2 signal. For prediction, we employed several machine learning algorithms to establish the 3-year risk prediction model in the Chinese Sleep Health Study, including 250 subjects without baseline hypertension who underwent sleep monitoring. The proposed random forest model achieved an accuracy of 84.4%, a sensitivity of 77.0%, a specificity of 91.5% and an area under the receiver operator characteristic of 84.3% using 10-fold crossvalidation. We show that the model outperformed two sleep medicine specialists using clinical experience to predict hypertension. Furthermore, we applied the prediction results in the public Sleep Heart Health Study database and showed the subjects who were predicted to have hypertension would be at a higher risk in 4-6 years. This work shows the potential of SpO2 signal during sleep for the prediction of hypertension and could be beneficial to the early detection and timely treatment of hypertension in OSA patients.Clinical Relevance-There is no prediction model for incident hypertension in OSA patients in clinical practice. Most patients are unaware of health complexity, symptoms and risk factors before hypertension. Establishing an accurate prediction model can effectively provide early intervention for OSA patients and reduce the prevalence of hypertension.

Obstructive sleep apnea is not associated with diabetic retinopathy in diabetes: a prospective case-control study

PURPOSE

Diabetic retinopathy (DR) is the most common ocular complication of type 2 diabetes mellitus (T2D) and is associated with diabetes duration, glycemic control, and hypertension (HTN). Obstructive sleep apnea (OSA) is frequent in T2D and is associated with poor glycemic control. However, it is unclear if there is an association between OSA and DR. This study aimed to assess whether or not the presence of OSA in patients with T2D was associated with DR.

METHODS

In this prospective case-control study, consecutive patients with DM attending the ophthalmology clinics were recruited to include patients with DR (cases) and without DR (controls). OSA was diagnosed by attended polysomnography (PSG). Blood pressure and a fasting morning blood sample, including glycosylated hemoglobin (HbA1c), were recorded. Patients were matched for age, body mass index (BMI), gender, and T2D duration.

RESULTS

Thirty diabetic patients with DR were matched with 30 controls. In all patients, the prevalence of moderate-to-severe OSA was 57%. In the logistic regression analysis, DR was associated with increased HbA1c (OR 2.63, 95% CI 1.35-5.16, p = 0.004) but not with any PSG parameter. In the DR group, PSG parameters were not associated with the severity of ocular disease (non-proliferative, proliferative, presence/absence of macular edema). The proliferative aspect of DR was correlated with age (p = 0.017). DR occurred more frequently in uncontrolled diabetes compared to well-controlled diabetes (80% vs 38%, p = 0.029).

CONCLUSIONS

In patients with T2D, the presence of DR is not associated with OSA, but with poorly controlled T2D.

Comparison of clinical features and surgical outcomes between hypopnea- and apnea-predominant obstructive sleep apnea

OBJECTIVES

This study is aimed to investigate the differences in the clinical features and surgical outcomes between hypopnea- and apnea-predominant obstructive sleep apnea (OSA).

DESIGN

Cohort study.

SETTING

Single tertiary care centre.

PARTICIPANTS

This study included 190 patients with OSA who underwent multilevel upper airway surgery between September 2012 and September 2021. The patients were divided into two groups according to the proportion of each respiratory event: hypopnea-predominant (n = 102) and apnea-predominant (n = 88).

MAIN OUTCOME MEASURES

The primary outcome measure was the percentage improvement in the apnea-hypopnea index (AHI) from baseline AHI after surgery.

RESULTS

The apnea-predominant group included more male patients and had higher AHI, respiratory disturbance index (RDI) and oxygen desaturation index (ODI) than the hypopnea-predominant group. Both groups showed significant improvements in AHI, apnea index, RDI, supine AHI, REM AHI, non-REM AHI, ODI, lowest O₂ saturation and Epworth Sleepiness Scale scores following the surgery. Notably, hypopnea index increased after surgery in the apnea-predominant OSA group. Although the improvement in the absolute value of AHI by surgery was significantly greater in the apnea-predominant group than in the hypopnea-predominant group, the two groups showed no significant difference in the percentage improvement in AHI from baseline AHI.

CONCLUSION

Patients with apnea-predominant OSA had more severe disease than those with hypopnea-predominant OSA; however, surgical outcomes, as evaluated by percentage AHI improvement, were comparable between the two groups. In addition, multilevel upper airway surgery may induce the transition from apnea to hypopnea in patients with apnea-predominant OSA.

Relative spectral power quantifying the distribution of intermittent hypoxemia in obstructive sleep apnea is strongly associated with hypertension

STUDY OBJECTIVES

To investigate the association between the periodicity of distribution of intermittent hypoxemia (IH) and hypertension in adults with obstructive sleep apnea (OSA) and search for an index to quantify the association.

METHODS

Samples were derived from two cross-sectional studies: The Sleep Heart Health Study (SHHS) including 3991 adults with age 64.7 ± 10.9 years; and the Chinese Changgung Sleep Health Study (CSHS) including 906 adults with age 59.5 ± 12.4 years. Spectral analysis of peripheral oxygen saturation (SpO₂) was performed and the relative spectral power (PFR) in the frequency band of 0.011-0.037 Hz (PFR_{0.011-0.037Hz}) was extracted to quantify the periodic distribution of IH. Multiple logistic regression models were used to calculate the partially and fully adjusted odd ratios for PFR_{0.011-0.037Hz}.

RESULTS

PFR_{0.011-0.037Hz} was significantly higher in the hypertension group than non-hypertension group (44.4% ± 0.3% vs. 42.1% ± 0.3%, p < 0.001 in SHHS and 57.4% ± 0.7% vs. 50.5% ± 0.8%, p < 0.001 in CSHS). In the fully adjusted model, individuals in the SHHS with PFR_{0.011-0.037Hz} in the highest quintiles had an odd ratio of 1.33 [95% confidence interval (CI) 1.06-1.67]. Similarly, the group in the CSHS with PFR_{0.011-0.037Hz} in the highest quintile had an odd ratio of 3.08 (95% CI 1.80-5.28).

CONCLUSIONS

We developed an IH distribution measure which is strongly associated with hypertension independent of multiple confounding variables. The finding suggests that the periodic distribution of sleep related upper airway obstructions is an essential hypertension characterizing feature.

Arterial bicarbonate is associated with hypoxic burden and uncontrolled hypertension in obstructive sleep apnea - The ESADA cohort

OBJECTIVE

Blood bicarbonate concentration plays an important role for obstructive sleep apnea (OSA) patients to maintain acid-base balance. We investigated the association between arterial standard bicarbonate ([HCO3^-]) and nocturnal hypoxia as well as comorbid hypertension in OSA.

METHODS

A cross-sectional analysis of 3329 patients in the European Sleep Apnea Database (ESADA) was performed. Arterial blood gas analysis and lung function test were performed in conjunction with polysomnographic sleep studies. The 4% oxygen desaturation index (ODI), mean and minimum oxygen saturation (SpO₂), and percentage of time with SpO₂ below 90% (T90%) were used to reflect nocturnal hypoxic burden. Arterial hypertension was defined as a physician diagnosis of hypertension with ongoing antihypertensive medication. Hypertensive patients with SBP/DBP below or above 140/90 mmHg were classified as controlled-, uncontrolled hypertension, respectively.

RESULTS

The [HCO3^-] level was normal in most patients (average 24.0 ± 2.5 mmol/L). ODI, T90% increased whereas mean and minimum SpO₂ decreased across [HCO3^-] tertiles (ANOVA, p = 0.030, <0.001, <0.001, and <0.001, respectively). [HCO3^-] was independently associated with ODI, mean SpO₂, minimum SpO₂, and T90% after adjusting for confounders (β value [95%CI]: 1.21 [0.88-1.54], -0.16 [-0.20 to -0.11], -0.51 [-0.64 to -0.37], 1.76 [1.48-2.04], respectively, all p < 0.001). 1 mmol/L elevation of [HCO3^-] was associated with a 4% increased odds of uncontrolled hypertension (OR: 1.04 [1.01-1.08], p = 0.013).

CONCLUSION

We first demonstrated an independent association between [HCO3^-] and nocturnal hypoxic burden as well as uncontrolled hypertension in OSA patients. Bicarbonate levels as an adjunctive measure provide insight into the pathophysiology of hypertension in OSA.

Investigation of the Possible Causes of NRBC in ICU Patients and the Dynamic Trend of NRBC Count in Survival and Death Patients or with Different Underlying Diseases: A Retrospective Study

Background

The mortality of intensive care unit (ICU) patients ranges from 5% to 30%, and nucleated red blood cells (NRBCs) were revealed to be related to mortality. However, few studies have discussed the causes of NRBC or compared the dynamic count among patients with underlying diseases.

Aim

To explore the possible causes of NRBC in ICU patients and the dynamic trends between survival and death groups and underlying disease subgroups.

Methods

A total of 177 ICU patients were retrospectively included. The possible causes of NRBC in ICU patients were discussed. The relationship between NRBC and in-hospital mortality and the dynamic trend of NRBC during hospitalization between the survival and death groups and underlying disease subgroups were compared.

Results

The Acute Physiology and Chronic Health Evaluation II (APACHE II) score and Sequential Organ Failure Assessment (SOFA) score in the NRBC-positive group were higher (23.52 ± 9.39 vs. 19.62 ± 7.59; 13.50 (9.00-17.50) vs. 8.00 (6.00-12.00)). Red blood cell count (RBC), hemoglobin (Hb) level, oxygen saturation (SO₂), oxygenation index (OI), and serum protein level were lower in the NRBC-positive group. However, D-dimer (D-D), liver and kidney function indices, lactate dehydrogenase (LDH), C-reactive protein (CRP), and procalcitonin (PCT) were higher than those in the NRBC-negative group. Correlation analysis showed that NRBC count was positively correlated with alkaline phosphatase (ALP) and red blood cell distribution width (RDW) and negatively correlated with SO₂ (r = 0.431, P < 0.05; r = 0.363, P < 0.05; r = -0.335, P < 0.05). The mortality rate in the NRBC-positive group was higher, and the median survival time was shorter than that in the NRBC-negative group (77.9% vs. 95.7%, P < 0.001; 15 days vs. 8.5 days, P < 0.01). Univariate and multivariate Cox regression analyses showed that NRBC was an independent risk factor for in-hospital mortality (HR: 1.12 (1.03-1.22), P < 0.01). The NRBC count had different hazard ratios (HRs) for in-hospital mortality in the subgroups. Locally weighted scatterplot smoothing (LOWESS) analysis revealed that the NRBC count in the death group was higher and had a sharp upward trend before death, whereas that in the survival group was negative or stayed at a low level. The changing trend of the NRBC count was different in patients with different underlying diseases.

Conclusion

The possible cause of NRBC in ICU patients was related to inflammation and hypoxia. The persistently high level and rapid upward trend of NRBC counts are risk factors for in-hospital mortality in ICU patients. The changing trend of the NRBC count varied in patients with different underlying diseases.

Optimal positive airway pressure requirement and polysomnography indices of obstructive sleep apnea severity in the Saudi population

CONTEXT

Positive airway pressure (PAP) is the first-line therapy for obstructive sleep apnea (OSA). Overnight PAP titration for determining optimal PAP requirements is expensive and often inconvenient. Prediction of optimal PAP requirements from diagnostic polysomnography via mathematical equations is possible but variable across populations.

AIMS

We aimed to (1) determine the optimal PAP requirement, (2) determine differences in optimal PAP requirements across OSA severity groups, (3) determine the relationship between optimal PAP requirement and diagnostic polysomnography measurements of OSA severity, and (4) develop a pilot equation to predict the optimal PAP requirement from diagnostic polysomnography in a sample from the Saudi population.

METHODS

We analyzed records pertaining to adult OSA patients (n = 215; 63% of males) who underwent standardized diagnostic and titration polysomnography in our sleep laboratory between 2015 and 2019. Demographic, anthropometric, and clinical information were also collected for the analysis. Inferential statistics were performed for comparisons between diagnostic and titration studies and between OSA severity groups. Regression analyses were also performed to determine the potential predictors of optimal PAP requirements. Data were presented as the mean (± standard deviation) or median (25th-75th quartiles) according to normality.

RESULTS

The median optimal PAP requirement was 13 (9-17) cmH2O. The optimal PAP requirement was significantly greater for male versus female participants (14 [10-17] vs. 12 [8-16] cmH2O) and for participants with severe OSA (16 [12-20] cmH2O, n = 119) versus those with moderate (11 [8-14] cmH2O, n = 63) or mild (9 [7-12] cmH2O, n = 33) OSA. When combined, nadir oxygen saturation, oxygen desaturation index, and arousal index could be used to predict the optimal PAP requirement (R 2= 0.39, F = 34.0, P < 0.001).

CONCLUSIONS

The optimal PAP requirement in the Saudi population is relatively high and directly correlated with OSA severity. Diagnostic polysomnography measurements of OSA severity predicted the optimal PAP requirement in this sample. Prospective validation is warranted.

Hypoxic Burden in Obstructive Sleep Apnea: Present and Future

Conventional measures of obstructive sleep apnea (OSA) severity, such as the apnea-hypopnea index (AHI) and oxygen desaturation index (ODI) are commonly used to quantify OSA severity and guide therapeutical decision-making processes. However, it is widely recognized that both AHI and ODI have important limitations and novel physiologically-informed metrics are needed to better capture the severity of OSA and characterize its physiological consequences, particularly the severity of recurrent nocturnal hypoxemia, ensuing the respiratory events. According to recent studies, the sleep apnea-specific "hypoxic burden (HB)", defined as the sum of individual areas under the oxygen desaturation curve, has shown some promise in identifying high risk individuals with OSA. In addition to the frequency of respiratory events, HB capture the depth and duration of OSA-related hypoxemia that may prove to be important disease characterizing features, not captured by the conventional "frequency-based" metrics, such as AHI and ODI. In this "perspective" paper the methods to quantify the HB, its characteristics, associations with health outcomes, and its limitations will be discussed.

Correlates of excessive daytime sleepiness in obstructive sleep apnea: Results from the nationwide SESAR cohort including 34,684 patients

Excessive daytime sleepiness (EDS) is a hallmark symptom in obstructive sleep apnea (OSA). It is commonly eliminated by obstructive sleep apnea therapy and constitutes a major treatment indication. This study aimed to identify determinants of excessive daytime sleepiness by the Epworth Sleepiness Scale (ESS) scores in the large, representative national obstructive sleep apnea patient cohort of the Swedish Sleep Apnea Registry (SESAR, www.sesar.se). Data from 34,684 patients with obstructive sleep apnea recruited at 23 sites (33% females, mean age 55.7 ± 13.7 years, BMI 30.2 ± 6.3 kg/m² , AHI 29.1 ± 22.3, and ODI 24.9 ± 21.4 events/h) had a mean ESS score in the mild to moderate excessive daytime sleepiness range (9.7 ± 4.9). The proportion of patients with excessive daytime sleepiness was 41.4% in men and 44.6% in women. Independent predictors of excessive daytime sleepiness included gender, age, and hypoxic markers (high ODI and low mean saturation). Univariate and multivariate analyses were used to identify significant predictors for the ESS score and for excessive daytime sleepiness (ESS ≥10) amongst anthropometric factors, sleep apnea frequency (apnea-hypopnea index (AHI)), markers of intermittent hypoxia (oxygen desaturation index (ODI), mean saturation (mSaO₂ )), as well as prevalent comorbidities. Depression was associated with higher ESS scores and hypertension/atrial fibrillation with lower scores. The oxygen desaturation index provided a stronger predictor of excessive daytime sleepiness than the apnea-hypopnea index. The severity of obstructive sleep apnea, captured as the apnea-hypopnea index, was only weakly associated with daytime sleepiness in this representative obstructive sleep apnea patient cohort. Age had different effects in men and women.The impact of obstructive sleep apnea in a wider patient related perspective needs to be determined after the inclusion of factors other than the apnea-hypopnea index.

Effects of solriamfetol on on-the-road driving performance in participants with excessive daytime sleepiness associated with obstructive sleep apnoea

OBJECTIVE

To evaluate the impact of solriamfetol, a dopamine and norepinephrine reuptake inhibitor, on on-the-road driving in participants with excessive daytime sleepiness (EDS) associated with obstructive sleep apnoea (OSA).

METHODS

Eligible participants were aged 21-75 years with OSA and EDS (Maintenance of Wakefulness Test mean sleep latency <30 minutes and Epworth Sleepiness Scale score ≥10). Participants were randomised 1:1 to solriamfetol (150 mg/day [3 days], then 300 mg/day [4 days]) or placebo for 7 days, before crossover to the other treatment paradigm. On Day 7 of each period, standardised on-road driving tests occurred (2 and 6 hours postdose). Standard deviation of lateral position (SDLP) was the primary endpoint.

RESULTS

Solriamfetol significantly reduced SDLP at 2 (n = 34; least squares mean difference, -1.1 cm; 95% CI, -1.85, -0.32; p = 0.006) and 6 hours postdose (n = 32; least squares mean difference, -0.8 cm; 95% CI, -1.58, -0.03; p = 0.043). Two hours postdose, 4 placebo-treated and 1 solriamfetol-treated participants had incomplete driving tests; 6 hours postdose, 7 and 3 participants, respectively, had incomplete tests. Common treatment-emergent adverse events included headache, nausea, and insomnia.

CONCLUSIONS

Solriamfetol 300 mg/day significantly improved on-the-road driving performance in participants with EDS associated with OSA.

The Burden of Respiratory Alterations during Sleep on Comorbidities in Obstructive Sleep Apnoea (OSA)

BACKGROUND

Obstructive sleep apnoea (OSA) has an important impact on the risk of morbidity and mortality, so we have designed the present study to understand which factor is most involved in the risk of developing a comorbidity between OSA severity and nocturnal hypoxemia.

METHODS

A retrospective study was conducted on 617 adult subjects who were referred to our unit for a suspicion of OSA between January 2018 and January 2020.

RESULTS

Sleep investigations performed by participants (72% male and obese in 70% of cases) reported an overall mean apnoea-hypopnoea index (AHI) of 44.0 ± 24.8 events·h-1. Overall, 66% were classified as severe OSA and 76% experienced nocturnal hypoxemia. By analysing the burden of OSA severity and nocturnal hypoxemia on the comorbidities risk, multivariate analysis highlighted the predominant role of age and obesity. Accordingly, after the exclusion of the older and obese participants from the analyses, we noticed that severe OSA was related to the risk of hypertension (odds ratio (OR) = 3.0 [95% confidence interval [CI] 1.4-6.2], p = 0.004) as well as nocturnal hypoxemia (OR = 2.6 [95% CI 1.2-5.4], p = 0.01).

CONCLUSIONS

The study seems to suggest that in young, non-obese subjects, OSA is a predisposing factor for the risk of developing hypertension.

Hellenic registry of patients with home mechanical ventilation (HR-HMV): profiling sleep Apnea-Hypopnea syndrome patients across Greece

Background

Chronic respiratory conditions are a prominent public health issue and thus, building a patient registry might facilitate both policy decision making and improvement of clinical management processes. Hellenic Registry of patients with Home Mechanical Ventilation (HR-HMV) was initiated in 2017 and a web-based platform is used to support patient data collection. Eighteen hospital departments (including sleep labs) across Greece participate in this initiative, focusing on recording data for both children and adult patients supported by mechanical ventilation at home, including patients with Sleep Apnea–Hypopnea Syndrome (SAHS) under Positive Airway Pressure (PAP) therapy.

Methods

The HR-HMV initiative ultimately aims to provide a database for evidence-based care and policy making in this specific domain. To this end, a web information system was developed and data were manually collected by clinics and hospital departments. Legal and privacy issues (such as General Data Protection Rule compliance and technical information security measures) have been considered while designing the web application. Based on the collected data, an exploratory statistical report of SAHS patients in Greece is presented.

Results

Eleven out of the eighteen participating clinics and hospital departments have contributed with data by the time of the current study. More than 5000 adult and children patient records have been collected so far, the vast majority of which (i.e., 4900 patients) diagnosed with SAHS.

Conclusion

The development and maintenance of patient registries is a valuable tool for policy decision making, observational/epidemiological research and beyond (e.g., health technology assessment procedures). However, as all data collection and processing approaches, registries are also related with potential biases. Along these lines, strengths and limitations must be considered when interpreting the collected data, and continuous validation of the collected clinical data per se should be emphasized. Especially for Greece, where the lack of national registries is eminent, we argue that HR-HMV could be a useful tool for the development and the update of related policies regarding the healthcare services for patients with home mechanical ventilation support and SAHS patients, which could be useful for related initiatives at a European level as well.

Hypoxic Burden in Obstructive Sleep Apnea: Present and Future

Conventional measures of obstructive sleep apnea (OSA) severity, such as the apnea-hypopnea index (AHI) and oxygen desaturation index (ODI) are commonly used to quantify OSA severity and guide therapeutical decision-making processes. However, it is widely recognized that both AHI and ODI have important limitations and novel physiologically informed metrics are needed to better capture the severity of OSA and characterize its physiological consequences, particularly the severity of recurrent nocturnal hypoxemia, ensuing the respiratory events. According to recent studies, the sleep apnea-specific "Hypoxic Burden (HB)", defined as the sum of individual areas under the oxygen desaturation curve, has shown some promise in identifying high risk individuals with OSA. In addition to the frequency of respiratory events, HB capture the depth and duration of OSA-related hypoxemia that may prove to be important disease characterizing features, not captured by the conventional "frequency-based" metrics, such as AHI and ODI. In this "Perspective" paper the methods to quantify the HB, its characteristics, associations with health outcomes, and its limitations will be discussed.

Sleep medicine in Europe: 50 years of evolution

The evolution of sleep medicine in Europe over the past 50 years https://bit.ly/3AVexV8.

Impact of Desaturation Patterns versus Apnea-Hypopnea Index in the Development of Cardiovascular Comorbidities in Obstructive Sleep Apnea Patients

Various phenotypes of obstructive sleep apnea (OSA) have been recently described and are poorly assessed by the commonly used polysomnographic indices, such as the apnea-hypopnea index and oxygen desaturation index. Nocturnal hypoxemia is the hallmark of OSA and new quantitative markers, as hypoxic burden or desaturation severity, have been shown to be associated with cardiovascular (CV) mortality. The purpose of this overview is to review the endophenotypical and clinical characteristics of OSA, the current metrics, and to analyze different measurements of hypoxemia in OSA to predict the cardiovascular impact (eg hypoxic burden). Potential interest of multidimensional models to classify OSA, such as BAVENO classification, is also discussed, with the goal of focusing on specific endophenotypes that are likely to develop CV comorbidities, in order to guide clinicians to more aggressive management of OSA in these individuals.

Obstructive sleep apnea: transition from pathophysiology to an integrative disease model

Obstructive sleep apnea (OSA) is characterised by recurring episodes of upper airway obstruction during sleep and the fundamental abnormality reflects the inability of the upper airway dilating muscles to withstand the negative forces generated within the upper airway during inspiration. Factors that result in narrowing of the oropharynx such as abnormal craniofacial anatomy, soft tissue accumulation in the neck, and rostral fluid shift in the recumbent position increase the collapsing forces within the airway. The counteracting forces of upper airway dilating muscles, especially the genioglossus, are negatively influenced by sleep onset, inadequacy of the genioglossus responsiveness, ventilatory instability, especially post arousal, and loop gain. OSA is frequently associated with comorbidities that include metabolic, cardiovascular, renal, pulmonary, and neuropsychiatric, and there is growing evidence of bidirectional relationships between OSA and comorbidity, especially for heart failure, metabolic syndrome, and stroke. A detailed understanding of the complex pathophysiology of OSA encourages the development of therapies targeted at pathophysiological endotypes and facilitates a move towards precision medicine as a potential alternative to continuous positive airway pressure therapy in selected patients.

Diabetes and cardiovascular diseases are associated with the worsening of intermittent hypoxaemia

Intermittent hypoxaemia is a risk factor for numerous diseases. However, the reverse pathway remains unclear. Therefore, we investigated whether pre-existing hypertension, diabetes or cardiovascular diseases are associated with the worsening of intermittent hypoxaemia. Among the included 2,535 Sleep Heart Health Study participants, hypertension (n = 1,164), diabetes (n = 170) and cardiovascular diseases (n = 265) were frequently present at baseline. All participants had undergone two polysomnographic recordings approximately 5.2 years apart. Covariate-adjusted linear regression analyses were utilized to investigate the difference in the severity of intermittent hypoxaemia at baseline between each comorbidity group and the group of participants free from all comorbidities (n = 1,264). Similarly, we investigated whether the pre-existing comorbidities are associated with the progression of intermittent hypoxaemia. Significantly higher oxygen desaturation index (β = 1.77 [95% confidence interval: 0.41-3.13], p = 0.011), desaturation severity (β = 0.07 [95% confidence interval: 0.00-0.14], p = 0.048) and desaturation duration (β = 1.50 [95% confidence interval: 0.31-2.69], p = 0.013) were observed in participants with pre-existing cardiovascular diseases at baseline. Furthermore, the increase in oxygen desaturation index (β = 3.59 [95% confidence interval: 1.78-5.39], p < 0.001), desaturation severity (β = 0.08 [95% confidence interval: 0.02-0.14], p = 0.015) and desaturation duration (β = 2.60 [95% confidence interval: 1.22-3.98], p < 0.001) during the follow-up were higher among participants with diabetes. Similarly, the increase in oxygen desaturation index (β = 2.73 [95% confidence interval: 1.15-4.32], p = 0.001) and desaturation duration (β = 1.85 [95% confidence interval: 0.62-3.08], p = 0.003) were higher among participants with cardiovascular diseases. These results suggest that patients with pre-existing diabetes or cardiovascular diseases are at increased risk for an expedited worsening of intermittent hypoxaemia. As intermittent hypoxaemia is an essential feature of sleep apnea, these patients could benefit from the screening and follow-up monitoring of sleep apnea.

Defining obstructive sleep apnoea syndrome: a failure of semantic rules

Obstructive sleep apnoea syndrome (OSAS) is one of the most ubiquitous medical conditions in industrialised society. Since the recognition that symptoms of excessive daytime somnolence, problems with concentration, mood and cognitive impairment, as well as cardiometabolic abnormalities can arise as a consequence of obstructed breathing during sleep, it has been subject to variation in its definition. Over the past five decades, attempts have been made to standardise the definitions and scoring criteria used for apnoeas and hypopnoea, which are the hallmarks of obstructive sleep apnoea (OSA). However, applying these definitions in clinical and research practice has resulted in over- and under-estimation of the severity and prevalence of OSAS. Furthermore, the definitions may eventually become redundant in the context of rapid technological advances in breathing measurement and other signal acquisition. Increased efforts towards precision medicine have led to a focus on the pathophysiology of obstructed breathing during sleep. However, the same degree of effort has not been focused on how and why the latter does or does not result in diurnal symptoms, integral to the definition of OSAS. This review focuses on OSAS in adults and discusses some of the difficulties with current definitions and the possible reasons behind them.

The definition of obstructive sleep apnoea syndrome appears to be in constant flux dependent on the definitions attributed to its diagnostic componentshttps://bit.ly/3zXrWKg

The 3% Oxygen Desaturation Index is an Independent Risk Factor for Hypertension Among Children with Obstructive Sleep Apnea

BACKGROUND

Obstructive sleep apnea (OSA) and obesity are both directional risk factors of hypertension. Chronic intermittent hypoxemia (IH) is a commonly observed pathophysiological mechanism involved in multiple comorbidities of OSA. However, their interactions are not well understood in children. This study aimed to investigate the associations of IH indexes (oxygen desaturation index 3% [ODI3], mean peripheral oxygen saturation [SpO₂], least SpO₂, and time with SpO₂ < 85%), apnea-hypopnea index, and weight status with hypertension in a sample of pediatric OSA patients.

METHODS

The medical records of 365 pediatric OSA patients were retrospectively reviewed in this cross-sectional study. Demographics, anthropometrics, standard in-laboratory polysomnography, and nocturnal blood pressure were collected. Multivariate logistic regression with forward selection was used to identify independent predictors of hypertension.

RESULTS

Multivariate logistic regression analysis showed that ODI3 (odds ratio [OR] = 1.02, 95% confidence interval [CI] = 1.01-1.03) and body mass index z-score (OR = 1.34, 95% CI = 1.12-1.60) were independent continuous predictors of pediatric hypertension, whilst severe OSA (OR = 2.62, 95% CI = 1.60-4.29) and overweight/obesity (OR = 2.63, 95% CI = 1.59-4.34) were independent categorical predictors. Traditional risk factors including male sex (OR = 2.33, 95% CI = 1.02-5.33), late childhood/adolescence (OR = 1.98, 95% CI = 1.01-3.88), and overweight/obesity (OR = 2.97, 95% CI = 1.56-5.67) combined with sleep hypoxemia (least SpO₂ ≤ 95%) (OR = 2.24, 95% CI = 1.16-4.04) predicted hypertension (R ² = 0.21) in the severe IH subgroup (n = 205), while the no/mild IH subgroup (n = 160) had an entirely different predictor, severe OSA (OR = 3.81, 95% CI = 1.49-9.74) (R ² = 0.07).

CONCLUSION

The close relationships among IH, overweight/obesity, and hypertension highlight the importance of reducing IH and body weight in children with OSA.

Prediction of Oxygen Desaturation by Using Sound Data From a Noncontact Device: A Proof-of-Concept Study

OBJECTIVES/HYPOTHESIS

Prediction of the apnea-hypopnea index (AHI) from breathing sounds during sleep could be used to prescreen for obstructive sleep apnea (OSA). In addition, the oxygen desaturation index (ODI) is a known risk factor for developing cardiovascular disease in OSA patients. This study focused on estimation of ODI from a noncontact manner from sleep breathing sounds.

STUDY DESIGN

Retrospective study.

METHODS

Patients who visited the sleep center due to snoring or sleep apnea underwent polysomnography in lab overnight. Sound recordings were made during polysomnography using a microphone. After noise reduction, the sound data were segmented into 5 seconds windows and features were extracted. Binary classification and regression analyses were performed to estimate the ODI during sleep (model 1). This was re-tested after inclusion of body mass index (BMI) and age as additional features (model 2: BMI only, model 3: BMI and age).

RESULTS

We included 116 patients. The mean age and AHI of all patients were 50.4 ± 16.7 years and 23.0 ± 24.0 events/hr. In binary classification, for ODI cutoff values of 5, 15, and 30 events/hr, the areas under the curve were 0.88, 0.93, 0.91, respectively, and accuracies were 85.34, 86.21, and 87.07, respectively. In regression analysis, the correlation coefficient and mean absolute error were 0.80 and 9.60 events/hr, respectively. In models 2 and 3, the correlation coefficient and mean absolute error were 0.82, 9.44 events/hr and 0.81, 9.6 events/hr, respectively.

CONCLUSION

Prediction of ODI from sleep sound seems to be feasible. Additional clinical feature such as BMI may increase overall predictability.

LEVEL OF EVIDENCE

IV Laryngoscope, 2021.

Getting More from the Sleep Recording

Sleep studies have typically followed criteria established many decades ago, but emerging technologies allow signal analyses that go far beyond the scoring rules for manual analysis of sleep recordings. These technologies may apply to the analysis of signals obtained in standard polysomnography in addition to novel signals more recently developed that provide both direct and indirect measures of sleep and breathing in the ambulatory setting. Automated analysis of signals such as electroencephalogram and oxygen saturation, in addition to heart rate and rhythm, provides a wealth of additional information on sleep and breathing disturbances and their potential for comorbidity.

Prevalence of Obstructive Sleep Apnea Syndrome: A Single-Center Retrospective Study

Obstructive sleep apnea syndrome (OSAS) is a sleep breathing disorder that often remains undiagnosed and untreated. OSAS prevalence is increasing exponentially. Starting on the dentist's role as an epidemiological and diagnostic "sentinel", the purpose of this study was to assess the prevalence of OSAS. The clinical diaries of 4659 patients were reviewed through a single-center retrospective analytic study. Descriptive statistical analysis was performed. Only 0.26% of patients reported to suffer from sleep apnea and were then diagnosed with OSAS. It was found that, out of 4487 patients, 678 suffered from hypertension (14.80%), 188 from gastro-esophageal-reflux-disease (GERD = 4.10%) and 484 from gastritis (10.78%). These results could be related to a difficult diagnosis of OSAS and to the absence of a dedicated section on sleep disorders in medical records. Therefore, the introduction of a question dedicated to sleep disorders, the administration of questionnaires (such as the STOP-BANG questionnaire) for early diagnosis, a multidisciplinary approach and pneumological examination could support the dentist in identifying patients at risk of OSAS.

Obstructive sleep apnea and cardiovascular comorbidity: common pathophysiological mechanisms to cardiovascular disease

Obstructive sleep apnea (OSA) is associated with many cardiovascular and metabolic diseases. Sleep apnea causes intermittent hypoxemia, chest pressure fluctuations and a reaction from the cerebral cortex in the form of a short awakening during sleep (EEG-activation). The consequences of pathological pathways are studied in experimental models involving cell cultures, animals, and healthy volunteers. At present, the negative impact of intermittent hypoxemia on a variety of pathophysiological disorders of the heart and blood vessels (vascular tone fluctuations, thickening of the intimamedia complex in the vascular wall, direct damaging effect on the myocardium) has a great evidence base. Two other pathological components of OSA (pressure fluctuations and EEG-activation) can also affect cardiovascular system, mainly affecting the increase in blood pressure and changing cardiac hemodynamics. Although these reactions are considered separately in the review, with the development of sleep apnea they occur sequentially and are closely interrelated. As a result, these pathological pathways trigger further pathophysiological mechanisms acting on the heart and blood vessels. It is known that these include excessive sympathetic activation, inflammation, oxidative stress and metabolic dysregulation. In many respects being links of one process, these mechanisms can trigger damage to the vascular wall, contributing to the formation of atherosclerotic lesions. The accumulated data with varying degrees of reliability confirm the participation of OSA through these processes in the formation of cardiovascular disorders. There are factors limiting direct evidence of this interaction (sleep deprivation, causing similar changes, as well as the inability to share the contribution of other risk factors for cardiovascular diseases, in particular arterial hypertension, obesity, which are often associated with OSA). It is necessary to continue the study of processes that implement the pathological effect of OSA on the cardiovascular system.

Nocturnal oximetry in bariatric surgery patients referred to overnight in-lab polysomnography

OBJECTIVE

This study aimed to evaluate nocturnal oximetry approaches in identifying obstructive sleep apnea (OSA) among bariatric surgical candidates.

METHODS

This was a cross-sectional study involving adult bariatric patients who were undergoing in-lab polysomnography and who were previously screened with the GOAL questionnaire. OSA severity was established as any OSA, moderate/severe OSA, and severe OSA. Oximetry data were evaluated as oxygen saturation (average and nadir), oxygen desaturation index (ODI) at 3%, and proportion of time spent with oxygen saturation <90%. Associations between oximetry data and the apnea-hypopnea index (AHI) were assessed by Spearman correlation index (r), linear regression, logistic regression, and discrimination.

RESULTS

All oximetry values were significantly correlated with the AHI among 1,178 individuals, with the ODI emerging as the better parameter (r = 0.911, p < 0.001). Using linear regression, the ODI was the only predictor of the AHI (β = 0.952, p < 0.001). In the multivariate analysis, the ODI was the only independent parameter predicting OSA at all severity levels. In addition, the ODI exhibited excellent discrimination to predict OSA and displayed improved performance among individuals screened as being at high risk versus those at low risk with the GOAL instrument.

CONCLUSIONS

The ODI emerges as a valid surrogate predictor of the AHI, particularly among those screened as being at high risk for OSA.

Non-dipping nocturnal blood pressure correlates with obstructive sleep apnoea severity in normotensive subjects and may reverse with therapy

Background

Obstructive sleep apnoea (OSA) is strongly associated with systemic hypertension, but there are limited data on the relationship with blood pressure (BP) in normotensive subjects. Here, we examined the relationship of OSA with nocturnal BP in a documented diurnal normotensive cohort, explored potential intermediate pathways and assessed the effects on BP of continuous positive airways pressure (CPAP) therapy.

Methods

65 males referred for assessment of possible OSA and normotensive on 24-hour BP monitoring underwent overnight inpatient polysomnography (age 41±7 years, body mass index (BMI) 34±6 kg·m⁻², apnoea–hypopnoea index (AHI) 14 (interquartile range 5–26)). Urine and serum were assessed for markers of sympathetic activation, renin–angiotensin–aldosterone system activity, oxidative stress, endothelial function and systemic inflammation. In a subset of patients, 24-hour BP monitoring was repeated after CPAP therapy.

Results

Within this normotensive cohort, night-time systolic and diastolic BP and nocturnal BP dip were highest in the fourth OSA severity quartile (p<0.05). Nocturnal BP dip correlated with AHI (r=−0.327, p<0.05) and oxygen desaturation index (ODI) (r=−0.371, p<0.05), but only ODI was an independent predictor of BP dip (B=–0.351, p<0.01) and non-dipping status (B=0.046, p<0.05). Overnight urinary norepinephrine correlated with nocturnal systolic BP (r=0.387, p<0.01) with a trend towards correlation with systolic dipping (p=0.087). In 20 CPAP-treated patients, night-time systolic BP decreased (p<0.05) and mean nocturnal BP dip increased (p≤0.05).

Conclusion

In this normotensive cohort, OSA severity was associated with higher nocturnal BP, which improved following CPAP therapy, and intermittent hypoxia was the most important OSA-related variable in this relationship.

There is a strong association in a normotensive cohort between OSA and nocturnal blood pressure, with intermittent hypoxia as an important mechanistic pathwayhttps://bit.ly/2SFvWiB

Mild obstructive sleep apnea increases hypertension risk, challenging traditional severity classification

STUDY OBJECTIVES

The association of mild obstructive sleep apnea (OSA) with important clinical outcomes remains unclear. We aimed to investigate the association between mild OSA and systemic arterial hypertension (SAH) in the European Sleep Apnea Database cohort.

METHODS

In a multicenter sample of 4,732 participants, we analyzed the risk of mild OSA (subclassified into 2 groups: mild_{AHI 5-<11/h} (apnea-hypopnea index [AHI], 5 to <11 events/h) and mild_{AHI 11-<15/h} (AHI, ≥11 to <15 events/h) compared with nonapneic snorers for prevalent SAH after adjustment for relevant confounding factors including sex, age, smoking, obesity, daytime sleepiness, dyslipidemia, chronic obstructive pulmonary disease, type 2 diabetes, and sleep test methodology (polygraphy or polysomnography).

RESULTS

SAH prevalence was higher in the mild_{AHI 11-<15/h} OSA group compared with the mild_{AHI 5-<11/h} group and nonapneic snorers (52% vs 45% vs 30%; P < .001). Corresponding adjusted odds ratios for SAH were 1.789 (mild_{AHI 11-<15/h}; 95% confidence interval [CI], 1.49-2.15) and 1.558 (mild_{AHI 5-<11/h}; 95%, CI, 1.34-1.82), respectively (P < .001). In sensitivity analysis, mild_{AHI 11-<15/h} OSA remained a significant predictor for SAH both in the polygraphy (odds ratio, 1.779; 95% CI, 1.403-2.256; P < .001) and polysomnography groups (odds ratio, 1.424; 95% CI, 1.047-1.939; P = .025).

CONCLUSIONS

Our data suggest a dose-response relationship between mild OSA and SAH risk, starting from 5 events/h in polygraphy recordings and continuing with a further risk increase in the 11- to <150-events/h range. These findings potentially introduce a challenge to traditional thresholds of OSA severity and may help to stratify participants with OSA according to cardiovascular risk.

Beyond the AHI-pulse wave analysis during sleep for recognition of cardiovascular risk in sleep apnea patients

Recent evidence supports the use of pulse wave analysis during sleep for assessing functional aspects of the cardiovascular system. The current study compared the influence of pulse wave and sleep study-derived parameters on cardiovascular risk assessment. In a multi-centric study design, 358 sleep apnea patients (age 55 ± 13 years, 64% male, body mass index 30 ± 6 kg m^-2 , apnea-hypopnea index 13 [5-26] events per hr) underwent a standard overnight sleep recording. A novel cardiac risk index was computed based on pulse wave signals derived from pulse oximetry, reflecting vascular stiffness, cardiac variability, vascular autonomic tone and nocturnal hypoxia. Cardiovascular risk was determined using the ESC/ESH cardiovascular risk matrix, and categorized to high/low added cardiovascular risk. Comparisons between cardiac risk index and sleep parameters were performed for cardiovascular risk prediction. Apnea-hypopnea index, oxygen desaturation index and cardiac risk index were associated with high cardiovascular risk after adjustment for confounders (p = .002, .001, < .001, respectively). In a nested reference model consisting of age, gender and body mass index, adding cardiac risk index but not apnea-hypopnea index or oxygen desaturation index significantly increased the area under the receiver operating characteristic curve (p = .012, .22 and .16, respectively). In a direct comparison of oxygen desaturation index and cardiac risk index, only the novel risk index had an independent effect on cardiovascular risk prediction (p_CRI  < .001, p_ODI  = .71). These results emphasize the association between nocturnal pulse wave and overall cardiovascular risk determined by an established risk matrix. Thus, pulse wave analysis during sleep provides a powerful approach for cardiovascular risk assessment in addition to conventional sleep study parameters.

Sex differences in the association between arterial hypertension, blood pressure, and sleep apnea in the general population

STUDY OBJECTIVES

To assess sex-related differences in the relationship between hypertension (HT), blood pressure (BP), and sleep apnea in the general population.

METHODS

We performed home polygraphy in a cohort of 1809 men and women in the general population. Office BP was measured. Presence of HT (drug-treated, physician-diagnosed, or high BP during study visit) was also recorded. HT rate and BP were assessed over a range of 7 sleep apnea severity categories based on the respiratory event index (REI).

RESULTS

The age-adjusted HT prevalence rate increased with higher REI in both sexes. After additional adjustment for obesity the association remained significant in women but not in men. In participants not treated with antihypertensive medications, age-adjusted BP increased with REI. Remarkably, the association was already significant within the normal range (REI < 5 events/h). The REI threshold for higher BP was situated at a distinctly lower cutoff point in women compared to men. After additional adjustment for obesity, the associations remained significant for diastolic but not systolic BP.

CONCLUSIONS

Significant increases in the age-adjusted BP and HT rate in the general population were present at lower REI cutoffs in women compared to men. Even a very low number of respiratory events was associated with higher BP and HT prevalence. Adjustment for obesity attenuated these associations, especially in men. Sex differences in BP susceptibility across the sleep apnea spectrum may be present.

Effects of sleep apnea hypopnea syndromes on cardiovascular events: a systematic review and meta-analysis

PURPOSE

Previous studies suggest that sleep apnea hypopnea syndrome (SAHS) is an independent risk factor that contributes to certain cardiovascular events. However, there are studies arguing that patients with SAHS had lower peak troponin levels when suffering cardiovascular events compared to patients without SAHS, which indicates that there may potentially be a protective effect of SAHS. This meta-analysis aimed to assess the impact of SAHS on cardiovascular events.

METHODS

Databases were searched for studies that examined cardiac biomarkers or reported angiographic data when patients with SAHS experienced cardiovascular events. The data about peak cardiac biomarkers and angiographic coronary lesion were extracted and then used to compute the pooled standardized mean difference (SMD) and 95% confidence interval (95% CI).

RESULTS

Among 26 studies included in the meta-analysis, there was not a definite difference between the SAHS group and the control group for troponins (SMD, 0.05; 95% CI, [- 0.16, 0.26]), creatine kinase (SMD, - 0.08; 95% CI, [- 0.38, 0.22]), and CK-MB (SMD, - 0.11; 95% CI, [- 0.51, 0.29]). However, patients with SAHS revealed worse coronary lesion condition grading via both Gensini score (SMD, 0.63; 95% CI, [0.31, 0.95]) and SYNTAX score (SMD, 0.99; 95% CI, [0.31-1.67]).

CONCLUSIONS

Ischemic preconditioning induced by the intermittent hypoxia at the early stage could generate a cardiac protection effect, which would then benefit SAHS patients encountering a major adverse cardiovascular event.

Association Between Intermittent Hypoxia and Left Ventricular Remodeling in Patients With Obstructive Sleep Apnea-Hypopnea Syndrome

The present study was undertaken to examine the association between intermittent hypoxia and left ventricular (LV) remodeling and explore which parameter of intermittent hypoxia is most relevant to LV remodeling in patients with obstructive sleep apnea-hypopnea syndrome (OSAHS). Two hundred eighty six patients underwent polysomnographic examination were enrolled. Based on apnea-hypoxia index (AHI), patients were divided into no, mild, moderate and severe OSAHS groups. Between-group differences in LV remodeling and the association between parameters of intermittent hypoxia and LV remodeling was evaluated. Patients with severe OSAHS were more likely to have hypertension, and higher values of LV mass (LVM) and LVM index (LVMI). In univariate regression analysis, male, body mass index (BMI), systolic and diastolic blood pressure (BP), statins, antihypertensive drugs, creatinine, and parameters of intermittent hypoxia (AHI, obstructive apnea index [OAI], lowest oxygen saturation [LSpO₂], oxygen desaturation index [ODI], time spent below oxygen saturation of 90% [TS90%], and mean nocturnal oxygen saturation [MSpO₂]) were associated with LVMI. After multivariate regression analyses, only male gender, BMI, systolic BP, creatinine, and ODI remained significantly associated with LVMI. Compared to those without LV hypertrophy (LVH), patients with LVH had higher ODI. Compared to patients with normal LV, concentric remodeling and eccentric LVH, those with concentric LVH had higher ODI. In conclusion, intermittent hypoxia was significantly associated with left ventricular remodeling; and among various parameters of intermittent hypoxia, ODI was the most relevant to LV remodeling.

Combined unsupervised-supervised machine learning for phenotyping complex diseases with its application to obstructive sleep apnea

Unsupervised clustering models have been widely used for multimetric phenotyping of complex and heterogeneous diseases such as diabetes and obstructive sleep apnea (OSA) to more precisely characterize the disease beyond simplistic conventional diagnosis standards. However, the number of clusters and key phenotypic features have been subjectively selected, reducing the reliability of the phenotyping results. Here, to minimize such subjective decisions for highly confident phenotyping, we develop a multimetric phenotyping framework by combining supervised and unsupervised machine learning. This clusters 2277 OSA patients to six phenotypes based on their multidimensional polysomnography (PSG) data. Importantly, these new phenotypes show statistically different comorbidity development for OSA-related cardio-neuro-metabolic diseases, unlike the conventional single-metric apnea-hypopnea index-based phenotypes. Furthermore, the key features of highly comorbid phenotypes were identified through supervised learning rather than subjective choice. These results can also be used to automatically phenotype new patients and predict their comorbidity risks solely based on their PSG data. The phenotyping framework based on the combination of unsupervised and supervised machine learning methods can also be applied to other complex, heterogeneous diseases for phenotyping patients and identifying important features for high-risk phenotypes.