OSA: the new cardiovascular disease: part II: Overview of cardiovascular diseases associated with obstructive sleep apnea

Sleep apnoea, gut dysbiosis and cognitive dysfunction

Sleep disorders are becoming increasingly common, and their distinct effects on physical and mental health require elaborate investigation. Gut dysbiosis (GD) has been reported in sleep-related disorders, but sleep apnoea is of particular significance because of its higher prevalence and chronicity. Cumulative evidence has suggested a link between sleep apnoea and GD. This review highlights the gut-brain communication axis that is mediated via commensal microbes and various microbiota-derived metabolites (e.g. short-chain fatty acids, lipopolysaccharide and trimethyl amine N-oxide), neurotransmitters (e.g. γ-aminobutyric acid, serotonin, glutamate and dopamine), immune cells and inflammatory mediators, as well as the vagus nerve and hypothalamic-pituitary-adrenal axis. This review also discusses the pathological role underpinning GD and altered gut bacterial populations in sleep apnoea and its related comorbid conditions, particularly cognitive dysfunction. In addition, the review examines the preclinical and clinical evidence, which suggests that prebiotics and probiotics may potentially be beneficial in sleep apnoea and its comorbidities through restoration of eubiosis or gut microbial homeostasis that regulates neural, metabolic and immune responses, as well as physiological barrier integrity via the gut-brain axis.

Sacubitril/valsartan mitigated intermittent hypoxia related intestinal microbiota alteration and aortic injury

OBJECTIVE

To investigate the influence of sacubitril valsartan sodium (SVS) on chronic intermittent hypoxia (IH) related gut microbiome composition alteration and aortic injury.

METHODS

Experiments were performed using SD rats, which were divided into three groups: control, IH, and SVS group. O2 concentration was decreased to 7-8% at nadir approximately every 3 min in IH group (8 h per day for 6 weeks) or was left unchanged in control group. Rats in SVS group were orally gavaged with SVS at the dosage of 30 mg/kg/day (2 weeks after chronic IH exposure). At week 6, fecal and aortic samples were harvested for 16 s rDNA analysis and histological analysis, respectively.

RESULTS

Principal coordinate analysis and non-metric multidimensional scaling analysis indicated that the bacterial community was altered by chronic IH exposure, while SVS treatment restored the intestinal microbial communities. Further analysis showed that IH decreased the relative abundance of Lactobacillus and Prevotella, while rats treated with SVS was enriched with Firmicutes, Bacilli, Prevotellaceae, and Lactobacillus, which was similar to control rats. Immunohistochemical staining showed that SVS prevented the upregulation of transforming growth factor-β1 and tumor necrosis factor-alpha in the aorta.

CONCLUSION

SVS prevented aortic adverse response to IH, possibly through modulating intestinal microbiota.

Obstructive Sleep Apnea-induced Endothelial Dysfunction Is Mediated by miR-210

Rationale: Obstructive sleep apnea (OSA)-induced endothelial cell (EC) dysfunction contributes to OSA-related cardiovascular sequelae. The mechanistic basis of endothelial impairment by OSA is unclear. Objectives: The goals of this study were to identify the mechanism of OSA-induced EC dysfunction and explore the potential therapies for OSA-accelerated cardiovascular disease. Methods: The experimental methods include data mining, bioinformatics, EC functional analyses, OSA mouse models, and assessment of OSA human subjects. Measurements and Main Results: Using mined microRNA sequencing data, we found that microRNA 210 (miR-210) conferred the greatest induction by intermittent hypoxia in ECs. Consistently, the serum concentration of miR-210 was higher in individuals with OSA from two independent cohorts. Importantly, miR-210 concentration was positively correlated with the apnea-hypopnea index. RNA sequencing data collected from ECs transfected with miR-210 or treated with OSA serum showed a set of genes commonly altered by miR-210 and OSA serum, which are largely involved in mitochondrion-related pathways. ECs transfected with miR-210 or treated with OSA serum showed reduced [Formula: see text]o2 rate, mitochondrial membrane potential, and DNA abundance. Mechanistically, intermittent hypoxia-induced SREBP2 (sterol regulatory element-binding protein 2) bound to the promoter region of miR-210, which in turn inhibited the iron-sulfur cluster assembly enzyme and led to mitochondrial dysfunction. Moreover, the SREBP2 inhibitor betulin alleviated intermittent hypoxia-increased systolic blood pressure in the OSA mouse model. Conclusions: These results identify an axis involving SREBP2, miR-210, and mitochondrial dysfunction, representing a new mechanistic link between OSA and EC dysfunction that may have important implications for treating and preventing OSA-related cardiovascular sequelae.

The effect of obstructive sleep apnea on the increased risk of cardiovascular disease: a systematic review and meta-analysis

BACKGROUND

Obstructive sleep apnea (OSA) is a disorder characterized by intermittent airway obstruction during sleep. The association between OSA and the incidence of cardiovascular disease (CVD) has been investigated in many studies; however, the results are not entirely consistent between studies. The aim of this study was to investigate the relationship between OSA and the risk of CVD through a meta-analysis of cohort studies.

METHODS

A systematic review and meta-analysis of literature was conducted using the PubMed, WoS, Embase, ScienceDirect, Scopus, and Web of Science databases up to the year 2020. In order to analyze the eligible studies, the stochastic effects model was used and the heterogeneity of the studies with the I² index was investigated. Data analysis was performed with Comprehensive Meta-Analysis software (Version 2).

RESULTS

A total of 24 studies were included in the meta-analysis according to the inclusion criteria. Twelve studies reported CVD results, 11 studies reported stroke results, 9 studies reported mortality results, and 8 studies reported CVD results. The odds ratio of CVD in patients with OSA 1.71 (1.17-2.27: 95% confidence interval) stroke in patients with OSA, 1.86 (1.28-2.69: 95% confidence interval), mortality in patients with OSA, 1.77 (1.37-2.29: 95% confidence interval) and CHD in patients with OSA, and 1.48 (1.06-2.28: 95% confidence interval) was obtained.

CONCLUSION

OSA is considered a cardiovascular risk factor. There is a relationship between the severity of OSA and the risk of cardiovascular disease. OSA increases the risk of heart attack, CHD, and death from cardiovascular disease.

Beat-to-beat blood pressure variability in patients with obstructive sleep apnea

STUDY OBJECTIVES

Cardiovascular comorbidities in obstructive sleep apnea (OSA) are difficult to treat, perhaps due to autonomic dysfunction. We assessed beat-to-beat blood pressure (BP) variability (BPV) in OSA while considering other markers derived from electrocardiogram and continuous BP signals.

METHODS

We studied 66 participants (33 participants with OSA: respiratory event index [mean ± SEM]: 21.1 ± 2.7 events/h; 12 females, aged 51.5 ± 2.4 years; body mass index: 32.8 ± 1.4 kg/m²; 33 healthy controls: 20 females; aged 45.3 ± 2.4 years; body mass index: 26.3 ± 0.7 kg/m²). We collected 5-minute resting noninvasive beat-to-beat BP and electrocardiogram values. From BP, we derived systolic, diastolic, and mean BP values, and calculated variability as standard deviations (systolic BPV, diastolic BPV, BPV). We also calculated diastole-to-systole time (time to peak). From the electrocardiogram, we derived QRS markers and calculated heart rate and heart rate variability. We performed a multivariate analysis of variance based on sex and group (OSA vs control), with Bonferroni-corrected post hoc comparisons (P ≤ .05) between groups. We calculated correlations of BPV with biological variables.

RESULTS

Multivariate analysis of variance showed effects of diastolic BPV and BPV in OSA; post hoc comparisons revealed high diastolic BPV and BPV only in female participants with OSA vs controls. QRS duration was higher in OSA, with post hoc comparisons showing the effect only in males. BPV correlated positively with heart rate variability in controls but not in participants with OSA. BPV correlated positively with time to peak in females with OSA and OSA combined, whereas there was no BPV-time-to-peak correlation in healthy participants.

CONCLUSIONS

The findings show sex-specific autonomic dysfunction reflected in beat-to-beat BP in OSA. The higher BPV may reflect poor baroreflex control or vascular damage in OSA, which are potential precursors to cardiovascular complications.

Soluble P-selectin levels in patients with obstructive sleep apnea: a systematic review and meta-analysis

PURPOSE

Obstructive sleep apnea (OSA) patients are at increased risk for cardiovascular disease, stroke, atherosclerosis, hypertension, and venous thromboembolism. Elevated soluble P-selectin (sP-selectin) levels are also associated with increased risk of above diseases. But whether sP-selectin levels in OSA patients are higher than their counterparts remain unclear, since previous studies yielded inconsistent results. Therefore, a meta-analysis is warranted.

METHODS

PubMed, Embase, Cochrane Library, and Web of Science databases were searched for eligible studies. Studies were included if they reported sP-selectin levels of both OSA patients and non-OSA controls. Standardized mean differences (SMDs) with 95% confidence intervals (CIs) were calculated to determine the effect sizes.

RESULTS

Nine eligible studies were finally evaluated. When all the studies were pooled, sP-selectin levels in OSA patients were significantly higher than that in controls (SMD = 0.54, 95% CI 0.29-0.78, I² = 66%, p < 0.0001). In the subgroup analysis based on BMI matched groups, sP-selectin levels were significantly higher in OSA patients than that in controls (SMD = 0.52, 95% CI 0.27-0.76, I² = 23%, p < 0.0001). In the subgroup analysis stratified by blood source, either serum sP-selectin levels or plasma sP-selectin levels in OSA patients were higher than that in controls. Moderate-to-severe OSA patients had significant higher sP-selectin levels (SMD = 0.80, 95% CI 0.45-1.15, I² = 67%, p < 0.00001), while mild OSA patients showed no significant difference with controls.

CONCLUSION

The pooled results reveal that OSA patients have higher sP-selectin levels than non-OSA controls. This conclusion remains unaltered in all subgroups other than the subgroup of mild OSA patients. Additional studies are warranted to better identify the role of sP-selectin as a potential biomarker in OSA patients.

Influence of head flexion and rotation on obstructive sleep apnea severity during supine sleep

Head posture influences the collapsibility of the passive upper airway during anaesthesia. However, little is known about the impact of head posture during sleep. The objective of this study was to develop and validate an instrument to measure head posture during supine sleep and to apply this instrument to investigate the influence of head posture on obstructive sleep apnea (OSA) severity. A customized instrument to quantify head flexion and rotation during supine sleep was developed and validated in a benchtop experiment. Twenty-eight participants with suspected OSA were successfully studied using diagnostic polysomnography with the addition of the customized instrument. Head posture in supine sleep was discretized into four categories by two variables: head flexed or not (flexion >15°); and head rotated or not (rotation >45°). Sleep time in each posture and the posture-specific apnea-hypopnea index (AHI) were quantified. Linear mixed-effect modelling was applied to determine the influence of flexion and rotation on supine OSA severity. Twenty-four participants had ≥15 min of supine sleep in at least one head-posture category. Only one participant had ≥15 min of supine sleep time with the head extended. Head flexion was associated with a 12.9 events/h increase in the AHI (95% CI: 3.7-22.1, p = .007). Head rotation was associated with an 11.0 events/h decrease in the AHI (95% CI: 0.3-21.6, p = .04). Despite substantial interparticipant variability, head flexion worsened OSA severity, and head rotation improved OSA severity. Interventions to promote rotation and restrict flexion may have therapeutic benefit in selected patients.

Adherence to prescribed overnight sleep study in patients suspected of sleep apnea: problem size and influential factors

PURPOSE

Despite the serious consequences of sleep apnea, some patients do not follow their physicians' advice to undergo a sleep study. The present study aimed to determine the rate of adherence and influencing factors in conducting a polysomnography test in patients suspected of obstructive sleep apnea.

METHODS

This qualitative and quantitative analysis was conducted between July 2017 and November 2019 on patients suspected of sleep apnea. The quantitative analysis aimed at determining the rate of adherence through a retrospective cross-sectional study. The qualitative content analysis was conducted on purposefully selected subgroup of patients suspected of obstructive sleep apnea who were referred for polysomnography. The required data were collected through the semi-structured in-depth interviews and then recorded, transcribed, and analyzed using SPSS.22 and MAXQDA10.

RESULTS

Quantitative part: Of 311 patients (mean age: 47.6 ± 13.1 years) referred for polysomnography, 283 patients (91%) were at a high risk of developing obstructive sleep apnea. Among those referred for polysomnography, 31% (n = 95) adhered to recommendations for a sleep study. Qualitative part: Factors affecting adherence to polysomnography were categorized as "barriers" and "triggers." Barriers included inadequate knowledge, psychological factors, cost, and the service system. Triggers included adequate knowledge and tangible experience of consequences of the illness.

CONCLUSION

The majority of patients at risk of developing obstructive sleep apnea did not follow the recommendation for polysomnography, indicating a need for systematic interventions. Among the identified barriers, knowledge and psychological factors are modifiable ones that can be addressed with the patient. We theorize that raising awareness among patients by providing additional information and eliminating concerns may help to increase the rate of adherence. Insurance coverage or subsidy to reduce the sleep study costs may also be an effective strategy to increase adherence to recommendations for polysomnography.

The Importance of Apneic Events in Obstructive Sleep Apnea Associated with Acute Coronary Syndrome

Background

Obstructive sleep apnea (OSA) is a potential cardiovascular risk factor. However, there is currently no prominent screening strategy for its diagnosis in patients with acute coronary syndrome (ACS). The aim of this study was to establish the impact of apneic events in case of OSA associated with ACS.

Methods

Between January 1st and June 30th, fifty-three subjects with ACS (first acute myocardial infarction) were prospectively evaluated for OSA. Each patient was evaluated by polysomnography (PSG) two months after the ACS.

Results

Mean age of 59±9,6 years, 81,1% males, BMI at 28,5±4,2 kg/m², neck circumference of 42,5±12,6 cm, and waist circumference os 102,5±16,5 cm. The majority of patients (73,6%) had moderate to severe OSA (apnea-hypopnea index (AHI) ≥ 15/h and arousal index ≥ 10/h). We defined the apneic coefficient (AC) as the ratio between apnea index (AI) and AHI. We chose as cut-off the median value of apnea coefficient in our population which was at 37%. The patients with a higher AC (AC ≥ 37% versus AC < 37%) had higher levels of Troponin-I (63,4±63,2 versus 29,7±36,1 ng/mL, p=0,016), higher levels of NT-proBNP (1879,8±2141,8 versus 480±621,3 pg/mL, p=0,001), higher SYNTAX score (15,8±11,5 versus 10,2±5,9, p=0,049), and lower left ventricle ejection fraction (LVEF 53,3±11,4 versus 59,4±6,4%, p=0,023) and were more likely to have a STEMI (21 patients (77,7%) vesus 14 patients (53,8%), p=0,031).

Conclusion

An apneic coefficient (AI/AHI) ≥ 37% is correlated with more severe cardiac impairment, as well as higher hypoxemia and arousal index.

Heated humidification did not improve compliance of positive airway pressure and subjective daytime sleepiness in obstructive sleep apnea syndrome: A meta-analysis

Introduction

We performed a meta-analysis on whether heated humidification during positive airway pressure (PAP) could improve compliance and subjective daytime sleepiness in obstructive sleep apnea syndrome (OSAS) patients.

Materials and methods

We searched PubMed, EMBASE, Medline, Cochrane Library, Clinical Trials, Web of Science and Scopus from inception to Oct 29, 2017. We made meta-analysis on the all available randomized controlled trials (RCTs) which assessed effects of heated humidification intervention on PAP compliance and subjective daytime sleepiness, by subgroups of automatic adjusting positive airway pressure/ continuous positive airway pressure (APAP/CPAP) usage and patients with/without upper airway symptoms prior to PAP therapy.

Results

A total of nine RCTs were evaluated finally in this meta-analysis. When all the studies were pooled, heated humidification did not improve PAP usage time [weighted mean difference(WMD) = 13.28, 95% confidence interval(CI): -5.85 to 32.41, P = 0.17] or Epworth sleepiness scale (ESS) score (WMD = -0.63, 95% CI: -1.32 to 0.07, P = 0.08). In terms of PAP usage time, heated humidification failed to enhance compliance in both APAP (WMD = 22.34, 95%CI: -21.08 to 65.77, P = 0.31) or CPAP subgroup (WMD = 11.09, 95%CI: -10.21 to 32.40, P = 0.31) and it was also ineffective among patients with upper airway symptoms prior to PAP therapy (WMD = 22.74, 95% CI: -7.77 to 53.24, P = 0.14) or without (WMD = 13.22, 95%CI: -35.84 to 62.29, P = 0.60). In terms of ESS score, heated humidification did not reduce ESS scores in both APAP (WMD = -1.59, 95% CI: -3.81 to 0.64, P = 0.16) or CPAP subgroup (WMD = -0.39, 95% CI: -1.16 to 0.37, P = 0.32) and it was also helpless among patients with upper airway symptoms prior to PAP therapy (WMD = -1.17, 95% CI: -3.10 to 0.75, P = 0.23) or without (WMD = -0.30, 95%CI: -2.25 to 1.66, P = 0.76).

Conclusion

Heated humidification during PAP therapy improves neither the compliance nor ESS scores in OSAS patients, no matter what types of PAP or whether the patients had upper airway symptoms prior to PAP therapy. But to the population with upper airway symptoms and the APAP users, the conclusions were limited because of small sample size and possible selection bias. More attentions should be paid to these potentially possible benefited subgroups.

Relation of Obstructive Sleep Apnea to Risk of Hospitalization in Patients With Heart Failure and Preserved Ejection Fraction from the National Inpatient Sample

Obstructive Sleep Apnea (OSA) increases the risk of diastolic dysfunction and heart failure. The impact of OSA on hospitalization for heart failure with preserved ejection fraction (HFpEF) is not well elucidated. We used data from the National Inpatient Sample for the years 2012 to 2014. We identified discharges (age ≥18 years) associated with OSA and HFpEF using the International Classification of Diseases, Ninth Revision, Clinical Modification codes (327.23 and 428.3x), respectively. Propensity score analysis, adjusting for age, gender, race, and comorbidities, compared the rates of admission for HFpEF in patients with OSA to those without OSA. Out of 12,608,637 discharges included, there were 147,463 patients with HFpEF, and 653,762 or 5.2% of all discharges had OSA. The prevalence of OSA in patients with HFpEF was 16.8%. Patients with OSA were older, more likely to be men, more likely to have diabetes, hypertension, history of coronary artery disease, chronic kidney disease, obesity, atrial fibrillation, African-American race, and smoking status. In patients with OSA, HFpEF occurred in 3.8% versus 1.0%, with adjusted odds ratio: 2.2 (95% confidence interval 2.16 to 2.23), p <0.001. Subgroup analysis showed similar results in men and women. After propensity score matching, OSA was associated with increased risk of admission with HFpEF, relative risk = 2.2 (95% confidence interval 2.12 to 2.21). In conclusion, OSA was associated with increased risk of hospitalization for HFpEF.

Modafinil and the risk of cardiovascular events: Findings from three US claims databases

PURPOSE

This study examined the potential risk of cardiovascular (CV) events associated with modafinil and the consistency of the risk estimates across databases.

METHODS

A retrospective, inception cohort design of patients who initiated treatment with modafinil between 2006 and 2008 was used in three US health care claims databases. Modafinil users were matched with nonusers. Patients were further divided into two cohorts of obstructive sleep apnea (OSA) and non-OSA (NOSA) cohorts. Endpoints of interest, including myocardial infarction (MI), stroke, CV hospitalizations, and all-cause death, were assessed using incidence rates and Cox proportional hazard ratios (HRs), adjusted for potential confounding factors.

RESULTS

The cohorts included a total of 175 524 patients in MarketScan CM; 77 266-in IMS LifeLink; and 8174-in MarketScan Medicaid. No increased risk for MI in the OSA and NOSA cohorts was observed across all three databases. The risks of CV hospitalization in the OSA and NOSA cohorts were not different between the modafinil users and nonusers, except for IMS LifeLink database where the HR was lower than one in the modafinil users compared with the nonusers (HR, 0.69; 95% confidence interval [CI], 0.54 to 0.87). For OSA patients with prior stroke, an adjusted HR of 1.96 (95% CI, 1.02 to 3.76) was observed for stroke among modafinil users compared with nonusers. Among the NOSA, the HRs for all-cause death in the OSA were inconsistent across databases.

CONCLUSIONS

Except for few CV outcomes, applying one common protocol generated consistent risk estimates of CV events following modafinil use across cohorts and databases.

Sleep Architecture in Patients With Primary Snoring and Obstructive Sleep Apnea

Introduction:

This study aimed to investigate sleep architecture in patients with primary snoring and obstructive sleep apnea.

Methods:

In this study, we analyzed polysomnographic data of 391 clients who referred to Sleep Disorders Research Center (SDRS). These people were classified into three groups based on their Apnea-Hypopnea Index (AHI) and snoring; control, Primary Snoring (PS), and Obstructive Sleep Apnea (OSA) group. Sleep architecture variables were then assessed in all groups.

Results:

The results of this study indicated a decrease in deep sleep or Slow Waves Sleep (SWS) and increase in light sleep or stage 1 of non-REM sleep (N1) in OSA patients compared with the control and PS groups. After controlling the effects of confounding factors, i.e. age and Body Mass Index (BMI) (which was performed through multiple regression analysis) significant differences were observed among the three groups with regard to N1. However, with regard to SWS, after controlling confounding variables (age and BMI), no significant difference was found among the groups.

Conclusion:

The results indicated that OSA, regardless of age and BMI, may increase light (N1) sleep possibly via a decline in blood oxygen saturation (SpO₂ ). Such increase in N1 may be responsible for brain arousal. In addition, by controlling confounding factors (age and BMI), OSA did not affect SWS in OSA patients. However, further research is necessary to determine sleep architecture in more detail in the patients with OSA.

Among middle-aged adults, snoring predicted hypertension independently of sleep apnoea

Objective

While the link between obstructive sleep apnoea (OSA) and hypertension is well established, the relationships between snoring, OSA, and hypertension remain unclear. This study aimed to evaluate the association between hypertension and snoring independently of OSA.

Methods

Adults with sleep difficulties underwent a one-night polysomnographic sleep assessment, including a thorough assessment of apnoea and snoring. Upon waking, blood pressure was measured, the measurement repeated after 15 min, in a resting position. Anthropometric data were recorded. Hypertension was defined as blood pressure ≥140/90 mmHg or the use of antihypertensive medications.

Results

The study enrolled 181 adults (mean age 48.8 years; 119 males). Snoring, apnoea, blood pressure and anthropometric dimensions were highly associated. Patients with hypertension had higher levels of snoring and apnoea, as well as indicators of excess weight. Snoring was the most robust predictor of hypertension.

Conclusions

Snoring is a risk factor for hypertension independently of apnoea and anthropometric dimensions. While the presence of snoring is not able to replace a thorough polysomnographic evaluation of the apnoea-hypopnoea index and OSA, snoring as an acoustic signal is easily detectable. The early identification and management of snoring may reduce cardiovascular risk.

Definition and Importance of Autonomic Arousal in Patients with Sleep Disordered Breathing

Autonomic arousal at the end of sleep apnea events are not well-explored. We prospectively studied 20 patients with obstructive sleep apnea (OSA) and 24 healthy volunteers for 2 nights with cardiorespiratory polysomnography and continuous noninvasive blood pressure (Portapres). Recordings were scored visually for cortical and autonomic arousal. In the OSA group, 2151 cortical arousals and in the controls 1089 cortical arousals were scored. Respiratory arousal caused most frequently an increase of highest mean arterial blood pressure in patients and controls. A useful definition for autonomic arousal for OSA and controls based on blood pressure and heart rate analysis was developed.

Gamma glutamyl transferase and oxidative stress in obstructive sleep apnea: a study in 1744 patients

OBJECTIVE

We analyze a large population of patients to determine whether gamma glutamyl transferase (GGT) levels are increased in sleep apnea-hypopnea syndrome (OSA) and whether these levels are related to clinical characteristics or polygraphic indexes.

METHODS

A cross-sectional study in a population of 1744 patients referred for OSA suspicion was conducted. The following variables were determined: glucose, cholesterol, triglycerides, aspartate aminotransferase (GOT), alanine aminotransferase (GPT), GGT, body mass index, waist-hip ratio (WHR), and overnight sleep study.

RESULTS

The 483 patients with GGT ≥40 IU/l were younger and more obese, and had a pattern of more centrally distributed fat than the 1261 with GGT <40 IU/l. Patients with high levels of GGT also consumed more alcohol, had a poorer biochemical profile, and had more respiratory and oximetric alterations during sleep. GGT levels were significantly correlated with AHI, DI, and CT90. In the binary regression test, WHR, glucose, cholesterol, triglycerides, and grams of alcohol consumed per day predicted GGT levels ≥40 IU/l, while none of the polygraphic variables had predictive value.

CONCLUSIONS

High GGT levels were associated with the severity of OSA. However, this relationship seems to be due to the coexistence of other associated factors, mainly central obesity, rather than to the respiratory disorders found in this disease.

The role of continuous positive airway pressure in blood pressure control for patients with obstructive sleep apnea and hypertension: a meta-analysis of randomized controlled trials

The aim of this study was to review the effect of continuous positive airway pressure (CPAP) on blood pressure (BP) in patients with obstructive sleep apnea (OSA) and hypertension. Biomedical databases were searched for randomized controlled trials (RCTs) comparing CPAP with control among these patients. Seven RCTs reporting 24-hour ambulatory BP were identified for meta-analysis. CPAP was associated with significant reductions in 24-hour ambulatory systolic blood pressure (SBP) (-2.32 mm Hg; 95% confidence interval [CI], -3.65 to -1.00) and diastolic blood pressure (DBP) (-1.98 mm Hg; 95% CI, -2.82 to -1.14). CPAP led to more significant improvement in nocturnal SBP than that in diurnal SBP. Subgroup analysis showed that patients with resistant hypertension or receiving antihypertensive drugs benefited most from CPAP. Meta-regression indicated that CPAP compliance, age, and baseline SBP were positively correlated with decrease in 24-hour DBP, but not reduction in 24-hour SBP.

Distinct associations between hypertension and obstructive sleep apnea in male and female patients

Obstructive sleep apnea (OSA) is highly associated with hypertension. However, the correlation between hypertension and OSA at different levels of severity and the influence of gender on that correlation are unclear. A total of 996 patients (776 males and 190 females) with OSA were recruited. The influence of gender on the correlation between hypertension and OSA at different stratifications of severity, based on the apnea-hypopnea index (AHI), was fully evaluated together with the major health risk factors obesity, age, and diabetes. Females with OSA were significantly older on average than males with OSA. Moreover, females had milder degrees of OSA on average than the extent of severity seen in males. The proportion of females with diabetes or hypertension was higher than that of males. The proportion of males with hypertension and obesity increased significantly with OSA, and age also increased with OSA. The percentage of females with hypertension at different degrees of OSA severity was stable at about 26% in the mild, moderate, and severe OSA groups. Among females, age was increased significantly in the moderate relative to the mild OSA group. Moreover, the proportion of obese subjects was increased significantly in the severe compared with the moderate OSA group. The proportions of males and females with diabetes were not significantly different among all OSA severity groups. An ordinal multivariate logistic regression analysis confirmed that hypertension, age, and obesity were associated with OSA severity in males, whereas only age and obesity were associated with OSA severity in females. Although the proportion of subjects with hypertension was higher in females with OSA than in males with OSA, the proportion of subjects with hypertension increased as the severity of OSA increased in males but not in females.

Increased risk of benign prostate hyperplasia in sleep apnea patients: a nationwide population-based study

Background

Sleep apnea (SA) is a common sleep disorder characterized by chronic intermittent hypoxia (IH). Chronic IH induces systemic inflammatory processes, which can cause tissue damage and contribute to prostatic enlargement. The purpose of this study was to evaluate the association between benign prostate hyperplasia (BPH) and SA in a Taiwanese population.

Methods

The study population was identified from Taiwan’s National Health Insurance Research Database (NHIRD) and contained 202 SA patients and 1010 control patients. The study cohort consisted of men aged ≥30 years who were newly diagnosed with SA between January 1997 and December 2005. Each patient was monitored for 5 years from the index date for the development of BPH. A Cox regression analysis was used to calculate the hazard ratios (HRs) for BPH in the SA and control patients.

Results

During the 5-year follow-up, 18 SA patients (8.9%) and 32 non-SA control patients (3.2%) developed BPH. The adjusted HR for BPH was 2.35-fold higher in the patients with SA than in the control patients (95% confidence interval (CI) 1.28–4.29, P<.01). We further divided the SA patients into 4 age groups. After adjusting for potential confounding factors, the highest adjusted HR for BPH in the SA patients compared with the control patients was 5.59 (95% CI = 2.19–14.31, P<.001) in the patients aged between 51 and 65 years.

Conclusion

Our study results indicate that patients with SA are associated with increased longitudinal risk of BPH development, and that the effects of SA on BPH development are age-dependent.

Obstructive sleep apnoea and cardiovascular complications: perception versus knowledge

Epidemiological evidence has confirmed that obstructive sleep apnoea (OSA) significantly promotes cardiovascular risk, independent of age, sex, race and other common risk factors for cardiovascular diseases, such as smoking, drinking, obesity, diabetes mellitus, dyslipidaemia and hypertension. Patients with severe OSA exhibit a higher prevalence of coronary artery disease, heart failure and stroke. Despite the tight correlation between sleep apnoea and these comorbidities, the mechanisms behind increased cardiovascular risk in OSA remain elusive. Several theories have been postulated, including sympathetic activation, endothelial dysfunction, oxidative stress and inflammation. The association between OSA and cardiovascular diseases may be rather complicated and compounded by the presence of components of metabolic syndrome, such as obesity, hypertension, diabetes mellitus and dyslipidaemia. The present minireview updates current knowledge with regard to the cardiovascular sequelae of OSA and the mechanisms involved.

Beliefs and attitudes toward obstructive sleep apnea evaluation and treatment among blacks

OBJECTIVE

Although blacks are at higher risk for obstructive sleep apnea (OSA), they are not as likely as their white counterparts to receive OSA evaluation and treatment. This study assessed knowledge, beliefs, and attitudes towards OSA evaluation and treatment among blacks residing in Brooklyn, New York.

METHODS

Five focus groups involving 39 black men and women (aged > or =18 years) were conducted at State University of New York (SUNY) Downstate Medical Center in Brooklyn to ascertain barriers preventing or delaying OSA evaluation and treatment.

RESULTS

Misconceptions about sleep apnea were a common theme that emerged from participants' responses. Obstructive sleep apnea was often viewed as a type of insomnia, an age-related phenomenon, and as being caused by certain bedtime activities. The major theme that emerged about barriers to OSA evaluation was unfamiliarity with the study environment. Barriers were categorized as: problems sleeping in a strange and unfamiliar environment, unfamiliarity with the study protocol, and fear of being watched while sleeping. Barriers to continuous positive airway pressure (CPAP) treatment adoption were related to the confining nature of the device, discomfort of wearing a mask while they slept, and concerns about their partner's perceptions of treatment.

CONCLUSION

Results of this study suggest potential avenues for interventions to increase adherence to recommended evaluation and treatment of OSA. Potential strategies include reducing misconceptions about OSA, increasing awareness of OSA in vulnerable communities, familiarizing patients and their partners with laboratory procedures used to diagnose and treat OSA. We propose that these strategies should be used to inform the development of culturally and linguistically tailored sleep apnea interventions to increase awareness of OSA among blacks who are at risk for OSA and associated comorbidities.

P2Y1 receptors expressed by C1 neurons determine peripheral chemoreceptor modulation of breathing, sympathetic activity, and blood pressure

Catecholaminergic C1 cells of the rostral ventrolateral medulla (RVLM) are key determinants of the sympathoexcitatory response to peripheral chemoreceptor activation. Overactivation of this reflex is thought to contribute to increased sympathetic activity and hypertension; however, molecular mechanisms linking peripheral chemoreceptor drive to hypertension remain poorly understood. We have recently determined that activation of P2Y1 receptors in the RVLM mimicked effects of peripheral chemoreceptor activation. Therefore, we hypothesize that P2Y1 receptors regulate peripheral chemoreceptor drive in this region. Here, we determine whether P2Y1 receptors are expressed by C1 neurons in the RVLM and contribute to peripheral chemoreceptor control of breathing, sympathetic activity, and blood pressure. We found that injection of a specific P2Y1 receptor agonist (MRS2365) into the RVLM of anesthetized adult rats increased phrenic nerve activity (≈55%), sympathetic nerve activity (38 ± 6%), and blood pressure (23 ± 1 mm Hg), whereas application of a specific P2Y1 receptor antagonist (MRS2179) decreased peripheral chemoreceptor-mediated activation of phrenic nerve activity, sympathetic nerve activity, and blood pressure. To establish that P2Y1 receptors are expressed by C1 cells, we determine in the brain slice preparation using cell-attached recording techniques that cells responsive to MRS2365 are immunoreactive for tyrosine hydroxylase (a marker of C1 cells), and we determine in vivo that C1-lesioned animals do not respond to RVLM injection of MRS2365. These data identify P2Y1 receptors as key determinants of peripheral chemoreceptor regulation of breathing, sympathetic nerve activity, and blood pressure.

[Polysomnography (PSG) for studying sleep disorders]

BACKGROUND

Sleeping problems are very common, and many patients need a comprehensive assessment with polysomnography, possibly followed by a sleep latency test. These methods and indications for the tests are described below.

METHOD

The article is based on the authors' own literature archives, clinical experience and Retningslinjer for metoder i klinisk neurofysiologi [Guidelines for methodology in clinical neurophysiology]

RESULTS

Polysomnography involves monitoring sleep through the course of one night and scoring the stages of sleep on the basis of EEG activity, eye movements and muscular tension. Also recorded are inter alia respiratory variables. Polysomnography followed by a multiple sleep latency test (MSLT) is used when narcolepsy or excessive daytime sleepiness is suspected. If parasomnia is suspected, the examination should include polysomnography, preferably with video recording. If sleep apnoea is suspected in adults, respiratory polygraphy is often sufficient. As a rule, polysomnography is preferable to respiratory polygraphy for studying sleep disorders in children.

INTERPRETATION

Sleep disorders take many forms and are dealt with by many different specialities. Good cooperation between the different specialities is necessary to ensure an optimal result for the patients.

Relationship Between Arrhythmia and Sleep Disordered Breathing

The association between obstructive sleep apnea (OSA) and cardiovascular disease is well known. Data from most studies investigating the prevalence of OSA in atrial fibrillation (AF), and of AF in patients with OSA, have supported the relationship between these common diseases. In addition, several studies have shown a detrimental effect of OSA on AF treatment. These reports vary considerably in methodology, and are particularly diverse in their definitions and diagnosis of OSA and patient populations studied. Considering these studies individually while exploring their methodological variations and the range of results achieved can reinforce the necessity of establishing standards for performing this important research. Reviewing these studies should en courage practitioners to reflect on how the methodologies, patients, and outcomes are relevant to their practices.

Sleep disordered breathing in patients with acute coronary syndromes

STUDY OBJECTIVES

Although the prevalence of obstructive sleep apnea/hypopnea syndrome (OSAHS) is high in patients with acute coronary syndromes (ACS), there is little knowledge about the persistence of OSAHS in ACS patients after the acute event. We aimed to assess the prevalence and time course of OSAHS in patients with ACS during and after the acute cardiac event.

METHODS

Fifty-two patients with first-ever ACS, underwent attended overnight polysomnography (PSG) in our sleep center on the third day after the acute event. In patients with an apnea hypopnea index (AHI) > 10/h, we performed a follow up PSG 1 and 6 months later.

RESULTS

Twenty-eight patients (54%) had an AHI > 10/h. There was a significant decrease in AHI 1 month after the acute event (13.9 vs. 19.7, p = 0.001), confirming the diagnosis of OSAHS in 22 of 28 patients (79%). At 6-month follow-up, the AHI had decreased further (7.5 vs. 19.7, p < 0.05), and at that time only 6 of the 28 patients (21%) were diagnosed as having OSAHS. Twelve of the 16 current smokers stopped smoking after the acute event.

CONCLUSIONS

We have demonstrated a high prevalence of OSAHS in ACS patients, which did not persist 6 months later, indicating that, to some degree, OSAHS may be transient and related with the acute phase of the underlying disease or the reduction in the deleterious smoking habit.

Sleep apnea is a stronger predictor for coronary heart disease than traditional risk factors

BACKGROUND

Sleep apnea (SA) may be linked to coronary artery disease (CAD). Both conditions have similar risk factors, confounding the analyses. Investigation of the lipid profile is routine in the adult population, even without symptoms or suspected cardiac ailment. SA, however, remains underdiagnosed even in the presence of unambiguous clinical manifestations.

PURPOSE

The aim of this study was to verify the association between SA and CAD, adjusting for usual CAD risk factors.

METHODS

Patients who underwent diagnostic or therapeutic coronariography and portable type III polysomnography were studied. The severity of SA was determined by the apnea-hypopnea index (AHI). We measured classic CAD risk factors: fasting glucose; total, HDL, and LDL cholesterols; triglycerides; uric acid, and high-sensitivity C-reactive protein. We excluded patients older than 65 years, with body mass index higher than 40 kg/m(2), with diabetes, and with history of smoking in the last year.

RESULTS

Of 55 included patients, 28 had AHI > 14, showing an odds ratio of 8.7 for CAD. Patients without (n = 29) and with CAD (n = 26), showed AHI of, respectively, 11 ± 11 and 23 ± 14 per hour (P = 0.001). In a binary logistic regression to predict CAD, controlling for all the above risk factors, the only variables entered in the stepwise model were AHI (either as continuous or categorical variable) and uric acid.

CONCLUSION

In a sample without smokers, morbidly obese, or diabetic patients, AHI is the main predictor of CAD. SA should integrate the set of risk factors routinely assessed in clinical investigation for coronary disease risk stratification.

Optimal treatment of obstructive sleep apnea and excessive sleepiness

INTRODUCTION

Collapsibility of the upper airway in obstructive sleep apnea (OSA) causes repeated arousals from sleep, decreased oxygen saturation of the blood, and excessive sleepiness (ES). Patients with OSA are at increased risk of cardiovascular and cerebrovascular disease, and experience occupational and vehicular accidents more frequently than the general population. Furthermore, the life expectancy of patients with untreated OSA is significantly reduced.

METHODS

A MEDLINE search of articles published between 2003 and 2008 was conducted using the search terms: obstructive sleep apnea [ti/ab] AND treatment; obstructive sleep apnoea [ti/ab] AND treatment; and excessive sleepiness [ti/ab] AND treatment. Searches were limited to articles in English; clinical trials; meta-analyses; practice guidelines; randomized, controlled trials; and reviews.

RESULTS

Continuous positive airway pressure (CPAP) is the reference-standard treatment for patients with OSA. CPAP addresses the symptoms of OSA and reduces the risk of heart disease and depression associated with this sleep disorder. However, the efficacy of CPAP is contingent on patient adherence, and >or=4 hours of therapy per night are required for patients with OSA to experience significant clinical benefits. However, reports of nonadherence to CPAP therapy range from 29% to 83%. Other therapies are available for patients who refuse or cannot adhere to CPAP treatment, including dental devices and surgery, but these treatments are generally considered to be less efficacious. A significant number of patients continue to experience residual ES despite CPAP treatment. Pharmacologic therapies, eg, modafinil and armodafinil, may be of use in patients with OSA to improve tolerance with CPAP or to address residual ES.

CONCLUSION

There are a variety of treatments available for patients with OSA. Successful treatment involves encouraging patient compliance with CPAP or oral appliances. Primary-care physicians play a crucial role in recognizing this disorder and ensuring the best possible outcome through support and education.