Obstructive sleep apnoea syndrome as a risk factor for hypertension: population study

Comparison of the indices of oxyhemoglobin saturation by pulse oximetry in obstructive sleep apnea hypopnea syndrome

OBJECTIVES

To comprehensively evaluate the ability and reliability of the representative previously proposed oxyhemoglobin indexes derived automatically for predicting the severity of obstructive sleep apnea hypopnea syndrome (OSAHS).

METHODS

Patients with a diagnosis of OSAHS by standard polysomnography were recruited from China Medical University Hospital Centre. There were 257 patients in the learning set and 279 patients in the validation set. The presence of OSAHS was defined as apnea-hypopnea index (AHI) > 5/h. Three kinds of oxyhemoglobin indexes, including the oxyhemoglobin desaturation index (ODI), time-domain index, and frequency-domain index, were used. Degrees of severity were AHI > 15/h and AHI > 30/h, representing moderate and severe OSAHS. A total of 28 oxyhemoglobin indexes were tested in our study.

RESULTS

Among the three kinds of indexes, ODI had a better diagnostic performance than the time-domain and frequency-domain indexes, with the results coincident in the validation set and learning set. For predicting the severity of OSAHS with AHI > 15/h or > 30/h, the ODI clinically had the higher correlation with AHI than time-domain and frequency-domain indexes, with sensitivity/specificity achieving 84.0%/84.3% in AHI > 15/h and 87.8%/96.6% in AHI > 30/h, respectively.

CONCLUSIONS

Based on the smaller SEE of the AHI, the ODI had a significantly smaller SEE than the time-domain and frequency-domain indexes. The ODI index provided a high level of diagnostic sensitivity and specificity at different degrees of OSAHS severity.

Mandibular advancement appliance for obstructive sleep apnoea: results of a randomised placebo controlled trial using parallel group design

The aim of this trial was to evaluate the efficacy of a mandibular advancement appliance (MAA) for obstructive sleep apnoea (OSA). Ninety-three patients with OSA and a mean apnoea-hypopnoea index (AHI) of 34.7 were centrally randomised into three, parallel groups: (a) MAA; (b) mandibular non-advancement appliance (MNA); and (c) no intervention. The appliances were custom made, in one piece. The MAAs had a mean protrusion of the mandible of 74% (range 64-85%). Outcome measures, assessed after continuous use for 4 weeks, were AHI (polysomnography), daytime sleepiness (Epworth) and quality of life (SF-36). Eighty-one patients (87%) completed the trial. The MAA group achieved mean AHI and Epworth scores significantly lower (P < 0.001 and P < 0.05) than the MNA group and the no-intervention group. No significant differences were found between the MNA group and the no-intervention group. The MAA group had a mean AHI reduction of 14.1 (95% CI 7.4-20.8), and a mean Epworth score reduction of 3.3 (95% CI 1.8-4.8). Eight MAA patients (30%) achieved a reduction in AHI > or = 75% ending with an AHI < 5, half of them having baseline AHI > 30. Sensitivity analyses confirmed these results. MAA had a significant beneficial effect on the vitality domain of SF-36. Four MAA patients (14.8%) and two MNA patients (8%) discontinued interventions because of adverse effects. Our conclusion is that MAA has significant beneficial effects on OSA, including cure in some cases of severe OSA. Protrusion of the mandible is essential for the effect. MNA has no placebo effect. MAA may be a good alternative to CPAP in subsets of OSA patients.

Risk for Obstructive Sleep Apnea by Berlin Questionnaire, but not daytime sleepiness, is associated with resistant hypertension: a case-control study

BACKGROUND

Obstructive Sleep Apnea Syndrome (OSAS) is a risk factor for resistant hypertension. Overnight polysomnography and portable sleep monitors are not generally available and questionnaires may be useful for screening OSAS. In a case-control study, we investigate the association between resistant hypertension and sleep disorders evaluated by the Berlin Questionnaire and Epworth Sleepiness Scale (ESS).

METHODS

Cases were 63 patients with resistant hypertension (either systolic blood pressure (BP) > or =140 mm Hg or diastolic BP > or =90 mm Hg using at least three BP-lowering drugs, including a diuretic). Controls were 63 patients with controlled BP under drug treatment. All the patients were submitted to ambulatory BP monitoring and level III polysomnography by means of a portable monitor. The prevalence of high risk in the Berlin Questionnaire and high score in the ESS (>10) was compared between the groups. Diagnostic performance for OSAS of both questionnaires was calculated.

RESULTS

The prevalence of high score in ESS was 44% in both groups. There was a higher prevalence of high risk for OSAS in Berlin Questionnaire in the cases group (78% vs. 48%; P < 0.001). In a logistic regression model, high risk for OSAS in Berlin Questionnaire was independently associated with resistant hypertension (odds ratio 4.1; confidence interval 95% 1.80-9.31; P < 0.01). Sensitivity and specificity for the diagnosis of OSAS was 85.5% (75.3-92.0%) and 65.0% (52.0-76.0%), respectively.

CONCLUSIONS

High risk for OSAS assessed by the Berlin Questionnaire is highly prevalent and associated with resistant hypertension. This questionnaire may be used as screening for OSAS in patients with this clinical condition.

Obstructive sleep apnea and cardiovascular disease: role of the metabolic syndrome and its components

Although obstructive sleep apnea and cardiovascular disease have common risk factors, epidemiologic studies show that sleep apnea increases risks for cardiovascular disease independently of individuals' demographic characteristics (i.e., age, sex, and race) or risk markers (i.e., smoking, alcohol, obesity, diabetes, dyslipidemia, atrial fibrillation, and hypertension). Individuals with severe sleep apnea are at increased risk for coronary artery disease, congestive heart failure, and stroke. The underlying mechanisms explaining associations between obstructive sleep apnea and cardiovascular disease are not entirely delineated. Several intermediary mechanisms might be involved including sustained sympathetic activation, intrathoracic pressure changes, and oxidative stress. Other abnormalities such as disorders in coagulation factors, endothelial damage, platelet activation, and increased inflammatory mediators might also play a role in the pathogenesis of cardiovascular disease. Linkage between obstructive sleep apnea and cardiovascular disease is corroborated by evidence that treatment of sleep apnea with continuous positive airway pressure reduces systolic blood pressure, improves left ventricular systolic function, and diminishes platelet activation. Several systematic studies are necessary to explicate complex associations between sleep apnea and cardiovascular disease, which may be compounded by the involvement of diseases comprising the metabolic syndrome (i.e., central obesity, hypertension, diabetes, and dyslipidemia). Large-scale, population-based studies testing causal models linking among sleep apnea, cardiovascular morbidity, and metabolic syndrome are needed.

Positive pressure therapy: a perspective on evidence-based outcomes and methods of application

The sleep medicine community has increasingly recognized the necessity that clinical care be based on high-quality levels of evidence. Although research supports a favorable influence of positive airway pressure (PAP) therapy on risk for significant adverse outcomes in patients with severe obstructive sleep apnea-hypopnea (OSAH), well-designed trials are still required to elucidate the effect of PAP on health, quality of life, and economic risks in patients with milder OSAH. Similarly, although there is strong evidence supporting various PAP titration strategies and PAP modalities in patients with severe OSAH without significant medical and psychiatric comorbidities, there is insufficient high-level evidence assessing and comparing the clinical efficacy and health care cost implications of various titration paradigms and various PAP modalities in individuals with milder OSAH and those with comorbid conditions. For ethical and other reasons, it may not be possible to apply a randomized controlled design to address all questions. However, whichever design is employed, it must be rigorously developed with attention to all potential confounders with adequate power to provide compelling, high-quality evidence.

Gastroesophageal reflux in patients with morbid obesity: a role of obstructive sleep apnea syndrome?

BACKGROUND

Obesity is a risk factor for gastroesophageal reflux disease (GERD) and for obstructive sleep apnea (OSA). Our aim was to evaluate in morbidly obese patients the prevalence of OSA and GERD and their possible relationship.

METHODS

Morbidly obese patients [body mass index (BMI) >40 or >35 kg/m(2) in association with comorbidities] selected for bariatric surgery were prospectively included. Every patient underwent a 24-h pH monitoring, esophageal manometry, and nocturnal polysomnographic recording.

RESULTS

Sixty-eight patients [59 women and 9 men, age 39.1 +/- 11.1 years; BMI 46.5 +/- 6.4 kg/m(2) (mean +/- SD)] were included. Fifty-six percent of patients had an abnormal Demester score, 44% had abnormal time spent at pH <4, and 80.9% had OSA [apnea hypopnea index (AHI) >10] and 39.7% had both conditions. The lower esophageal sphincter (LES) pressure was lower in patients with GERD (11.6 +/- 3.4 vs 13.4 +/- 3.6 mm Hg, respectively; P = 0.039). There was a relationship between AHI and BMI (r = 0.337; P = 0.005). Patients with OSA were older (40.5 +/- 10.9 vs 33.5 +/- 10.4 years; P = 0.039). GERD tended to be more frequent in patients with OSA (49.1% vs 23.1%, respectively; P = 0.089). There was no significant relationship between pH-metric data and AHI in either the 24-h total recording time or the nocturnal recording time. In multivariate analysis, GERD was significantly associated with a low LES pressure (P = 0.031) and with OSA (P = 0.045) but not with gender, age, and BMI.

CONCLUSION

In this population of morbidly obese patients, OSA and GERD were frequent, associated in about 40% of patients. GERD was significantly associated with LES hypotonia and OSA independently of BMI.

Intermittent hypoxia: cause of or therapy for systemic hypertension?

During acute episodes of hypoxia, chemoreceptor-mediated sympathetic activity increases heart rate, cardiac output, peripheral resistance and systemic arterial pressure. However, different intermittent hypoxia paradigms produce remarkably divergent effects on systemic arterial pressure in the post-hypoxic steady state. The hypertensive effects of obstructive sleep apnea (OSA) vs. the depressor effects of therapeutic hypoxia exemplify this divergence. OSA, a condition afflicting 15-25% of American men and 5-10% of women, has been implicated in the pathogenesis of systemic hypertension and is a major risk factor for heart disease and stroke. OSA imposes a series of brief, intense episodes of hypoxia and hypercapnia, leading to persistent, maladaptive chemoreflex-mediated activation of the sympathetic nervous system which culminates in hypertension. Conversely, extensive evidence in animals and humans has shown controlled intermittent hypoxia conditioning programs to be safe, efficacious modalities for prevention and treatment of hypertension. This article reviews the pertinent literature in an attempt to reconcile the divergent effects of intermittent hypoxia therapy and obstructive sleep apnea on hypertension. Special emphasis is placed on research conducted in the nations of the former Soviet Union, where intermittent hypoxia conditioning programs are being applied therapeutically to treat hypertension in patients. Also reviewed is evidence regarding mechanisms of the pro- and anti-hypertensive effects of intermittent hypoxia.

Oxidative stress in obstructive sleep apnea: putative pathways to the cardiovascular complications

Obstructive sleep apnea (OSA) is a major public health problem because of its high prevalence in morbidity and mortality. A growing body of evidence suggests that OSA is an important risk factor for cardiovascular diseases. Although the mechanism for the initiation and aggravation of cardiovascular disease has not been fully elucidated, one theorized mechanism is intermittent hypoxia, which is produced by each sleep-disordered breathing event. This repeated hypoxia and reoxygenation cycle is similar to hypoxia-reperfusion injury, which initiates oxidative stress. Recent studies have suggested that OSA is associated with increased levels of oxidative stress or antioxidant deficiencies or both. Oxidative stress is involved in the activation of redox-sensitive transcription factors, which regulate downstream products such as inflammatory cytokines, chemokines, and adhesion molecules. This pathway may be able to explain the pathogenesis of atherosclerosis, a common pathologic factor underlying all types of cardiovascular disease. In addition, endothelial dysfunction derived from oxidative stress can contribute to cardiovascular diseases. This review summarizes current available evidence for and against the occurrence of oxidative stress in OSA and discusses the putative pathways initiating cardiovascular consequences associated with OSA.

Metabolic syndrome and sleep apnea

Metabolic syndrome is a disorder characterized by abdominal obesity, hypertension, increased triglycerides, decreased HDL cholesterol and increased blood glucose. Accumulating evidence strongly indicates that insulin resistance and an increased amount of abdominal fat are the pathogenic factors for the characteristics of metabolic syndrome. The metabolic syndrome is characterized by an increased risk for the development of cardiovascular disease and type 2 diabetes mellitus. Studies indicate that sleep apnea may be a manifestation of the metabolic syndrome. It has also been suggested that the metabolic syndrome or "syndrome X" should also comprise obstructive sleep apnea and should then be called syndrome "Z". It appears that obstructive sleep apnea and the metabolic syndrome are characterized by the same pathophysiologic environment, which increases the risk for the development of cardiovascular disease. The increased amount of visceral fat and the accompanying insulin resistance seem to be the main characteristics responsible for the development of obstructive sleep apnea and the metabolic syndrome.

Independent association between obstructive sleep apnea and subclinical coronary artery disease

BACKGROUND

Obstructive sleep apnea (OSA) is associated with coronary risk factors, but it is unknown if OSA is associated with development of coronary disease. We evaluated the association between OSA and the presence of subclinical coronary disease assessed by coronary artery calcification (CAC).

METHODS

Consecutive patients with no history of coronary disease who underwent electron-beam CT within 3 years of polysomnography between March 1991 and December 2003 were included. OSA was defined by an apnea-hypopnea index (AHI) > or = 5 events per hour, and patients were grouped by quartiles of AHI severity. Logistic regression modeled the association between OSA severity and presence of CAC.

RESULTS

There were 202 patients (70% male; median age, 50 years; mean body mass index, 32 kg/m(2); 8% diabetic; 9% current smokers; 60% hypercholesterolemic; and 47% hypertensive). OSA was present in 76%. CAC was present in 67% of OSA patients and 31% of non-OSA patients (p < 0.001). Median CAC scores (Agatston units) were 9 in OSA patients and 0 in non-OSA patients (p < 0.001). Median CAC score was higher as OSA severity increased (p for trend by AHI quartile < 0.001). With multivariate adjustment, the odds ratio for CAC increased with OSA severity. Using the first AHI quartile as reference, the adjusted odds ratios for the second, third, and fourth quartiles were 2.1 (p = 0.12), 2.4 (p = 0.06), and 3.3 (p = 0.03), respectively.

CONCLUSIONS

In patients without clinical coronary disease, the presence and severity of OSA is independently associated with the presence and extent of CAC. OSA identifies patients at risk for coronary disease and may represent a highly prevalent modifiable risk factor.

Automated detection of sleep disordered breathing using a nasal pressure monitoring device

To assess the accuracy of a single channel portable monitoring device (RUSleepingtrade mark RTS, Respironics, Murrysville, PA) that measures nasal pressure (a surrogate for airflow) to detect sleep disordered breathing (SDB). Twenty-five adult patients referred to a community sleep laboratory with suspected obstructive sleep apnea (OSA) participated in this investigation. The portable monitoring device was used in the sleep laboratory to acquire data concurrently with a standard multi-channel polysomnogram (PSG) to assess SDB. Respiratory events were scored manually on the PSG using standard criteria for clinical research to quantify an apnea-hypopnea index (AHI) based on events during sleep. The portable monitoring device automatically calculated an unedited respiratory event index (REI) based on recording time. These data were then compared using the Pearson product-moment correlation coefficient, Bland-Altman analysis, receiver operating characteristic (ROC) curves, and likelihood ratios. All 25 subjects completed the study. Mean age of subjects was 42.4 +/- 12.9 years and mean body mass index was 31.0 +/- 7.4 kg m(-2). There was good agreement between the REI and the AHI (R = 0.77, p < 0.001, mean difference 2.6 events per hour [2 SD: 39.8] using a Bland-Altman plot). The area under the ROC curve for detecting SDB (PSG AHI greater than or equal to five events per hour) with the REI was 0.94 (95% CI 0.84-1.0). For an REI >11.9 events per hour, the sensitivity was 0.89 (95% CI 0.65-0.99) and the specificity was 0.86 (95% CI 0.42-1.0) with a likelihood ratio of 6.2 for a positive test (LR+) and 0.13 for a negative test (LR-). Similar results were observed for detecting moderate-severe SDB (PSG AHI > or = 15 events h(-1)) using REI >15.2 events h(-1). In a population of subjects with suspected OSA, this portable monitoring device can automatically quantify an REI that compares well to the AHI scored manually on a concurrent PSG. Such a device may prove useful to assess SDB in high risk populations with self-administered testing in ambulatory settings such as the home.

Obstructive sleep apnea and resistant hypertension: a case-control study

BACKGROUND

Obstructive sleep apnea syndrome (OSAS) has been linked to resistant hypertension, but the magnitude of this association and its independence of confounding have not been established.

METHODS

Case patients were 63 patients with resistant hypertension (BP >or= 140/90 mm Hg using at least three BP-lowering drugs, including a diuretic), and control subjects were 63 patients with controlled BP receiving drug treatment. The primary outcome was the frequency of OSAS (apnea-hypopnea index [AHI] >or= 10 episodes per hour) determined with a portable home monitor. The comparison of AHI episodes in patients truly normotensive, truly hypertensive, and in patients with white coat or masked hypertension, based on BP determined at office and by ambulatory BP monitoring (ABPM) was a secondary outcome.

RESULTS

Case patients and control subjects were well matched for confounding factors. OSAS was present in 45 case patients (71%) and in 24 control subjects (38%) [p < 0.001]. In a logistic regression model, OSAS was strongly and independently associated with resistant hypertension (odds ratio, 4.8; 95% confidence interval, 2.0 to 11.7). The AHI of case patients with normal BP in ABPM (white coat hypertension) and control subjects with abnormal BP in ABPM (masked hypertension) was intermediate between the AHI of individuals with normal and abnormal BP measures in both settings (p < 0.001).

CONCLUSIONS

The magnitude and independence of the risk of OSAS for resistant hypertension strengthen the concept that OSAS is a risk factor for resistant hypertension. Comorbid OSAS should be considered in patients with resistant hypertension.

Distinct behavioral and neurochemical alterations induced by intermittent hypoxia or paradoxical sleep deprivation in rats

The current study investigated the effects of paradoxical sleep deprivation and intermittent hypoxia by examining whether a combination of the two would induce anxiety-like alterations in behavior. The neurochemical effects of these manipulations were investigated by measuring cortical, striatal and hippocampal monoamine concentrations. Wistar Hannover rats were submitted to subchronic (3 days) intermittent hypoxia exposure (alternating cycles of 2 min room air-2 min 10% O2 from 0700-1900 h) and paradoxical sleep deprivation using the single platform method. Rats were randomly assigned to four different protocols: 1) control, 2) intermittent hypoxia during the light period (12 h/day), 3) paradoxical sleep deprivation (24 h/day), and 4) intermittent hypoxia combined with paradoxical sleep deprivation. Rats subjected to intermittent hypoxia showed no modification in the behavioral or neurochemical parameters assessed. Although paradoxical sleep deprivation did not produce alterations in anxiety-like behavior, the rats did increase exploratory activity in the elevated plus-maze. Moreover, a significant increase in striatal epinephrine and hippocampal homovanilic acid (HVA) concentrations was found in the paradoxical sleep deprivation groups, but not in the intermittent hypoxia/paradoxical sleep deprivation group. Of note, both paradoxical sleep deprivation and intermittent hypoxia/paradoxical sleep deprivation groups showed an increase in plasma corticosterone concentration. These results suggest that paradoxical sleep deprivation induces behavioral alterations, and these abnormalities may reflect altered neurotransmission in the brain. When paradoxical sleep deprivation was combined with intermittent oxygen depletion, the behavioral and biochemical parameters were comparable to those of control rats.

Increased nocturnal sodium excretion in obstructive sleep apnoea. Relation to nocturnal change in diastolic blood pressure

OBJECTIVE

The mechanisms involved in the development and maintenance of hypertension in obstructive sleep apnoea (OSA) are not clear. We hypothesized that OSA patients have an abnormal renal handling of sodium and water during the night.

MATERIAL AND METHODS

We studied 29 OSA patients and 19 healthy controls at night with serial determinations of atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), arginine vasopressin (AVP), aldosterone (Aldo), fractional urinary excretion of sodium (FE(Na)), free water clearance (C(H2O)), urinary excretion of aquaporin 2 (u-AQP2), systolic blood pressure (SBP), diastolic blood pressure (DBP) and oxygen saturation.

RESULTS

OSA patients had a higher FE(Na) (0.6 (0.4-1.0) versus 0.4 (0.3-0.6) %; p = 0.017), SBP (129 (114-145) versus 114 (106-122) mmHg; p = 0.001) and DBP (81 (72-87) versus 71 (65-74) mmHg; p<0.001) than healthy controls at night. In hypertensive OSA patients, the FE(Na) correlated significantly with the change in nocturnal DBP (r (2) = 0.411; p = 0.010). Mean level of AVP during the night was higher in OSA patients compared with healthy controls (1.1 (0.8-1.4) versus 0.8 (0.6-1.1) pmol/L; p = 0.033) and correlated with SBP. ANP, BNP, Aldo, C(H2O) and u-AQP2 were the same in OSA and controls.

CONCLUSIONS

We conclude that the higher fractional excretion of sodium in OSA is most likely attributable to pressure natriuresis. The correlation between mean AVP and blood pressure suggests that AVP may be part of the pathogenetic mechanism underlying hypertension in these patients.

Abnormally increased nitric oxide synthesis and increased endothelin-1 in plasma in patients with obstructive sleep apnoea

OBJECTIVE

Obstructive sleep apnoea (OSA) is a risk factor for cardiovascular morbidity and mortality. The mechanism is unknown, but endothelial dysfunction might contribute. We tested the hypothesis that patients with OSA have abnormal nitric oxide (NO) synthesis, which results in an abnormal response in blood pressure, renal hemodynamics, renal tubular function and vasoactive hormones in response to inhibition of the NO synthesis with L-NMMA.

MATERIAL AND METHODS

A randomized, placebo-controlled, single-blinded, crossover study was done in 13 OSA patients and 14 controls. We measured changes in systolic and diastolic blood pressure (SBP and DBP), pulse rate, glomerular filtration rate, renal plasma flow, fractional excretion of sodium and lithium and plasma concentrations of vasoactive hormones after injection of L-NMMA and placebo.

RESULTS

L-NMMA induced a significant increase in SBP and DBP in both groups. The placebo-corrected increase in DBP was more pronounced in patients with OSA than in controls (9 (5-11) versus 3 (1-6) mmHg; p=0.01). Endothelin-1 (ET-1) was significantly higher in patients compared with controls (1.1 (1.0-1.3) versus 0.8 (0.7-0.9) pg/mL; p<0.01). In controls, L-NMMA induced a small increase in ET-1, while no changes were seen in patients. The placebo-corrected change in ET-1 was lower in patients compared to controls (-01 (-0.3-0.0) versus 0.1 (0.0-0.1) pg/mL; p=0.04).

CONCLUSIONS

Patients with OSA have abnormally increased NO synthesis and an increased unresponsive level of ET-1 in plasma. This might be due to an imbalance between NO synthesis and ET-1 production.

Assessment of sleep and breathing in adults with prader-willi syndrome: a case control series

OBJECTIVES

Prader-Willi syndrome (PWS) is a genetic disorder (linked to chromosome 15q11-13) characterized by hypotonia and developmental delay, hyperphagia and obesity, hypersomnia and abnormal sleep, and behavioral problems. Such patients may also be at increased risk of obstructive sleep apnea (OSA), although whether this risk is explained by known risk factors has not previously been directly tested. Our aim was to compare sleep and breathing in an older group of patients with Prader-Willi syndrome with a control group-matched on the basis of age, sex, and body mass index (BMI)-in order to determine which specific features are not explained by these known confounders.

METHODS

Consecutive patients with PWS attending the PWS clinic at Royal Prince Alfred Hospital Sydney, Australia, were recruited. Age-, sex-, and BMI-matched controls were selected from the Sleep Investigation Unit at Royal Prince Alfred Hospital, and polysomnography-derived sleep and other parameters were compared across the groups.

RESULTS

Nineteen subjects with PWS (14 males) were included in the study. Eighteen (95%) had a total respiratory disturbance index (TRDI) of greater than 5 events per hour, with 4 (21%) having severe obstructive sleep apnea (TRDI > or = 30 events/hour) and 9 (47%) having evidence of obesity hypoventilation syndrome. Patients with PWS, as compared with the control group, had evidence of more nocturnal hypoxemia, with lower oxyhemoglobin saturations and percentages of sleep time at less than 80% oxyhemoglobin saturation (all p values < 0.05). There were no significant differences in sleep architecture; however, there was a reduction in rapid eye movement latency seen in the PWS group (p < 0.05). Serum leptin was higher than the reference range in the PWS group but was not measured in the control group.

CONCLUSION

Patients with PWS drawn from an adult and adolescent PWS clinic have a high rate of sleep-disordered breathing. There is evidence that patients with PWS may have more nocturnal hypoventilation than a well-matched control group. These data suggest that the chromosome region 15q11-13 may be involved in some aspects of the regulation of breathing, although whether putative molecular mechanisms act directly or indirectly will require further investigation.

[Spanish version of the Functional Outcomes of Sleep Questionnaire: scores of healthy individuals and of patients with sleep apnea-hypopnea syndrome]

OBJECTIVE

The main symptom of sleep apnea-hypopnea syndrome (SAHS) is excessive daytime sleepiness. The self-administered Functional Outcomes of Sleep Questionnaire (FOSQ) was designed to evaluate the impact of sleepiness on a patient's daily life. The aim of this study was to determine the scores of patients with SAHS and of healthy individuals on the Spanish version of the FOSQ and to assess its usefulness for evaluating the impact of excessive sleepiness in patients with suspected SAHS.

POPULATION AND METHODS

Thirty-one patients with SAHS diagnosed by conventional polysomnography and 31 healthy individuals were included in the study. The following data were collected: patient information; use of tobacco, alcohol, or street drugs; blood pressure; and sleep schedule. Sleepiness was assessed on the Epworth Sleepiness Scale and the impact of sleepiness on activities of daily living by the FOSQ.

RESULTS

Patients with SAHS (apnea-hypopnea index, 57) had a mean FOSQ total score of 88.7; healthy individuals had a mean score of 110.9 (P< .001) Significant differences were found between the 2 groups on all the FOSQ subscales, except for the one that measured social outcome. There was a moderate correlation between the 2 questionnaires (r=--0.54; P=.01) and between FOSQ and the AHI (r=--0.39; P=.05). While the capacity to predict SAHS, based on receiver operating characteristic curves was greater for the Epworth Sleepiness Scale than for the FOSQ (area under the curve, 0.91 and 0.77, respectively), the diagnostic yield increased when both questionnaires were considered together.

CONCLUSIONS

We obtained FOSQ reference scores for Spanish patients with SAHS and for healthy individuals. The study showed that the Spanish version of the FOSQ is a good instrument for assessing the impact of excessive sleepiness on activities of daily living in patients with suspected SAHS.

Obstructive sleep apnea in pregnancy and fetal outcome

OBJECTIVE

To simultaneously investigate the polysomnography (PSG) and nonstress test (NST) records of pregnant women with obstructive sleep apnea (OSA) to observe NST changes during maternal desaturation and determine maternal and fetal outcomes.

METHODS

A prospective observational study of pregnant women assessed by questionnaire for symptoms of OSA. Women with self-reported frequent snoring or apnea were offered PSG and NST.

RESULT

OSA was diagnosed in 4 (11.4%) of the 35 pregnant women who underwent PSG. Three (75%) had fetal heart decelerations accompanying maternal desaturation. The neonates of women diagnosed with OSA had lower mean Apgar scores and birth weights compared with neonates of women without OSA. Three neonates from the women diagnosed with OSA were admitted to the newborn healthcare unit.

CONCLUSION

OSA in pregnancy has important maternal and fetal outcomes. Pregnant women should be assessed for symptoms of OSA and suspected cases should be offered PSG.

Sleep apnea: epidemiology, pathophysiology, and relation to cardiovascular risk

Several studies have shown the occurrence of an independent association between obstructive sleep apnea syndrome (OSAS) and cardiovascular disease, including arterial hypertension, ischemic heart disease, and stroke. The pathogenesis of the cardiovascular complications of OSAS is still poorly understood, however. Several mechanisms are likely to be involved, including sympathetic overactivity, selective activation of inflammatory molecular pathways, endothelial dysfunction, abnormality in the process of coagulation, and metabolic dysregulation. The latter may involve insulin resistance and disorders of lipid metabolism. The aim of this review, which reports the data presented at a workshop jointly endorsed by the European Society of Hypertension and by the European Union COST action on OSAS (COST B26), is to critically summarize the evidence available to support an independent association between OSAS and cardiovascular disease.

Interações entre síndrome da apnéia obstrutiva do sono e resistência à insulina

Estudos anteriores mostraram que pacientes com Apnéia Obstrutiva do Sono (AOS) apresentam maior risco para doenças cardiovasculares. Entretanto, permanece controverso se essa associação depende da obesidade ou se ocorre devido a alterações fisiológicas decorrentes da desordem do sono, como ativação do sistema nervoso simpático, da inflamação e desordens do eixo corticotrófico e somatotrófico, que predispõem a danos vasculares. Além disso, muitos fatores de risco para doenças cardiovasculares (DCV) estão fortemente associados ao distúrbio respiratório, entre eles hipertensão, obesidade, resistência à insulina e diabetes tipo 2 (DM2). Neste artigo, vamos discutir a interação entre resistência à insulina e AOS e os possíveis mecanismos fisiopatológicos que contribuem para suas co-morbidades.

Evidence for activation of nuclear factor kappaB in obstructive sleep apnea

Obstructive sleep apnea (OSA) is a risk factor for atherosclerosis, and atherosclerosis evolves from activation of the inflammatory cascade. We propose that activation of the nuclear factor kappaB (NF-kappaB), a key transcription factor in the inflammatory cascade, occurs in OSA. Nine age-matched, nonsmoking, and non-hypertensive men with OSA symptoms and seven similar healthy subjects were recruited for standard polysomnography followed by the collection of blood samples for monocyte nuclear p65 concentrations (OSA and healthy groups). In the OSA group, p65 and of monocyte production of tumor necrosis factor alpha (TNF-alpha) were measured at the same time and after the next night of continuous positive airway pressure (CPAP). p65 Concentrations in the OSA group were significantly higher than in the control group [median, 0.037 ng/microl (interquartile range, 0.034 to 0.051) vs 0.019 ng/microl (interquartile range, 0.013 to 0.032); p = 0.008], and in the OSA group were significantly correlated with apnea-hypopnea index and time spent below an oxygen saturation of 90% (r = 0.77 and 0.88, respectively) after adjustment for age and BMI. One night of CPAP resulted in a reduction in p65 [to 0.020 ng/mul (interquartile range, 0.010 to 0.036), p = 0.04] and levels of TNF-alpha production in cultured monocytes [16.26 (interquartile range, 7.75 to 24.85) to 7.59 ng/ml (interquartile range, 5.19 to 12.95), p = 0.01]. NF-kappaB activation occurs with sleep-disordered breathing. Such activation of NF-kappaB may contribute to the pathogenesis of atherosclerosis in OSA patients.

Diuretics in Obstructive Sleep Apnea With Diastolic Heart Failure

BACKGROUND

Upper airway edema might contribute to pharyngeal collapsibility and account for the high prevalence of obstructive sleep apnea (OSA) in patients with heart disease. The aim of this study was to evaluate if intensive unloading with diuretics improves sleep-disordered breathing and increases pharyngeal caliber in patients with severe OSA and diastolic heart failure.

METHODS

Fifteen patients with severe OSA, hypertension, and diastolic heart failure were hospitalized to receive IV furosemide, 20 mg, and spironolactone, 100 mg, bid for 3 days. Polysomnography was performed for assessment of apnea-hypopnea index (AHI), acoustic pharyngometry was performed for assessment of the oropharyngeal junction (OPJ) area, and forced midinspiratory flow (FIF(50)), forced midexpiratory flow (FEF(50))/FIF(50) percentage, and exhaled nitric oxide (FeNO) were measured before and after diuretic treatment.

RESULTS

Diuretic treatment produced a significant decrease in body weight, BP, and AHI (from 74.89 +/- 6.95 to 57.17 +/- 5.40/h, p < 0.001), associated with an improvement in OPJ area (from 1.33 +/- 0.10 to 1.78 +/- 0.16 cm(2), p = 0.007), FIF(50) (from 3.16 +/- 0.4 to 3.94 +/- 0.4 L/s, p = 0.006), and FEF(50)/FIF(50) percentage (from 117.9 +/- 11.8 to 93.15 +/- 10.1%, p = 0.002). Weight loss was significantly related to the decrease of AHI (R = 0.602; p = 0.018), to the increase of FIF(50) (R = 0.68; p = 0.005), and to the decrease of FEF(50)/FIF(50) (R = 0.635; p = 0.011).

CONCLUSIONS

These findings suggest that pharyngeal edema contributes to sleep-disordered breathing in obese patients with severe OSA, hypertension, and diastolic heart failure. Upper airway edema may contribute to the frequent occurrence of OSA in patients with heart disease.

Effects of intermittent hypoxia on the heart

Obstructive sleep apnea (OSA) is associated with cardiovascular diseases such as hypertension through mechanisms involving intermittent hypoxia (IH). However, it is not yet clear whether IH directly affects the heart. In a mouse model of OSA, we found that IH causes time-dependent alterations of the susceptibility of the heart to oxidative stress. Acute IH can exert preconditioning-like cardioprotection, in part, through the transcriptional activation of genes such as bcl-x(L) and gata4. We cloned the mouse gata4 promoter and identified an IH-responsive region. The exposure of mice to prolonged IH results in the increased susceptibility of the heart to ischemia-reperfusion injury by increasing the oxidative stress status. This might resemble conditions of OSA patients. In our mouse model, further exposure to prolonged IH allowed reversal of the enhancement of myocardial damage. Understanding the complex effects of IH on the heart should help ultimately to develop therapeutic strategies against OSA-induced complications.

Sildenafil versus continuous positive airway pressure for erectile dysfunction in men with obstructive sleep apnea: a comparative study of their efficacy and safety and the patient's satisfaction with treatment

AIM

To assess the efficacy of sildenafil and continuous positive airway pressure (CPAP) in the treatment of concurrent erectile dysfunction (ED) with obstructive sleep apnea (OSA), and to gauge the level of treatment satisfaction in patients and their partners.

METHODS

Forty men were treated for 12 weeks with sildenafil 100 mg (20 men) or CPAP during nighttime sleep (20 men). Treatment efficacy was assessed by the rate of successful intercourse attempts, and satisfaction with treatment was assessed by patients' and partners' answers to question 1 of the Erectile Dysfunction Inventory of Treatment Satisfaction.

RESULTS

Under sildenafil, 128 of 249 (51.4%) intercourse attempts were successful; under CPAP, 51 of 193 (26.9%) attempts were successful ((c)P < 0.001). Erectile function was improved in both groups. After sildenafil and CPAP treatment, the mean International Index for Erectile Function domain scores were 14.3 and 10.8, respectively ((b)P = 0.025), compared to 7.8 and 7 at baseline, respectively. CPAP and sildenafil were well tolerated. Sporadic episodes of nasal dryness under CPAP and transient headache and flushing under sildenafil were not significant. Fifty percent of patients treated with sildenafil and 25% with CPAP were satisfied with the treatment, and their partners were equally satisfied. The satisfaction scores for both patients and partners under sildenafil were superior to those under CPAP ((c)P < 0.002).

CONCLUSION

Both sildenafil 100 mg and CPAP, used separately, had positive therapeutic impact but sildenafil was superior. Patients and their partners were more satisfied with sildenafil for the treatment of ED. However, because of the high proportion of dissatisfied men and partners, new therapeutic agents or a combination of the two methods must be studied further.

Non-arteritic anterior ischaemic optic neuropathy and presumed sleep apnoea syndrome screened by the Sleep Apnea scale of the Sleep Disorders Questionnaire (SA-SDQ)

BACKGROUND

Two recent studies reported over 70% of the patients with non-arteritic anterior ischaemic optic neuropathy (NAION) had sleep apnoea syndrome (SAS) diagnosed by overnight polysomnography. The current study used the Sleep Apnea scale of the Sleep Disorders Questionnaire (SA-SDQ) to evaluate this association.

METHODS

A matched case-control study was conducted among 73 cases of NAION matched on age and gender to 73 controls without a history of NAION. Information regarding demographics, medical conditions, health behaviours and SAS was obtained via a telephone questionnaire that included the SA-SDQ. Conditional logistic regression was used to calculate odds ratios (OR) and the 95% confidence intervals (CI) for the association between NAION and the SA-SDQ.

RESULTS

Cases were significantly more likely to report symptoms and characteristics consistent with SAS than controls (OR 2.62; 95% CI 1.03 to 6.60) when adjusted for medical and health behaviour characteristics.

CONCLUSIONS

The results of this study suggest that patients with SAS are at increased risk of NAION. Additional research in a larger population is needed to confirm the observed results and validate the use of the SA-SDQ in patients with NAION.

Obstructive sleep apnoea, cigarette smoking and serum testosterone levels in a male sleep clinic cohort

This study evaluated the impact of obstructive sleep apnoea (OSA) and smoking on total serum testosterone levels in 96 men (mean age 43.3 years; range 25 - 60 years) attending a sleep clinic. Fifty-five men (57.3%) had OSA, defined as an apnoea-hypopnoea index of > or = 15 events/h, recorded during overnight polysomnography, and 42 (43.8%) were current smokers. Mean serum total testosterone levels were significantly lower in OSA subjects (3.4 ng/ml) than in non-OSA subjects (3.9 ng/ml), whereas no significant difference was observed between current smokers and nonsmokers. In a multiple linear regression analysis, serum testosterone was negatively correlated with body mass index and the apnoea-hypopnoea index, but not with age and pack-years of smoking. Our results support previous observations regarding testosterone levels in men with OSA, but, contrary to some earlier reports, there was no positive relationship between smoking and total testosterone in the present cohort.

The effects of 1-year treatment with a herbst mandibular advancement splint on obstructive sleep apnea, oxidative stress, and endothelial function

BACKGROUND

Obstructive sleep apnea (OSA) is associated with endothelial dysfunction. In the current study, we assessed the effect of long-term modified Herbst mandibular advancement splint (MAS) treatment on OSA, oxidative stress markers, and on endothelial function (EF).

METHODS

A total of 16 subjects participated (11 men and 5 women; mean [+/- SD] age, 54.0 +/- 8.3 years; mean body mass index, 28.0 +/- 3.1 kg/m(2)), 12 of whom completed the 1-year evaluation. Apnea severity, levels of oxidative stress markers, and EF were assessed after 3 months and 1 year of receiving treatment. For comparison, 6 untreated patients underwent two evaluations 9 months apart, and 10 non-OSA individuals were assessed once as a reference group. The results are presented as the mean +/- SD.

RESULTS

The mean apnea-hypopnea index (AHI) decreased significantly from 29.7 +/- 18.5 events/h before treatment to 17.7 +/- 11.1 events/h after 3 months of treatment and 19.6 +/- 11.5 events/h after 1 year of treatment (p < 0.005 for both). The mean Epworth sleepiness scale score decreased significantly from 12.4 +/- 6.0 before treatment to 10.2 +/- 6.6 after 3 months of treatment and 7.8 +/- 3.8 after 1 year of treatment (p < 0.001 for both). The mean EF improved significantly from 1.77 +/- 0.4 before treatment to 2.1 +/- 0.4 after 3 months of treatment (p < 0.05) and 2.0 +/- 0.3 after 1 year of treatment (p = 0.055), which were similar to the values of the reference group. Thiobarbituric acid-reactive substance (TBARS) levels decreased from 18.8 +/- 6.2 nmol malondialdehyde (MDA)/mL before treatment to 15.8 +/- 3.9 MDA/mL after 3 months of treatment (p = 0.09) and 15.5 +/- 3.2 nmol MDA/mL after 1 year of treatment (p < 0.05). There was a correlation between the improvement in AHI and in EF or TBARS levels (r = 0.55; p = 0.05). The untreated control group remained unchanged.

CONCLUSIONS

The Herbst MAS may be a moderately effective long-term treatment for patients with OSA. EF improved to levels that were not significantly different than reference levels, even though apneic events were not completely eliminated. We think that these data are encouraging and that they justify the performance of larger randomized controlled studies.

Relationship between Obstructive Sleep Apnea and Liver Abnormalities in Morbidly Obese Patients: A Prospective Study

BACKGROUND

Morbid obesity is a risk factor of nonalcoholic steatohepatitis (NASH). Obstructive sleep apnea (OSA) could also be an independent risk factor for elevated liver enzymes and NASH. The relationships between liver injuries and OSA in morbidly obese patients requiring bariatric surgery were studied prospectively.

METHODS

Every consecutive morbidly obese patient (BMI > or =40 kg/m2 or > or =35 kg/m2 with severe comorbidities) requiring bariatric surgery was included between January 2003 and October 2004. Polygraphic recording, serum aminotransferases (ALT, AST), gamma-glutamyltransferase (GGT) and liver biopsy were systematically performed. OSA was present when the apnea-hypopnea index (AHI) was >10/h.

RESULTS

62 patients (54 F; age 38.5 +/- 11.0 (SD) yrs; BMI 47.8 +/- 8.4 kg/m2) were included. Liver enzymes (AST, ALT or GGT) were increased in 46.6%. NASH was present in 34.4% and OSA in 84.7%. Patients with OSA were significantly older (P = 0.015) and had a higher BMI (P = 0.003). In multivariate analysis, risk factors for elevated liver enzymes were the presence of OSA and male sex. The presence of NASH was similar in patients with or without OSA (32.7% vs 44.4% of patients, P = 0.76).

CONCLUSION

In this cohort of morbidly obese patients requiring bariatric surgery, one-third of patients had NASH, a prevalence similar to previous studies. OSA was found to be a risk factor for elevated liver enzymes but not for NASH.

Cerebrovascular disease and the pathophysiology of obstructive sleep apnea

Obstructive sleep apnea (OSA) is a common disorder and the major sleep-related risk factor for cerebrovascular disease. There is a dose-response relationship between the severity of OSA and the odds ratio for development of systemic hypertension. Observational studies have shown that patients with clinically significant OSA have increased incidence of cardiovascular and cerebrovascular disease, as well as increased incidence of sudden death in sleep. Following stroke, patients have a high prevalence of OSA, which diminishes the potential for rehabilitation, increases the risk of secondary stroke, and heightens mortality. Successful treatment of OSA with noninvasive positive airway pressure ventilation and with mandibular advancement devices lowers mean blood pressure. There is suggestive evidence that in patients with advanced OSA, permanent structural cerebral lesions may occur. Circadian changes during sleep contribute to an increase in the risk of cardiovascular and cerebrovascular accidents.

Early investigation and treatment of obstructive sleep apnoea after acute stroke

Obstructive sleep apnoea (OSA) is an independent risk factor for hypertension, which is a major cause of stroke. The prevalence and associations of OSA in a cohort of stroke patients were studied. The safety and tolerability of early treatment with nasal continuous airways pressure (nCPAP) was also assessed. Consecutive subjects admitted with acute stroke were assessed clinically, radiologically and with scales assessing prior OSA risk, dysphagia and disability. Sleep studies were performed within the first few days of admission using a portable diagnostic system. Twenty-nine of 55 (53%) subjects had evidence of OSA, using an apnoea-hypopnoea index (AHI) of 10 or greater. The AHI was significantly associated with an index of prior OSA symptoms, but not with history of hypertension, degree of dysphagia, or type and severity of stroke. Use of a portable diagnostic system for detecting OSA in the acute stroke setting was well tolerated. OSA is common after acute stroke and exceeds rates seen in control populations of similar age (53% vs. 11%). Early treatment with nCPAP was effective and well tolerated.

Prevalence of normal tension glaucoma in obstructive sleep apnea syndrome patients

PURPOSE

To explore the prevalence of normal tension glaucoma (NTG) among patients with obstructive sleep apnea syndrome (OSAS) and to examine OSAS as a risk factor of NTG.

PATIENTS AND METHODS

Fifty-one consecutive white patients with OSAS were compared with 40 healthy subjects. All the study subjects underwent blood gas analysis, polysomnography, oxyhemoglobin saturation, and an ophthalmologic examination including visual field, visually evoked potential (VEP), and pattern electroretinography (PERG) and disc analysis with the Heidelberg Retina Tomograph II.

RESULTS

Three of 51 OSAS patients (5.9%) had NTG. No patient in the control group had OSAS or NTG. The severity of OSAS correlated with intraocular pressure, the mean deviation of the visual field, the cup/disk ratio and the mean of the retinal nerve fiber layer thickness (P<0.01 to 0.001). Apnea hypopnea index and intraocular pressure were significantly greater in OSAS patients with abnormal VEP and PERG, compared to those with normal PERG and VEP.

CONCLUSIONS

The present study suggests that the prevalence of NTG in our OSAS patients is higher than expected in a white population of the same age and that OSAS may be an important risk factor for NTG. Our data underline the importance of taking an accurate sleep history from patients with NTG and referring patients with sleep disturbance for polysomnography.

Mortality risk factors in sleep apnoea: a matched case?control study

Sleep apnoea syndrome was reported to be associated with increased mortality but it is not known if this association is independent of obesity and co-morbidities. The present study investigated predictors of mortality in a large cohort of men with sleep apnoea using a case-control design. The study population consisted of 10,981 men diagnosed during 1991-2000 by whole-night polysomnography with sleep apnoea; 331 men died prior to 1 September 2001, of whom 277 were matched by age, gender, site and time of study to patients who were alive in September 2001. Multivariate analysis revealed that all-cause mortality was associated with chronic obstructive pulmonary disease (COPD) (odds ratio, OR: 7.07, 95% CI 2.75-18.16), chronic heart failure (CHF) (OR: 5.47, 95% CI 1.06-28.31), diabetes mellitus (DM) (OR: 3.30, 95% CI 1.51-7.20) and body mass index (BMI) (increase of 5 kg m(-2), OR: 1.44, 95% CI: 1.04-1.99). Chronic upper airway problems were associated with survival (OR: 0.45, 95% CI 0.23-0.90). There were significant interactions between respiratory disturbance index and BMI and COPD. Mortality of patients younger than the median age (62 years) was associated with COPD, DM and an interaction between BMI and apnoea severity. Predictors of mortality for the older patients were COPD, CHF and DM. We conclude that all-cause mortality in sleep apnoea is associated with co-morbidities and obesity. Severity of sleep apnoea affects mortality by interacting with obesity and lung disease.

Prise en charge du syndrome d’apnées obstructives du sommeil en médecine générale en Midi-Pyrénées

INTRODUCTION

Obstructive sleep apnoea syndrome (OSAS) is a significant public health problem. In the French care system general practitioners have an important role to play in its management especially in the field of early diagnosis.

METHODS

The first part of this work is a descriptive case-control study looking at health resource usage of OSAS patients treated with continuous positive airway pressure (CPAP) in the MidiPyrénées area. The second part is a descriptive study which involved by interviewing 100 general practitioners settled in the area in order to evaluate their knowledge and their practice regarding OSAS. Results were compared with a previous study (1) performed in 2002 with similar methodology.

RESULTS

Our results confirm that OSAS remains to a large extent undiagnosed (mean OSAS patients was less than 6 per physician) and underline the close connection between OSAS and cardiovascular diseases. A low degree of knowledge concerning the symptoms, main complications and treatment of OSAS was observed in this group of physicians. There was, however a relative improvement in the answers compared to the study performed in 2002. Two or more complications were mentioned by 67% of practitioners (33% in 2002) and only 13% of them were unable to identify at least one possible complication of OSAS (50% in 2002).

CONCLUSION

This study confirms the impact on health of OSAS, characterized by a higher consumption of various medications than in non OSAS patients. Knowledge of OSAS remains low in general practitioner population in France. An important effort has to be made to improve learning of this disease by continuous medical training and during initial medical course.

Sildenafil combined with continuous positive airway pressure for treatment of erectile dysfunction in men with obstructive sleep apnea

OBJECTIVES

To assess efficacy and safety of the combination of sildenafil and continuous positive airway pressure (CPAP), and satisfaction with treatment for erectile dysfunction (ED) in men with obstructive sleep apnea (OSA).

PATIENTS AND METHODS

Forty men suffering from OSA and concurrent ED were treated with CPAP after a thorough investigation. After a 4-week run-in period, the patients were randomly allocated to treatment for 6 weeks; 20 men to the combination group, receiving additionally 100 mg sildenafil on demand for intercourse, and 20 men to CPAP alone. After a 1-week washout phase, the two groups switched to the other treatment arm for an additional 6 weeks period. End points for efficacy evaluation were the percentage of successful attempts for intercourse based on an event log and the overall satisfaction with sildenafil in the treatment of ED.

RESULTS

The patients recorded a total of 149 attempts for intercourse during the run-in phase with a success rate of 19.5%. During the 12 weeks of treatment, the success rate of intercourse attempts was 24.8% when only on CPAP and 61.1% when in combination with sildenafil (P < 0.001). Of the studied men, 70% were satisfied with the use of sildenafil while 30% remained unhappy with this additional treatment.

CONCLUSIONS

Sildenafil in combination with CPAP appears clearly superior to CPAP alone. The efficacy of this combination is superior to that of sildenafil alone, as reported in previous studies. Both treatment modalities are safe and well tolerated. However, approximately one-third of the patients remain unsatisfied even from the combination treatment. Further treatment options are needed.

Effects of intermittent hypoxia on oxidative stress-induced myocardial damage in mice

Obstructive sleep apnea is associated with increased risk for cardiovascular diseases. As obstructive sleep apnea is characterized by episodic cycles of hypoxia and normoxia during sleep, we investigated effects of intermittent hypoxia (IH) on ischemia-reperfusion-induced myocardial injury. C57BL/6 mice were subjected to IH (2 min 6% O(2) and 2 min 21% O(2)) for 8 h/day for 1, 2, or 4 wk; isolated hearts were then subjected to ischemia-reperfusion. IH for 1 or 2 wk significantly enhanced ischemia-reperfusion-induced myocardial injury. However, enhanced cardiac damage was not seen in mice treated with 4 wk of IH, suggesting that the heart has adapted to chronic IH. Ischemia-reperfusion-induced lipid peroxidation and protein carbonylation were enhanced with 2 wk of IH, while, with 4 wk, oxidative stress was normalized to levels in animals without IH. H(2)O(2) scavenging activity in adapted hearts was higher after ischemia-reperfusion, suggesting the increased antioxidant capacity. This might be due to the involvement of thioredoxin, as the expression level of this protein was increased, while levels of other antioxidant enzymes were unchanged. In the heart from mice treated with 2 wk of IH, ischemia-reperfusion was found to decrease thioredoxin. Ischemia-reperfusion injury can also be enhanced when thioredoxin reductase was inhibited in control hearts. These results demonstrate that IH changes the susceptibility of the heart to oxidative stress in part via alteration of thioredoxin.

An analysis of the evidence-practice continuum: is surgery for obstructive sleep apnoea contraindicated?

RATIONALE, AIMS AND OBJECTIVES

Currently there are multiple surgical interventions utilized in the treatment of adult obstructive sleep apnoea (OSA). The role of these operations remains controversial, with perspectives on treatment efficacy varying considerably. Despite this, their use is proliferating.

OBJECTIVES

In this paper, we present the degree of variability that occurs in the application of these procedures, and examine the effectiveness of surgical intervention as a treatment for OSA.

METHOD

A multi-centre retrospective clinical audit of consecutive, unselected surgical cases presenting at the sleep disorder clinics of two teaching hospitals in a major Australian city. Patients acted as their own historical controls, undergoing polysomnography pre and post surgery to gauge effectiveness.

RESULTS

On variability demonstrate 94 individuals in this cohort received 220 individual upper airway surgical procedures, 184 occurred in their first operation (mean 2.5 per person; range 1-7) and 36 occurred in a second operation (n=18; cumulative mean of 4 per person; range 3-7). These 94 individuals received 41 varying combinations of surgery. Results on effectiveness demonstrate an overall physiological success rate of 13% (87% fail). One operation reduced OSA severity by 20% (patients still had severe OSA), and two operations by 35% (still moderate OSA). In contrast, conventional Continuous Positive Airway Pressure therapy controlled OSA (n=64).

CONCLUSIONS

This case study demonstrates substantial procedural variability and limited effectiveness. This raises questions as to the quality of care, the treatment-derived health outcomes of this population and of efficient resource allocation. This issue requires greater policy attention.

[Obstructif sleep apnea-hypopnea syndrome: evolution of an old concept]

This review summarizes the well-known clinical features of the obstructive sleep apnea-hypopnea syndrome (OSAHS) and emphasizes new research on this syndrome. Though described in the seventies, the prevalence OSAHS is known mainly in the US. A dramatic increasing in prevalence has been related to the increase prevalence of obesity, raising a substantial public health problem. Discussion continues on the proper definition of the syndrome and degrees of severity. Multiple factors are involved in the pathogenesis of sleep apnea: anatomic abnormalities, mechanical factors, nervous alterations, muscular imbalance between pharyngeal constrictor and dilator muscles or part of a metabolic syndrome? Indeed, obstructive sleep apnea with and without obesity is increasingly implicated in the initiation and progression of metabolic disorders and of cardiovascular diseases (hypertension, cardiac ischemia and probably congestive heart failure, cardiac arrhythmias and strokes). An extended literature reports the neural, humoral, thrombotic, metabolic and inflammatory mechanisms linking OSAHS to endocrinology and cardiovascular diseases. Daytime sleepiness, cognitive, memory and performance deficits with their risks are also stressed. These consequences require treating this syndrome as soon as possible. Multiple interventions (medical, mechanical-nasal positive airway pressure or oral appliances, and sometimes surgical management) can be used but nasal continuous positive airway pressure is the "gold standard" treatment in severe OSAHS. More often multiple interventions are appropriate in a given patient. Finally, there is growing evidence that genetic factors influence the expression of OSAHS. Numerous genetic studies have investigated the etiology of OSAHS with the goal of improving our understanding of its pathogenesis.