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

Dental side-effects of mandibular advancement splint wear in patients who snore

OBJECTIVES

(a) To evaluate the longer term orthodontic side-effects of a Herbst mandibular advancement splint (MAS) in subjects with sleep disordered breathing. (b) To determine whether these are related to dental occlusion, degree of mandibular advancement or duration of appliance wear.

DESIGN

Retrospective, cohort study.

SETTING

Teaching hospital dental school.

PARTICIPANTS

Subjects with sleep disordered breathing who had been wearing an MAS regularly (a minimum of 5 h per night, six nights a week) for at least 2 years. Of 192 subjects who were identified, 30 fulfilled the inclusion criteria and were prepared to attend for review.

INTERVENTIONS

Dental casts were obtained and BMI and Epworth Sleepiness Scale scores recorded. These data were compared with those collected when the subject was first referred. A questionnaire was completed concerning MAS use, side-effects and any problems associated with the device.

MAIN OUTCOME MEASURES

Changes in incisor tooth position.

RESULTS

Median duration of MAS wear was 3.64 years. Small, statistically significant reductions in both vertical (-0.4 mm) and horizontal (-0.5 mm) overlap of the incisor teeth were found. This correlated with the degree of vertical opening of the MAS but was not related to the amount of mandibular protrusion or the duration of appliance wear.

CONCLUSIONS

Patients who are considered suitable for MAS should be warned that dental changes may occur. Thus referring surgeons should also be aware of this possibility.

Sleep-disordered breathing and cardiovascular disease

Untreated sleep apnea is a risk factor for hypertension, and CPAP treatment effects a blood pressure reduction comparable to that of pharmacologic monotherapy. Nevertheless, many current papers addressing the rapid increase in prevalence of hypertension and purporting to outline its management do not mention looking for or treating sleep apnea as a strategy. In addition to hypertension, virtually every adverse cardiovascular condition has been strongly associated with sleep disordered breathing in cross-sectional studies. There are also small prospective studies of the relationship between sleep-disordered breathing (SDB) and coronary heart disease and atrial fibrillation. Further, treatment studies show improvement or reduced risk of most cardiovascular sequelae of SDB with CPAP treatment. Beyond hypertension, which is well established, the strongest relationships between SDB and cardiovascular disease appear to be with congestive heart failure and bradyarrhythmias. Prospective studies are needed to confirm these relationships and to further delineate the risk.

Sleep-disordered breathing and hypertension among African Americans

This study investigated differences in sleep-disordered breathing (SDB) between hypertensives without a family history of hypertension and hypertensives with a family history. Furthermore, it examined whether these two groups differed in the severity of SDB. Patients were African Americans (n=162, mean age=51.19+/-13.77 years; mean body mass index (BMI)=37.85+/-9.51 kg/m2, male=57%), who were referred to the clinic because of a sleep complaint. Sleep was recorded in the laboratory using standard physiological parameters; all parameters were analysed by a trained scorer. Altogether, 91% of the patients received an SDB diagnosis. Of these patients, 25% were hypertensives without a family history, 20% were hypertensives with a family history, and 55% were normotensives. We found a significant difference between these patient groups regarding the severity of SDB (F14,158=1.823, P<0.05), but no significant group difference was observed in the rate of SDB. Increasing weight was accompanied by increasing severity of SDB. The finding that hypertensive patients with or without a positive family history showed worse oxygenation and respiratory characteristics than did normotensives is consistent with previous research. Of note, hypertensives reporting a family history were characterized by a greater number of oxygen desaturations and apnoea hypopnoea index than those typified only by a current diagnosis of hypertension. Hypertensives with a family history are likely to show a profile of greater blood pressure, higher BMI, and more severe SDB, which by all accounts are more common among African Americans.

Implantable Pacing Devices and Sleep Apnea: Implications for Diagnosis and Therapy

Sleep apnea has been increasingly recognized for its prevalence and its impact on cardiovascular health. The disorder has considerable impact on cardiovascular disease states, particularly congestive heart failure. Implantable cardiac pacing devices may have a role in both the diagnosis and therapy of sleep apnea, which may be of particular importance given the seemingly wide coprevalence of cardiac disorders and sleep apnea.

Sleep.7: positive airway pressure therapy for obstructive sleep apnoea/hypopnoea syndrome

The use of continuous positive airway pressure (CPAP) in treating symptoms associated with OSAHS is reviewed. Although it is an imperfect intervention, it continues to evolve and improve in such a way that patients who would not have been able to use this treatment even in the recent past can benefit from it today.

Nocturnal Oxygen Desaturation as a Predictive Risk Factor for Coronary Restenosis After Coronary Intervention Serial Quantitative Coronary Angiography Study

BACKGROUND

Sleep-disordered breathing may affect coronary artery disease, so patients treated by percutaneous transluminal coronary angioplasty were studied to investigate the relationship between nocturnal oxygen desaturation (NOD) and the loss index.

METHODS AND RESULTS

The nocturnal oxygen desaturation index (ODI) was determined by means of a pulse oximeter in 35 patients with coronary artery disease treated by stent placement. The patients were divided into 3 groups according to ODI: <5 events/h (group N, n=6), between 5 and 14 events/h (group A, n=19), and >or=15 events/h (group B, n=10). The relationship between the ODI and loss index was examined in each group. The loss index, 0.27+/-0.23 in group N, 0.30+/-0.27 in group A, and 0.70+/-0.32 in group B, differed significantly between groups N and B (p=0.007). In all patients, the loss index showed a significant positive correlation with the ODI (R=0.585, p=0.002).

CONCLUSIONS

These findings suggest that NOD may be an important contributor to coronary restenosis in patients treated with stent placement.

Sleep . 6: obstructive sleep apnoea/hypopnoea syndrome and hypertension

The use of CPAP to control excessive daytime sleepiness in OSAHS probably also produces a substantial reduction in vascular risk. This is reviewed with particular reference to hypertension.

Sleep Apnea Syndrome and Diastolic Blood Pressure Elevation during Exercise

BACKGROUND

Several studies assessing the role of obstructive sleep apnea syndrome (OSAS) as an independent risk factor for hypertension have produced conflicting results. Although the sleep apnea syndrome is associated with hypertension, there are no references regarding the blood pressure response of normotensive OSAS patients during exercise.

STUDY OBJECTIVES

The aim of this study was to investigate the relationship between diastolic blood pressure (DBP) response during exercise and the severity of OSAS.

METHODS

We performed exercise testing a day after polysomnography in 17 normotensive males who were admitted for the first time because of OSAS and in 10 normal subjects who were members of the same families. During maximal incremental exercise test (bicycle ergometry) oxygen consumption (VO(2)) and the DBP were estimated at rest and at peak exercise. VO(2) was also measured when DBP were 100 and 110 mm Hg.

RESULTS

At peak exercise DBP was significantly higher in OSAS patients (115.3 +/- 9.2 mm Hg) than in normal subjects (101 +/- 8.4 mm Hg, p < 0.01). OSAS patients reached a DBP of 110 mm Hg with a significantly lower VO(2) than normal subjects (1,881.5 +/- 703.4 vs. 1,972.3 +/- 108.6 ml/min, p = 0.045). VO(2) was not different between the two groups at a DBP of 100 mm Hg (1,211.2 +/- 371.7 vs. 1,536.6 +/- 267.2 ml/min, p = 0.089) but OSAS patients had a significantly lower heart rate than normals (111.2 +/- 13 vs. 118.6 +/- 27.6, p = 0.009). None of the aspects of quality of life, according to the Nottingham Health Profile Questionnaire, Part 1, were significantly different between patients and normal subjects.

CONCLUSIONS

Normotensive OSAS patients develop DBP elevation at an earlier stage during exercise compared to normal subjects. This hypertensive response was not correlated with the severity (apnea-hypopnea index, oxygen desaturation parameters) of OSAS. DBP elevation could be a limiting factor of physical performance in this group of patients.

[The availability in Spanish public hospitals of resources for diagnosing and treating sleep apnea-hypopnea syndrome]

INTRODUCTION AND OBJECTIVE

Sleep apnea-hypopnea syndrome is associated with an overall deterioration in the patients health and affects between 1 and 2 million people in Spain. The objective of the present study was to evaluate the diagnostic and therapeutic resources available in Spain for dealing with this problem in terms of both infrastructure and human resources.

METHODS

We selected 461 general hospitals, 457 (99.1%) of which answered a questionnaire in the course of a telephone interview.

RESULTS

At the time of response, 219 hospitals (47.5%) reported performing sleep studies. Conventional polysomnography was available in 53% of those hospitals, respiratory polygraphy was used in 42%, and oximetry in 5%. In 47% of the hospitals, continuous positive airway pressure was titrated empirically in most cases; the number of patients being treated with CPAP was 109,752, that is, 269 per 100,000 population in Spain.

CONCLUSIONS

The level of resources available for diagnosing and treating sleep apnea-hypopnea syndrome, although improving, is clearly still inadequate. Currently, only 0.49 polysomnograph and 0.72 polygraph machines are available per 100,000 population, whereas 1 and 3 machines, respectively, are deemed necessary. Only 5% to 10% of the affected population has been diagnosed, and in 47% of the hospitals interviewed continuous positive airway pressure is not properly titrated. These results should be a clarion call to the health authorities to take the appropriate steps to address this health problem.

Obstructive sleep apnea and cardiovascular disease

Obstructive sleep apnea (OSA) is a common medical condition that occurs in approximately 5% to 15% of the population. The pathophysiology of OSA is characterized by repetitive occlusions of the posterior pharynx during sleep that obstruct the airway, followed by oxyhemoglobin desaturation, persistent inspiratory efforts against the occluded airway, and termination by arousal from sleep. Obstructive sleep apnea is associated with daytime sleepiness and fatigue, likely due to fragmented sleep from recurrent arousals. Substantial evidence shows that patients with OSA have an increased incidence of hypertension compared with individuals without OSA and that OSA is a risk factor for the development of hypertension. Recent studies show that OSA may be implicated in stroke and transient ischemic attacks. Obstructive sleep apnea appears to be associated with coronary heart disease, heart failure, and cardiac arrhythmias. Pulmonary hypertension may be associated with OSA, especially in patients with preexisting pulmonary disease. Although the exact cause that links OSA with cardiovascular disease is unknown, there is evidence that OSA is associated with a group of proinflammatory and prothrombotic factors that have been identified to be important in the development of atherosclerosis. Obstructive sleep apnea is associated with increased daytime and nocturnal sympathetic activity. Autonomic abnormalities seen in patients with OSA include increased resting heart rate, decreased R-R interval variability, and increased blood pressure variability. Both atherosclerosis and OSA are associated with endothelial dysfunction, increased C-reactive protein, interleukin 6, fibrinogen, and plasminogen activator inhibitor, and reduced fibrinolytic activity. Obstructive sleep apnea has been associated with enhanced platelet activity and aggregation. Leukocyte adhesion and accumulation on endothelial cells are common in both OSA and atherosclerosis. Clinicians should be aware that OSA may be a risk factor for the development of cardiovascular disease.

Using a wrist-worn device based on peripheral arterial tonometry to diagnose obstructive sleep apnea: in-laboratory and ambulatory validation

STUDY OBJECTIVES

To assess the accuracy of a wrist-worn device (Watch_PAT 100) to diagnose obstructive sleep apnea in the home.

DESIGN

Participants completed 2 overnight diagnostic studies with the test device: 1 night in the laboratory with concurrent polysomnography and 1 night in the home with only the Watch_PAT. The order of the laboratory and home study nights was random. The frequency of respiratory events on the PSG was quantified using indexes based on 2 definitions of hypopnea: the respiratory disturbance index (RDI) using American Academy of Sleep Medicine Task Force criteria for clinical research, also referred to as the Chicago criteria (RDI.C), and the Medicare guidelines (RDI.M). The Watch_PAT RDI (PAT RDI) and oxygen desaturation index (PAT ODI) were then evaluated against the polysomnography RDI.C and RDI.M, respectively, for both Watch_PAT diagnostic nights, yielding IN-LAB and HOME-LAB comparisons.

SETTING

Sleep laboratory affiliated with a tertiary-care academic medical center.

PATIENTS

30 patients referred with suspected OSA.

INTERVENTIONS

N/A.

MEASUREMENTS AND RESULTS

The polysomnography and PAT measures were compared using the mean [2 SD] of the differences and the intra-class correlation coefficient (ICC). The receiver-operator characteristic curve was used to assess optimum sensitivity and specificity and calculate likelihood ratios. For the IN-LAB comparison, there was high concordance between RDI.C and PAT RDI (ICC = 0.88, mean difference 2.5 [18.9] events per hour); RDI.M and PAT ODI (ICC = 0.95, mean difference 1.4 [12.9] events per hour; and sleep time (ICC = 0.70, mean difference 7.0 [93.1] minutes) between the test device and PSG. For the HOME-LAB comparison, there was good concordance between RDI.C and PAT RDI (ICC = 0.72, mean difference 1.4 [30.1] events per hour) and RDI.M and PAT ODI (ICC = 0.80, mean difference 1.6 [26.4] events per hour) for the test device and PSG. Home studies were performed with no technical failures.

CONCLUSIONS

In a population of patients suspected of having obstructive sleep apnea, the Watch_PAT can quantify an ODI that compares very well with Medicare criteria for defining respiratory events and an RDI that compares favorably with Chicago criteria for defining respiratory events. The device can be used with a low failure rate for single use in the lab and home for self-administered testing.

The Heart Rate Response to Exercise Is Blunted in Patients with Sleep-Related Breathing Disorder

BACKGROUND

This study addressed the hypothesis that cardiovascular reactivity during graded bicycle exercise is influenced by a coexisting sleep-related breathing disorder (SRBD).

METHODS

Blood pressure and heart rate were assessed at rest and during graded exercise (110 W and maximal load) in 1,149 patients of a Sleep Disorders Center. The degree of SRBD, and potential confounders, including blood gases and pulmonary function, were determined.

RESULTS

Maximal exercise capacity tended to decrease with SRBD activity (p = 0.07). The heart rate reactivity was blunted and reduced by -0.07 and -0.09 beats/min for every SRBD unit at 110 W (p < 0.001) and at maximal load (p < 0.001), respectively. Systolic and diastolic blood pressure reactivity at maximal load were positively associated with SRBD severity. These associations were independent of possible confounders.

CONCLUSION

SRBD is associated with reduced physical working capacity and a modified hemodynamic response to exercise.

Sleep apnoea in the older adult : pathophysiology, epidemiology, consequences and management

Sleep apnoea is a breathing disorder in sleep usually caused by repetitive upper airway obstruction. Its primary symptoms include snoring, daytime sleepiness and decreased cognitive functioning. Risk factors for the condition include obesity, anatomical abnormalities, aging, and family history. It has been associated with hypertension, cardiovascular and pulmonary diseases and increased mortality. The prevalence of sleep apnoea increases with age, although the severity of the disorder, as well as the morbidity and mortality associated with it, may actually decrease in the elderly. A decline in cognitive functioning in older adults with sleep apnoea may resemble dementia. Medical management of sleep apnoea rarely relies on drug treatment, as the few drugs (antidepressants and respiratory stimulants) tested for treatment have been found to be ineffective, or cause tolerance or serious adverse effects and complications. The treatment of choice for sleep apnoea is continuous positive airway pressure, a device which generates positive air pressure through a nose mask, creating a splint which keeps the airway unobstructed throughout the night. Weight loss significantly decreases or eliminates apnoeas. Oral appliances are used to enlarge the airway at night by moving the tongue and mandible forward. Positional therapy involves avoiding the supine position during sleep in patients who mostly have apnoeas while lying on their back. Surgical management may also be considered, although with great caution in the elderly, because of their increased risk of complications related to surgery. Surgical procedures include nasal reconstruction, somnoplasty, laser-assisted uvuloplasty, uvulopalatopharyngoplasty, genioglossus advancement and hyoid myotomy, and maxillomandibular advancement for severe cases when other treatments have failed. As a last option, tracheostomy may be performed.

Effects of simulated obstructive sleep apnoea on the human carotid baroreceptor-vascular resistance reflex

Obstructive sleep apnoea (OSA), which is characterized by periodic inspiratory obstruction, is associated with hypertension and possibly with changes in the baroreceptor reflex. In this investigation we induced changes in inspiratory resistance and in inspiratory oxygen and carbon dioxide content, which simulate some of the changes in OSA, to determine whether this caused changes in the gain or setting of the carotid baroreflex. In eight healthy subjects (aged 21-62 years) we changed the stimulus to carotid baroreceptors, using neck chambers and graded pressures of -40 to +60 mmHg, and assessed vascular resistance responses in the brachial artery from changes in blood pressure (Finapres) divided by brachial artery blood flow velocity (Doppler ultrasound). Stimulus-response curves were defined during (a) sham (no additional stimulus), (b) addition of an inspiratory resistance (inspiratory pressure -10 mmHg), (c) breathing asphyxic gas (12% O(2), 5% CO(2)), and (d) combined resistance and asphyxia. Sigmoid or polynomial functions were applied to the curves and maximum differentials (equivalent to peak gain) and the corresponding carotid pressures (equivalent to 'set point') were determined. The sham test had no effect on either gain or 'set point'. Inspiratory resistance alone had no effect on blood pressure and did not displace the curve. However, it reduced gain from -3.0 +/- 0.6 to -2.1 +/- 0.4 units (P < 0.05). Asphyxia alone did increase blood pressure (+7.0 +/- 1.1 mmHg, P < 0.0005) and displaced the curve to higher pressures by +16.8 +/- 2.1 mmHg (P < 0.0005). However, it did not affect gain. The combination of resistance and asphyxia both reduced gain and displaced the curve to higher pressures. These results suggest that inspiratory resistance and asphyxia cause changes in the baroreceptor reflex which could lead to an increase in blood pressure. These changes, if sustained, could provide a mechanism linking hypertension to obstructive sleep apnoea.

The Effects of Nasal Continuous Positive Airway Pressure on Platelet Activation in Obstructive Sleep Apnea Syndrome

OBJECTIVE

A case-controlled study to assess the effects of nasal continuous positive airway pressure (CPAP) on platelet activation in patients with obstructive sleep apnea (OSAS) syndrome.

METHODS

We recruited 65 patients with suspected OSAS for this study. Blood samples were taken with the patient in the supine position in the morning immediately after polysomnography, and 1 night and 3 months after the start of nasal CPAP therapy to measure an index of platelet activation (IPA+), which reflected both the quantity and quality of platelet activation. Significant OSAS was defined as an apnea-hypopnea index (AHI) of > or = 10 events per hour.

RESULTS

There were 42 patients with significant OSAS and 23 control subjects with AHI < 10 events per hour. The mean (+/- SD) age for the OSAS patients was 48 +/- 9 years, the mean body mass index was 30.7 +/- 4.8, the mean AHI was 47 +/- 25 events per hour, the mean arousal index (AI) was 37 +/- 23 events per hour, and the mean minimum arterial oxygen saturation was 74 +/- 11%. Following multiple linear regression analyses of the clinical and polysomnography parameters, AI was the independent factor that correlated best with the baseline IPA+ (beta-coefficient, 0.386; p = 0.006). Following nasal CPAP treatment with a mean objective CPAP compliance of 3.9 +/- 1.9 h per night, there was a significant decrease in IPA+ from 15.1 +/- 12.2 U (at baseline) to 12.2 +/- 5.2 U (p < 0.001) and 9.8 +/- 4.3 U (p = 0.005), respectively, after 1 night and 3 months, whereas no significant change was noted among the control subjects. Using univariate analysis of variance to compare the changes in IPA+ between the two groups at 3 months with adjustment for the baseline value, nasal CPAP reduced IPA+ by 5.63 (SE, 1.85), whereas IPA+ increased in control subjects by 1.33 (SE, 1.27) [least-squared mean difference between groups, 3.34; 95% confidence interval, 0.42 to 6.26; p = 0.026].

CONCLUSIONS

OSAS, through repeated episodes of arousals, may lead to platelet activation, which can be reduced by nasal CPAP therapy.

Patient discomfort in polysomnography with esophageal pressure measurements

The reference method for measuring respiratory effort and for differentiating between obstructive and central apneas in the diagnosis of sleep-related breathing disorders is overnight monitoring of esophageal pressure. Despite this being the reference method, it is not widely used because it is considered invasive and uncomfortable for the patients. The aim of this study was to assess patient discomfort and insertion difficulty when using an esophageal catheter during polysomnography. We have performed a prospective questionnaire-based clinical study in 799 consecutive patients where polysomnography with an esophageal catheter was routinely performed in the diagnosis of sleep-related breathing disorders. The main outcome measures were the catheter-related discomfort experienced by the patient and difficulty of catheter insertion reported by the sleep technician. Ninety-six percent of the patients accepted the insertion of the catheter, and most of the patients considered it acceptable to sleep with the catheter. Correspondingly, in most of the patients, the catheter was easily inserted, and there were difficulties in only a few patients. Specifically, no complications or side effects were reported when using the catheter. To optimize the diagnosis of sleep-related breathing disorders, an esophageal sensor catheter can be used during polysomnography, without causing major patient discomfort.

Cerebrovascular disease and sleep

Sleep is a function of the brain and sleep affects brain function, contributing to cerebral pathology through a diversity of direct and indirect mechanisms. Sleep-disordered breathing (SDB) is a very common disorder and is the major sleep-related risk factor for cerebrovascular disease. Epidemiologic studies have shown a dose-response relationship between the severity of SDB and the odds ratio for development of systemic hypertension. Following stroke, both in the acute and chronic stages, patients have a high prevalence of SDB that reduces the potential for rehabilitation, further increases the risk of secondary stroke, and heightens mortality. There is proof that successful correction of SDB with noninvasive positive airway pressure ventilation lowers mean blood pressure. In patients with advanced SDB, altered cerebral evoked potentials are not corrected with applications of noninvasive ventilation, suggesting permanent cerebral structural damage. This is supported by reports of increased leukoaraiosis in patients with advanced SDB. Circadian changes during sleep may increase the risk of both cardiovascular and cerebrovascular accidents.

Continuous positive airway pressure therapy in sleep apnoea

Sleep apnoea is associated with increased mortality and morbidity. The treatment goal is to reduce the neurocognitive and cardiovascular sequelae. CPAP therapy in sleep apnoea is discussed in two parts in the article. The first part will consider CPAP therapy in the more common form of sleep apnoea (i.e. obstructive or mixed sleep apnoea) and the second part will consider CPAP therapy in central sleep apnoea. Alternative positive airway pressure modalities are discussed. CPAP therapy has been extensively studied and it remains the mainstay of treatment in obstructive sleep apnoea, as it is still the most consistently efficacious and safe option. However, its major disadvantage is that it does not confer a cure to this disorder and hence therapy is generally life long with its usual treatment compliance problems. As such, there are continuous improvement strategies. The role of CPAP therapy in central sleep apnoea is more limited. There has been increasing data on the beneficial effect of CPAP on central sleep apnoea/Cheyne-Stokes respiration in congestive heart failure. Evidence for CPAP therapy in sleep apnoea has evolved significantly over the last decade. However, more research and publication of large-scale long-term randomized trials of treatment in sleep apnoea to assess patient-orientated outcomes and preferences are necessary.

DAILY HEMODIALYSIS-SELECTED TOPICS: Sleep Apnea and Daytime Sleepiness in End-Stage Renal Disease

Sleep disorders are common in patients with end-stage renal disease (ESRD). The prevalence of sleep apnea is 10 times greater in patients with ESRD than in the general population. Although sleep apnea is not improved by conventional modes of dialysis, it is corrected by nocturnal hemodialysis, which provides a new and unique model to study its pathophysiology in this patient population. In addition to causing sleep disruption and impairment of daytime function, sleep apnea may also increase the cardiovascular morbidity and mortality that is commonly found in patients with ESRD. "Pathological" daytime sleepiness is found in 50% of patients with ESRD. Although its pathogenesis has been related both to sleep apnea and periodic limb movements, it has also been attributed to a variety of metabolic factors, including the severity of uremia. Further research is required to evaluate the impact of sleep disorders on the clinical outcome of patients with ESRD.

Erectile dysfunction in men with obstructive sleep apnea syndrome: a randomized study of the efficacy of sildenafil and continuous positive airway pressure

The aim of this study was to compare the efficacy of sildenafil and continuous positive airway pressure (CPAP) in men with erectile dysfunction (ED) and obstructive sleep apnea syndrome (OSAS). In all, 30 men were randomly treated for 12 weeks either with sildenafil 100 mg before intercourse (15 men) or CPAP during night time sleep (15 men). Under sildenafil, 97/180 (53.9%) of attempted intercourses were successful compared to 33/138 (23.9%) under CPAP. The mean IIEF (erectile function domain score) was 12.9 and 9.3 after sildenafil and CPAP treatment, respectively (P=0.007), compared to 7.9 and 7 at baseline. In all, 53.3% of patients were satisfied with sildenafil and 20% with CPAP for ED treatment (P=0.058). Although sildenafil was superior to CPAP, comorbidities and OSAS per se possibly resulted in a lower effectiveness of sildenafil compared to that in the general population of ED men. While about half of the patients were not satisfied even with the more effective treatment, we conclude that a combination of the two therapeutic tools or a different therapeutic mode should be studied further.

Recent advances in understanding the pathogenesis of obstructive sleep apnea

PURPOSE OF REVIEW

The pathogenesis of obstructive sleep apnea (OSA) is incompletely understood. Historically it was believed that patients with OSA have a small upper airway (often due to obesity) that is kept patent during wakefulness by the activity of upper airway dilating muscles. With the reduction in muscle tone at sleep onset, the airway collapses and causes apnea. While this appears to be the case for many patients with OSA, other patients show no major airway anatomic defects or minimal obesity.

RECENT FINDINGS

This has led to the concept that other factors such as unstable ventilatory control and changes in lung volume during sleep may be involved in the pathogenesis of OSA. Recently there have been several advances in our understanding of how these mechanisms are involved in OSA pathogenesis.

SUMMARY

A more complete understanding of apnea pathogenesis may improve therapeutic techniques and reduce the consequences of OSA.

Snoring, hypertension and Type 2 diabetes in obesity. Protection by physical activity

Sleep-related breathing disorders are recognized as major health problems in obesity. They are involved in both hypertension and Type 2 diabetes, through mechanisms possibly related to increased sympathetic tone. We studied the association of habitual snoring with diabetes, hypertension, weight cycling and physical activity in a large Italian database of treatment-seeking obese subjects. Clinical and behavioral data were assessed by standardized questionnaires. Consecutive data of 1890 obese patients were analyzed [average body mass index (BMI), 38.2 kg/m2, median age: 46 yr, 78% females], from 25 obesity Italian centers, with low prevalence of clinical manifestations of cardiovascular disease. Habitual snoring was reported in 56% of the cases, and was associated with day-time sleepiness. The prevalence increased with obesity class and waist circumference, and was positively associated with weight cycling and weight gain since the age of 20, and smoking. Regular physical activity had a protective effect. Snoring was associated with diabetes and hypertension at univariate analysis, but in multivariate analysis an independent effect was only observed for hypertension. After adjustment for age, gender and BMI, physical activity maintained an independent, protective effect on both snoring (odds ratio 0.65, 95% confidence interval 0.49-0.84; p=0.001), diabetes (0.50, 0.30-0.86; p=0.011) and hypertension (0.71, 0.53-0.95; p=0.023). We conclude that in treatment-seeking, obese subjects with low prevalence of cardiovascular disease, snoring independently increases the risk of hypertension, whereas physical activity exerts a protection on both snoring and complications. These data underline the importance of lifestyle interventions to limit the burden of obesity and associated diseases.

Pharmacotherapies for Obstructive Sleep Apnoea

Obstructive sleep apnoea (OSA) is common, causes considerable morbidity and probably contributes to mortality particularly through associated cardiovascular disease. The physical therapy of continuous positive airway pressure (CPAP) is extremely effective in the majority of patients but most patients would prefer an alternative. Intuitively, OSA should be amenable to pharmacotherapy. The upper airway of affected individuals can be narrowed but is patent during wakefulness. Collapse of the airway during sleep occurs when negative intra-luminal pressure generated by inspiratory effort exceeds the tone of the upper airway dilators. This mismatch may be in part due to respiratory drive instability but the state-dependent fall in drive to the airway dilator muscles is the biggest factor in most patients. Various drugs have been investigated as treatment for OSA. Acetazolamide, theophylline, nicotine, opioid antagonists and medroxyprogesterone have been used to increase respiratory drive. Clonidine has been tested with the aim of reducing rapid eye movement sleep when OSA is often most severe. Various antidepressants have been used to suppress rapid eye movement sleep and to preferentially activate the upper airway dilators. The drug trials have often been of poor design and none has included more than a few patients. Most of the drugs have been found to be ineffective and those that have worked for some patients (acetazolamide and protriptyline) have produced intolerable adverse effects. There have been recent advances in the understanding of the neurotransmitters involved in the control of sleep and the upper airway motor neurones, offering the possibility of novel approaches to the drug treatment of OSA for those patients who cannot tolerate or do not benefit from CPAP. It seems likely that a better understanding of the mechanisms of OSA in individual patients and tailoring of drug therapy will be the way forward.

Vascular reactivity to norepinephrine and acetylcholine after chronic intermittent hypoxia in mice

This study assessed the early vascular reactivity changes in mice after exposure to 14 days intermittent hypoxia (IH) with active or inactive sympathetic nervous system (SNS). Hindquarters of mice exposed to 14 days of IH, sham exposed mice or unhandled mice were perfused at constant flow with Krebs-Albumin (5%). Changes in perfusion pressure were assessed after injection of several doses of norepinephrine in anaesthetized mice (active SNS) or in euthanized mice (inactive SNS). Response to several doses of acetylcholine was recorded after precontraction of hindquarter vascular bed by methoxamine in euthanized mice. Vasoconstrictor response was increased after IH for high dose of NE (50 microg) in euthanized mice and for all doses of NE (2-10-50 microg) in anaesthetized mice, but no change in vasodilatation was observed. These findings suggest that 14 days of IH altered vascular reactivity of mice hindquarter in an early pattern. Vasoconstriction was enhanced, particularly with active SNS, while there was no dysfunction of endothelium-relaxation.

The prevalence of glaucoma in patients with sleep apnea syndrome: same as in the general population

PURPOSE

An association of glaucoma and sleep apnea syndrome (SAS) has been widely reported. We investigated the largest group of patients with SAS thus far to determine the prevalence of glaucoma among these patients.

DESIGN

Cross-sectional study.

METHODS

An institutional study.

STUDY POPULATION

A total of 228 patients with SAS.

OBSERVATION PROCEDURES

Sleep studies determined the respiratory disturbance index (RDI) during night sleep. Ocular examination included intraocular pressure (IOP) measurement, optic disk evaluation, and Humphrey visual field examination.

MAIN OUTCOME MEASURES

The SAS was diagnosed as an RDI > 10. The RDI was graded to determine the severity of SAS: mild (RDI, 10-19), moderate (RDI, 20-39), and severe (RDI > 40). Open-angle glaucoma was diagnosed when a glaucomatous visual field defect matched the optic disk changes, irrespective of IOP levels.

RESULTS

Nineteen participants had mild SAS (mean +/- standard deviation, RDI = 15 +/- 3), 129 had moderate SAS (RDI = 28 +/- 5), and 80 had severe SAS (RDI = 54 +/- 11). Open-angle glaucoma was found in five SAS subjects, a prevalence of 2% (95% confidence interval, 0.7% to 5%). There was no correlation between RDI and the presence of glaucoma (chi-square = 1.18; degrees of freedom = 2; P =.6) or between the RDI and the IOP (r = -0.067; P =.316).

CONCLUSION

The prevalence of glaucoma in SAS patients was similar to that in the general Caucasian population.

Plasma cytokine levels in patients with obstructive sleep apnea syndrome: a preliminary study

The levels of some pro- and anti-inflammatory cytokines [interleukin (IL)-1beta, tumor necrosis factor (TNF)-alpha, IL-6, IL-10, and transforming growth factor (TGF)-beta], were measured by enzyme-linked immunosorbent assay (ELISA) method in the plasma of patients affected by obstructive sleep apnea syndrome (OSAS) at 22:00 hours before polysomnographic recording and immediately after the first obstructive apnea causing an SaO2 below 85%. Significantly higher levels of TNF-alpha were found in OSAS patients assessed before polysomnography compared with the control group (P < 0.01). A slight but significant increase in the plasma levels of IL-6 was also present (P < 0.05). Conversely, a significant decrease in the plasma levels of IL-10 was evident at baseline in OSAS patients (P < 0.04). No significant difference emerged between the mean values of IL-1alpha and TGF-beta between OSAS patients and controls. The present data support a prevailing activation of the Th1-type cytokine pattern in OSAS patients, which is not associated with the severity and duration of OSAS. This can have important consequences for the outcome of OSAS patients, especially with regard to the increased risk for developing atherosclerosis and cardiovascular and cerebrovascular diseases. Immediately after the first obstructive apnea causing an SaO2 <85%, a significant variation was observed in the plasma levels of TNF-alpha in OSAS patients compared with those measured before the beginning of polysomnographic recording (P < 0.001). The role played by this further increase in TNF-alpha levels after the obstructive apnea in OSAS patients remains to be established in the light of the pathogenic mechanisms of this sleep disorder.

Prevalence of sleep-disordered breathing and sleep apnea in middle-aged urban Indian men

No data are available on the prevalence of sleep-disordered breathing (SDB) and obstructive sleep apnea-hypopnea syndrome (OSAHS) in Indians. We conducted a two-phase cross-sectional prevalence study for the same in healthy urban Indian males (35-65 years) coming to our hospital in Bombay for a routine health check. We also investigated its risk factors and evaluated the significance of the most commonly asked questions that best correlated with the presence of OSAHS. In the first phase, 658 subjects (94%) returned completed questionnaires regarding their sleep habits and associated medical conditions. In the second phase, 250 of these underwent an overnight home sleep study. The estimated prevalence of SDB (apnea-hypopnea index of 5 or more) was 19.5%, and that of OSAHS (SDB with daytime hypersomnolence) was 7.5%. Multiple stepwise logistic regression determined body mass index, neck girth, and history of diabetes mellitus as the principal covariates of SDB. The presence of snoring, nocturnal choking, unrefreshing sleep, recurrent awakening from sleep, daytime hypersomnolence, and daytime fatigue was each statistically significant for identifying patients with OSAHS. The higher prevalence of OSAHS in urban Indian men is striking and may have major public health implications in a developing country.

Obstructive Sleep Apnea in a Referral Population in India

There are few published studies of obstructive sleep apnea in the Asian subcontinent. The objectives were to describe the syndrome and evaluate the utility of computed tomography (CT) cephalometry in patients found to have obstructive sleep apnea (OSA) by polysomnography. This article reports on a retrospective case series in a referral population. A total of 880 patients (560 males and 320 females) were seen in a referral center in Hyderabad, South India, during the last 7 years. All patients with suspected obstructive sleep apnea were evaluated with 16-channel polysomnogram by overnight sleep study; 600 subjects (68%; 480 males and 120 females) underwent evaluation with CT cephalometry. Mean age was 51.4 +/- 9.5 years (standard deviation). The mean apnea-hypopnea index (AHI) was 27.93 +/- 3.8. The majority of patients had more than 10 AHI; mean percentage of sleep efficiency was 80.62 +/- 15.38; mean percentage of rapid eye movement (REM) sleep was 13.79 +/- 7.89; mean awake arterial oxygen saturation (SaO2) was 90%; mean sleep SaO2 was 84% +/- 4.4%; mean Epworth Sleepiness Scale (ESS) score was 12.3 +/- 2.8. The tongue base area (TBA) was found to be significantly associated with obstructive sleep apnea (OSA), with mean TBA 1032.8 +/- 427 mm2 compared with normal controls at 561.1 +/- 197.6 mm2 (p < 0.001). Mean gonion-gnathion-hyoid angle (Go-Gn-H) was 28.5 +/- 10.5 in OSA and 16 +/- 16.7 in controls; uvula area was 452.5 +/- 145.8 mm2 in OSA and 221.4 +/- 49.85 mm2 in controls; uvula diameter was 13.8 +/- 2.74 mm in OSA and 10.1 +/- 1.72 mm in controls. A total of 704 patients with OSA (80%) were found to be hypertensive, with daytime mean blood pressure of 160/100 +/- 8.5/4.8 mm Hg. Mean duration of reported hypertension was 2 years. The present study showed moderate to severe OSA in a majority of suspected cases referred for polysomnogram. Mild disease was seen in 20.45% of patients (n = 180). On CT cephalometry, the TBA correlated significantly with OSA; hypertension is common in patients with OSA.

Obstructive sleep apnoea syndrome impairs insulin sensitivity independently of anthropometric variables

OBJECTIVES

Obstructive sleep apnoea syndrome (OSAS) is strongly associated with obesity and characterized by endocrine and metabolic changes including impairment of insulin sensitivity. The aim of this study was to further clarify the insulin dynamics and glucose metabolism in this condition.

DESIGN, PATIENTS AND MEASUREMENTS

We studied 30 obese patients with OSAS [OSA, 21 males, 9 females; age, mean +/- SEM: 53.1 +/- 1.7 years; body mass index (BMI): 38.6 +/- 1.1 kg/m2; waist-to-hip ratio (WHR): 0.99 +/- 0.07; Apnoea/Hypopnoea Index (AHI): 40.5 +/- 5.8 events/h of sleep] by means of overnight polysomnography and oral glucose tolerance testing. Mathematical models were used to assess: (i) whole-body insulin sensitivity index (ISI composite); (ii) hepatic ISI; (iii) the first phase of insulin secretion (DeltaI30'-0'/DeltaG30'-0'). Results were compared with those in 27 weight-matched patients with simple obesity (OB, 12 males, 15 females; age: 48.1 +/- 2.8 years, BMI: 38.5 +/- 1.4 kg/m2, WHR: 0.94 +/- 0.09; AHI: 2.15 +/- 0.5 events/h of sleep) and with 20 normal subjects (NS, 15 females; 5 males, age: 40.4 +/- 2.9 years; BMI: 22.2 +/- 0.6 kg/m2).

RESULTS

ISI composite value was significantly lower in OSAS (1.71 +/- 1.41) than in OB (3.08 +/- 0.27) and in NS (6.1 +/- 0.4) even after age-, BMI- and WHR-adjustment. Similarly, hepatic ISI was significantly different among the three groups (OB = 0.25 +/- 0.02, OSAS = 0.16 +/- 0.014 and NS = 0.55 +/- 0.04). Sex did not affect ISI indices. Insulin secretion estimates were not significantly different among the three groups.

DISCUSSION

Obese patients with obstructive sleep apnoea syndrome are more insulin resistant than patients with simple obesity independently of the degree and distribution of adiposity. The worsening in insulin sensitivity in obstructive sleep apnoea syndrome patients could reflect the hypoxic state and would account for the increased vascular risk in this condition.

Nocturnal oxygen desaturation correlates with the severity of coronary atherosclerosis in coronary artery disease

STUDY OBJECTIVES

It has been suggested that sleep-disordered breathing (SDB) is a risk factor for ischemic heart disease, and may be associated with increased morbidity and mortality due to cardiovascular disease. The aim of this study was to examine the relation between nocturnal oxygen desaturation (NOD) due to SDB and the Gensini score, which is given to define the severity of coronary atherosclerosis, based on coronary angiograms findings, in patients with coronary artery disease.

DESIGN

We examined the NOD index (ODI) (desaturation of > 3%/events per hour) using pulse oximetry in 59 consecutive patients with coronary artery disease (ejection fraction, > 40%) that was diagnosed by coronary angiography, 30 patients with angina pectoris and 29 patients with old myocardial infarction. The Gensini score was calculated for each patient from the coronary arteriogram. The patients were classified into the following three groups according to the severity of oxygen desaturation: ODI of < 5 events per hour (group N; 16 patients); ODI of > or = 5 but < 15 events per hour (group A; 27 patients); and ODI of > or = 15 events per hour (group B; 16 patients). The groups then were examined for the relation between the ODI and the Gensini score.

RESULTS

Of the total number of patients, 72.9% had a nocturnal ODI of more than five events per hour. The Gensini score was significantly higher in groups A and B than in group N, and showed a significant positive correlation with the ODI (R = 0.45; p = 0.01) in all patients. Multiple regression analysis showed that the ODI was the most significant, independent determinant of the Gensini score among the coronary risk factors tested, and that it explained 13.4% of the variance.

CONCLUSION

These findings suggest that NOD due to SDB may be an important contributor to coronary atherosclerosis in the patients with cardiovascular disease.

Within-breath control of genioglossal muscle activation in humans: effect of sleep-wake state

Pharyngeal dilator muscles are clearly important in the pathogenesis of obstructive sleep apnoea syndrome. Substantial data support the role of a local negative pressure reflex in modifying genioglossal activation across inspiration during wakefulness. Using a model of passive negative pressure ventilation, we have previously reported a tight relationship between varying intrapharyngeal negative pressures and genioglossal muscle activation (GGEMG) during wakefulness. In this study, we used this model to examine the slope of the relationship between epiglottic pressure (Pepi) and GGEMG, during stable NREM sleep and the transition from wakefulness to sleep. We found that there was a constant relationship between negative epiglottic pressure and GGEMG during both basal breathing (BB) and negative pressure ventilation (NPV) during wakefulness (slope GGEMG/Pepi 1.86+/-0.3 vs. 1.79+/-0.3 arbitrary units (a.u.) cmH2O(-1)). However, while this relationship remained stable during NREM sleep during BB, it was markedly reduced during NPV during sleep (2.27+/-0.4 vs. 0.58+/-0.1 a.u. cmH2O(-1)). This was associated with a markedly higher pharyngeal airflow resistance during sleep during NPV. At the transition from wakefulness to sleep there was also a greater reduction in peak GGEMG seen during NPV than during BB. These data suggest that while the negative pressure reflex is able to maintain GGEMG during passive NPV during wakefulness, this reflex is unable to do so during sleep. The loss of this protective mechanism during sleep suggests that an airway dependent upon such mechanisms (as in the patient with sleep apnoea) will be prone to collapse during sleep.

Left ventricular hypertrophy is a common echocardiographic abnormality in severe obstructive sleep apnea and reverses with nasal continuous positive airway pressure

STUDY OBJECTIVES

To determine cardiac structural abnormalities by echocardiography in subjects with severe obstructive sleep apnea (OSA), and to determine the long-term effects of nasal continuous positive airway pressure (CPAP) on such abnormalities.

DESIGN

Polysomnography was conducted on oximetry-screened patients who showed a desaturation index > 40/h and > or = 20% cumulative time spent below 90%. From these, 25 patients with severe OSA but without daytime hypoxemia underwent echocardiography prior to, then 1 month and 6 months following initiation of CPAP treatment.

SETTING

Outpatient sleep disorders center.

RESULTS

Of the 25 patients, 13 patients (52%) had hypertension by history or on physical examination. Baseline echocardiograms showed that severe OSA was associated with numerous cardiovascular abnormalities, including left ventricular hypertrophy (LVH) [88%], left atrial enlargement (LAE) [64%], right atrial enlargement (RAE) [48%], and right ventricular hypertrophy (16%). In all patients (intent to treat) as well as those patients compliant with CPAP therapy (84% > 3 h nightly), there was a significant reduction in LVH after 6 months of CPAP therapy as measured by interventricular septal distance (baseline diastolic mean, 13.0 mm; 6-month mean after CPAP, 12.3 mm; p < 0.02). RAE and LAE were unchanged after CPAP therapy.

CONCLUSIONS

LVH was present in high frequency in subjects with severe OSA and regressed after 6 months of nasal CPAP therapy.

[Cardiovascular consequences of obstructive sleep apnea syndrome]

PURPOSE

This article is an update of past and current data on the relationship between obstructive sleep apnea syndrome and cardiovascular diseases.

CURRENT KNOWLEDGE AND KEY POINTS

Obstructive sleep apnea syndrome is a common, but under-recognised, condition and should not be considered simplistically as the association of snoring and obesity. It may be suspected by the clinical history but a definite diagnosis requires the practice of polysomnography. Numerous studies have found a significant relationship between the presence of obstructive sleep apnea syndrome and the occurrence of cardiovascular events. Nonetheless, a definite causal relationship has only been established for the occurrence of hypertension. There are multiple immediate and delayed cardiovascular responses to the apneic events and thus there are many possible physiopathological mechanisms to explain the association of obstructive sleep apnea and cardiac and vascular events, the primary one being sympathetic hyperactivity. The prognosis of obstructive sleep apnea syndrome is closely related to the incidence of cardiovascular events. FUTURE PROSPECTS AND PROJECS: The existence of an independent relationship between obstructive sleep apnea syndrome and atherosclerosis is not yet demonstrated. The beneficial effects of continuous positive airway pressure, the treatment of choice for this condition, on the incidence of cardiovascular diseases remains to be confirmed although recent studies suggest that correct treatment of obstructive sleep apnea syndrome by continuous positive airway pressure may reduce the cardiovascular risk and in particular that of hypertension.

Phenotypic and functional characterization of blood gammadelta T cells in sleep apnea

Hypoxia-induced lymphocyte dysfunction may be implicated in endothelial cell damage in obstructive sleep apnea (OSA) syndrome. gammadelta T cells' unique migration, cytotoxic features, and accumulation in atherosclerotic plaques are considered critical in cardiovascular disorders. We characterized the phenotype, cytokine profile, adhesion properties, and cytotoxicity of gammadelta T cells in patients with OSA and control subjects. The following is a summary of our major findings regarding OSA gammadelta T cells: (1) a significant increase in the expression of the inhibitory natural killer B1 receptors was found; (2) the intracellular content of proinflammatory cytokines tumor necrosis factor (TNF)-alpha and interleukin-8 was increased, and the content of the antiinflammatory cytokine interleukin-10 was decreased; (3) gammadelta T cells of patients with OSA adhered significantly more avidly to nonactivated endothelial cells in culture than those of control subjects; (4) L-selectin expression was higher; (5) anti-E/P-selectin antibodies and anti-TNF-alpha antibodies decreased the adhesion index of OSA gammadelta T lymphocytes/endothelial cells but not of control subjects; and (6) cytotoxicity of OSA gammadelta T lymphocytes against endothelial cells in culture was 2.5-fold higher than that of control subjects and could be prevented by pretreatment with anti-TNF-alpha. Collectively these data implicate gammadelta T lymphocyte function in atherogenic sequelae in OSA.

Nitric oxide (NO) and obstructive sleep apnea (OSA)

Nitric oxide (NO) and obstructive sleep apnea are inseparable. Obstructive sleep apnea could be described as the intermittent failure to transport the full complement of nasal NO to the lung with each breath. There NO matches perfusion to ventilation. NO is utilized by the efferent pathways that control the unequal, inspiratory battle between the pharyngeal dilators and the closing negative pressures induced by the thoracic musculature. Recurrent cortical arousals are a major short-term complication, and the return to sleep after each arousal uses NO. The long-term complications, namely hypertension, myocardial infarction, and stroke, might be due to the repeated temporary dearth of NO in the tissues, secondary to a lack of oxygen, one of NO's two essential substrates.

Obstructive sleep apnea and cardiovascular disease

Obstructive sleep apnea (OSA) is a common disorder associated with an increased risk of cardiovascular disease and stroke. As it is strongly associated with known cardiovascular risk factors, including obesity, insulin resistance, and dyslipidemia, OSA is an independent risk factor for hypertension and has also been implicated in the pathogenesis of congestive cardiac failure, pulmonary hypertension, arrhythmias, and atherosclerosis. Obesity is strongly linked to an increased risk of OSA, and weight loss can reduce the severity of OSA. The current standard treatment for OSA-nasal continuous positive airway pressure (CPAP)-eliminates apnea and the ensuing acute hemodynamic changes during sleep. Long-term CPAP treatment studies have shown a reduction in nocturnal cardiac ischemic episodes and improvements in daytime blood pressure levels and left ventricular function. Despite the availability of effective therapy, OSA remains an underdiagnosed and undertreated condition. A lack of physician awareness is one of the primary reasons for this deficit in diagnosis and treatment.

Comparison of the NovaSom QSG™, a new sleep apnea home-diagnostic system, and polysomnography

BACKGROUND

Obstructive sleep apnea (OSA) is a serious, common, and underdiagnosed disorder that challenges health care resources. While polysomnography (PSG) represents the standard diagnostic test for OSA, portable devices provide an alternative diagnostic tool when issues of cost, time, geographic availability, or other constraints pose impediments to in-lab testing. This study compares the NovaSom QSG, a new sleep apnea home diagnostic system, to PSG both in the laboratory and in the home.

METHODS

Fifty-one consecutive adults referred to the sleep lab for suspicion of OSA underwent one night of in-lab, simultaneous recording of PSG and NovaSom QSG in addition to using the NovaSom QSG at home for three nights. Two separate comparisons were made using the apnea-hypopnea index (AHI): in-lab PSG to in-lab NovaSom QSG and in-lab PSG to home NovaSom QSG.

RESULTS

Using a clinical cut-off of AHI=15, the sensitivity and specificity of the in-lab NovaSom QSG vs. PSG were 95% and 91%, respectively. For home NovaSom QSG vs. in-lab PSG, the sensitivity was 91% and specificity was 83%. The intra-class correlation coefficient for the agreement between three separate nights of NovaSom QSG home data was 0.88.

CONCLUSIONS

In a patient population suspected of having OSA, the NovaSom QSG demonstrated acceptable sensitivity and specificity both in the lab and self-administered in the home, when compared to PSG.