Relation of sleep-disordered breathing to cardiovascular disease risk factors: the Sleep Heart Health Study

Demographics and diagnosis of obstructive sleep apnea

This article reviews the terminology of obstructive sleep apnea and the associated diagnostic tests and provides an overview of the risk factors for this chronic condition. Sleep apnea affects 2% to 4% of middle-aged working adults in the general population, however, a considerable number of affected individuals remain undiagnosed. Patients with the disease may be at a higher risk for adverse perioperative outcomes. Knowledge of factors associated with an increased risk of obstructive sleep apnea is vital to the perioperative assessment and anesthetic plan.

Association of sleep apnea and type II diabetes: a population-based study

RATIONALE

Cross-sectional association has been reported between sleep-disordered breathing (SDB) and insulin resistance, but no prospective studies have been performed to determine whether SDB is causal in the development of diabetes.

OBJECTIVES

The purpose of our study was to investigate the prevalence and incidence of type II diabetes in subjects with SDB and whether an independent relationship exists between them.

METHODS

A cross-sectional and longitudinal analysis was performed in 1,387 participants of the Wisconsin Sleep Cohort. Full polysomnography was used to characterize SDB. Diabetes was defined in two ways: (1) physician-diagnosis alone or (2) for those with glucose measurements, either fasting glucose > or = 126 mg/dl or physician diagnosis.

MEASUREMENTS AND MAIN RESULTS

There was a greater prevalence of diabetes in subjects with increasing levels of SDB. A total of 14.7% of subjects with an apnea-hypopnea index (AHI) of 15 or more had a diagnosis of diabetes compared with 2.8% of subjects with an AHI of less than 5. The odds ratio for having a physician diagnoses of diabetes mellitus with an AHI of 15 or greater versus an AHI of less than 5 was 2.30 (95% confidence interval, 1.28-4.11; p = 0.005) after adjustment for age, sex, and body habitus. The odds ratio for developing diabetes mellitus within 4 yr with an AHI of 15 or more compared with an AHI of less than 5 was 1.62 (95% confidence interval, 0.67-3.65; p = 0.24) when adjusting for age, sex, and body habitus.

CONCLUSIONS

Diabetes is more prevalent in SDB and this relationship is independent of other risk factors. However, it is not clear that SDB is causal in the development of diabetes.

Heart failure and sleep apnoea: to sleep perchance to dream

Heart failure and sleep apnoea are major health problems with an increasingly recognized association; evidence suggests that sleep apnoea may play a role in the progression of heart failure. However, confounding factors such as obesity, hypertension and coronary heart disease make this relationship uncertain and an independent correlation remains unproven. Diagnosis of sleep apnoea is suboptimal, as it is often asymptomatic and polysomnography is expensive and time-consuming. A simple and reliable screening protocol is required. All heart failure patients should be considered to be at high risk of sleep apnoea, as this association might be linked to adverse outcome. Continuous positive airway pressure has shown some beneficial effects, but long-term outcome and improvement in survival remains to be demonstrated. Despite recent advances in the understanding of the complex relationship between heart failure and sleep apnoea, there are a number of areas requiring further investigation, which may have important implications for the management and prognosis of a significant number of patients.

Determinants Affecting Health-Care Utilization in Obstructive Sleep Apnea Syndrome Patients

STUDY OBJECTIVE

To investigate determinants of health-care utilization in patients with obstructive sleep apnea syndrome (OSAS).

DESIGN

Case-control prospective study with OSAS patients and a control group. We compared 218 patients with OSAS to those of age-, gender-, geographically-, and family physician-matched control subjects from the general population, matched 1:1 (chi2 = 0.999).

PARTICIPANTS

All participants were members of Clalit Health Care Services, a health maintenance organization in the southern region of Israel. All OSAS patients underwent nocturnal polysomnography studies. Indexes of health-care utilization 2 years prior to the polysomnography were analyzed.

MEASUREMENTS AND RESULTS

Health-care utilization was 1.7-fold higher (p < 0.001) in the OSAS patients due to more hospitalization days (p < 0.001), consultations (p < 0.001), and cost for drugs (p < 0.05), particularly those for the cardiovascular system. In comparison to men, women consumed significantly more health-care resources (p < 0.001). OSAS patients < or = 65 of age years consumed 2.2-fold more health-care resources than control subjects (p < 0.001). Polysomnography findings and OSAS severity and body mass index (BMI) did not predict health-care utilization, using multivariate logistic regression analysis. Age > 65 (odds ratio [OR], 2.2; p < 0.04) and female gender (OR, 2.0; p < 0.05) were the leading elements predicting the most costly OSAS patients. Arbitrarily dividing the OSAS group by cost of health-care utilization, the upper 25% (n = 55) of patients who were the "most costly" consumed sevenfold more health-care resources than the lower 75% of the patients. This was due to higher comorbidity, ie, 10 to 30% more hypertension, ischemic heart disease, diabetes mellitus, and pulmonary disease.

CONCLUSIONS

OSAS patients are heavy users of health-care resources. Age > 65 years and female gender were the leading elements predicting the most costly OSAS patients, and not necessarily patients with a high BMI and classic OSAS severity indexes.

Intermittent hypoxia induces hyperlipidemia in lean mice

Obstructive sleep apnea, a syndrome leading to recurrent intermittent hypoxia (IH), has been associated previously with hypercholesterolemia, independent of underlying obesity. We examined the effects of experimentally induced IH on serum lipid levels and pathways of lipid metabolism in the absence and presence of obesity. Lean C57BL/6J mice and leptin-deficient obese C57BL/6J-Lep(ob) mice were exposed to IH for five days to determine changes in serum lipid profile, liver lipid content, and expression of key hepatic genes of lipid metabolism. In lean mice, exposure to IH increased fasting serum levels of total cholesterol, high-density lipoprotein (HDL) cholesterol, phospholipids (PLs), and triglycerides (TGs), as well as liver TG content. These changes were not observed in obese mice, which had hyperlipidemia and fatty liver at baseline. In lean mice, IH increased sterol regulatory element binding protein 1 (SREBP-1) levels in the liver, increased mRNA and protein levels of stearoyl-coenzyme A desaturase 1 (SCD-1), an important gene of TG and PL biosynthesis controlled by SREBP-1, and increased monounsaturated fatty acid content in serum, which indicated augmented SCD-1 activity. In addition, in lean mice, IH decreased protein levels of scavenger receptor B1, regulating uptake of cholesterol esters and HDL by the liver. We conclude that exposure to IH for five days increases serum cholesterol and PL levels, upregulates pathways of TG and PL biosynthesis, and inhibits pathways of cholesterol uptake in the liver in the lean state but does not exacerbate the pre-existing hyperlipidemia and metabolic disturbances in leptin-deficient obesity.

Sleep symptoms and clinical markers of illness in patients with heart failure

The purpose of this study was to survey patients with heart failure (HF) for sleep symptoms using a standardized questionnaire and correlate symptoms with conventional markers of clinical status. A self-report paper questionnaire was offered to patients presenting to a tertiary care HF clinic. Symptoms were grouped according to "risk" categories and correlated with routine clinical information. One hundred six (52.7% of 201 with all data) respondents had a high pretest probability for sleep apnea syndrome. Sixty three (31.3%) reported symptoms suggesting the presence of chronic insomnia; seven (3.5%) and eight (4%) reported symptoms of narcolepsy and restless legs syndrome, respectively. High-risk respondents for sleep apnea had a higher body mass index (p<0.001), were younger (p<0.05), and had a higher ejection fraction (p<0.05). The odds ratio (confidence interval) for paroxysmal nocturnal dyspnea (PND) to a complaint of sleepiness was 1.99 (1.1-3.6) and to a complaint of insomnia was 3.5 (1.8-6.5). In men, complaints of sleepiness in patients with PND were correlated, 4.47 (1.9-10.3), as was a correlation to high pretest probability for sleep apnea, 2.47 (1.1-5.5). There were no correlation of New York Heart Association status classification to high risk for sleep apnea, but a complaint of insomnia tended to occur with worsening functional status (p<0.05). There was only modest correlation of self-reported symptoms as elicited by a questionnaire and risk for sleep disorders with common clinical assessments for HF. Such collection of symptoms might be useful in establishing guidelines for routine sleep testing or as an adjunct to clinical trials.

A longitudinal evaluation of sleep and breathing in the first year after cervical spinal cord injury

OBJECTIVES

To establish the incidence of sleep disordered breathing (SDB) after acute tetraplegia and to determine the relation between the Apnea-Hypopnea Index (AHI) score and the previously postulated predictors of SDB in tetraplegia.

DESIGN

Inception cohort. We performed full polysomnography immediately after acute tetraplegia and at 2, 4, 13, 26, and 52 weeks postinjury. Spirometry, maximum inspiratory and expiratory pressures, medication usage, and neck and abdominal girth were also assessed. Preinjury SDB was estimated using the multivariate apnea prediction equation.

SETTING

Acute care, subacute care, and community.

PARTICIPANTS

Consecutive sample with acute tetraplegia. Thirty subjects (25 men) were initially included. Thirteen completed 12 months of follow-up.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

SDB (AHI score >10 events/h) and respiratory function.

RESULTS

Three subjects (10%; 95% confidence interval [CI], 2%-28%) had probable SDB before injury. In the first 48 hours after injury, no subject had SDB. At 2 weeks, 60% (95% CI, 26%-88%) had SDB; at 4 weeks, 62% (95% CI, 38%-82%); at 13 weeks, 83% (95% CI, 61%-95%); at 26 weeks, 68% (95% CI, 44%-88%); and at 52 weeks, 62% (95% CI, 32%-86%). No consistent relation was found between the previously postulated predictors and SDB.

CONCLUSIONS

SDB is highly prevalent within 4 weeks of acute tetraplegia.

Prevalence and Comorbidity of Insomnia and Effect on Functioning in Elderly Populations

A good night's sleep is often more elusive as we age, because the prevalence of insomnia in older people is high. Insufficient sleep can have important effects on daytime function by increasing the need to nap, reducing cognitive ability including attention and memory, slowing response time, adversely affecting relationships with friends and family, and contributing to a general sense of being unwell. However, rather than aging per se, circadian rhythm shifts, primary sleep disorders, comorbid medical/psychiatric illnesses, and medication use cause sleep difficulties in older people, which psychosocial factors may also affect. Clinicians should ask elderly patients about satisfaction with sleep. Any sleep complaints warrant careful evaluation of contributing factors and appropriate treatment.

Repetitive hypoxia increases lipid loading in human macrophages-a potentially atherogenic effect

Obstructive sleep apnea (OSA) is characterized by repetitive episodes of hypoxia and is associated with an increase in cardiovascular disease. We, therefore, investigated the effect of repetitive hypoxia on two key early events in atherogenesis; lipid loading in foam cells and monocyte adhesion to endothelial cells. Human macrophages were loaded with acetylated low-density lipoproteins. During lipid loading, the cells were exposed to 30 min cycles of 2%/21% oxygen or control (room air, 5% CO(2) incubator). Human umbilical vein endothelial cells (HUVECs) were also exposed to 30 min cycles of repetitive hypoxia or control conditions and monocyte adhesion measured. Cell adhesion molecules E-selectin, ICAM-1 and VCAM-1 were measured by ELISA. Repetitive hypoxia increased cholesteryl ester uptake by macrophages (127+/-5% compared to controls; p=0.003). By contrast, monocyte adhesion to HUVECs and cell adhesion molecule expression were unchanged by exposure to repetitive hypoxia, compared to controls (p >0.1). Repetitive hypoxia, at levels relevant to tissues such as the arterial wall, enhances lipid uptake into human macrophages. This may contribute to accelerated atherosclerosis in OSA patients.

Sleep apnea in a high risk population: a study of Veterans Health Administration beneficiaries

BACKGROUND AND PURPOSE

In the present study we attempt to determine the prevalence of International Classification of Disease-ninth revision, Clinical Modification (ICD-9 CM) coded sleep apnea with cardiovascular and metabolic co-morbidities in Veterans Health Administration (VHA) beneficiaries.

PATIENTS AND METHODS

Using VHA administrative databases, we gathered available medical information on more than 4 million veterans using the VHA during the period between 1998 and 2001. We identified database entries for codes indicating sleep apnea using the ninth revision of the Clinical Modification of the International Classification of Diseases (ICD-9 CM); and tabulated demographic data including age, gender, ethnicity, and cardiovascular and metabolic co-morbidities.

RESULTS

We found 118,105 unique cases (out of 4,060,504) with sleep apnea ICD-9 CM codes (prevalence of 2.91%). Mean age at diagnosis was 57.6 with more than 38% older than 65 years. Comorbid diagnoses in this group included hypertension (60.1%), obesity (30.5%), diabetes mellitus (32.9%), cardiovascular disease (including MI and angina) (27.6%), heart failure (13.5%), and cerebrovascular accident (including Transient Ischemic Attack (TIA)) (5.7%).

CONCLUSIONS

We found a high prevalence of diagnosed sleep apnea among VHA beneficiaries. Additionally, cardiovascular and metabolic conditions were common in these patients.

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.

Linkage of serum leptin levels in families with sleep apnea

OBJECTIVE

To identify regions on the genome linked to plasma leptin levels.

DESIGN

Full genome scan with 402 microsatellite markers, spaced approximately 10 cM apart. Data were analyzed using the Haseman-Elston regression linkage analysis.

SUBJECTS

A total of 160 sibling pairs from 59 predominantly African American, obese families recruited to participate in a genetic-epidemiological study of obstructive sleep apnea.

MEASUREMENTS

Serum leptin levels adjusted for age, sex, race and body mass index (BMI).

RESULTS

Suggestive linkage peaks were observed on chromosomes 2 (P=0.00170; marker D2S1384), 3 (P=0.00007; marker D3S3034), 4 (P=0.00020; marker D4S1652) and 21 (P=0.00053; marker D21s1411).

CONCLUSION

The peak on chromosome 3 is near the gene for glycogensynthase kinase 2 beta, an important factor in glucose homeostasis. Linkage was generally stronger after BMI adjustment, suggesting the potential influence of a number of metabolic pathways on leptin levels other than those that directly determine obesity levels. The evidence of linkage for leptin levels is consistent with prior linkage analyses for cholesterol, hypertension and other metabolic phenotypes.

Gender differences in obstructive sleep apnea syndrome: a clinical study of 1166 patients

The objective of this study was to compare the frequency of some sociocultural, clinical, and anthropometric data between men and women in a sample of 1745 patients referred to a Sleep Unit for symptoms of obstructive sleep apnea (OSA). A standardized questionnaire was administered and anthropometric data were measured. Patients underwent a polysomnography (during a night or a nap) or an overnight home cardiorespiratory polygraphy. A total of 1166 patients (male/female ratio 4.9:1) fulfilled criteria of OSA (apnea-hypopnea index > or = 10). Women were employed, habitual drivers or workers at risk occupations in a lower percentage than men. Women came to the clinical interview accompanied by their partner less frequently than men. The frequency of snoring and daytime hypersomnolence was similar in both genders, although witnessed apneas were more frequent in males. Fatigue, morning headaches, insomnia, depression and use of sedatives were more frequent in women than in men. Women were older than men, more obese (although with an obesity pattern less centrally distributed), and referred hypertension more frequently. It is concluded that it is likely that women with OSA may be underdiagnosed due to circumstances related to the family lifestyle and sociocultural factors in addition to different OSA clinical expression.

A semiparametric method for analyzing matched case-control family studies with a continuous outcome and proband sampling

We consider matched case-control familial studies which match a group of patients, called "case probands," with a group of disease-free subjects, called "control probands," using a set of family-level matching variables. Family members of each proband are then recruited into the study. Of interest here is the familial aggregation of the response variable and the effects of subject-specific covariates on the response. We propose an estimating equation approach to jointly estimate the main effects and intrafamilial correlations for matched family studies with a continuous outcome. Only knowledge of the first two joint moments of the response variable is required. The induced estimators for the main effects and intrafamilial correlations are consistent and asymptotically normally distributed. We apply the proposed method to sleep apnea data. A simulation study demonstrates the usefulness of our approach.

Risk factors associated with habitual snoring and sleep-disordered breathing in a multi-ethnic Asian population: a population-based study

INTRODUCTION

There is scant data on the risk factors of sleep-disordered breathing (SDB) in the general population in Asian countries.

METHODS

Cross-sectional survey of a random population sample of 2298 adults aged 20-75 years, stratified by gender, ethnicity (Chinese, Malay and Indian) and age. An interviewer-administered questionnaire was used to elicit responses to questions on daytime somnolence and nocturnal events. Three categories of SDB were defined for analysis: habitual snoring; apnoeic snoring (SDB I); and apnoeic snoring or snoring with diurnal hypersomnia (SDB II).

RESULTS

Snoring was reported by 201 persons (6.8%), SDB-I in 44 (1.9%) and SDB-II in 112 (4.9%) in the sample. The adjusted odds ratio (95% C.I.) of association with snoring were: male gender, 3.79 (2.69-5.33); older age (>60 years old), 2.15 (1.41-3.29); Indian versus Chinese, 1.54 (1.05-2.25); family history, 2.21 (1.56-3.12); obesity (BMI>30), 2.64 (1.62-4.30); neck circumference (>40 cm), 2.57 (1.59-4.11); and cigarette smoking, 2.05 (1.21-3.45). The risk factors for SDB were similar to that of snoring.

CONCLUSION

Population risk factors associated with habitual snoring and SDB in Singapore are largely similar to those reported in other populations. Differential risks underscore the importance of ethnicity in determining the burden of SDB.

Sleep apnea: a model for studying cytokines, sleep, and sleep disruption

Obstructive sleep apnea (OSA) is a highly prevalent sleep disorder, characterized by repeated disruptions of breathing during sleep. The sleep fragmentation and accompanying hypoxemia lead to many negative consequences including cardiac arrhythmias, nocturnal hypertension, confusion, cognitive impairment, daytime sleepiness, as well as depressive symptoms. From the perspective of psychoneuroimmunology (PNI), OSA holds promise as a model for studying sleep and cytokines because of its many relevant characteristics, including neuroimmune interactions, mood changes, and behaviors that directly affect the course of the disorder. In this minireview we briefly summarize the existing literature on cytokines and sleep and then discuss work on cytokines and OSA. We believe that the study of OSA presents researchers with an excellent opportunity to tease apart the many complex and interwoven components of sleep that are relevant to PNI.

Obstructive sleep apnoea and stroke

Many patients with stroke have concomitant sleep apnoea, which can affect recovery potential. Although stroke can lead to the development of sleep-disordered breathing, the current evidence suggests that sleep-disordered breathing may function as a risk factor for stroke. In this review, we focus on the association between obstructive sleep apnoea and stroke reviewing both the epidemiological data with respect to causation and the biological data, which explores pathogenesis. There is convincing evidence to believe that sleep apnoea is a modifiable risk factor for stroke; however, prospective studies are needed to establish the cause-and-effect relationship.

Obstructive sleep apnea presenting as pseudopheochromocytoma: a case report

Sudden arousal from sleep causes a transient surge in sympathetic nervous activity. Repeated arousals, as occur in obstructive sleep apnea (OSA), are well documented to cause a more prolonged sympathetic overactivity and consequent elevations in 24-h urinary catecholamine levels. We describe here a series of five patients, each presenting with a clinical and biochemical picture indistinguishable from that of pheochromocytoma. Thorough investigations have failed to find catecholamine-secreting tumor in any of these subjects, but all have been diagnosed with OSA. Primary treatment of OSA with nasal continuous positive airways pressure has led to normalization of systemic blood pressure and urinary catecholamines. Pseudopheochromocytoma is therefore a rare, but treatable, presentation of obstructive sleep apnea.

Two case study reports of sleep apnoea in patients with paraplegia

STUDY DESIGN

Case studies of sleep apnoea occurring in two patients with paraplegia.

OBJECTIVE

To raise awareness of sleep apnoea in paraplegia.

SETTING

Belfast, Northern Ireland.

CASE REPORT

We report two patients with paraplegia, one who was having apparent episodes of loss of consciousness and the other daytime somnolence, who were found to have sleep apnoea. The first patient had been medically investigated extensively and a diagnosis of epilepsy was being considered. A joint consultation with the respective partners in each case revealed periods of night-time apnoea and led to sleep study investigations.

CONCLUSION

Sleep apnoea is a treatable condition that can occur in patients with paraplegia who are not necessarily obese. Once diagnosed, resolution of symptoms can be rapid and can result in improved quality of life for patients.

Whole genome scan for obstructive sleep apnea and obesity in African-American families

Obstructive sleep apnea (OSA) is a common, chronic disease associated with obesity. OSA and obesity are both prevalent in African Americans, who are also at increased risk for secondary complications. To identify susceptibility loci for OSA, we undertook a 9-centimorgans genome scan in 59 African-American pedigrees ascertained on the basis of either an affected individual with laboratory-confirmed disease or a proband who was a neighborhood control subject. Variance component linkage analysis was performed for the quantitative phenotypes apnea-hypopnea index (AHI) and body mass index. A candidate region on chromosome 8q (logarithm of odds [LOD] = 1.29, p = 0.006) gave the only evidence for linkage to the AHI. Body mass index was linked to multiple regions, most significantly to markers on chromosome 4q (LOD = 2.63, p = 0.0006) and 8q (LOD = 2.56, p = 0.0007). Evidence of linkage to the AHI was only slightly reduced after adjustment for body mass index. After adjustment for the AHI, some of the primary linkages to body mass index were greatly reduced whereas others remained suggestive. Our results suggest that there are both shared and unshared genetic factors underlying susceptibility to OSA and obesity, and that the genetic determinants of obesity in this population may be modulated by apnea severity.

White Coat Hypertension in Patients With Obstructive Sleep Apnea-Hypopnea Syndrome

BACKGROUND

The strength of the association between obstructive sleep apnea-hypopnea syndrome (OSAHS) and systemic hypertension could be affected by methodologic problems in the definition of hypertension.

STUDY OBJECTIVES

To determine the frequency of white coat hypertension (WCH) in patients with OSAHS, and to analyze the characteristics of patients with OSASH and WCH.

PATIENTS AND INTERVENTIONS

Ninety-nine consecutive patients with OSAHS and 20 healthy control subjects were included into the study. Twenty-four-hour ambulatory BP monitoring (ABPM) and urinary catecholamines were determined simultaneously with the polysomnographic study. Arterial blood gases and lung volumes were also measured.

RESULTS

Office hypertension was diagnosed in 45 patients, while the control group included 54 normotensive patients with OSAHS. After ABPM, hypertension was confirmed in 30 patients with OSAHS and office hypertension. WCH was diagnosed in the remaining 15 patients (33%). Patients with WCH presented higher values of sleep onset latency and wake after sleep onset than normotensive and sustained hypertensive patients. No other differences in sleep parameters, function tests, or urinary catecholamines were found between the OSAHS groups.

CONCLUSION

The results indicate that WCH is a frequent phenomenon in patients with OSAHS, and that it is not predictable by clinical variables.

Obstructive sleep apnea and thoracic aorta dissection

Obstructive sleep apnea syndrome (OSAS) is a process that is associated with the development of arterial hypertension, the main risk factor for aortic dissection and during obstructive episodes of the upper airways with marked increases in transmural pressure of the aorta wall. The aim of this work was to study the association between aortic dissection and OSAS. Nineteen consecutive patients with thoracic aorta dissection and 19 hypertensive patients of similar age, sex, and body mass index were studied by clinical questionnaire and polysomnography. Snoring and nonrefreshing sleep were common in both groups. Thirteen patients (68%) from each group showed an apnea-hypopnea index of more than 5 per hour. However, patients with aortic dissection presented a higher apnea-hypopnea index (28 [30.3] versus 11.1 [10.4], p=0.032). Seven patients with dissection presented an apnea-hypopnea index of more than 30 versus 1 patient in the control group (p=0.042). Patients with thoracic aorta dissection presented a high prevalence of previously undiagnosed and frequently severe OSAS. Further studies, including this diagnosis as a prognostic variable in the follow-up of patients with aortic dissection, are required. Our results suggest that in patients with aortic dissection and symptoms consistent with OSAS, a sleep study should be considered in their clinical management.

Seventh report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure

The National High Blood Pressure Education Program presents the complete Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure. Like its predecessors, the purpose is to provide an evidence-based approach to the prevention and management of hypertension. The key messages of this report are these: in those older than age 50, systolic blood pressure (BP) of greater than 140 mm Hg is a more important cardiovascular disease (CVD) risk factor than diastolic BP; beginning at 115/75 mm Hg, CVD risk doubles for each increment of 20/10 mm Hg; those who are normotensive at 55 years of age will have a 90% lifetime risk of developing hypertension; prehypertensive individuals (systolic BP 120-139 mm Hg or diastolic BP 80-89 mm Hg) require health-promoting lifestyle modifications to prevent the progressive rise in blood pressure and CVD; for uncomplicated hypertension, thiazide diuretic should be used in drug treatment for most, either alone or combined with drugs from other classes; this report delineates specific high-risk conditions that are compelling indications for the use of other antihypertensive drug classes (angiotensin-converting enzyme inhibitors, angiotensin-receptor blockers, beta-blockers, calcium channel blockers); two or more antihypertensive medications will be required to achieve goal BP (<140/90 mm Hg, or <130/80 mm Hg) for patients with diabetes and chronic kidney disease; for patients whose BP is more than 20 mm Hg above the systolic BP goal or more than 10 mm Hg above the diastolic BP goal, initiation of therapy using two agents, one of which usually will be a thiazide diuretic, should be considered; regardless of therapy or care, hypertension will be controlled only if patients are motivated to stay on their treatment plan. Positive experiences, trust in the clinician, and empathy improve patient motivation and satisfaction. This report serves as a guide, and the committee continues to recognize that the responsible physician's judgment remains paramount.

Insulin resistance and obstructive sleep apnea: is increased sympathetic stimulation the link?

The science of sleep is in early stages of development, and the biochemical consequences of obstructive sleep apnea (OSA) are slowly being identified. Only recently have investigators begun to identify the commonalities and interaction between OSA and insulin resistance, the underlying pathology of type 2 diabetes. Obesity and increasing age play important parts in the natural history of both conditions, which frequently coexist. The purpose of this article is, first, to examine the extent and strength of studies that have investigated the association between OSA and increased insulin resistance or type 2 diabetes and, second, to propose a model that explains the association and cyclical interaction between OSA, obesity, and insulin resistance.

Nocturnal sleep, daytime sleepiness, and quality of life in stable patients on hemodialysis

BACKGROUND

Although considerable progress has been made in the treatment of chronic kidney disease, compromised quality of life continues to be a significant problem for patients receiving hemodialysis (HD). However, in spite of the high prevalence of sleep complaints and disorders in this population, the relationship between these problems and quality of life remains to be well characterized. Thus, we studied a sample of stable HD patients to explore relationships between quality of life and both subjective and objective measures of nocturnal sleep and daytime sleepiness

METHODS

The sample included forty-six HD patients, 24 men and 22 women, with a mean age of 51.6 (10.8) years. Subjects underwent one night of polysomnography followed the next morning by a Multiple Sleep Latency Test (MSLT), an objective measure of daytime sleepiness. Subjects also completed: 1) a brief nocturnal sleep questionnaire; 2) the Epworth Sleepiness Scale; and, 3) the Quality of Life Index (QLI, Dialysis Version) which provides an overall QLI score and four subscale scores for Health & Functioning (H&F), Social & Economic (S&E), Psychological & Spiritual (P&S), and Family (F). (The range of scores is 0 to 30 with higher scores indicating better quality of life.)

RESULTS

The mean (standard deviation; SD) of the overall QLI was 22.8 (4.0). The mean (SD) of the four subscales were as follows: H&F - 21.1 (4.7); S&E - 22.0 (4.8); P&S - 24.5 (4.4); and, F - 26.8 (3.5). H&F (rs = -0.326, p = 0.013) and F (rs = -0.248, p = 0.048) subscale scores were negatively correlated with periodic limb movement index but not other polysomnographic measures. The H&F subscale score were positively correlated with nocturnal sleep latency (rs = 0.248, p = 0.048) while the H&F (rs = 0.278, p = 0.030) and total QLI (rs = 0.263, p = 0.038) scores were positively associated with MSLT scores. Both of these latter findings indicate that higher life quality is associated with lower sleepiness levels. ESS scores were unrelated to overall QLI scores or the subscale scores. Subjective reports of difficulty falling asleep and waking up too early were significantly correlated with all four subscale scores and overall QLI. Feeling rested in the morning was positively associated with S&E, P&S, and Total QLI scores.

CONCLUSION

Selected measures of both poor nocturnal sleep and increased daytime sleepiness are associated with decreased quality of life in HD patients, underscoring the importance of recognizing and treating these patients' sleep problems.

Sleep-disordered breathing, glucose intolerance, and insulin resistance

Sleep-disordered breathing (SDB) is a common condition with prevalence estimates of 2-4% in the general population. Epidemiological data suggest that SDB is an independent risk factor for cardiovascular disease. Glucose intolerance and insulin resistance are also well-recognized risk factors for the development of cardiovascular disease. A number of recent clinic-based studies suggest that, independent of obesity, SDB may adversely affect glucose tolerance and insulin sensitivity. The purpose of this study was to systematically review the evidence for the link between SDB, glucose intolerance, and insulin resistance. A MEDLINE search for SDB and metabolic disorders was performed and 24 articles that met the inclusion criteria were identified. Population-based studies indicate that habitual snoring is independently associated with glucose intolerance and insulin resistance. Studies that have used objective measures of SDB (e.g. polysomnography) provide further support for an independent link between SDB, glucose intolerance, and insulin resistance. However, studies on the treatment of SDB with continuous positive airway pressure (CPAP) have yielded inconsistent results and overall do not reveal an improvement in the metabolic disturbance after treatment. Although population-based prospective data on the metabolic implications of SDB are still lacking, current data point to an independent association between SDB and impaired glucose homeostasis. Potential mediators of this association include altered adrenergic function, the direct effects of hypoxemia on glucose regulation, and release of proinflammatory cytokines that affect metabolism.

Evidence-based medicine in sleep apnea surgery

Since the first description of sleep apnea as a clinical entity, the understanding of it within the medical community has increased significantly. Much research has explored the causes, assessment, and treatment of this disease. This research has resulted in a variety of tools for assessment and approaches to treatment. As research progresses, new data have shed light on the strengths of traditional approaches and their limitations. This article gives background for current approaches and charts a potential future course for sleep apnea assessment and treatment.

Sleep-disordered breathing and stroke

Sleep-related breathing disorders are strongly associated with increased risk of stroke independent of known risk factors. The direction of causation favors sleep-disordered breathing leading to stroke rather than the other way around, although definitive proof of this awaits the results of prospective cohort studies. If causal, even a moderately elevated risk of stroke coupled with the high prevalence of sleep-disordered breathing could have significant public health implications. The relationship between sleep-disordered breathing and stroke risk factors is complex, and likely part of the risk for cerebrovascular events is because of higher cardiovascular risk factors in patients with increased RDI. The mechanisms underlying this increased risk of stroke are multi-factorial and include reduction in cerebral blood flow, altered cerebral autoregulation, impaired endothelial function, accelerated atherogenesis, thrombosis, and paradoxic embolism. Because of the effects of sleep-disordered breathing on vascular tone, hypertension is believed to be a major mechanism by which sleep-disordered breathing might influence risk of stroke. Because sleep-related breathing disorders are treatable patients with stroke/TIA should undergo investigation, with a thorough sleep history interview, physical examination, and polysomnography. Treatment of sleep apnea has been shown to improve quality of life, lower blood pressure, improve sleep quality, improve neurocognitive functioning, and decrease symptoms of excessive daytime sleepiness [98]. Further treatment trials are needed to determine whether treatment improves outcome after stroke and whether treatment may serve as secondary prophylaxis and modify the risk of recurrent stroke or death.

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.

Reliability of the Wisconsin Sleep Questionnaire: a French contribution to international validation

We evaluated the reliability of a French version of the Wisconsin Sleep Questionnaire designed to investigate snoring, obstructive apnoeas, and sleeping problems. The assessment of reliability included the study of internal consistency and the 3 months repeatability of the questionnaire. The questionnaire was first completed at a Center of Preventive Medicine by a random sample of 122 subjects from the community. Three months later the same form was mailed and 82 questionnaires were returned (67.2%). No significant differences existed between responders and nonresponders for anthropometric data or life habits. The internal consistency in each domain was good or satisfactory (Cronbach's alpha=0.67 to 0.81). The concordance between the answers at a 3-month interval was excellent for questions on ever snoring, frequency of snoring, gasping/choking during sleep, and breathing stops during sleep (Cohen kappa>0.60). The questions on snoring loudness, a history of sleep apnoea, and excessive daytime sleepiness were fairly reproducible (kappa 0.28 to 0.60). We found no difference in reproducibility by gender or age. In conclusion, this reliability assessment in a sample of middle-aged subjects from the community in northeastern France showed satisfactory internal consistency and 3-months reproducibility of the main questions of a French translation of the Wisconsin Sleep Questionnaire.

Sleep disturbances in dialysis patients

Sleep disturbances are extremely common in dialysis patients. Subjective sleep complaints are reported in up to 80% of those surveyed and sleep apnoea syndrome, restless legs syndrome, and periodic limb movement disorder are much more prevalent than in the general population. Excessive daytime sleepiness is also an important problem. These sleep abnormalities appear to have significant negative effects on quality of life and functional health status. Although long-term studies regarding other effects on health outcomes remain to be conducted, available data also suggest that sleep disturbances may have an important impact on morbidity and mortality. Achieving a more complete understanding of the sleep problems experienced by this group is absolutely imperative if improving health outcomes is the goal. Clinicians and researchers alike face numerous challenges in this regard, especially when considering the complex clinical presentation and treatment needs typical of these patients. Therefore, the purpose of this article is to present an up-to-date review of the literature regarding sleep disturbances in dialysis patients with special emphasis on the numerous factors potentially contributing to these problems and associated clinical and research implications.

Diabetes and sleep disturbances: findings from the Sleep Heart Health Study

OBJECTIVE

To test the hypothesis that diabetes is independently associated with sleep-disordered breathing (SDB), and in particular that diabetes is associated with sleep abnormalities of a central, rather than obstructive, nature.

RESEARCH DESIGN AND METHODS

Using baseline data from the Sleep Heart Health Study (SHHS), we related diabetes to 1). the respiratory disturbance index (RDI; number of apneas plus hypopneas per h of sleep); 2). obstructive apnea index (OAI; >or=3 apneas/h of sleep associated with obstruction of the upper airway); 3). percent of sleep time < 90% O(2) saturation; 4). central apnea index (CAI; >or=3 apneas [without respiratory effort]/h sleep); 5). occurrence of a periodic breathing (Cheyne Stokes) pattern; and 6) sleep stages. Initial analyses excluding persons with prevalent cardiovascular disease (CVD) were repeated including these participants.

RESULTS

Of the 5874 participants included in this report, 692 (11.8%) reported diabetes or were taking oral hypoglycemic medications or insulin and 1002 had prevalent CVD. Among the 4872 persons without CVD, 470 (9.6%) had diabetes. Diabetic participants had worse CVD risk factor profiles than their nondiabetic counterparts, including higher BMI, waist and neck circumferences, triglycerides, higher prevalence of hypertension, and lower HDL cholesterol (P < 0.001, all). Descriptive analyses indicated differences between diabetic and nondiabetic participants in RDI, sleep stages, sleep time <90% O(2) saturation, CAI, and periodic breathing (P < 0.05, all). However, multivariable regression analyses that adjusted for age, sex, BMI, race, and neck circumference eliminated these differences for all sleep measures except percent time in rapid eye movement (REM) sleep (19.0% among diabetic vs. 20.1% among nondiabetic subjects, P < 0.001) and prevalence of periodic breathing (odds ratio [OR] for diabetic subjects versus nondiabetic subjects 1.80, 95% CI 1.02-3.15). Additionally, adjusted analyses showed diabetes was associated with nonstatistically significant elevations in the odds of an increased central breathing index (OR 1.42, 95% CI 0.80-2.55). Addition to the analysis of the 1002 persons with prevalent CVD (including 222 people with diabetes) did not materially change these results.

CONCLUSIONS

These data suggest that diabetes is associated with periodic breathing, a respiratory abnormality associated with abnormalities in the central control of ventilation. Some sleep disturbances may result from diabetes through the deleterious effects of diabetes on central control of respiration. The high prevalence of SDB in diabetes, although largely explained by obesity and other confounders, suggests the presence of a potentially treatable risk factor for CVD in the diabetic population.

Estudio de la validez de un equipo de poligrafía respiratoria (BREAS SC–20) para el diagnóstico del síndrome de apneas-hipopneas durante el sueño

OBJECTIVE

To validate the BREAS SC20 (Breas Medical AB, Mölnlyke, Sweden) polygraphic screening device, comparing it with conventional polysomnography (PSG), in the diagnosis of sleep apnea-hypopnea syndrome. A validity study of the diagnostic test was carried out at the sleep clinic of a tertiary hospital.

PATIENTS AND METHODS

Seventy patients clinically suspected of sleep apnea-hypopnea syndrome and treated at the sleep laboratory of the Hospital Txagorritxu, Vitoria, Spain, from November, 2001 until August, 2002 were consecutively enrolled in the study. Patient characteristics, comorbidities, and results on the Epworth sleepiness scale were recorded. The apneahypopnea index (AHI) per hour of sleep was determined by PSG; the respiratory events index (REI) per hour of screening was determined by the polygraphic screening device.

RESULTS

Sixty studies were valid (77% were men; mean [SD] age: 51.6 [13.2]; body mass index: 30.3 [5]; AHI: 31.0 [27.6]). The intraclass correlation coefficient between the AHI by PSG and the manual REI was 0.92. The mean difference between the AHI and the manual REI was 2.92 (9.75). The area under the receiver operating characteristic curve was 0.924 for the cut point AHI >or =5. The optimal cut point for an AHI > or = 5 was 3.6 in the REI (98% sensitivity). The respiratory screening device correctly classified 90% to 95% of the patients.

CONCLUSIONS

The BREAS SC20 is a valid system for identifying patients clinically suspected of sleep apnea-hypopnea syndrome.

Sleep disorders and the failure to lower nocturnal blood pressure

PURPOSE OF REVIEW

The failure to lower systolic blood pressure at night (called non-dipping) and sleep apnea are both associated with adverse cardiovascular outcomes. Sleep apnea is a common cause of non-dipping blood pressure.

RECENT FINDINGS

Sleep apnea increases night time blood pressure through enhanced cardiac pre-load, sleep disturbance and hypoxia. Hypoxia elicits increased levels of norepinephrine, endothelin and erythropoetin. Patients with sleep apnea tend to be elderly and obese, so they have poor endothelial nitric oxide release and blunted baroreflexes. They thus have several stimuli for high blood pressure and poor compensatory mechanisms to lower blood pressure.

SUMMARY

Non-dipping patients without sleep apnea have evidence of volume overload and correct their blood pressure pattern in response to diuretics. Individuals with sleep apnea have evidence of increased cardiac pre-load from episodes of negative intrathoracic pressure. Their daytime blood pressure responds poorly to many drugs, but beta blockers may be effective. Their night time blood pressure responds only slightly to therapy of their sleep apnea with continuous positive airway pressure, even though continuous positive airway pressure decreases their norepinephrine, erythropoetin and endothelin levels.

Sleep and sleep-disordered breathing in adults with predominantly mild obstructive airway disease

Neither the association between obstructive airways disease (OAD) and sleep apnea-hypopnea (SAH) nor the sleep consequences of each disorder alone and together have been characterized in an adult community setting. Our primary aims were (1) to determine if there is an association between OAD and SAH and (2) identify predictors of oxyhemoglobin desaturation during sleep in persons having OAD with and without SAH. Polysomnography and spirometry results from 5,954 participants in the Sleep Heart Health Study were analyzed. OAD was defined by a FEV1/FVC value less than 70%. Assessment of SAH prevalence in OAD was performed using thresholds of respiratory disturbance index (RDI) greater than 10 and greater than 15. A total of 1,132 participants had OAD that was predominantly mild (FEV1/FVC 63.81 +/- 6.56%, mean +/- SD). SAH was not more prevalent in participants with OAD than in those without OAD (22.32 versus 28.86%, with and without OAD, respectively, at RDI threshold values greater than 10; and 13.97 versus 18.63%, with and without OAD, respectively, at RDI threshold value greater than 15). In the absence of SAH, the adjusted odds ratio for sleep desaturation (> 5% total sleep time with saturation < 90%) was greater than 1.9 when FEV1/FVC was less than 65%. Participants with both OAD and SAH had greater sleep perturbation and desaturation than those with one disorder. Generally mild OAD alone was associated with minimally altered sleep quality. We conclude that (1) there is no association between generally mild OAD and SAH; (2) exclusive of SAH and after adjusting for demographic factors and awake oxyhemoglobin saturation, an FEV1/FVC value less than 65% is associated with increased risk of sleep desaturation; (3) desaturation is greater in persons with both OAD and SAH compared with each of these alone; and (4) individuals with generally mild OAD and without SAH in the community have minimally perturbed sleep.

Sleep disordered breathing

Cause and effect relationships between sleep disordered breathing (SDB) and illness, poorer quality of life, and public health have been largely overlooked and undertreated by healthcare providers. Obstructive sleep apnea (OSA), central sleep apnea, upper airway resistance syndrome, and obesity hypoventilation are the primary syndromes that fall under the rubric of SDB. Each of these syndromes is defined; however, OSA is the most common form of SDB, and is the focus of this article. Epidemiology, pathophysiology, behavioral manifestations, cardiovascular comorbidity, clinical evaluation, and treatment for OSA are the main topics covered. The article concludes with the role of the nurse in SDB.

Gender-specific association of perceived stress and inhibited breathing pattern

Stress can potentiate the development of hypertension via inhibition of renal excretory function. One potential mediating mechanism is an inhibited breathing pattern, because hypoventilation can decrease renal sodium excretion acutely via effects on pCO2 and acid-base balance. Large individual differences in resting breathing patterns have been well-documented, with some individuals maintaining slow frequency and high pCO2. Whether this breathing pattern is related to chronic stress has not been investigated. This study reports that high perceived stress over the past month was associated with significantly lower frequency breathing at rest, independently of age, race, or body mass index. This finding was more marked in women than in men. In addition, slow breathing frequency was independently associated with higher resting end tidal CO2 in both men and women. This is the first known report of an association of sustained stress with an inhibited breathing pattern in humans, and points to a pathway by which chronic stress might contribute to the development of hypertension, especially in women.

The genetics of sleep disorders

The contribution of genetic components to the pathology of sleep disorders is increasingly recognised as important. Genetic studies have identified genes that may be important in the regulation of circadian rhythms, which in turn determine the time of sleep onset and waking. Recent studies have shown that mutations in hPER2 are associated with autosomal-dominant familial advanced-sleep-phase syndrome. Genetic studies in a canine model of narcolepsy and in knock-out mice have led to the identification of the hypothalamic hypocretin (orexin) neurotransmitter system as a key target for human narcolepsy. The contribution of genetic factors to obstructive sleep apnoea syndrome (OSAS) has led to a better understanding of this complex disorder that may be part of a larger syndrome associated with respiratory, cardiovascular, and metabolic dysfunction. The aim of this review is to discuss the current knowledge on the role of genetic factors in sleep disorders, in particular circadian disorders, narcolepsy, restless-legs syndrome, and OSAS.

Underdiagnosis of sleep apnea syndrome in U.S. communities

We hypothesize that clinical recognition rates for obstructive sleep apnea-hypoapnea syndrome (OSAHS) are influenced by comorbidity and demographic factors. Data on medical disorders, symptoms of sleep disorders, and cardiovascular risk factors gathered from 15,699 individuals in the Sleep Heart Health Study were compared. Participants were classified into three groups: those with a self-reported physician diagnosis of OSAHS, those with self-reported physician-diagnosed and -treated OSAHS, and those reporting both frequent snoring and daytime sleepiness (two-symptom group). Among all participants, 4.1% reported two symptoms (range across sites: 1.55 to 7.23%), whereas 1.6% reported a physician diagnosis of OSAHS (range: 0.66 to 2.88%) and 0.6% reported physician diagnosis and treatment (range: 0.11 to 0.88%). Recognized OSAHS groups were similar to the two-symptom group in age, having a sleeping partner, measured blood pressure, total cholesterol, and race. In a logistic model that included age along with characteristics found to vary significantly among the three groups (gender, body mass index [BMI], high-density lipoprotein cholesterol levels, hypertension), only male gender and BMI were increased in those with physician-diagnosed and -treated OSAHS. We conclude that disparities (especially in women and in those with lower BMI) exist between current recognition rates for OSAHS and the estimated prevalence by symptom report across the United States.

Epidemiology of obstructive sleep apnea: a population health perspective

Population-based epidemiologic studies have uncovered the high prevalence and wide severity spectrum of undiagnosed obstructive sleep apnea, and have consistently found that even mild obstructive sleep apnea is associated with significant morbidity. Evidence from methodologically strong cohort studies indicates that undiagnosed obstructive sleep apnea, with or without symptoms, is independently associated with increased likelihood of hypertension, cardiovascular disease, stroke, daytime sleepiness, motor vehicle accidents, and diminished quality of life. Strategies to decrease the high prevalence and associated morbidity of obstructive sleep apnea are critically needed. The reduction or elimination of risk factors through public health initiatives with clinical support holds promise. Potentially modifiable risk factors considered in this review include overweight and obesity, alcohol, smoking, nasal congestion, and estrogen depletion in menopause. Data suggest that obstructive sleep apnea is associated with all these factors, but at present the only intervention strategy supported with adequate evidence is weight loss. A focus on weight control is especially important given the expanding epidemic of overweight and obesity in the United States. Primary care providers will be central to clinical approaches for addressing the burden and the development of cost-effective case-finding strategies and feasible treatment for mild obstructive sleep apnea warrants high priority.