Sleep apnoea and sympathetic nervous system activity: a review

Predictors of weight loss in obese patients with obstructive sleep apnea

PURPOSE

Consistent predictors of weight loss outcomes with very low-energy diets (VLEDs) in obstructive sleep apnea (OSA) have not been identified. This study aimed to identify variables predictive of weight loss success in obese patients with OSA undertaking an intensive weight loss programme.

METHODS

We analysed biological, psychological, and behavioural variables as potential predictors of weight loss in obese patients with OSA after a 2-month VLED followed by one of two 10-month weight loss maintenance diets. Actigraphy, in-lab polysomnography, urinary catecholamines, and various psychological and behavioural variables were measured at baseline, 2, and 12 months. Spearman's correlations analysed baseline variables with 2-month weight loss, and 2-month variables with 2-12 month-weight change.

RESULTS

Forty-two patients completed the VLED and thirty-eight completed the maintenance diets. Actigraphy data revealed that late bedtime (r_s =  - 0.45, p =  < 0.01) was correlated with 2-month weight loss. The change in the time that participants got out of bed (rise-time) from baseline to two months was also correlated with 2-month weight loss (r_s = 0.36, p = 0.03). The Impact of Weight on Quality of Life-Lite questionnaire (IWQOL) Public Distress domain (r_s =  - 0.54, p =  < 0.01) and total (r_s =  - 0.38, p = 0.02) scores were correlated with weight loss maintenance from 2 to 12 months.

CONCLUSIONS

Results from this small patient sample reveal correlations between actigraphy characteristics and weight loss in obese patients with OSA. We suggest the IWQOL may also be a useful clinical tool to identify OSA patients at risk of weight regain after initial weight loss.

CLINICAL TRIAL REGISTRATION

This clinical trial was prospectively registered on 18/02/2013 with the Australia and New Zealand Clinical Trials Registry (ACTRN12613000191796).

PUBLIC REGISTRY TITLE

Sleep, Lifestyle, Energy, Eating, Exercise Program for the management of sleep apnea patients indicated for weight loss treatment: A randomised, controlled pilot study. URL: https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=363680.

Obstructive sleep apnoea and cardiovascular disease: a literature review

As obesity becomes more common worldwide, the prevalence of obstructive sleep apnoea (OSA) continues to rise. Obstructive sleep apnoea is a well-known disorder that causes chronic intermittent hypoxia (CIH), which is considered a risk factor for atherosclerosis directly and indirectly. Ischaemic heart disease remains the leading cause of death. Most risk factors for atherosclerosis are well understood. However, other factors such as CIH are less well understood. Several studies have investigated the pathophysiology of CIH, attempting to uncover its link to atherosclerosis and to determine whether OSA treatment can be a therapeutic modality to modify the risk for atherosclerosis. In this article, we will review the pathophysiology of OSA as an independent risk factor for cardiovascular disease and discuss the most common markers that have been studied. We will also examine the potential impact of OSA management as a risk factor modifier on the reversibility of atherosclerosis.

Does septoplasty affect 24-h ambulatory blood pressure measurements in patients with type 2 and 3 pure nasal septal deviation?

PURPOSE

To investigate day, night and 24 h all blood pressure effects of septoplasty by comparing pre- and post-operative 24-h ambulatory blood pressure monitoring (ABPM) values of NSD patients undergoing septoplasty.

MATERIALS AND METHODS

The prospective study included 20 patients with type 2 and 3 pure NSD (mean age, 23.60 ± 6.51) who underwent septoplasty in our clinic. Nasal obstruction symptom evaluation (NOSE) questionnaire was applied to each participant both pre- and post-operatively to evaluate their views on the severity of NSD and the effectiveness of surgical outcomes. A comprehensive ABPM examination was performed both 2 days before surgery and at three months postoperatively for each patient and the findings were compared among patients.

RESULTS

Preoperative NOSE score was 87.75 ± 7.34% and the postoperative score was 12.50 ± 6.58% (p = 0.000). Following septoplasty, 24-h systolic blood pressure (24SBP) declined from 119.4 ± 9.9 mmHg to 112.2 ± 8.0 mmHg (p = 0.000), daytime SBP (DSBP) declined from 125.9 ± 11.0 mmHg to 117.9 ± 8.4 mmHg (p = 0.000), nighttime SBP (NSBP) declined from 112.7 ± 9.5 mmHg to 105.5 ± 7.9 mmHg (p = 0.000), 24-h pulse pressure (24PP) declined from 46.7 ± 10.1 mmHg to 44.0 ± 8.4 mmHg (p = 0.015), and mean daytime PP (DPP) declined from 46.9 ± 9.7 mmHg to 44.6 ± 8.6 mmHg (p = 0.026).

CONCLUSION

The decline in NOSE percentages following septoplasty demonstrated that the satisfaction levels of the patients were increased. Upper airway obstruction secondary to NSD may affect ABPM measurements. Moreover, the significant decrease in the 24SBP, DSBP, NSBP, 24PP and DPP following septoplasty showed that NSD may cause cardiovascular risk and this risk may be prevented by septoplasty.

Prevalence of obstructive sleep apnea in female patients with fibromyalgia

Objectives:

To determine the prevalence of obstructive sleep apnea in female patients with fibromyalgia (FM) presenting to physical therapy outpatient clinics.

Methods:

The 36-item short form health survey (SF-36) questionnaire, Berlin test, and epworth sleepiness scale were administered, along with a polysomnography to 38 female patients. This cross-sectional study comprised diagnosed with FM according to the diagnostic criteria of the American College of Rheumatology, between March 2017 and August 2019, at the Faculty of Medicine Hospital, Çanakkale Onsekiz Mart University, Çanakkale, Turkey.

Results:

Of the participants, 65.9% were found to have obstructive sleep apnea (OSA). Patients with OSA were older and had a higher disease activity score for FM. A strong positive correlation was identified between the apnea-hypopnea index (AHI) and the FA disease activity score. A negative correlation was found between AHI and the subscales of SF-36.

Conclusion:

A clinical assessment of female patients with FM requires a multidisciplinary approach, and patients with excessive daytime sleepiness in particular are recommended to undergo polysomnography. The authors believe that the early detection and treatment of accompanying OSA will contribute not only to the quality of life, but also to the survival of patients with FM.

Carbamazepine Improves Apneic Episodes in Congenital Central Hypoventilation Syndrome (CCHS) With a Novel PHOX2B Exon 1 Missense Mutation

ABSTRACT

Pathogenic variants in Paired-Like Homeobox 2B (PHOX2B) gene cause congenital central hypoventilation syndrome (CCHS), a rare disorder of the nervous system characterized by absent or reduced ventilatory response to hypoxia and hypercapnia. The focus of management in CCHS is optimizing ventilation. Thus far, no medication has proved effective in improving ventilation. Most CCHS cases are caused by polyalanine repeat expansion mutations. Non-polyalanine repeat expansion mutations are the cause in 8% of cases and result in a more severe clinical presentation. PHOX2B has 3 exons. Exon 3 of PHOX2B is the most common location for CCHS-causing mutations. Thus far, only 9 CCHS-causing mutations have been reported in exon 1, 8 of which were nonsense mutations. We report a child with CCHS who was found to have a novel heterozygous missense variant in exon 1; c.95A > T. Improvement in his apneic episodes was observed following treatment with carbamazepine.

Sleep and the Cardiovascular System in Children

Subspecialty pediatric practice provides comprehensive medical care for a range of ages, from premature infants to children, and often includes adults with complex medical and surgical issues that warrant multidisciplinary care. Normal physiologic variations involving different body systems occur during sleep and these vary with age, stage of sleep, and underlying health conditions. This article is a concise review of the cardiovascular (CV) physiology and pathophysiology in children, sleep-disordered breathing (SDB) contributing to CV morbidity, congenital and acquired CV pathology resulting in SDB, and the relationship between SDB and CV morbidity in different clinical syndromes and systemic diseases in the expanded pediatric population.

Is There a Link Between Obstructive Sleep Apnea Syndrome and Fibromyalgia Syndrome?

OBJECTIVES

Fibromyalgia syndrome (FMS) is characterized by complaints of chronic musculoskeletal pain, fatigue, and difficulty in falling asleep. Obstructive sleep apnea syndrome (OSAS) is associated with symptoms, such as morning fatigueness and unrefreshing sleep. We aimed to investigate the presence of OSAS and objectively demonstrate changes in sleep pattern in patients with FMS.

MATERIAL AND METHODS

Polysomnographic investigations were performed on 24 patients with FMS. Patients were divided into two groups: patients with and without OSAS (Group 1 and Group 2, respectively). A total of 40 patients without FMS who presented to the sleep disorders polyclinic with an initial diagnosis of OSAS were included in Group 3. Based on their apnea hypopnea index (AHI), OSAS in the patients were categorized as mild (AHI, 5-15), moderate (30), or severe (>30).

RESULTS

OSAS was detected in 50% of patients with FMS. The most prominent clinical findings were morning fatigue and sleep disorder, which were similar in three groups. In polysomnography (PSG) evaluation, patients with FMS had mild (33%), moderate (25%), and severe (42%) OSAS. In correlation analyses, negative correlations were observed between fibromyalgia impact questionnaire (FIQ) and mean oxygen saturation, visual analogue scale (VAS), and minimum oxygen saturation, whereas a positive correlation was found between FIQ and desaturation times in patients with FMS.

CONCLUSION

Detection of OSAS in 50% of the patients with FMS, and similar rates of complaints of sleep disorder and morning fatigue of OSAS and FMS cases are important results. Detection of correlation between the severity of hypoxemia and FIQ and VAS scores are significant because it signifies the contribution of increased tissue hypoxemia to the deterioration of clinical status. Diagnosis and treatment of OSAS associated with FMS are important because of their favorable contributions to the improvement of the clinical picture of FMS.

Obstructive Sleep Apnea, Daytime Sleepiness, and Type 2 Diabetes

PURPOSE

The purpose of this article is to review the literature on obstructive sleep apnea, resultant daytime sleepiness, and type 2 diabetes mellitus, as the state of evidence exists.

METHODS

A search was conducted on Medline and CINAHL using the search terms sleep apnea syndromes, obstructive sleep apnea, disorders of excessive somnolence, type 2 diabetes mellitus, and insulin resistance. This review includes only published research studies in English, in adults aged 19 years or older. There were 109 citations when the terms were combined, 36 citations that were identified as research studies, no randomized clinical trials, and only 1 qualitative study.

RESULTS

Obstructive sleep apnea and type 2 diabetes share the risk factors of age and central abdominal obesity. Recent studies suggest that obstructive sleep apnea and type 2 diabetes not only frequently coexist but also have a bidirectional association wherein each condition exacerbates the other. The mechanism whereby obstructive sleep apnea affects glucose metabolism is likely repetitive hypoxia and sleep fragmentation, which cause a stress response with increased sympathetic nervous system activity, increased fatigue-causing cytokines, and altered leptin levels that result in weight gain. In addition, daytime sleepiness results in an impaired mood state that may impede diabetes management.

CONCLUSIONS

Type 2 diabetes is prevalent in persons with obstructive sleep apnea, although the direction of causality is unknown. More research, including randomized clinical trials, is needed to determine how obstructive sleep apnea and daytime sleepiness affect persons with type 2 diabetes.

Platelet-lymphocyte ratio is an independent predictor for cardiovascular disease in obstructive sleep apnea syndrome

There is a strong relationship between obstructive sleep apnea syndrome (OSAS) and cardiovascular disease (CVD). Chronic intermittent hypoxia, inflammation, oxidative stress, and endothelial dysfunction may constitute etiologic mechanisms, linking OSAS to CVD. Inflammation play an important role in the development of CVD. Platelet-lymphocyte ratio (PLR) is a new biomarker showing inflammation. No previous study has ever investigated the association between PLR, CVD and OSAS severity in patients with OSAS. This study was designed to investigate the association between PLR and CVD in patients with OSAS, and relationship between severity of OSAS, polysomnographic parameters and PLR. This was a cohort study in which patients who had undergone a full night polysomnoraphy for diagnosis of OSA were recruited. Patients were divided according to their apnea-hypopnea index (AHI) scores into OSAS negative (Group 1: AHI < 5), mild (Group 2: AHI, 5-15), moderate (Group 3:AHI,15-30), and severe OSAS (Group 4: AHI > 30) groups. The presence of heart failure, coronary artery disease or arrhythmia was defined as CVD. A total of 424 patients were included in this study. There were 57, 93, 82, and 192 patients in Groups 1, 2, 3, and 4, respectively. PLR were significantly different between groups (Group 1: 87.38; Group 2: 95.07; Group 3: 97.01, Group 4: 126.9, P < 0.05). PLR were significantly correlated with AHI, oxygen desaturation index, average and minimum O2 saturation values (P < 0.05). Values of PLR were significantly higher in patients with CVD compared with those without. Multiple regression analysis demonstrated that PLR is an independent predictor of CVD. PLR cut-off value for demonstrating the presence of CVD is higher than 108.56. In the light oh findings, PLR is strongly associated with the severity of OSAS and cardiovascular disease in OSAS patients. PLR might be used as a biomarker to predict CVD in OSAS patients.

Effects of continuous positive airway pressure therapy on glycaemic control, insulin sensitivity and body mass index in patients with obstructive sleep apnoea and type 2 diabetes: a systematic review and meta-analysis

Background:

Evidence suggests that 15–30% of individuals with obstructive sleep apnoea (OSA) have type 2 diabetes mellitus (T2DM), and that OSA is an independent risk factor for T2DM. There is considerable interest in ascertaining whether OSA treatment improves glycaemic control and insulin sensitivity in patients with OSA and T2DM.

Aims:

To assess the effects of continuous positive airway pressure (CPAP) therapy on glycosylated haemoglobin (HbA1c) level, insulin sensitivity and body mass index (BMI) in patients with OSA and T2DM.

Methods:

MEDLINE, EMBASE and the Cochrane Library were searched to identify prospective studies involving patients with OSA and T2DM who had received CPAP, and data on primary outcome (change in HbA1c) and/or secondary outcomes (changes in insulin sensitivity and BMI) were reported. All relevant studies published before 31 January 2014 were included.

Results:

Six studies were included in the systematic review and meta-analysis. The numbers of patients ranged from 9 to 44 (total=128), and mean age ranged from 50.7 to 66.1 years. For the change in HbA1c (six studies, 128 patients), the combined standardised paired difference revealed no significant effect of CPAP (−0.071, 95% confidence interval (CI)=−0.245, 0.103; P=0.421). Similarly, there was no significant effect of CPAP on the change in BMI (−0.102, 95% CI=−0.296, 0.092; P=0.302; five studies, 103 patients). In contrast, there was a significant effect of CPAP on the change (improvement) in insulin sensitivity (0.330, 95% CI=0.001, 0.658; P=0.049; three studies, 39 patients).

Conclusion:

The limited available evidence from randomised controlled trials and prospective observational studies suggests that CPAP does not decrease HbA1c level or BMI in patients with OSA and T2DM but may improve insulin sensitivity.

Evaluation and validation of a method for determining platelet catecholamine in patients with obstructive sleep apnea and arterial hypertension

Background

Measurements of plasma and urinary catecholamine are susceptible to confounding factors that influence the results, complicating the interpretation of sympathetic nervous system (SNS) activity in the Obstructive sleep apnea (OSA) and arterial hypertension (HYP) conditions.

Objective

In this study, we validated a test for platelet catecholamine and compared the catecholamine levels (adrenaline and noradrenaline) in urine, plasma and platelets in patients with OSA and HYP compared with controls.

Methods

In the validation, 30 healthy, nonsmoking volunteers who were not currently undergoing treatment or medication were selected as the control group. One hundred fifty-four individuals (114 OSA, 40 non-OSA) were consecutively selected from the outpatient clinic of the Sleep Institute and underwent clinical, polysomnographic and laboratory evaluation, including the urinary, plasma and platelet levels of adrenaline (AD) and noradrenaline (NA). Patients were then allocated to groups according to the presence of OSA and/or hypertension.

Results

A logistic regression model, controlled for age and BMI, showed that urinary AD and urinary NA were risk factors in the OSA+HYP group and the HYP group; however, the model showed higher levels of platelet NA for OSA without HYP. After 1 year of CPAP (continuous upper airway pressure) treatment, patients (n = 9) presented lower levels of urinary NA (p = 0.04) and platelet NA (p = 0.05).

Conclusion

Urinary NA and AD levels were significantly associated with the condition of hypertension with and without OSA, whereas platelet NA with OSA without comorbidity. These findings suggest that platelet catecholamine levels might reflect nocturnal sympathetic activation in OSA patients without hypertension.

[Correlation between urinary catecholamines dosage and apnea-hypopnea index in a hypertension population: pilot study]

AIMS

Sleep disorders like obstructive sleep apnea in adults are associated with increased sympathetic activity, which induced high blood pressure and could be associated with resistant hypertension. Some studies have demonstrated that high urinary catecholamine levels in obstructive sleep apnea patients may be decreased with continuous positive airway pressure therapy. However, very few studies have demonstrated a correlation between apnea-hypopnea index and urinary catecholamine levels in hypertension patients.

METHODS

In this pilot study, 20 hypertensive patients referred for hypertension work-up including night-time polygraphy and 24h urinary catecholamine dosage were included.

RESULTS

Mean age was 51±11 years (30-76), 68% were males. Diagnosis of obstructive sleep apnea was confirmed in 13 patients at the end of the work-up. Mean apnea-hypopnea index was 14±9 (2-32). The only urinary catecholamine parameter significantly increased in patients with obstructive sleep apnea was 24h urinary normetanephrine (1931±1285 vs 869±293nmol/24h; P<0.05). However, this difference was not significant when this parameter was adjusted to 24h urinary creatinine. We observed a significant positive correlation between AHI and 24h urinary normetanephine (r=0.486; P=0.035).

CONCLUSION

This pilot study confirms an isolated elevation of 24h urinary normetanephrine in hypertensive patients with obstructive sleep apnea and shows a significant correlation between sleep disorders expressed by apnea-hypopnea index and urinary catecholamines excretion.

Effect of continuous positive airway pressure on type 2 diabetes mellitus and glucose metabolism

BACKGROUND

Obstructive sleep apnea (OSA) is a prevalent condition that is associated with significant comorbidities, including obesity, hypertension, cardiovascular disease, and insulin resistance. Continuous positive airway pressure (CPAP) is an effective treatment for OSA. The effect of CPAP on glucose metabolism in patients with OSA has been controversial. This study evaluates the impact of CPAP on patients with OSA and type 2 diabetes mellitus (T2DM) or prediabetes.

MATERIALS AND METHODS

PubMed, Ovid Medline, and EMBASE were searched for original English language studies performed on or after 2003. Subjects were aged > 18 years, were diagnosed with OSA via polysomnography, and had either T2DM or prediabetes according to laboratory evaluation.

RESULTS

Of the 22 articles that met the selection criteria, 17 studies (77%) showed that a prolonged use of CPAP produced significant changes in glucose metabolism of patients who had T2DM and prediabetes. These changes were observed in studies measuring glycosylated hemoglobin (HbA1c), postprandial or nocturnal glucose, and insulin sensitivity or resistance. Of the 17 studies, 4 showed improvement in HbA1c levels or increased insulin sensitivity only after long-term use of CPAP for ≥ 3 months.

CONCLUSION

This literature review shows that CPAP improves not only hypoxia while restoring normal breathing during sleep, but also glucose metabolism in patients with OSA and T2DM or prediabetes. A few studies have shown that patients can experience even better results with long-term CPAP treatment (≥ 3 months of daily use) for > 4 hours a night. Therefore, this improvement in glucose metabolism with the use of CPAP may contribute to T2DM prevention and decrease further progression of the disease. However, additional studies are needed to confirm these findings.

Continuous positive airway pressure and type 2 diabetes mellitus

Obstructive sleep apnea (OSA) is a sleep disorder, increasingly recognized. It is commonly present in obese persons, treated with continuous positive airway pressure (CPAP), being the gold standard. The disorder has been associated with diabetes mellitus and possibly related to hypoxia per se, increased sympathetic activity, disturbed hypothalamic-pituitary-adrenal axis and increased inflammatory cytokines and leptin, all of which can adversely affect both glucose metabolism and insulin sensitivity. Given this association and the presence of common risk factors, this review assessed the impact of CPAP on diabetes mellitus through various metabolic parameters including HbA1c, nocturnal glucose and insulin resistance, in addition to the effect of CPAP on the prevention of diabetes mellitus. Results have been conflicting; Randomized controlled trials are recommended to allow objective and definite conclusions.

Hypertension and catecholamine levels in sleep apnoea

BACKGROUND

Sleep-disordered breathing has been strongly associated with systemic hypertension. Increased sympathetic activity in sleep-disordered breathing may be responsible for this association.

METHOD

In this sleep clinic-based study, 82 newly diagnosed patients of sleep-disordered breathing were evaluated for hypertension, and their plasma and urinary levels of catecholamines were measured. Catecholamine levels were then compared separately with the severity of sleep apnoea and blood pressure (BP).

RESULTS

The prevalence of hypertension in the study population was 46.3%. The BP showed a strong and statistically significant correlation with apnoea-hypopnoea index (diastolic, r = 0.65, P < 0.001 and systolic, r = 0.60, P < 0.001) which was maintained even after the results were analysed separately for obese and non-obese subjects. Both plasma and urinary levels of catecholamines were greater in patients with severe sleep apnoea (compared to nonsevere cases) and in those with hypertension compared to normotensives. However, statistical significance was achieved only for urine catecholamines and not for plasma catechol-amines in both the cases.

CONCLUSION

Hypertension is highly prevalent among Indian subjects with obstructive sleep apnoea. Catecholamine levels are significantly higher in hypertensive than in normotensive apnoeics and are also directly related to the severity of obstructive sleep apnoea. Twenty-four hour urinary catecholamine levels are more valid measures of sympathetic activity than spot plasma samples.

Prevalence of comorbid obstructive sleep apnea and metabolic syndrome: syndrome Z and maxillofacial surgery implications

PURPOSE

To determine the prevalence of the recently identified syndrome Z (SZ), which is the co-occurrence of obstructive sleep apnea (OSA; hypoxia, systemic and pulmonary hypertension, nocturnal arrhythmias) and metabolic syndrome (MetS; increased abdominal girth, hypertriglyceridemia, decreased high-density lipoprotein, hypertension, increased fasting glucose), which places the surgical patient at heightened risk of perioperative complications (myocardial infarction, stroke, pneumonia, wound infection).

MATERIALS AND METHODS

Electronic medical records of 296 male veterans were assessed for the presence of SZ using the American Academy of Sleep Medicine definition of OSA and a modified Adult Treatment Panel III definition of MetS, where obesity was defined by a body mass index of at least 30 kg/m(2) rather than by waist circumference.

RESULTS

SZ was diagnosed in 59% of patients. These individuals commonly exhibited severe OSA and least commonly mild OSA. The more severe the OSA, the more likely (60%) that patients manifested moderate (4 risk markers) or severe (5 risk markers) MetS. Furthermore, with increasing apnea-hypopnea index values, the more severe were the MetS elements.

CONCLUSIONS

The results of this study demonstrate the high prevalence rate of MetS in patients with OSA seeking treatment. Given the risk of perioperative complications, it is suggested that all patients scheduled for maxillofacial surgical procedures to treat OSA be evaluated for SZ.

Pathophysiology of resistant hypertension: the role of sympathetic nervous system

Resistant hypertension (RH) is a powerful risk factor for cardiovascular morbidity and mortality. Among the characteristics of patients with RH, obesity, obstructive sleep apnea, and aldosterone excess are covering a great area of the mosaic of RH phenotype. Increased sympathetic nervous system (SNS) activity is present in all these underlying conditions, supporting its crucial role in the pathophysiology of antihypertensive treatment resistance. Current clinical and experimental knowledge points towards an impact of several factors on SNS activation, namely, insulin resistance, adipokines, endothelial dysfunction, cyclic intermittent hypoxaemia, aldosterone effects on central nervous system, chemoreceptors, and baroreceptors dysregulation. The further investigation and understanding of the mechanisms leading to SNS activation could reveal novel therapeutic targets and expand our treatment options in the challenging management of RH.

Sleep and diabetes

Sleep apnea is clinically recognized as a heterogeneous group of disorders characterized by recurrent apnea and/or hypopnea. Its prevalence ranges from 4% to 24%. It has been implicated as an independent risk factor for several conditions such as hypertension, stroke, arrhythmia, and myocardial infarction. Recently data has been emerging which suggests an independent association of obstructive sleep apnea with several components of the metabolic syndrome, particularly insulin resistance and abnormalities in lipid metabolism. We hereby review the salient features of the association between sleep and diabetes.

CPAP treatment in the coexistence of obstructive sleep apnea syndrome and metabolic syndrome, results of one year follow up

OBJECTIVE

To investigate the effect of one year continuous positive airway pressure (CPAP) treatment on metabolic syndrome (MS) prevalence and components in patients diagnosed with both obstructive sleep apnea syndrome (OSAS) and metabolic syndrome.

METHODS

This was a single center, observational prospective cohort study. 38 patients who were diagnosed with OSAS after polysomnographic analysis in sleep laboratory and diagnosed with MS according to National Cholesterol Education Program Adult Treatment Panel III (NCEP ATP III) guideline and underwent CPAP treatment were followed for one year. After the 1 year of follow up period on CPAP treatment, the prevalence of MS was evaluated again.

RESULTS

20 (13 male, 7 female) of 38 patients completed the entire study. Mean age was 50+/-7.7.4 patients were under treatment for diabetes mellitus (DM), 9 for hypertension (HT). After one year of follow up on CPAP treatment, the prevalence of MS decreased by 45%. When each components of MS were evaluated, no significant difference was found in fasting blood glucose, triglyceride levels and systolic and diastolic blood pressure after treatment (p>0.05). However, significant difference was observed in waist circumference (p=0.002), HDL cholesterol (p=0.001) and BMI (p=0.01) after treatment.

DISCUSSION

If MS accompanies OSAS, which is a cardiovascular risk factor by itself, treatment indications of CPAP should be reevaluated. Thus, if OSA patients meet the criteria of MS even though they do not have obvious DM, HT and hyperlipidemia, initiating CPAP treatment at lower AHI levels may contribute to the prevention and development of cardiovascular disease.

Diurnal variability of C-reactive protein in obstructive sleep apnea

OBJECTIVE

The objective of this study is to examine the diurnal variability of C-reactive protein (CRP) in obstructive sleep apnea (OSA).

METHODS AND MEASUREMENTS

Participants included 44 women and men with untreated OSA (mean apnea/hypopnea index = 37.5, SD +/- 28) and 23 healthy adults with no OSA. Sleep was monitored with polysomnography in the University of California San Diego General Clinical Research Center. Over a 24-h period, blood was collected every 2 h, and CRP levels were determined.

RESULTS

Adjusting for age, gender, and body mass index, a significant group by time interaction showed that patients with OSA had higher CRP levels during the daytime (8:00 a.m.-8:00 p.m.) versus the nighttime (10:00 p.m. until 6:00 p.m.; p < 0.001). Non-apneics showed no significant change in CRP levels during the 24 h.

CONCLUSIONS

The findings indicate that sleep apnea patients have disproportionately elevated CRP levels in the day versus the nighttime, possibly as a result of carryover effects of nighttime arousal into the daytime.

Catecholamine alterations in pediatric obstructive sleep apnea: effect of obesity

STUDY OBJECTIVES

Obstructive sleep apnea (OSA) elicits increased sympathetic activity in adults and increased urinary catecholamines. Moreover, urinary catecholamine excretion is altered in obese patients. We hypothesized that morning urine catecholamine levels would be correlated with the severity of obstructive sleep apnea and degree of obesity in children.

METHODS

Children referred to the pediatric sleep center for habitual snoring underwent overnight polysomnography, and the first morning voided urine sample was collected. Urinary concentrations of norepinephrine, epinephrine and dopamine were measured and corrected for creatinine levels. In a subset of children, blood samples were drawn and gene expression of catecholamine-relevant genes analyzed by quantitative real-time PCR.

RESULTS

One hundred fifty-nine children were recruited and completed the protocol. Children with OSA had significantly higher urinary norepinephrine and epinephrine levels, but not dopamine, compared to habitual snorers (norepinephrine: 40.1 +/- 24.7 ng/mg creatinine vs. 31.6 +/- 16.2 ng/mg creatinine, P < 0.01; epinephrine: 6.4 +/- 10.5 ng/mg vs. 4.5 +/- 0.5 ng/mg, P < 0.01). There was a positive correlation between norepinephrine and epinephrine values and polysomnographic indices, but no effect of obesity on catecholamine levels. In addition, expression of several of the major genes involved in synthesis and transport of catecholamines, as well as in selected receptors were compatible with increased bioavailability of catecholamines.

CONCLUSIONS

In children with OSA, morning urinary norepinephrine and epinephrine levels are significantly higher than those without OSA, and correlate with the severity of the disease. Gene expression patterns are in agreement with such findings. Urine catecholamine levels do not appear to be influenced by the presence of obesity. Thus, altered sympathetic activity in OSA patients appears to occur independently of the presence of obesity.

Urine levels of catecholamines in Greek children with obstructive sleep-disordered breathing

INTRODUCTION

Adults with obstructive sleep apnea have increased sympathetic activity. It was hypothesized that in children with symptoms of obstructive sleep-disordered breathing (SDB), morning urine levels of catecholamines correlate with severity of nocturnal hypoxemia.

METHODS

Children with snoring referred for polysomnography and controls without snoring were recruited. Morning urine norepinephrine, epinephrine, normetanephrine, and metanephrine levels were measured (ng/mg urine creatinine).

RESULTS

Twelve children (age 5.2 +/- 2.3 years) with severe hypoxemia (oxygen saturation of hemoglobin-SpO2 nadir < or =86%), 20 subjects (age 6.1 +/- 2.1 years) with moderate hypoxemia (SpO2 nadir < or =90% and >86%), 22 children (age 6.6 +/- 1.5 years) with mild nocturnal hypoxemia (SpO2 nadir >90%), and 10 controls (age 7.1 +/- 2.8 years) were studied. Children with severe hypoxemia had significantly higher log-transformed norepinephrine levels (1.63 +/- 0.29) compared to those with moderate hypoxemia (1.43 +/- 0.22; P < 0.05) or compared to controls (1.39 +/- 0.31; P < 0.05). In subjects with SDB, log-transformed oxygen desaturation of hemoglobin index or SpO2 nadir predicted log-transformed norepinephrine levels after adjustment by age, gender and body mass index (r2 = 0.24; and r2 = 0.24, respectively; P < 0.01).

CONCLUSIONS

Severity of nocturnal hypoxemia in children with intermittent upper airway obstruction during sleep correlates with morning urine levels of norepinephrine suggesting increased sympathetic tone.

No evidence of enhanced oxidant production in blood obtained from patients with obstructive sleep apnea

Background

Obstructive sleep apnea syndrome (OSAS) is a recognized risk factor for cardiovascular morbidity and mortality, perhaps due to causative exacerbations of systemic oxidative stress. Putative oxidative stress related to numerous episodes of intermittent hypoxia, may be an oxidants chief driving force in OSAS patients.

Methods

We assessed the resting and n-formyl-methionyl-leucyl-phenylalanine (fMLP)- induced whole blood chemiluminescence (as a measure of oxidant production by polymorphonuclear leukocytes and monocytes), ferric reducing ability of plasma (FRAP) and H₂O₂ generation in the whole blood of 27 untreated OSAS patients, 22 subjects after a night of CPAP therapy and 11 controls without OSAS. All of them were matched to age, BMI (body mass index) and smoking habits. All parameters were measured before and after polysomnography-controlled sleep, individual results were obtained as a mean from duplicated experiments.

Results

No significant differences were distinguished between evening and morning blood chemiluminescence, H₂O₂ activity and FRAP within and between all three study groups.

For instance patients with untreated OSAS had similar morning and evening resting whole blood chemiluminescence (2.3 +/- 2.2 vs. 2.4 +/- 2.2 [aU·10^-4 phagocytes]), total light emission after stimulation with fMLP (1790 +/- 1371 vs. 1939 +/- 1532 [aU·s·10^-4 phagocytes]), as well as FRAP after 3 min. plasma incubation (602 +/- 202 vs. 671 +/- 221 [uM]). Although, in the subgroup of 11 patients with severe OSAS (apnea/hypopnea index 58 +/- 18/h and oxygen desaturation index 55 +/- 19/h), the morning vs. evening resting chemiluminescence and total light emission after stimulation with fMLP observed a propensity to elevate 2.5 +/- 2.7 vs. 1.9 +/- 1.8 [aU·10^-4 phagocytes] and 1778 +/- 1442 vs. 1503 +/- 1391 [aU·s·10^-4 phagocytes], respectively, these did not attain statistical significance (p > 0.05).

Conclusion

Our investigation exposed no evidence in the overproduction of oxidants via circulating phagocytes, once considered a culprit in the oxidative stress of OSAS patients.

Risk factors and prognostic value of daytime Cheyne-Stokes respiration in chronic heart failure patients

BACKGROUND

Sleep-related Cheyne-Stokes (CS) respiration is a known phenomenon in chronic heart failure (CHF). We aimed to study the prevalence, clinical correlates, risk factors and prognostic relevance of daytime CS, as well as its relation with neurohormonal derangement.

METHODS

One hundred forty seven CHF patients with left ventricular systolic dysfunction (age: 64+/-12 years, ejection fraction, EF, 31+/-8%, mean+/-SD) underwent morning polygraphic recording, in addition to comprehensive clinical and neurohormonal evaluation.

RESULTS

Daytime CS was detected in 87 patients (59%), and associated with worse NYHA class (2.6+/-0.7 vs 2.2+/-0.8, P<0.05), lower EF (29+/-8 vs 33+/-8%, P<0.05), peak oxygen consumption (11.3+/-8.3 vs 13.4+/-4 mL/min/kg, P<0.05), resting carbon dioxide level (33.1+/-4.2 vs 37.9+/-3.8 mm Hg, P<0.001), higher norepinephrine [588 (395-939) vs (331-681) ng/L, median (interquartile range) P<0.01] and natriuretic peptides [ANP: 136 (57-230) vs 66 (18-103); BNP: 284 (99-510) vs 64 (21-202); NT-proBNP: 2575 (814-3320) vs 448 (147-1599) ng/L, all: P<0.001]. At univariate analysis, CS risk factors were age, EF, carbon dioxide, creatinine, norepinephrine, natriuretic peptides, whereas age and NT-proBNP level were the only multivariate predictors. On a 33-month follow-up, CS resulted among univariate predictors of cardiac death, NT-proBNP emerging as the only variable at multivariate analysis.

CONCLUSIONS

Daytime CS is frequent in CHF and is correlated with clinical severity, neurohormonal derangement, particularly of NT-proBNP, and long-term prognosis.

Beneficial effects of severe sleep apnea therapy on nocturnal glucose control in persons with type 2 diabetes mellitus

Given the consequences of sleep apnea and coexisting diabetes, satisfactory treatment of both diseases is required. Our results of continuous glucose monitoring in severe sleep apnea diabetic patients before and during continuous positive airway pressure/CPAP therapy showed significant reduction of nocturnal glucose variability and improved overnight glucose control on CPAP.

Microneurography as a tool in clinical neurophysiology to investigate peripheral neural traffic in humans

Microneurography is a method using metal microelectrodes to investigate directly identified neural traffic in myelinated as well as unmyelinated efferent and afferent nerves leading to and coming from muscle and skin in human peripheral nerves in situ. The present paper reviews how this technique has been used in clinical neurophysiology to elucidate the neural mechanisms of autonomic regulation, motor control and sensory functions in humans under physiological and pathological conditions. Microneurography is particularly important to investigate efferent and afferent neural traffic in unmyelinated C fibers. The recording of efferent discharges in postganglionic sympathetic C efferent fibers innervating muscle and skin (muscle sympathetic nerve activity; MSNA and skin sympathetic nerve activity; SSNA) provides direct information about neural control of autonomic effector organs including blood vessels and sweat glands. Sympathetic microneurography has become a potent tool to reveal neural functions and dysfunctions concerning blood pressure control and thermoregulation. This recording has been used not only in wake conditions but also in sleep to investigate changes in sympathetic neural traffic during sleep and sleep-related events such as sleep apnea. The same recording was also successfully carried out by astronauts during spaceflight. Recordings of afferent discharges from muscle mechanoreceptors have been used to understand the mechanisms of motor control. Muscle spindle afferent information is particularly important for the control of fine precise movements. It may also play important roles to predict behavior outcomes during learning of a motor task. Recordings of discharges in myelinated afferent fibers from skin mechanoreceptors have provided not only objective information about mechanoreceptive cutaneous sensation but also the roles of these signals in fine motor control. Unmyelinated mechanoreceptive afferent discharges from hairy skin seem to be important to convey cutaneous sensation to the central structures related to emotion. Recordings of afferent discharges in thin myelinated and unmyelinated fibers from nociceptors in muscle and skin have been used to provide information concerning pain. Recordings of afferent discharges of different types of cutaneous C-nociceptors identified by marking method have become an important tool to reveal the neural mechanisms of cutaneous sensations such as an itch. No direct microneurographic evidence has been so far proved regarding the effects of sympathoexcitation on sensitization of muscle and skin sensory receptors at least in healthy humans.

Metabolic risk factors for vascular disease in obstructive sleep apnea: a matched controlled study

RATIONALE

Obstructive sleep apnea (OSA) is reported to have a metabolic profile predisposing to cardiovascular disease. However, previous case-control studies have not adequately controlled for confounders.

OBJECTIVES

To determine whether OSA is associated with increased insulin resistance and related metabolic risk factors.

METHODS

We performed a matched case-control study (n = 42) examining putative metabolic risks among men with OSA attending a sleep clinic (apnea-hypopnea index [AHI] > 15] compared with no OSA (AHI < 5). Participants were matched for age +/- 5 yr, body mass index +/- 10%, and current smoking status. They were free of diabetes, clinically demonstrable cardiovascular disease, marked hypertension, and dyslipidemia.

MEASUREMENTS AND MAIN RESULTS

Mean +/- SD AHI was higher in patients with OSA (40 +/- 27) than in control subjects (3 +/- 1.3, p = 0.02), and median (interquartile range) nocturnal oxygen saturation was lower (OSA, 83 [76-88]; control, 91 [90-93]%; p < 0.001). Patients with OSA had a higher median (interquartile range) homeostasis model assessment score for insulin resistance (OSA, 1.7 [0.8-4.1]; control, 1.0 [0.7-1.8] mU.mmol/L(2); p = 0.02), total cholesterol (OSA, 5.6 [4.8-6.2]; control, 4.8 [4.3-5.4] mmol/L; p = 0.049), and low-density-lipoprotein cholesterol (OSA, 3.8 [2.9-4.2]; control, 3.1 [2.6-3.6] mmol/L; p = 0.04). Patients with OSA had higher 24-h and nocturnal (12-h) urinary norepinephrine excretion and plasma leptin levels, and lower insulin-like growth factor (IGF)-1 levels (all, p < or = 0.02). Multiple linear regression, adjusting for central obesity, age, and alcohol consumption, confirmed an independent association between OSA and metabolic risks (all, p < 0.05), with a trend for IGF-1 (p = 0.053).

CONCLUSIONS

In a sleep clinic population, men with OSA and no identifiable cardiovascular disease have increased insulin resistance and other metabolic changes that act to increase the risk of vascular disease, compared with age- and body mass index-matched attendees without OSA.

A case of sleep apnea syndrome manifesting severe hypertension with high plasma norepinephrine levels

A 55-year-old female was admitted to our hospital with severe hypertension (274/140 mmHg). Endocrinological examination revealed that her plasma levels of norepinephrine (NE) was elevated with high levels of urinary NE, normetanephrine and vanillylmandelic acid (VMA), suggesting the presence of pheochromocytoma. However, neither computed tomography nor MIBG scintigraphy detected any catecholamine-producing tumor in or outside the adrenal glands. She was screened with full polysomnography because of heavy snoring, and the diagnosis of severe obstructive sleep apnea syndrome (OSAS) was made. She was treated with calcium channel blocker for three weeks, but severe hypertension persisted. After treatment with nasal continuous positive airway pressure (CPAP) was added, her blood pressure gradually lowered week by week. Concomitantly, the levels of plasma and urinary NE, urinary normetanephrine and urinary VMA were normalized following nasal CPAP therapy for 2 weeks. Additional treatments with alpha-adrenergic blocker further decreased her home blood pressure. After a year, she continued nasal CPAP therapy and her blood pressure was nearly below 160/100 mmHg. Urinary NE level was slightly above normal range and other catecholamines stayed within the normal range. This case shows that patients with OSAS could develop severe hypertension through elevated sympathetic tone, mimicking pheochromocytoma. Nasal CPAP therapy is recommended not only to improve hypertension and catecholamine excess but also to distinguish the condition from pheochromocytoma.

Multidimensional scaling of pediatric sleep breathing problems and bio-behavioral correlates

STUDY OBJECTIVES

Complex relationships exist between pediatric sleep disorders and daytime behavior. Using a multidimensional scaling model, we investigated these relationships in 126 children with sleep breathing disorders (SBD).

METHOD

Validated questionnaires on nighttime behavior, daytime behavior, and respiratory health were administered to a large number of school children in Belgium. Children who met the criterion of having at least one sleep-related breathing problem (three or more times per week during the past six months) were selected for further analyses. A total of 26 indicators were defined and modeled, including sleep problems, sleep efficiency, sleep environment, sleep enuresis, internalised and externalised behavioral problems, respiratory health of the child and relatives, smoking exposure, and caffeine consumption.

RESULTS

From 3,045 questionnaire responses 4.1% of the children were reported to have a SBD symptom. SBD children differed on sleep and health domains from non-SBD children. Furthermore, through scaling of the (dis)similarities among the 26 indicators the SBD child was able to be modeled. By way of an internal analysis of the data-matrix the following indicators were eliminated: sleep correlates, health of the family, and behavior rated by teachers, followed by caffeine intake, drugs, and behavior rated by the parents. This revealed a two-dimensional model, consisting of primary SBD and secondary SBD.

CONCLUSION

Children with SBD differ on many domains from children without such disorders and an underlying two-fold SBD concept was found. Firstly, the SBD-indicator positioned in between investigated correlates with disorders of initiating and maintaining sleep and sleep hyperhydrosis on one hand and with respiratory-related illnesses on the other; this was labeled primary SBD. Secondly, the SDB-indicator not closely associated with any of the investigated correlates can be interpreted as secondary SBD.

What role do adrenoreceptor polymorphisms play in modifying cardiovascular responses in obstructive sleep apnoea?

OSA (obstructive sleep apnoea) is a common condition that is strongly associated with cardiovascular disease. It is remains unclear what role OSA plays in determining cardiovascular risk. The immediate physiological changes that occur during upper airway obstruction are potential contributors to cardiovascular risk in OSA. These changes include increased sympathetic activity, which is responsive to treatment of OSA with CPAP (continuous positive airway pressure). In this issue of Clinical Science, the possible role of a common polymorphism in the beta1-adrenoreceptor [R389G (Arg389Gly)] has been investigated by Börgel and co-workers. Measurements of heart rate and blood pressure in untreated OSA patients were not related to the R389G polymorphism. There were changes in heart rate and diastolic blood pressure with CPAP treatment that were related to this polymorphism. Reduction in heart rate with CPAP treatment was associated with the R389R genotype. By contrast, a reduction in diastolic blood pressure was associated with the Gly389 carriers. These findings are intriguing, but difficult to fully explain. Further study is needed to determine if there is an important role of the R389G polymorphism in modifying cardiovascular responses among OSA patients.

Clinical effects of sleep fragmentation versus sleep deprivation

Common symptoms associated with sleep fragmentation and sleep deprivation include increased objective sleepiness (as measured by the Multiple Sleep Latency Test); decreased psychomotor performance on a number of tasks including tasks involving short term memory, reaction time, or vigilance; and degraded mood. Differences in degree of sleepiness are more related to the degree of sleep loss or fragmentation rather than to the type of sleep disturbance. Both sleep fragmentation and sleep deprivation can exacerbate sleep pathology by increasing the length and pathophysiology of sleep apnea. The incidence of both fragmenting sleep disorders and chronic partial sleep deprivation is very high in our society, and clinicians must be able to recognize and treat Insufficient Sleep Syndrome even when present with other sleep disorders.

Transitory increased blood pressure after upper airway surgery for snoring and sleep apnea correlates with the apnea-hypopnea respiratory disturbance index

A transitory increase in blood pressure (BP) is observed following upper airway surgery for obstructive sleep apnea syndrome but the mechanisms implicated are not yet well understood. The objective of the present study was to evaluate changes in BP and heart rate (HR) and putative factors after uvulopalatopharyngoplasty and septoplasty in normotensive snorers. Patients (N = 10) were instrumented for 24-h ambulatory BP monitoring, nocturnal respiratory monitoring and urinary catecholamine level evaluation one day before surgery and on the day of surgery. The influence of postsurgery pain was prevented by analgesic therapy as confirmed using a visual analog scale of pain. Compared with preoperative values, there was a significant (P < 0.05) increase in nighttime but not daytime systolic BP (119 5 vs 107 3 mmHg), diastolic BP (72 4 vs 67 2 mmHg), HR (67 4 vs 57 2 bpm), respiratory disturbance index (RDI) characterized by apnea-hypopnea (30 10 vs 13 4 events/h of sleep) and norepinephrine levels (22.0 4.7 vs 11.0 1.3 g l-1 12 h-1) after surgery. A positive correlation was found between individual variations of BP and individual variations of RDI (r = 0.81, P < 0.01) but not between BP or RDI and catecholamines. The visual analog scale of pain showed similar stress levels on the day before and after surgery (6.0 0.8 vs 5.0 0.9 cm, respectively). These data strongly suggest that the cardiovascular changes observed in patients who underwent uvulopalatopharyngoplasty and septoplasty were due to the increased postoperative RDI.

Hemostatic Alterations in Patients With Obstructive Sleep Apnea and the Implications for Cardiovascular Disease *

STUDY OBJECTIVES

Patients with obstructive sleep apnea (OSA) are at increased risk for coronary artery and cerebrovascular diseases. Numerous studies suggest that a hypercoagulable state is prospectively related to atherothrombotic events. This review explores whether changes in hemostasis may constitute one biological link between OSA and vascular disease.

DESIGN

Ten studies on hemostatic variables in OSA were located by electronic library search and descriptively reviewed. Work on hemostatic function with physiologic conditions similar to those found in OSA (hypoxemia and hyperactivity of the sympathetic nervous system) was considered to discuss potential molecular mechanisms of procoagulant disturbances in OSA.

MEASUREMENTS AND RESULTS

The reviewed data suggest that, as compared to non-OSA control subjects, patients with OSA have elevated plasma fibrinogen levels, exaggerated platelet activity, and reduced fibrinolytic capacity. Although not consistently shown, severity of OSA (ie, apnea-hypopnea index) and plasma epinephrine were independent predictors of platelet activity, and average minimal oxygen saturation was an independent predictor of fibrinogen. In some studies, treatment with continuous positive airway pressure decreased platelet activity, plasma fibrinogen levels, and activity of clotting factor VII.

CONCLUSIONS

There is some evidence for a hypercoagulable state in OSA, which might help explain the increased prevalence of vascular diseases in this population. To further confirm such a notion, future studies need to be performed on sufficiently large samples to be able to control for confounders of hemostatic activity. Prospective studies are needed to examine the association between hemostasis molecules and strong vascular end points.

Continuous positive airway pressure treatment rapidly improves insulin sensitivity in patients with obstructive sleep apnea syndrome

The obstructive sleep apnea syndrome is typically associated with conditions known to increase insulin resistance as hypertension, obesity, and diabetes. We investigated whether obstructive sleep apnea itself is an independent risk factor for increased insulin resistance and whether continuous positive airway pressure (CPAP) treatment improves insulin sensitivity. Forty patients (apnea-hypopnea index > 20) were treated with CPAP. Before, 2 days after, and after 3 months of effective CPAP treatment, hyperinsulinemic euglycemic clamp studies were performed. Insulin sensitivity significantly increased after 2 days (5.75 +/- 4.20 baseline versus 6.79 +/- 4.91 micromol/kg.min; p = 0.003) and remained stable after 3 months of treatment. The improvement in insulin sensitivity after 2 days was much greater in patients with a body mass index less than 30 kg/m2 than in more obese patients. The improved insulin sensitivity after 2 nights of treatment may reflect a decreasing sympathetic activity, indicating that sleep apnea is an independent risk factor for increased insulin resistance. The effect of CPAP on insulin sensitivity is smaller in obese patients than in nonobese patients, suggesting that in obese individuals insulin sensitivity is mainly determined by obesity and, to a smaller extent, by sleep apnea.

Blood pressure variability in obstructive sleep apnea: role of sympathetic nervous activity and effect of continuous positive airway pressure

BACKGROUND

Many studies support a link between obstructive sleep apnea (OSA), increased blood pressure (BP) and/or BP variability, and sympathetic nervous system (SNS) activity. We assessed the relationship between SNS activity and 24-h BP variability in patients with OSA, and the effect of continuous positive airway pressure (CPAP) on BP variability.

DESIGN

Forty-one patients with a respiratory disturbance index (RDI) > 15 were randomized into CPAP or CPAP placebo groups for a 1-week trial.

METHODS

Ambulatory BP, 24-h urine norepinephrine (NE) and polysomnography were measured prior to treatment and after 1 and 7 days of treatment.

RESULTS

Neither RDI nor 24-h urine NE levels were related to 24-h mean BP levels. While RDI was associated only with night-time BP variability, daytime urine NE levels were associated with both night-time and daytime BP variability. After treatment, the BP variability decreased significantly but equally in both active and placebo CPAP groups.

CONCLUSIONS

Obstructive sleep apnea is more related to BP variability than BP. Sympathetic nervous activity, as inferred from daytime urine NE, is related to changes in BP variability in OSA patients. BP variability is not specifically affected by CPAP.

Hormones and breathing

A number of hormones, including hypothalamic neuropeptides acting as neurotransmitters and neuromodulators in the CNS, are involved in the physiologic regulation of breathing and participate in adjustment of breathing in disease. In addition to central effects, some hormones also control breathing at peripheral chemoreceptors or have local effects on the lungs and airways. Estrogen and progesterone seem to protect from sleep-disordered breathing, whereas testosterone may predispose to it. Progesterone and thyroxine have long been known to stimulate respiration. More recently, several hormones such as corticotropin-releasing hormone and leptin have been suggested to act as respiratory stimulants. Somatostatin, dopamine, and neuropeptide Y have a depressing effect on breathing. Animal models and experimental human studies suggest that also many other hormones may be involved in respiratory control.

Sleep disturbance in association with elevated pulse rate for prediction of mortality--consequences of mental strain?

OBJECTIVES

Sleep deprivation has experimentally been shown to adversely influence glucose metabolism, endocrine function and sympathovagal balance in young men without known serious disease. We investigated the impact of sleep problems and resting heart rate in a large sample of self-reported, healthy middle-aged men and women on long-term mortality.

METHODS

In all 22,444 men and 10,902 women participated in a population-based health screening (71% mean attendance), including blood sampling and examination of blood pressure (BP) and pulse rate after 10 min supine rest, as well as a self-administered questionnaire on sleep problems. Mortality was assessed from national death registers.

RESULTS

Sleep disturbances were related to increased cardiovascular risk factor levels at baseline in both sexes, and predicted total and cause-specific mortality after a mean of 12 years (women) and 17 years (men) of follow-up. In men, self-reported healthy at baseline, total mortality during follow-up was independently predicted by both sleep problems and increased resting heart rate, also after adjustment for smoking, body mass index (BMI), systolic BP, cholesterol, smoking and problematic alcohol drinking habits. A step-wise increased total mortality was shown in men reporting successively worse sleep problems and higher heart rate, highest hazard ratio 2.7 [95% confidence interval (CI) = 2.1-3.4] after adjustments, compared with men free from sleep problems and with normal heart rate.

CONCLUSIONS

Sleep disturbance is a predictor of total and cause-specific mortality in both sexes, but only interacts with increased resting heart rate for this prediction in healthy men. Sleep problems correlated cross-sectional with disturbances in lipid and glucose metabolism, even after adjustment for degree of obesity and smoking. Sleep disturbance is a symptom for a biological pathway that is correlated to premature mortality. One possible explanation would be that it acts in concert with sympathetic nervous activation (SNA), both being consequences of chronic stress exposure.

Obstructive sleep apnea and hypertension: are peripheral chemoreceptors involved?

The mechanism of pathogenesis of hypertension in patients with obstructive sleep apnea (OSA) is unknown. Many investigators point to the high sympathetic nervous system activity (SNS) observed in OSA patients. However, there is no clear explanation as to the mechanism for the development of SNS hyperactivity in these patients. A common feature of patients with OSA is repetitive bouts of transient hypoxemia during sleep. Repetitive transient hypoxemia in rats has resulted in hypertension. In OSA patients, resolution of nocturnal hypoxemia with CPAP has corrected nocturnal and diurnal hypertension. Also, exposure to hyperoxia reduces blood pressure and sympathetic activity in OSA patients, but not in normals. These data suggest a significant role of peripheral chemoreceptors in the regulation of vascular tone. We hypothesize that peripheral chemoreceptors significantly contribute to the pathogenesis of hypertension in patients with OSA and that this is associated with chemoreceptor hyperactivity. This implies that correcting the intermittent nocturnal hypoxemia alone may prevent the cardiovascular morbidity associated with obstructive sleep apnea.

Sleep bruxism in patients with sleep-disordered breathing

The aim was to test the hypothesis of a direct association between sleep-disordered breathing and sleep bruxism. The frequency of masseter contraction (MC) episodes and rhythmic jaw movements (RJM) was measured in patients with mild and moderate obstructive sleep apnoea (OSA). The diagnosis of sleep bruxism was made from a combination of questionnaire, clinical observation and all-night polysomnographic recording which included masseter electromyography. A total of 21 patients (19 males/two females, mean age 40.0 years+/-9.2 SD) were randomly selected from a provisional diagnosis of snoring and OSA by a sleep physician. In the patients with mild OSA [n=11, mean apnoea hypopnoea index (AHI)=8.0+/-4.1 SD, body mass index (BMI)=29.1+/-5.0], the diagnosis of sleep bruxism was made in six out of 11 patients (54%); similarly, four out of 10 patients (40%) with moderate OSA (n=10, mean AHI=34.7+/-19.1, BMI=30.6+/-5.0) were identified as bruxists. Although the combination of clinical, subjective estimation and nocturnal electromyographic recording of masseter muscle might provide a more solid base for the diagnosis of sleep bruxism, the result is biased by the variation in the bruxing activity. MC episodes were associated with the termination of apnoea or hypopnoea episodes in only 3.5% of the mild group and 14.4% of the moderate group (p<0.05). It appears that sleep bruxism is rarely directly associated with apnoeic events, but is rather related to the disturbed sleep of OSA patients.

Cardiac rhythm disturbances in the obstructive sleep apnea syndrome: effects of nasal continuous positive airway pressure therapy

STUDY OBJECTIVES

A high incidence of nocturnal cardiac rhythm disturbances among patients with obstructive sleep apnea (OSA) syndrome has been described in some reports, but not in others. We wished to examine the prevalence of significant cardiac rhythm disturbance in patients with established moderate to severe OSA syndrome and, in particular, to assess the impact of nasal continuous positive airway pressure (nCPAP) therapy.

DESIGN AND SETTING

A prospective study of consecutive eligible patients in a dedicated sleep disorders unit of a university teaching hospital.

MEASUREMENTS AND RESULTS

Holter monitoring was performed for 18 h in 45 patients with previously diagnosed OSA syndrome (mean [SD] apnea/hypopnea frequency [AHI] of 50 [23]/h) and repeated within 2 to 3 days after institution of nCPAP therapy. Investigators were blinded to the patients' treatments during data analysis. Thirty-five patients were found to have some cardiac rhythm disturbance, but only 8 had pathologically significant disturbances (ventricular tachycardia or fibrillation, complex ventricular ectopy, new-onset supraventricular tachycardia other than sinus tachycardia, pauses of > 2 s, and second- or third-degree heart block). Significant rhythm disturbances occurred only during the nighttime, and there was a significant correlation between OSA severity and the severity of rhythm disturbance (p = 0.04, r = 0.301). No significant correlation was found between OSA severity and any other anthropometric parameter measured. nCPAP therapy resulted in abolition of rhythm disturbance in seven of these eight patients; the eighth patient was found to have coexisting severe aortic valve disease requiring valve replacement.

CONCLUSION

The data indicate that OSA syndrome predisposes to clinically significant cardiac rhythm disturbances that can be successfully controlled by nCPAP therapy.

Mechanisms of acute cardiovascular response to periodic apneas in sedated pigs

This study was designed to evaluate the importance of sympathoadrenal activation in the acute cardiovascular response to apneas and the role of hypoxemia in this response. In addition, we evaluated the contribution of the vagus nerve to apnea responses after chemical sympathectomy. In six pigs preinstrumented with an electromagnetic flow probe and five nonpreinstrumented pigs, effects of periodic nonobstructive apneas were tested under the following six conditions: room air breathing, 100% O2 supplementation, both repeated after administration of hexamethonium (Hex), and both repeated again after bilateral vagotomy in addition to Hex. With room air apneas, during the apnea cycle, there were increases in mean arterial pressure (MAP; from baseline of 108 +/- 4 to 124 +/- 6 Torr, P < 0.01), plasma norepinephrine (from 681 +/- 99 to 1,825 +/- 578 pg/ml, P < 0.05), and epinephrine (from 191 +/- 67 to 1,245 +/- 685 pg/ml, P < 0.05) but decreases in cardiac output (CO; from 3.3 +/- 0.6 to 2.4 +/- 0.3 l/min, P < 0.01) and cervical sympathetic nerve activity. With O2 supplementation relative to baseline, apneas were associated with small increases in MAP (from 112 +/- 4 to 118 +/- 3 Torr, P < 0.01) and norepinephrine (from 675 +/- 97 to 861 +/- 170 pg/ml, P < 0.05). After Hex, apneas with room air were associated with small increases in MAP (from 103 +/- 6 to 109 +/- 6 Torr, P < 0.05) and epinephrine (from 136 +/- 45 to 666 +/- 467 pg/ml, P < 0.05) and decreases in CO (from 3.6 +/- 0.4 to 3.2 +/- 0. 5 l/min, P < 0.05). After Hex, apneas with O2 supplementation were associated with decreased MAP (from 107 +/- 5 to 100 +/- 5 Torr, P < 0.05) and no other changes. After vagotomy + Hex, with room air and O2 supplementation, apneas were associated with decreased MAP (from 98 +/- 6 to 76 +/- 7 and from 103 +/- 7 to 95 +/- 6 Torr, respectively, both P < 0.01) but increased CO [from 2.7 +/- 0.3 to 3. 2 +/- 0.4 l/min (P < 0.05) and from 2.4 +/- 0.2 to 2.7 +/- 0.2 l/min (P < 0.01), respectively]. We conclude that sympathoadrenal activation is the major pressor mechanism during apneas. Cervical sympathetic nerve activity does not reflect overall sympathoadrenal activity during apneas. Hypoxemia is an important but not the sole trigger factor for sympathoadrenal activation. There is an important vagally mediated reflex that contributes to the pressor response to apneas.

Sympathetic nervous system alterations in sleep apnea. The relative importance of respiratory disturbance, hypoxia, and sleep quality

Numerous alterations in the sympathetic nervous system have been reported in patients with obstructive sleep apnea. It is unclear whether such alterations can be attributed to the respiratory disturbance itself, the resulting hypoxia, or disruption of sleep. We examined urinary norepinephrine levels in 45 individuals with varying amounts of respiratory disturbance and sleep disruption. All were of similar age (40 to 60 years) and body weight (100 to 160% ideal body weight), and all were free from antihypertensive medications that could influence norepinephrine levels. Twenty-four-hour urinary norepinephrine levels were correlated with respiratory disturbance index (r = 0.39, p < 0.01) and mean oxygen saturation (r = -0.36, p < 0.05). These variables, together with the time in slow-wave sleep, accounted for a statistically significant but modest percentage of the variance in urinary norepinephrine (R2 = 0.19, p < 0.05). However, the variables were so tightly intercorrelated that no single variable independently predicted norepinephrine levels in multiple regression analysis.