Obstructive sleep apnoea and stroke

How does obstructive sleep apnea alter cerebral hemodynamics?

STUDY OBJECTIVES

We aimed to characterize the cerebral hemodynamic response to obstructive sleep apnea/hypopnea events, and evaluate their association to polysomnographic parameters. The characterization of the cerebral hemodynamics in obstructive sleep apnea (OSA) may add complementary information to further the understanding of the severity of the syndrome beyond the conventional polysomnography.

METHODS

Severe OSA patients were studied during night sleep while monitored by polysomnography. Transcranial, bed-side diffuse correlation spectroscopy (DCS) and frequency-domain near-infrared diffuse correlation spectroscopy (NIRS-DOS) were used to follow microvascular cerebral hemodynamics in the frontal lobes of the cerebral cortex. Changes in cerebral blood flow (CBF), total hemoglobin concentration (THC), and cerebral blood oxygen saturation (StO2) were analyzed.

RESULTS

We considered 3283 obstructive apnea/hypopnea events from sixteen OSA patients (Age (median, interquartile range) 57 (52-64.5); females 25%; AHI (apnea-hypopnea index) 84.4 (76.1-93.7)). A biphasic response (maximum/minimum followed by a minimum/maximum) was observed for each cerebral hemodynamic variable (CBF, THC, StO2), heart rate and peripheral arterial oxygen saturation (SpO2). Changes of the StO2 followed the dynamics of the SpO2, and were out of phase from the THC and CBF. Longer events were associated with larger CBF changes, faster responses and slower recoveries. Moreover, the extrema of the response to obstructive hypopneas were lower compared to apneas (p < .001).

CONCLUSIONS

Obstructive apneas/hypopneas cause profound, periodic changes in cerebral hemodynamics, including periods of hyper- and hypo-perfusion and intermittent cerebral hypoxia. The duration of the events is a strong determinant of the cerebral hemodynamic response, which is more pronounced in apnea than hypopnea events.

Obstructive sleep apnea and cardiovascular events in acute coronary syndrome: a meta-analysis

OBJECTIVE

Obstructive sleep apnea (OSA) in patients with the acute coronary syndrome (ACS) were at high risk for cardiovascular events, but the results are currently inconclusive. We aimed to conduct a systematic review to determine the incidence of cardiovascular events among ACS patients with OSA by a meta-analysis of observational studies.

METHODS

PubMed, Embase, and Cochrane Library were searched for studies related to the association between OSA and the risk of cardiovascular events in patients with ACS. Risk of bias in observational studies was assessed according to the Risk Of Bias In the Non-randomized Studies-Of Interventions tool.We performed a meta-analysis using a random-effects model to calculate estimates of pooled hazard ratios (HR) with 95% confidence intervals (CI), and heterogeneity was assessed using the statistics.

RESULTS

A total of 12 studies evaluating ACS patients with OSA were included in the meta-analysis. OSA was related to the increased risk of MACE (HR = 2.2; 95% CI, 1.274-3.805, I2  = 76.1%). The effect of OSA on MACCE (HR = 1.921; 95% CI, 1.45-2.546; I2  = 19.1%) and readmission for unstable angina (HR = 3.137, 95% CI, 1.06-9.283; I2  = 52.4%) were statistically significant in the pooled analysis. All of the outcomes in the included studies had a serious risk of bias and the Grading of Recommendation, Assessment, Development, and Evaluation evidence level of all the evaluation results were very low.

CONCLUSIONS

OSA was associated with a significant increase in the risk of cardiovascular events for patients with ACS. Additional randomized controlled trial studies are required to confirm the results and to prove the treatment of OSA can change the prognosis.

The potential link between obstructive sleep apnea and postoperative neurocognitive disorders: current knowledge and possible mechanisms

PURPOSE

This narrative review examines the current evidence on whether obstructive sleep apnea (OSA) is associated with postoperative delirium (POD) and postoperative cognitive dysfunction (POCD). The mechanisms that could predispose OSA patients to these disorders are also explored.

SOURCE

Relevant literature was identified by searching for pertinent terms in Medline®, Pubmed, ScopusTM, and Google scholar databases. Case reports, abstracts, review articles, original research articles, and meta-analyses were reviewed. The bibliographies of retrieved sources were also searched to identify relevant papers.

PRINCIPAL FINDINGS

Seven studies have investigated the association between OSA and POD, with mixed results. No studies have examined the potential link between OSA and POCD. If these relationships exist, they could be mediated by several mechanisms, including increased neuroinflammation, blood-brain barrier breakdown, cerebrovascular disease, Alzheimer's disease neuropathology, disrupted cerebral autoregulation, sleep disruption, sympathovagal imbalance, and/or disrupted brain bioenergetics.

CONCLUSION

There is very limited evidence that OSA plays a role in postoperative neurocognitive disorders because few studies have been conducted in the perioperative setting. Additional perioperative prospective observational cohort studies and randomized controlled trials of sleep apnea treatment are needed. These investigations should also assess potential underlying mechanisms that could predispose patients with OSA to postoperative neurocognitive disorders. This review highlights the need for more research to improve postoperative neurocognitive outcomes for patients with OSA.

Neurological effects of respiratory dysfunction

The respiratory and the nervous systems are closely interconnected and are maintained in a fine balance. Central mechanisms maintain strict control of ventilation due to the high metabolic demands of brain which depends on a continuous supply of oxygenated blood along with glucose. Moreover, brain perfusion is highly sensitive to changes in the partial pressures of carbon dioxide and oxygen in blood, which in turn depend on respiratory function. Ventilatory control is strictly monitored and regulated by the central nervous system through central and peripheral chemoreceptors, baroreceptors, the cardiovascular system, and the autonomic nervous system. Disruption in this delicate control of respiratory function can have subtle to devastating neurological effects as a result of ensuing hypoxia or hypercapnia. In addition, pulmonary circulation receives entire cardiac output and this may act as a conduit to transmit infections and also for metastasis of malignancies to brain resulting in neurological dysfunction. Furthermore, many neurological paraneoplastic syndromes can have underlying lung malignancies resulting in respiratory dysfunction. It is essential to understand the underlying mechanisms and the resulting manifestations in order to prevent and effectively manage the many neurological effects of respiratory dysfunction. This chapter explores the various neurological effects of respiratory dysfunction with focus on their pathophysiology, etiologies, clinical features and long-term neurological sequelae.

The Effect of Obstructive Sleep Apnea and Continuous Positive Airway Pressure Therapy on Skeletal Muscle Lipid Content in Obese and Nonobese Men

Obstructive sleep apnea (OSA), independently of obesity (OBS), predisposes to insulin resistance (IR) for largely unknown reasons. Because OSA-related intermittent hypoxia triggers lipolysis, overnight increases in circulating free fatty acids (FFAs) including palmitic acid (PA) may lead to ectopic intramuscular lipid accumulation potentially contributing to IR. Using 3-T-¹H-magnetic resonance spectroscopy, we therefore compared intramyocellular and extramyocellular lipid (IMCL and EMCL) in the vastus lateralis muscle at approximately 7 am between 26 male patients with moderate-to-severe OSA (17 obese, 9 nonobese) and 23 healthy male controls (12 obese, 11 nonobese). Fiber type composition was evaluated by muscle biopsies. Moreover, we measured fasted FFAs including PA, glycated hemoglobin A_1c, thigh subcutaneous fat volume (ScFAT, 1.5-T magnetic resonance tomography), and maximal oxygen uptake (VO₂max). Fourteen patients were reassessed after continuous positive airway pressure (CPAP) therapy. Total FFAs and PA were significantly (by 178% and 166%) higher in OSA patients vs controls and correlated with the apnea-hypopnea index (AHI) (r ≥ 0.45, P < .01). Moreover, IMCL and EMCL were 55% (P < .05) and 40% (P < .05) higher in OSA patients, that is, 114% and 103% in nonobese, 24.4% and 8.4% in obese participants (with higher control levels). Overall, PA, FFAs (minus PA), and ScFAT significantly contributed to IMCL (multiple r = 0.568, P = .002). CPAP significantly decreased EMCL (–26%) and, by trend only, IMCL, total FFAs, and PA. Muscle fiber composition was unaffected by OSA or CPAP. Increases in IMCL and EMCL are detectable at approximately 7 am in OSA patients and are partly attributable to overnight FFA excesses and high ScFAT or body mass index. CPAP decreases FFAs and IMCL by trend but significantly reduces EMCL.

A Gap in Post-Stroke Blood Pressure Target Attainment at Entry to Cardiac Rehabilitation

BACKGROUND

Recurrent events account for approximately one-third of all strokes and are associated with greater disability and mortality than first-time strokes. Blood pressure (BP) is the most important modifiable risk factor. Objectives were to determine the proportion of post-stroke patients enrolled in cardiac rehabilitation (CR) meeting systolic and diastolic BP (SBP/DBP) targets and to determine correlates of meeting these targets.

METHODS

A retrospective study of 1,804 consecutively enrolled post-stroke patients in a CR program was conducted. Baseline data (database records 2006-2017) included demographics, anthropometrics, clinical/medication history, and resting BP. Multivariate analyses determined predictors of achieving BP targets.

RESULTS

Mean age was 64.1 ± 12.7 years, median days from stroke 210 (IQR 392), with most patients being male (70.6%; n = 1273), overweight (66.8%; n = 1196), and 64.2% diagnosed with hypertension (n = 1159), and 11.8% (n = 213) with sleep apnea. A mean of 1.69 ± 1.2 antihypertensives were prescribed, with 26% (n = 469) of patients prescribed 3-4 antihypertensives. SBP target was met by 71% (n = 1281) of patients, 83.3% (n = 1502) met DBP target, and 64.3% (n = 1160) met both targets. Correlates of meeting SBP target were not having diabetes, younger age, fewer prescribed antihypertensives, and more recent program entry. Correlates of meeting DBP target were not having diabetes, older age, fewer prescribed antihypertensives, and more recent stroke.

CONCLUSIONS

Up to one-third of patients were not meeting BP targets. Patients with diabetes, and those prescribed multiple antihypertensives are at greater risk for poorly controlled SBP and DBP. Reasons for poor BP control such as untreated sleep apnea and medication non-adherence need to be investigated.

Wake-up stroke: From pathophysiology to management

Wake-up strokes (WUS) are strokes with unknown exact time of onset as they are noted on awakening by the patients. They represent 20% of all ischemic strokes. The chronobiological pattern of ischemic stroke onset, with higher frequency in the first morning hours, is likely to be associated with circadian fluctuations in blood pressure, heart rate, hemostatic processes, and the occurrence of atrial fibrillation episodes. The modulation of stroke onset time also involves the sleep-wake cycle as there is an increased risk associated with rapid-eye-movement sleep. Furthermore, sleep may have an impact on the expression and perception of stroke symptoms by patients, but also on brain tissue ischemia processes via a neuroprotective effect. Obstructive sleep apnea syndrome is particularly prevalent in WUS patients. Until recently, WUS was considered as a contra-indication to reperfusion therapy because of the unknown onset time and the potential cerebral bleeding risk associated with thrombolytic treatment. A renewed interest in WUS has been observed over the past few years related to an improved radiological evaluation of WUS patients and the recent demonstration of the clinical efficacy of reperfusion in selected patients when the presence of salvageable brain tissue on advanced cerebral imaging is demonstrated.

Microvascular cerebral blood flow fluctuations in association with apneas and hypopneas in acute ischemic stroke

In a pilot study on acute ischemic stroke (AIS) patients, unexpected periodic fluctuations in microvascular cerebral blood flow (CBF) had been observed. Motivated by the relative lack of information about the impact of the emergence of breathing disorders in association with stroke on cerebral hemodynamics, we hypothesized that these fluctuations are due to apneic and hypopneic events. A total of 28 patients were screened within the first week after stroke with a pulse oximeter. Five (18%) showed fluctuations of arterial blood oxygen saturation ( ≥ 3 % ) and were included in the study. Near-infrared diffuse correlation spectroscopy (DCS) was utilized bilaterally to measure the frontal lobe CBF alongside respiratory polygraphy. Biphasic CBF fluctuations were observed with a bilateral increase of 27.1 % ± 17.7 % and 29.0 % ± 17.4 % for the ipsilesional and contralesional hemispheres, respectively, and a decrease of - 19.3 % ± 9.1 % and - 21.0 % ± 8.9 % for the ipsilesional and contralesional hemispheres, respectively. The polygraph revealed that, in general, the fluctuations were associated with apneic and hypopneic events. This study motivates us to investigate whether the impact of altered respiratory patterns on cerebral hemodynamics can be detrimental in AIS patients.

Self-reported snoring and incident cardiovascular disease events: results from the Jackson Heart Study

PURPOSE

Evidence suggests that snoring is associated with increased risk for cardiovascular disease (CVD) events such as myocardial infarction and stroke. Limited data exists pertaining to this association among African Americans. We therefore examined the association between self-reported habitual snoring and incident CVD in the Jackson Heart Study (JHS), a population-based cohort study of African Americans.

METHODS

Self-reported data on snoring and risk factors for CVD were collected at baseline (2000-2004). Participants were followed prospectively for the development of incident CVD. Habitual snoring was defined as present if the participants reported it as "often" or "almost always" or absent if reported as "sometimes," "never," or "seldom." A CVD event included stroke, myocardial infarction, coronary revascularization procedure, or fatal CHD event. Cox proportional hazards models assessed the independent association between self-reported habitual snoring and incident CVD event adjusting for multiple covariates, including age, sex, hypertension, body mass index, diabetes, hypercholesterolemia, and smoking status.

RESULTS

The snorer group consisted of 787 participants (mean age 52.1 years) and the nonsnorer group consisted of 3708 participants (mean age 54.9 years). Frequency of incident CVD events in the snorer group was not significantly different from the nonsnorer group. The fully adjusted hazard ratio for a CVD event in the snorer group was 1.01 (95% confidence interval [0.69, 1.47], p value of 0.96).

CONCLUSION

In conclusion, self-reported habitual snoring was not associated with incident CVD among this large African American cohort. Future studies providing objective data on snoring and sleep apnea may provide more information on the snoring-CVD association among African Americans.

TRIAL REGISTRATION

Identification Number: NCT00005485.

International consensus (ICON) on the ENT role in diagnosis of obstructive sleep apnea syndrome

During the 2017 IFOS ENT World Congress, an international expert panel was asked to clarify the role of ENT in the diagnosis process of the obstructive sleep apnea syndrome (OSA) in adults around the world. OSA is a major public health issue throughout the world. OSA is a highly prevalent disease with heavy clinical, social and economical outcomes. This high prevalence raises serious difficulties of diagnosis accessibility if only somnologists are able to confirm OSA diagnosis. First of all, the panellists reviewed the impact of OSA. Secondly, they defined the ENT role stressing ENT legitimacy, professional expertise and academic and institutional tasks. They also defined when somnologists were necessary. For the international panel, the ENT is a major player in the OSA diagnosis process.

Role of Positive Airway Pressure Therapy for Obstructive Sleep Apnea in Patients With Stroke: A Randomized Controlled Trial

STUDY OBJECTIVES

Obstructive sleep apnea (OSA) is an independent risk factor for stroke. The objective of this study was to assess the effect of continuous positive airway pressure (CPAP) treatment on prevention of new vascular events among patients with stroke and OSA.

METHODS

Consecutive conscious patients presenting with first imaging-confirmed arterial stroke were included, 6 weeks or more after ictus. All patients underwent clinical and polysomnography (PSG) testing. Patients with an apnea-hypopnea index (AHI) of > 15 events/h were randomized to posttitration nightly CPAP treatment and non-CPAP (received best medical treatment) groups. On follow-up at 3, 6, and 12 months from randomization, evaluation was carried out for any new vascular events as the primary outcome measure, and for clinical stroke outcomes (using the Barthel Index and modified Rankin scale) and neuropsychological parameters as the secondary outcome measures.

RESULTS

Among the 679 patients with stroke who were screened, 116 reported for PSG, 83 had AHI > 15 events/h, and 70 (34 in CPAP and 36 in non-CPAP) were randomized. Thirteen patients could not be randomized because of a lack of CPAP devices. Four patients crossed over from the CPAP to the non-CPAP group. Age (mean age 53.41 ± 9.85 in CPAP versus 52.69 ± 13.23 years in non-CPAP, P = .81) and sex distribution (24 males in CPAP versus 33 males in non-CPAP, P = .79) were similar in both groups. At 12-month follow-up, there was 1 vascular event (3.33%) in the CPAP group and 6 events (15%) in the non-CPAP group (P = .23). Modified Rankin scale score improvement by ≥ 1 at 12-month follow-up was found in significantly more patients in the CPAP group than in the non-CPAP group (53% versus 27%).

CONCLUSIONS

These findings suggest significantly better stroke outcomes and statistically nonsignificant favorable outcomes in terms of recurrence of vascular events for patients with stroke and OSA who use CPAP treatment.

CLINICAL TRIAL REGISTRATION

Registry: Clinical Trials Registry - India, CTRI Registration No: CTRI/2016/07.007104, Title: Sleep Disordered Breathing in stroke patients: Effect of treatment trial, URL: http://ctri.nic.in/Clinicaltrials/showallp.php?mid1=8682&EncHid=&userName=sleep%20disordered%20breathing.

Increased Risk of Ischemic Stroke during Sleep in Apneic Patients

Background and Purpose

The literature indicates that obstructive sleep apnea (OSA) increases the risk of ischemic stroke. However, the causal relationship between OSA and ischemic stroke is not well established. This study examined whether preexisting OSA symptoms affect the onset of acute ischemic stroke.

Methods

We investigated consecutive patients who were admitted with acute ischemic stroke, using a standardized protocol including the Berlin Questionnaire on symptoms of OSA prior to stroke. The collected stroke data included the time of the stroke onset, risk factors, and etiologic subtypes. The association between preceding OSA symptoms and wake-up stroke (WUS) was assessed using multivariate logistic regression analysis.

Results

We identified 260 subjects with acute ischemic strokes with a definite onset time, of which 25.8% were WUS. The presence of preexisting witnessed or self-recognized sleep apnea was the only risk factor for WUS (adjusted odds ratio=2.055, 95% confidence interval=1.035–4.083, p=0.040).

Conclusions

Preexisting symptoms suggestive of OSA were associated with the occurrence of WUS. This suggests that OSA contributes to ischemic stroke not only as a predisposing risk factor but also as a triggering factor. Treating OSA might therefore be beneficial in preventing stroke, particularly that occurring during sleep.

Quantitative Retinal Vascular Changes in Obstructive Sleep Apnea

PURPOSE

To examine the relationship between both static and dynamic retinal vascular caliber and the severity of obstructive sleep apnea (OSA).

DESIGN

Prospective cross-sectional study.

METHODS

Adult patients undergoing diagnostic polysomnography studies at a private Australian university teaching hospital were recruited. OSA severity was defined by the apnea-hypopnea index (AHI): severe >30, moderate >15-30, mild 5-15, and controls <5. Of 115 patients recruited (73 male; mean age 58 ± 13 years), there were 41 severe, 35 moderate, and 25 mild OSA patients and 14 controls. Static retinal vascular caliber was measured as the average diameter of retinal arterioles (CRAE) and venules (CRVE), and summarized as the arteriovenous ratio (AVR). Dynamic retinal vascular caliber was evaluated as the average pulsation amplitude of retinal arterioles (SRAP) and venules (SRVP). Comparisons across groups were performed using multivariate linear regression analysis. All results were adjusted for age, body mass index, and mean arterial pressure.

RESULTS

Increasing AHI was significantly associated with decreasing AVR (P = .008) and CRAE (P = .016). A significant relationship was demonstrated between increasing AHI and attenuated retinal vascular pulsation amplitude (arterioles P = .028; venules P < .0001).

CONCLUSIONS

Increasing OSA severity is independently associated with retinal arteriolar narrowing and attenuated vascular pulsation amplitude. The retinal vasculature is easily imaged, and may be a surrogate biomarker of cerebral and systemic vascular risk in patients with OSA requiring further comprehensive investigation.

Effects of continuous positive airway pressure and isocapnic-hypoxia on cerebral autoregulation in patients with obstructive sleep apnoea

KEY POINTS

Altered cerebral autoregulation (CA) in obstructive sleep apnoea (OSA) patients may contribute to increased stroke risk in this population; the gold standard treatment for OSA is continuous positive airway pressure, which improves cerebrovascular regulation and may decrease the risk of stroke. Isocapnic-hypoxia impairs CA in healthy subjects, but it remains unknown in OSA whether impaired CA is further exacerbated by isocapnic-hypoxia and whether it is improved by treatment with continuous positive airway pressure. During normoxia, CA was altered in the more severe but not in the less severe OSA patients, while, in contrast, during isocapnic-hypoxia, CA was similar between groups and tended to improve in patients with more severe OSA compared to normoxia. From a clinical perspective, one month of continuous positive airway pressure treatment does not improve CA. From a physiological perspective, this study suggests that sympathetic overactivity may be responsible for altered CA in the more severe OSA patients.

ABSTRACT

Cerebral autoregulation (CA) impairment may contribute to the increased risk of stroke associated with obstructive sleep apnoea (OSA). It is unknown if impaired CA is further exacerbated by isocapnic-hypoxia and whether it is improved by treatment of OSA with continuous positive airway pressure (CPAP). CA was assessed during wakefulness in 53 OSA patients (50.3 ± 9.3 years) and 21 controls (49.8 ± 8.6 years) at baseline and following a minimum of 1 month of effective CPAP therapy (OSA patients, n = 40). Control participants (n = 21) performed a follow-up visit to control for time effects within OSA patients between baseline and the post-CPAP visit. Beat-by-beat middle cerebral artery blood flow velocity and mean arterial blood pressure (MBP), and breath-by-breath end-tidal partial pressure of CO₂ (P ET ,CO2) were monitored. CA was determined during normoxia and isocapnic-hypoxia using transfer function (phase and gain) and coherence analysis (including multiple and partial coherence (using MBP and P ET ,CO2 as inputs)) in the very low frequency range (0.03-0.07 Hz). OSA patients were divided into two subgroups (less severe and more severe) based upon the median respiratory disturbance index (RDI). During normoxia, the more severe OSA patients (RDI 45.9 ± 10.3) exhibited altered CA compared to controls and the less severe OSA patients (RDI 24.5 ± 5.9). In contrast, during isocapnic-hypoxia, CA was similar between groups. CPAP had no effect on CA. In conclusion, CA is altered in the more severe OSA patients during normoxia but not during isocapnic-hypoxia and CPAP treatment does not impact CA.

Obesity, Cardiovascular Disease and Sleep Disorders: Insights into the Rising Epidemic

Cardiovascular disease (CVD) is the main cause of death among adult men and women in the USA and impacts millions around the globe. Traditional risk factors for CVD include obesity, diabetes, hypertension and dyslipidemia. The modern-day epidemic of obesity not only increased the rate of CVD but also ushered in an additional CVD risk factor to be added to the list; that is obstructive sleep apnea (OSA). In this review, we discuss the growing epidemic of obesity and OSA, highlighting the common pathogenic hypotheses linking these risk factors to CVD. We will also highlight the therapeutic rationale of OSA as a way to reduce CVD risk.

Rehabilitation of Cardiovascular Disorders and Sleep Apnea

Obstructive sleep apnea (OSA) is present in more than 50% of patients referred to cardiac rehabilitation units. However, it has been under-recognized in patients after stroke and heart failure. Those with concurrent OSA have a worse clinical course. Early treatment of coexisting OSA with continuous positive airway pressure (CPAP) results in improved rehabilitation outcomes and quality of life. Possible mechanisms by which CPAP may improve recovery include decreased blood pressure fluctuations associated with apneas, and improved left ventricular function, cerebral blood flow, and oxygenation. Early screening and treatment of OSA should be integral components of patients entering cardiac rehabilitation units.

Hypoxia after stroke: a review of experimental and clinical evidence

Background

Hypoxia is a common occurrence following stroke and associated with poor clinical and functional outcomes. Normal oxygen physiology is a finely controlled mechanism from the oxygenation of haemoglobin in the pulmonary capillaries to its dissociation and delivery in the tissues. In no organ is this process more important than the brain, which has a number of vascular adaptions to be able to cope with a certain threshold of hypoxia, beyond which further disruption of oxygen delivery potentially leads to devastating consequences. Hypoxia following stroke is common and is often attributed to pneumonia, aspiration and respiratory muscle dysfunction, with sleep apnoea syndromes, pulmonary embolism and cardiac failure being less common but important treatable causes. As well as treating the underlying cause, oxygen therapy is a vital element to correcting hypoxia, but excessive use can itself cause molecular and clinical harm. As cerebral vascular occlusion completely obliterates oxygen delivery to its target tissue, the use of supplemental oxygen, even when not hypoxic, would seem a reasonable solution to try and correct this deficit, but to date randomised clinical trials have not shown benefit.

Conclusion

Whilst evidence for the use of supplemental oxygen therapy is currently lacking, it is vital to rapidly identify and treat all causes of hypoxia in the acute stroke patient, as a failure to will lead to poorer clinical outcomes. The full results of a large randomised trial looking at the use of supplemental oxygen therapy are currently pending.

Association of sleep apnea and sleep duration with peripheral artery disease: The Multi-Ethnic Study of Atherosclerosis (MESA)

BACKGROUND AND AIMS

Numerous biological pathways linking sleep disturbances to atherosclerosis have been identified, such as insulin resistance, inflammation, hypertension, and endothelial dysfunction. Yet, the association of sleep apnea and sleep duration with peripheral artery disease (PAD) is not well characterized.

METHODS

We evaluated the cross-sectional association between objectively measured sleep and prevalent PAD in 1844 participants (mean age 68 years) who in 2010-2013 had in-home polysomnography, 7-day wrist actigraphy and ankle-brachial index (ABI) measurements. We also evaluated the relation between self-reported diagnosed sleep apnea and PAD incidence in 5365 participants followed from 2000 to 2012. PAD was defined as ABI < 0.90.

RESULTS

In cross-sectional analyses, severe sleep apnea [apnea-hypopnea index (AHI) ≥30 vs. AHI <5] was associated with greater prevalent PAD only among black participants [multivariate adjusted prevalence ratio (95% CI): 2.29 (1.07-4.89); p-interaction = 0.05]. Short and long sleep duration was also associated with a 2-fold higher prevalence of PAD as compared with those who slept 7 h/night, in the full sample. In longitudinal analyses, participants with self-reported diagnosed sleep apnea were at higher risk of incident PAD [multivariable adjusted hazard ratio (95% CI): 1.93 (1.05-3.53)], with no evidence of interaction by race/ethnicity.

CONCLUSIONS

These findings support a significant association between sleep apnea and prevalent and incident PAD, with evidence for stronger associations with objectively measured sleep apnea and cross sectional PAD in blacks. In addition, short and long sleep duration was associated with PAD. These results identify sleep disturbances as a potential risk factor for PAD.

Prolonged sleep increases the risk of intracerebral haemorrhage: a nationwide case-control study

BACKGROUND AND PURPOSE

Although abnormal sleep duration is positively associated with increased risk for cardiovascular disease and mortality, the specific impact on intracerebral haemorrhage (ICH) risk remains unclear. The relationship between sleep duration and the risk of ICH was investigated in our study.

METHODS

A nationwide, multicentre matched case-control study was performed to investigate the risk factors for haemorrhagic stroke, using patients from 33 hospitals in Korea. In all, 490 patients with ICH and 980 age- and sex-matched controls were enrolled. Detailed information regarding sleep, sociodemographic factors, lifestyle and medical history before ICH onset was obtained using qualified structured questionnaires. Sleep duration was categorized and the adjusted odds ratios (ORs) and 95% confidence intervals (CIs) were estimated using a conditional logistic regression with 7 h as the reference duration.

RESULTS

The number of subjects with long sleep duration, more than 8 h, was significantly greater in the ICH group than in the control group (≥8 h, 30.4% vs. 22.6%, P = 0.002). After controlling for relevant confounding factors, longer sleep duration was found to be independently associated with the risk of ICH in a dose-response manner (8 h, OR 1.57, 95% CI 1.00-2.47; ≥9 h, OR 5.00, 95% CI 2.18-11.47).

CONCLUSIONS

Our study suggested that long sleep duration is positively associated with an increased ICH risk in a dose-dependent manner. Further studies on the relationship linking long sleep duration with increased risk of ICH are required.

Reducing cardiovascular risk through treatment of obstructive sleep apnea: 2 methodological approaches

Obstructive sleep apnea (OSA) significantly impacts cardiovascular health, demonstrated by observational investigations showing an independently increased risk of ischemic heart disease, diabetes, hypertension, congestive heart failure, acute coronary syndrome, stroke, cardiovascular mortality, and all-cause mortality. Positive airway pressure (PAP), a medical therapy for sleep apnea, reverses airway obstruction and may help reduce cardiovascular risk. Prior to planning large phase III randomized controlled trials to test the impact of PAP on cardiovascular outcomes, several gaps in knowledge need to be addressed. This article describes 2 independent studies that worked collaboratively to fill these gaps. The populations, design features, and relative benefits/challenges of the 2 studies (SleepTight and BestAIR) are described. Both studies were encouraged to have multidisciplinary teams with expertise in behavioral interventions to improve PAP compliance. Both studies provide key information that will be useful to the research community in future large-scale, event-driven, randomized trials to evaluate the efficacy and/or effectiveness of strategies to identify and treat significant OSA for decreasing risk of major adverse cardiovascular events in high-risk patients.

Obstructive sleep apnea: a new preventive and therapeutic target for stroke: a new kid on the block

Stroke is the second leading cause of death worldwide and a major cause of mental and physical impairment. Numerous studies have identified risk factors for stroke, including hypertension, atrial fibrillation, diabetes, and smoking. However, even after considering these well-recognized risk factors, there is substantial variation in stroke rates and stroke-related outcomes. There is emerging evidence that obstructive sleep apnea increases the risk of stroke independently of traditional risk factors. Obstructive sleep apnea is present in the majority of patients with stroke and contributes to persistent neurologic impairment. Early recognition and treatment of obstructive sleep apnea during the post-stroke period lead to better neurologic outcome. Healthcare providers should be aware of the strong association of obstructive sleep apnea as a risk factor for stroke and its effect on neurologic recovery. The presence of hypertension and diabetes-the 2 most common comorbid conditions in obstructive sleep apnea-should prompt diagnostic workup for and treatment of obstructive sleep apnea as a way of primary and secondary prevention of stroke.

Decreased Regional Cerebral Perfusion in Moderate-Severe Obstructive Sleep Apnoea during Wakefulness

STUDY OBJECTIVES

To investigate gray matter volume and concentration and cerebral perfusion in people with untreated obstructive sleep apnea (OSA) while awake.

DESIGN

Voxel-based morphometry to quantify gray matter concentration and volume. Arterial spin labeling perfusion imaging to quantify cerebral perfusion.

SETTING

Lying supine in a 3-T magnetic resonance imaging scanner in the early afternoon.

PARTICIPANTS

19 people with OSA (6 females, 13 males; mean age 56.7 y, range 41-70; mean AHI 18.5, range 5.2-52.8) and 19 controls (13 females, 6 males; mean age: 50.0 y, range 41-81).

INTERVENTIONS

N/A.

MEASUREMENTS AND RESULTS

There were no differences in regional gray matter concentration or volume between participants with OSA and controls. Neither was there any difference in regional perfusion between controls and people with mild OSA (n = 11). However, compared to controls, participants with moderate-severe OSA (n = 8) had decreased perfusion (while awake) in three clusters. The largest cluster incorporated, bilaterally, the paracingulate gyrus, anterior cingulate gyrus, and subcallosal cortex, and the left putamen and left frontal orbital cortex. The second cluster was right-lateralized, incorporating the posterior temporal fusiform cortex, parahippocampal gyrus, and hippocampus. The third cluster was located in the right thalamus.

CONCLUSIONS

There is decreased regional perfusion during wakefulness in participants with moderate-severe obstructive sleep apnea, and these are in brain regions which have shown decreased regional gray matter volume in previous studies in people with severe OSA. Thus, we hypothesize that cerebral perfusion changes are evident before (and possibly underlie) future structural changes.

First night of CPAP: impact on memory consolidation attention and subjective experience

OBJECTIVE

Neurocognitive deficits are common and serious consequences of obstructive sleep apnea (OSA). Currently, the gold standard treatment is continuous positive air pressure (CPAP) therapy, although the clinical responses to this intervention can be variable. This study examined the effect of one night of CPAP therapy on sleep-dependent memory consolidation, attention, and vigilance as well as subjective experience.

METHODS

Fifteen healthy controls and 29 patients with obstructive sleep apnea of whom 14 underwent a full-night CPAP titration completed the psychomotor vigilance test (PVT) and motor sequence learning task (MST) in the evening and the morning after undergoing overnight polysomnography. All participants also completed subjective evaluations of sleep quality.

RESULTS

Participants with OSA showed significantly less overnight improvement on the MST compared to controls without OSA, independent of whether or not they had received CPAP treatment, while there was no significant difference between the untreated OSA and CPAP-treated patients. Within the OSA group, only those receiving CPAP exhibited faster reaction times on the PVT in the morning. Compared to untreated OSA patients, they also felt subjectively more rested and reported that they slept better.

CONCLUSION

Our results demonstrate an instant augmentation of subjective experience and, based on PVT results, attention and vigilance after one night of CPAP, but a lack of an effect on offline sleep-dependent motor memory consolidation. This dissociation may be explained by different brain structures underlying these processes, some of which might require longer continued adherence to CPAP to generate an effect.

Comorbidity of diabetes and obstructive sleep apnea in hospitalized patients

Obstructive sleep apnea (OSA) and type 2 diabetes are two morbidities commonly encountered in the hospitalized setting. Both diseases will present with an array of complications if not managed in a timely, competent manner. However, a growing body of evidence suggests a link between these two pathologies. It is our hope that through careful review of the literature, we may generate heightened awareness of the OSA/diabetes comorbidity. Through better understanding of these conditions and their interactions, we may insure efficient management in the clinical setting and prevent exacerbation of common complications.

The prevalence of obstructive sleep apnea-hypopnea syndrome-related symptoms and their relation to airflow limitation in an elderly population receiving home care

Background

Both airflow limitation and obstructive sleep apnea-hypopnea syndrome (OSAHS)-related symptoms are most prevalent in the elderly population. Previous studies revealed significant associations between OSAHS-related symptoms and obstructive airway diseases in the general population. However, other studies showed that the frequency of OSAHS-related symptoms in patients with obstructive airway diseases decreases after the age of 60 and older.

Aims

To investigate the prevalence of OSAHS-related symptoms (snoring, breathing pauses, and excessive daytime sleepiness [EDS]) and their relations to airflow limitation, for people over 65 years old.

Methods

A full screening spirometry program was performed in a total of 490 aging participants (mean age 77.5 years – range 65–98) who were attending 16 home care settings in central Greece. Airflow limitation was assessed according to the Global Initiative for Chronic Obstructive Lung Disease (GOLD) spirometric criteria (FEV₁/FVC <70%). The Berlin Questionnaire and the Epworth Sleepiness Scale were used to screen individuals for OSAHS-related symptoms. Bivariate associations were described using odds ratio (OR) with 95% confidence intervals (CI).

Results

Airflow limitation prevalence was 17.1% (male 24.2% and female 9.9%) and was strongly related to male gender and smoking status. The prevalence rates of frequent snoring, breathing pauses, and EDS were 28.1%, 12.9%, and 11.6%, respectively. However, participants with airflow limitation were less likely to report breathing pauses, frequent snoring, EDS, and obesity. Finally, frequent snoring was significantly more common in males than females.

Conclusion

This study revealed decreased frequency of OSAHS-related symptoms in participants with airflow limitation suggesting that OSAHS-related symptoms and airflow limitation are not related in our elderly population.

Sleep duration, snoring habits and risk of acute myocardial infarction in China population: results of the INTERHEART study

BACKGROUND

Less sleep time and snoring have been associated with cardiovascular disease (CVD) risk in Western populations; however, few studies have evaluated the different aspects of sleep duration and snoring frequency in relation to CVD, and this association has not been examined in China. The present study aimed to address the relation between sleep duration, snoring frequency and risk of acute myocardial infarction (AMI) in China population.

METHODS

We conducted a hospital-based case-control study. Cases were first AMI (n = 2909). Controls were matched to cases on age and sex. 2947 controls who did not report previous angina or physical disability completed a questionnaire on sleep duration and snoring frequency. We used logistic regression to control for other risk factors.

RESULTS

We observed an inverse association between serious snoring frequency and AMI risk. After adjustment for all the risk factors, and the OR for everyday group and 3-5 times per week group was 1.45 (95% CI: 1.01 to 1.91) and 1.93 (95% CI: 1.52-2.46) compared to no snoring group. The OR for serious level group and moderate group was 1.77 (95% CI: 1.29 to 2.43) and 1.37 (95% CI: 1.10 to 1.69) compared to no snoring group. People having serious snoring increased 77% risk of AMI. 15.2% people in control group have ≤ 6 hours sleeping, compared with 17.4% in AMI group.

CONCLUSIONS

Snoring frequency, including as much as everyday and 3-5 times per week, was positively associated with AMI risk and less sleep duration was associated with risk of AMI. Less sleep time could increase AMI risk in China population.

Volumetric Brain Morphometry Changes in Patients with Obstructive Sleep Apnea Syndrome: Effects of CPAP Treatment and Literature Review

INTRODUCTION

Obstructive sleep apnea syndrome (OSAS) is a frequent breathing disorder occurring during sleep that is characterized by recurrent hypoxic episodes and sleep fragmentation. It remains unclear whether OSAS leads to structural brain changes, and if so, in which brain regions. Brain region-specific gray and white matter volume (GMV and WMV) changes can be measured with voxel-based morphometry (VBM). The aims of this study were to use VBM to analyze GMV and WMV in untreated OSAS patients compared to healthy controls (HC); examine the impact of OSAS-related variables (nocturnal hypoxemia duration and sleep fragmentation index) on GMV and WMV; and assess the effects of therapeutic vs. sham continuous positive airway pressure (CPAP) treatment. We discuss our results in light of previous findings and provide a comprehensive literature review.

METHODS

Twenty-seven treatment-naïve male patients with moderate to severe OSAS and seven healthy age- and education-matched HC were recruited. After a baseline fMRI scan, patients randomly received either active (therapeutic, n = 14) or sham (subtherapeutic, n = 13) nasal CPAP treatment for 2 months.

RESULTS

Significant negative correlations were observed between nocturnal hypoxemia duration and GMV in bilateral lateral temporal regions. No differences in GMV or WMV were found between OSAS patients and HC, and no differences between CPAP vs. sham CPAP treatment effects in OSAS patients.

CONCLUSION

It appears that considering VBM GMV changes there is little difference between OSAS patients and HC. The largest VBM study to date indicates structural changes in the lateral aspect of the temporal lobe, which also showed a significant negative correlation with nocturnal hypoxemia duration in our study. This finding suggests an association between the effect of nocturnal hypoxemia and decreased GMV in OSAS patients.

Sleep duration and risk of stroke mortality among Chinese adults: Singapore Chinese health study

BACKGROUND AND PURPOSE

Prospective relation between sleep duration and stroke risk is less studied, particularly in Asians. We examined the association between sleep duration and stroke mortality among Chinese adults.

METHODS

The Singapore Chinese Health Study is a population-based cohort of 63 257 Chinese adults aged 45 to 74 years enrolled during 1993 through 1998. Sleep duration at baseline was assessed via in-person interview, and death information during follow-up was ascertained via record linkage with the death registry up to December 31, 2011. Cox proportional hazard models were used to calculate hazard ratios with adjustment for other comorbidities and lifestyle risk factors of stroke mortality.

RESULTS

During 926 752 person-years of follow-up, we documented 1381 stroke deaths (322 from hemorrhagic and 1059 from ischemic or nonspecified strokes). Compared with individuals with 7 hours per day of sleep, the multivariate-adjusted hazard ratio (95% confidence interval) of total stroke mortality was 1.25 (1.05-1.50) for ≤5 hours per day (short duration), 1.01 (0.87-1.18) for 6 hours per day, 1.09 (0.95-1.26) for 8 hours per day, and 1.54 (1.28-1.85) for ≥9 hours per day (long duration). The increased risk of stroke death with short (1.54; 1.16-2.03) and long durations of sleep (1.95; 1.48-2.57) was seen among subjects with a history of hypertension, but not in those without hypertension. These findings were limited to risk of death from ischemic or nonspecified stroke, but not observed for hemorrhagic stroke.

CONCLUSIONS

Both short and long sleep durations are associated with increased risk of stroke mortality in a Chinese population, particularly among those with a history of hypertension.

Central sleep apnea

Neurophysiologically, central apnea is due to a temporary failure in the pontomedullary pacemaker generating breathing rhythm. As a polysomnographic finding, central apneas occur in many pathophysiological conditions. Depending on the cause or mechanism, central apneas may not be clinically significant, for example, those that occur normally at sleep onset. In contrast, central apneas occur in a number of disorders and result in pathophysiological consequences. Central apneas occur commonly in high-altitude sojourn, disrupt sleep, and cause desaturation. Central sleep apnea also occurs in number of disorders across all age groups and both genders. Common causes of central sleep apnea in adults are congestive heart failure and chronic use of opioids to treat pain. Under such circumstances, diagnosis and treatment of central sleep apnea may improve quality of life, morbidity, and perhaps mortality. The mechanisms of central sleep apnea have been best studied in congestive heart failure and hypoxic conditions when there is increased CO2 sensitivity below eupnea resulting in lowering eupneic PCO2 below apneic threshold causing cessation of breathing until the PCO2 rises above the apneic threshold when breathing resumes. In many other disorders, the mechanism of central sleep apnea (CSA) remains to be investigated.

Early diagnosis and treatment of obstructive sleep apnea after stroke: Are we neglecting a modifiable stroke risk factor?

Sleep-disordered breathing is an increasingly recognized disorder that is particularly prevalent among stroke patients. Obstructive sleep apnea, a form of sleep-disordered breathing, is associated with multiple major stroke risk factors but is also an independent risk factor for stroke. In addition, untreated sleep apnea is associated with poor functional outcome after stroke. Sleep apnea is amenable to treatment and should be considered a modifiable stroke risk factor, though long-term compliance remains a major barrier. A better understanding of the relationship between sleep apnea and stroke may prompt providers to pursue the early diagnosis and treatment of underlying sleep-disordered breathing to both improve the chance of recovery from stroke in the short term and to reduce the risk of recurrent stroke in the long term.

Profile of circulating cytokines: impact of OSA, obesity and acute cardiovascular events

Obstructive sleep apnea (OSA) is inducing oxidative stress and consequently promotes systemic inflammation and cardiovascular morbidity. The respective impact of obesity, sleep apnea and acute cardiovascular events on the profile of inflammatory cytokines has not been extensively evaluated. We examined the profile of circulating cytokines in a case-control study comparing nonobese or obese patients with or without sleep apnea and with or without an acute cardiovascular event. Patients were assessed by sleep studies and inflammatory (hs-CRP, Leptin, RANTES, MCP1, IL6, IL8, TNF-α) and anti-inflammatory (adiponectin, IL1-Ra) cytokines profile. A cardiovascular phenotyping was performed including carotid intima-media thickness, pulse wave velocity and 24h blood pressure monitoring. In comparison with patients without sleep apnea or without comorbidities, patients with the combination of an acute cardiovascular event and pre-existing sleep apnea showed a higher burden of systemic inflammation with significant increase in serum levels of hs-CRP, IL1-Ra, IL-8, IL-6, TNF-α, Rantes and sICAM. Rantes and sICAM serum levels were independently associated with AHI after an acute cardiovascular event. Serum levels of different inflammatory markers were significantly increased in patients with the combination of sleep apnea and an acute cardiovascular event. Since these biomarkers could be associated with worsened cardiovascular outcome, diagnosing and treating associated sleep apnea is potentially important in patients after an acute cardiovascular event.

Interaction between Sleep-Disordered Breathing and Acute Ischemic Stroke

BACKGROUND AND PURPOSE

Sleep-disordered breathing (SDB) is suggested to be strongly associated with ischemic strokes. Risk factors, stroke subtypes, stroke lesion distribution, and the outcome of SDB in stroke patients remain unclear in Korea.

METHODS

We prospectively studied 293 patients (159 men, 134 women; age 68.4±10.5) with acute ischemic stroke. Cardiovascular risk factors, stroke severity, sleep-related stroke onset, distribution of stroke lesions, and 3-month score on the modified Rankin Scale (mRS) were assessed. Stroke severity was assessed by the US National Institutes of Health Stroke Scale (NIHSS) and the mRS. The apnea-hypopnea index (AHI) was determined 6.3±2.2 days after stroke onset with the Apnea Link portable sleep apnea monitoring device.

RESULTS

The prevalence of SDB (defined as an AHI of ≥10) was 63.1% (111 men, 74 women). Those in the SDB group were older, had higher NIHSS and mRS scores, greater bulbar weakness, and a higher incidence of sleep-associated stroke onset. Among risk-factor profiles, alcohol consumption and atrial fibrillation were significantly related to SDB. The stroke outcome was worse in patients with SDB than in those without SDB. The lesion location and specific stroke syndrome were not correlated with SDB.

CONCLUSIONS

SDB is very common in acute cerebral infarction. Different risk-factor profiles and sleep-related stroke onsets suggest SDB as a cause of ischemic stroke. The higher NIHSS score and greater bulbar involvement in the SDB group seem to show the influence of ischemic stroke on the increased SDB prevalence.

The relationship between cephalometric carotid artery calcification and Framingham Risk Score profile in patients with obstructive sleep apnea

PURPOSE

The morbidity rate of arteriosclerosis becomes clinically manifested as acute cardiovascular events. In the progress of atherosclerosis, the carotid artery calcifies and sometimes appears as a calcified mass on a cephalometric radiograph. This study was designed to evaluate cardiovascular risks according to the Framingham Risk Score (FRS) between subjects with and without visible carotid artery calcification on a cephalogram.

METHODS

Subjects diagnosed with obstructive sleep apnea (OSA) were divided into two groups according to whether or not calcification was visible on a cephalometric radiograph in the carotid artery area, and the characteristic differences between the two groups were analyzed. The evaluated variables included age, BMI, apnea-hypopnea index (AHI), SpO2, ESS, blood pressure, medication history, diabetes mellitus (DM), drinking, smoking, and lipid-related measurements. FRSs for stroke, general cardiovascular disease (GCD), and coronary heart disease (CHD) were calculated. Statistical analyses were performed (SPSS 18.0) with significance defined as a two-tailed p value less than 0.05.

RESULTS

A total of 811 subjects completed the data collection (727 males, age 53.0 ± 12.5 years, AHI 31.7 ± 22.6, times/h). From FRSs, probabilities of a GCD, stroke, and CHD within 10 years were 16.0 ± 9.7, 9.8 ± 6.7, and 11.9 ± 8.3 %, respectively. Some 84 subjects exhibited calcification in the carotid arterial area. Calcification subjects were higher GCD risk and older than subjects who had no identified calcification (20.3 ± 10.1 vs 15.6 ± 20.3 %, p = 0.013, 58.8 ± 11.4 vs. 52.3 ± 12.5 years, p < 0.001). Although there is no significant difference in OSA-related variables and FRSs, subjects with visible calcifications have higher prevalence of high blood pressure medication and DM (p < 0.01).

CONCLUSION

While the presence of a calcified mass on a cephalometric radiograph is not diagnostic of atherosclerosis, this information indicates some cardiovascular risk.

Fibrinolytic activity and platelet function in subjects with obstructive sleep apnoea and a patent foramen ovale: is there an option for prevention of ischaemic stroke?

Obstructive sleep apnoea (OSA) carries an increased risk of ischaemic stroke, but the underlying mechanism is not clear. As right-to-left shunting can occur through a patent foramen ovale (PFO) during periods of apnoea, we investigated nocturnal changes in fibrinolytic activity and platelet function in subjects who had OSA with or without PFO and in controls. We determined plasminogen activator inhibitor 1 (PAI-1) activity and antigen and platelet activation parameters. The severity of OSA was verified by polygraphy and PFO was detected by ear oximetry. We found a higher PAI-1 activity and antigen and a lower ratio of 2,3-dinor-PGF(1α) to 2,3-dinor-TXB(2) in the subjects with OSA than in the controls. Linear regression analysis showed the apnoea-hypopnoea index (β-coefficient, 0.499; P = 0.032) and PFO (β-coefficient, 0.594; P = 0.015) to be associated independently with PAI-1 activity in the morning, while the increment in PAI-1:Ag from evening to morning was significantly associated with the presence of PFO (r(s) = 0.563, P = 0.002). Both OSA and PFO reduce fibrinolytic activity during nocturnal sleep. We hypothesize that subjects having both OSA and PFO may develop a more severe prothrombotic state during sleep than those having either OSA or PFO alone.

Neuropsychological functioning after CPAP treatment in obstructive sleep apnea: a meta-analysis

The generally held clinical view is that treatment with continuous positive airway pressure (CPAP) improves cognition in patients with obstructive sleep apnea (OSA). However, the cognitive domains in which recovery is found differ between studies. A meta-analysis was conducted to quantify the effect of CPAP treatment in OSA on neuropsychological functioning. A literature search of studies published from January 1990 to July 2012 was performed. The inclusion criteria were: randomized controlled trial, diagnosis of OSA by poly(somno)graphy, apnea/hypopnea index, duration and compliance of CPAP treatment reported, use of one or more standardized neuropsychological tests. Mean weighted effect sizes of CPAP treatment for seven cognitive domains were calculated, including processing speed, attention, vigilance, working memory, memory, verbal fluency and visuoconstruction. Thirteen studies encompassing 554 OSA patients were included. A small, significant effect on attention was observed in favor of CPAP (d = 0.19). For the other cognitive domains the effect sizes did not reach significance. Improvement on measures of sleepiness was modest (d = 0.30-0.53) and comparable to prior research. In conclusion, this meta-analysis indicates that the effect of CPAP on cognition is small and limited to attention. Contrary to the general assumption, only slight improvement of neuropsychological functioning after CPAP treatment can be expected.

Respiratory diseases and muscle dysfunction

Many respiratory diseases lead to impaired function of skeletal muscles, influencing quality of life and patient survival. Dysfunction of both respiratory and limb muscles in chronic obstructive pulmonary disease has been studied in depth, and seems to be caused by the complex interaction of general (inflammation, impaired gas exchange, malnutrition, comorbidity, drugs) and local factors (changes in respiratory mechanics and muscle activity, and molecular events). Some of these factors are also present in cystic fibrosis and asthma. In obstructive sleep apnea syndrome, repeated exposure to hypoxia and the absence of reparative rest are believed to be the main causes of muscle dysfunction. Deconditioning appears to be crucial for the functional impairment observed in scoliosis. Finally, cachexia seems to be the main mechanism of muscle dysfunction in advanced lung cancer. A multidimensional therapeutic approach is recommended, including pulmonary rehabilitation, an adequate level of physical activity, ventilatory support and nutritional interventions.

Self-reported snoring frequency and incidence of cardiovascular disease: the Circulatory Risk in Communities Study (CIRCS)

Background

Although associations between snoring and cardiovascular disease have been reported in several prospective studies, there is limited evidence from Asian populations. The objective of this study was to determine if there is an association between self-reported snoring frequency and the incidence of cardiovascular disease in Japanese.

Methods

The subjects were 2350 men and 4163 women aged 40 to 69 years who lived in 3 communities in Japan. All subjects were participants in the Circulatory Risk in Communities Study (CIRCS) and were followed for 6 years. Incidence of cardiovascular disease during the follow-up period comprised events of myocardial infarction, angina pectoris, sudden cardiac death and stroke.

Results

During the 6-year follow-up period, 97 participants (56 men and 41 women) had cardiovascular events. After adjustment for potential confounding factors, self-reported snoring frequency was associated with an increased risk of cardiovascular events among women but not men. The hazard ratios (95% CI) for cardiovascular events were 0.9 (0.4–2.0) for sometimes snoring and 2.5 (1.0–6.1) for everyday snoring in women and 0.7 (0.3–1.3) and 1.0 (0.5–2.1), respectively, in men. Further adjustment for body mass index attenuated the association in women; the respective hazard ratios for cardiovascular events were 0.9 (0.4–1.9) and 2.1 (0.9–5.4).

Conclusions

Self-reported habitual snoring was associated with increased risk of cardiovascular events among Japanese women. Overweight may partly mediate this association.

Sleep disordered breathing in patients with acute coronary syndromes

STUDY OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Obstructive sleep apnoea syndrome and weight loss: review

Obstructive sleep apnoea (OSA) syndrome is common, and obesity is a major risk factor. Increased peripharyngeal and central adiposity result in increased pharyngeal collapsibility, through increased mechanical loading around the upper airway, reduced tracheal traction on the pharynx, and reduced neuromuscular activity, particularly during sleep. Significant and sustained weight loss, if achieved, is likely to be a useful therapeutic option in the management of OSA and may be attempted by behavioural, pharmacological, and surgical approaches. Behavioural therapy programs that focus on aspects such as dietary intervention, exercise prescription patients and general lifestyle counselling have been tested. Bariatric surgery is an option in the severely obese when nonsurgical measures have failed, and laparoscopic adjustable gastric banding and Roux-en-Y gastric bypass are the most commonly employed techniques in the United Kingdom. Most evidence for efficacy of surgery comes from cohort studies. The role of sibutramine in OSA in the obese patients has been investigated, however, there are concerns regarding associated cardiovascular risk. In this paper the links between obesity and OSA are discussed, and the recent studies evaluating the behavioural, pharmacological and surgical approaches to weight loss in OSA are reviewed.