Gender‐specific anthropometric markers of adiposity,metabolic syndrome and visceral adiposity index (VAI) in patients with obstructive sleep apnea

Obstructive sleep apnea often coexists with visceral adiposity and metabolic syndrome. In this study, we analysed gender‐related differences in anthropometrics according to sleep apnea severity and metabolic abnormalities. In addition, the visceral adiposity index, a recently introduced marker of cardiometabolic risk, was analysed. Consecutive subjects with suspected obstructive sleep apnea (n = 528, 423 males, mean age ± standard deviation: 51.3 ± 12.8 years, body mass index: 31.0 ± 6.2 kg m^?2) were studied by full polysomnography (apnea–hypopnea index 43.4 ± 27.6 h^?1). Variables of general and visceral adiposity were measured (body mass index, neck, waist and hip circumferences, waist‐to‐hip ratio). The visceral adiposity index was calculated, and metabolic syndrome was assessed (NCEP‐ATP III criteria). The sample included controls (apnea–hypopnea index <10 h^?1, n = 55), and patients with mild–moderate (apnea–hypopnea index 10–30 h^?1, n = 144) and severe sleep apnea (apnea–hypopnea index >30 h^?1, n = 329). When anthropometric variables were entered in stepwise multiple regression, body mass index, waist circumference and diagnosis of metabolic syndrome were associated with the apnea–hypopnea index in men (adjusted R² = 0.308); by contrast, only hip circumference and height‐normalized neck circumference were associated with sleep apnea severity in women (adjusted R² = 0.339). These results changed little in patients without metabolic syndrome; conversely, waist circumference was the only correlate of apnea–hypopnea index in men and women with metabolic syndrome. The visceral adiposity index increased with insulin resistance, but did not predict sleep apnea severity. These data suggest gender‐related interactions between obstructive sleep apnea, obesity and metabolic abnormalities. The visceral adiposity index was a good marker of metabolic syndrome, but not of obstructive sleep apnea.     

Low leptin concentration may identify heart failure patients with central sleep apnea

Low leptin concentration has been shown to be associated with central sleep apnea in heart failure patients. We hypothesized that low leptin concentration predicts central sleep apnea. Consecutive ambulatory New York Heart Association (NYHA ) classes I–IV heart failure patients were studied prospectively, including measurement of serum leptin, echocardiography and polysomnography. Sleep apnea was defined by type (central/mixed/obstructive) and by apnea–hypopnea index ≥5 by polysomnography. Subjects were divided into four groups by polysomnography: (1) central sleep apnea, (2) mixed apnea, (3) no apnea and (4) obstructive sleep apnea. Fifty‐six subjects were included. Eighteen subjects were diagnosed with central sleep apnea, 15 with mixed apnea, 12 with obstructive apnea and 11 with no sleep apnea. Leptin concentration was significantly lower in central sleep apnea compared to obstructive apnea (8 ± 10.7 ng mL^?1 versus 19.7 ± 14.7 ng mL^?1, P  ? 0.01) or no sleep apnea (8 ± 10.7 ng mL^?1 versus 17.1 ± 8.4 ng mL^?1, P  ? 0.01). Logistic regression showed leptin to be associated independently with central sleep apnea [odds ratio (OR ): 0.19; 95% confidence interval (CI ): 0.06–0.62; area under the curve (AUC ): 0.80, P  < 0.01]. For the detection of central sleep apnea, a cut‐off value for leptin concentration 5 ng mL^?1 yielded a sensitivity of 50% and specificity of 89%. In conclusion, a low leptin concentration may have utility for the screening of heart failure patients for central sleep apnea.     

Chronic kidney disease in European patients with obstructive sleep apnea: the ESADA cohort study

The cross‐sectional relationship of obstructive sleep apnea with moderate to severe chronic kidney disease, defined as an estimated glomerular filtration rate <60 mL min^?1?1.73 m^?2, was investigated in a large cohort of patients with suspected obstructive sleep apnea studied by nocturnal polysomnography or cardiorespiratory polygraphy. Data were obtained from the European Sleep Apnea Database, where information from unselected adult patients with suspected obstructive sleep apnea afferent to 26 European sleep centres had been prospectively collected. Both the Modification of Diet in Renal Disease and the Chronic Kidney Disease‐Epidemiology Collaboration equations were used for the assessment of estimated glomerular filtration rate. The analysed sample included 7700 subjects, 71% male, aged 51.9 ± 12.5 years. Severe obstructive sleep apnea (apnea–hypopnea index ≥30) was found in 34% of subjects. The lowest nocturnal oxygen saturation was 81 ± 10.2%. Chronic kidney disease prevalence in the whole sample was 8.7% or 6.1%, according to the Modification of Diet in Renal Disease or the Chronic Kidney Disease‐Epidemiology Collaboration equations, respectively. Subjects with lower estimated glomerular filtration rate were older, more obese, more often female, had worse obstructive sleep apnea and more co‐morbidities (P < 0.001, each). With both equations, independent predictors of estimated glomerular filtration rate <60 were: chronic heart failure; female gender; systemic hypertension; older age; higher body mass index; and worse lowest nocturnal oxygen saturation. It was concluded that in obstructive sleep apnea, chronic kidney disease is largely predicted by co‐morbidities and anthropometric characteristics. In addition, severe nocturnal hypoxaemia, even for only a small part of the night, may play an important role as a risk factor for kidney dysfunction.     

Obstructive sleep apnea is associated with increased arterial stiffness in severe obesity

Obstructive sleep apnea is associated with obesity and metabolic syndrome, leading to greater cardiovascular risk. Severely obese patients with obstructive sleep apnea may still be at risk of adverse health outcomes, even without previous cardiovascular disease. Pulse wave analysis non‐invasively measures peripheral pulse waveforms and derives measures of haemodynamic status, including arterial stiffness, augmentation pressure and subendocardial viability ratio. We hypothesized that the presence of obstructive sleep apnea in severe obesity, even in the absence of an antecedent history of cardiovascular disease, would affect measurements derived from pulse wave analysis. Seventy‐two severely obese adult subjects [obstructive sleep apnea 47 (body mass index 42 ± 7 kg m^?2), without obstructive sleep apnea (non‐OSA) 25 (body mass index 40 ± 5 kg m^?2)] were characterised using anthropometric, respiratory and cardio‐metabolic parameters. Groups were similar in age, body mass index and gender. More subjects with obstructive sleep apnea had metabolic syndrome [obstructive sleep apnea 60%, without obstructive sleep apnea (non‐OSA) 12%]. Those with obstructive sleep apnea had greater arterial stiffness, augmentation pressure and decreased subendocardial viability ratio (all P < 0.001), with significantly higher systolic (P = 0.003), diastolic (P = 0.04) and mean arterial pressures (P = 0.004) than patients without obstructive sleep apnea (non‐OSA). Arterial stiffness correlated with mean arterial blood pressure (P = 0.003) and obstructive sleep apnea severity (apnea–hypopnea index; P < 0.001). apnea–hypopnea index significantly predicted arterial stiffness in multiple regression analysis, but components of the metabolic syndrome did not. Thus, patients with obstructive sleep apnea with severe obesity have increased arterial stiffness that may potentially influence cardiovascular risk independently of metabolic abnormalities. The presence of obstructive sleep apnea in severe obesity identifies a group at high cardiovascular risk; clinicians should ensure that risk factors are managed appropriately in this group whether or not treatment of obstructive sleep apnea is offered or accepted by patients.     

Nocturnal nasal obstruction is frequent and reduces sleep quality in patients with obstructive sleep apnea

The prevalence and consequences of nasal obstruction in untreated obstructive sleep apnea patients are not known. The study objectives were to investigate the frequency of subjective and objective nasal obstruction in untreated sleep apnea patients and the associations with sleep and quality of life. Patients in the Icelandic Sleep Apnea Cohort were subjected to a type 3 sleep study, answered questionnaires and had their nasal dimensions measured by acoustic rhinometry. In total, 810 patients participated (including 153 females), aged 54.5 ± 10.6 years [mean ± standard deviation (SD)] with an apnea/hypopnea index 44.7 ± 20.7 h^?1. Nocturnal nasal obstruction (greater than or equal to three times per week) was reported by 35% of the patients. These patients had smaller nasal dimensions measured by the minimum cross‐sectional area within the smaller nasal valve (0.42 ± 0.17 versus 0.45 ± 0.16 cm², P = 0.013), reported more daytime sleepiness (Epworth Sleepiness Scale score 12.5 ± 4.9 versus 10.8 ± 5.0; P < 0.001) and slightly lower mental quality of life than patients without nocturnal nasal obstruction. Nocturnal nasal obstruction is reported in one‐third of the sleep apnea patients and they are more likely to suffer from daytime sleepiness and slightly reduced quality of life than other sleep apnea patients.     

Insomnia complaints in lean patients with obstructive sleep apnea negatively affect positive airway pressure treatment adherence

The objective of this study was to evaluate the determinants of long‐term adherence to positive airway pressure treatment among patients with obstructive sleep apnea, with special emphasis on patients who stop positive airway pressure treatment within 1 year. This is a prospective long‐term follow‐up of subjects in the Icelandic Sleep Apnea Cohort who were diagnosed with obstructive sleep apnea between 2005 and 2009, and started on positive airway pressure treatment. In October 2014, positive airway pressure adherence was obtained by systematically evaluating available clinical files (n = 796; 644 males, 152 females) with moderate to severe obstructive sleep apnea (apnea–hypopnea index ≥15 events per h). The mean follow‐up time was 6.7 ± 1.2 years. In total, 123 subjects (15.5%) returned their positive airway pressure device within the first year, 170 (21.4%) returned it later and 503 (63.2%) were still using positive airway pressure. The quitters within the first year had lower body mass index, milder obstructive sleep apnea, less sleepiness, and more often had symptoms of initial and late insomnia compared with long‐term positive airway pressure users at baseline. Both initial and late insomnia were after adjustment still significantly associated with being an early quitter among subjects with body mass index <30 kg m⁻², but not among those with body mass index ≥30 kg m⁻². The prevalence of early quitters decreased significantly during the study period (2005–2009). Almost two‐thirds of patients with moderate to severe obstructive sleep apnea are positive airway pressure users after 7 years. Obesity level, obstructive sleep apnea severity and daytime sleepiness are important determinants of long‐term adherence. Symptoms of initial and late insomnia are associated with early quitting on positive airway pressure among non‐obese subjects.     

Changes of vitamin D levels and bone turnover markers after CPAP therapy: a randomized sham‐controlled trial

The aim was to investigate whether continuous positive airway pressure treatment could modulate serum vitamin D (25‐hydroxyvitamin D) and bone turnover markers (collagen‐type 1 cross‐linked C‐telopeptide, osteocalcin and N‐terminal propeptide of type 1 collagen) in secondary analysis from a randomized controlled trial. Sixty‐five continuous positive airway pressure‐naïve male patients with obstructive sleep apnea (age = 49 ± 12 years, apnea–hypopnea index = 39.9 ± 17.7 events h^?1, body mass index = 31.3 ± 5.2 kg m^?2) were randomized to receive either real (n  = 34) or sham (n  = 31) continuous positive airway pressure for 12 weeks. At 12 weeks, all participants received real continuous positive airway pressure for an additional 12 weeks. After 12 weeks of continuous positive airway pressure (real versus sham), there were no between‐group differences for any of the main outcomes [Δ25‐hydroxyvitamin D: ?0.80 ± 5.28 ng mL ^?1 (mean ± SE ) versus 3.08 ± 3.66 ng mL ^?1, P  = 0.42; Δcollagen‐type 1 cross‐linked C‐telopeptide: 0.011 ± 0.014 ng mL ^?1 versus ?0.004 ± 0.009 ng mL ^?1, P  = 0.48; Δosteocalcin: 1.13 ± 1.12 ng mL ^?1 versus 0.46 ± 0.75 ng mL ^?1, P  = 0.80; ΔN‐terminal propeptide of type 1 collagen: 2.07 ± 3.05 μ g L^?1 versus ?1.05 ± 2.13 μ g L^?1, P  = 0.48]. There were no further differences in subgroup analyses (continuous positive airway pressure‐compliant patients, patients with severe obstructive sleep apnea or sleepy patients). However, after 24 weeks irrespective of initial randomization, vitamin D increased in patients with severe obstructive sleep apnea (9.56 ± 5.51 ng mL ^?1, P  = 0.045) and in sleepy patients (14.0 ± 4.69 ng mL ^?1, P  = 0.007). Also, there was a significant increase in osteocalcin at 24 weeks (3.27 ± 1.06 ng mL ^?1, P  = 0.01) in compliant patients. We conclude that 12 weeks of continuous positive airway pressure did not modulate vitamin D or modulate any of the bone turnover markers compared with sham. However, it is plausible that continuous positive airway pressure may have late beneficial effects on vitamin D levels and bone turnover markers in selected groups of patients with obstructive sleep apnea.     

Electric field aspects in hypoglossal nerve stimulation for obstructive sleep apnea: A bilateral electrophysiological evaluation of unilateral electrode configuration changes

Hypoglossal nerve stimulation is an established treatment option for obstructive sleep apnea in selected patients. A unilateral hypoglossal nerve stimulation system was approved a decade ago, yet the physiological effect of unilateral hypoglossal stimulation on bilateral tongue motion remains unclear. This study examined how electrode configuration, stimulation cuff position, or body mass index influenced the contralateral genioglossus electromyography (EMG) signal. Twenty-nine patients underwent three EMG recordings in a polysomnographic setting after being implanted with a unilateral hypoglossal nerve stimulator for at least 6 months. The ratio of EMG signals between the ipsi- and contralateral sides was evaluated. No difference in EMG signals was demonstrated based on electrode configurations, stimulation-cuff position, body-mass-index, or sleep apnea severity, even in patients with right tongue protrusion only. Our findings may be explained by a significant level of cross-innervation and by a smaller and less variable circumferential electric field than expected based on prior biophysical models. A patient's individual anatomy needs to be considered during therapy titration in order to achieve an optimal response.     

Sleep endoscopy with simulation bite for prediction of oral appliance treatment outcome

The aim of this study was to assess the value of drug‐induced sleep endoscopy (DISE) using a custom‐made simulation bite in maximal comfortable protrusion (MCP) of the mandible, in the prediction of treatment outcome for obstructive sleep apnea (OSA) with a mandibular advancement device (MAD). Two hundred patients (74% male; age 46 ± 9 years; apnea–hypopnea index [AHI] 19 ± 13 h^?1 sleep; body mass index [BMI] 27 ± 4 kg m^?2) with sleep‐disordered breathing underwent DISE with a simulation bite in MCP. One hundred and thirty‐five patients with an established diagnosis of OSA commenced MAD treatment. The associations between the findings during DISE with simulation bite and treatment outcome were evaluated. Treatment response was defined as a reduction in AHI following MAD treatment of ≥ 50% compared to baseline. Overall MAD treatment response in the studied population was 69%. The results of this study demonstrated a statistically significant association between a positive effect of the simulation bite on the upper airway patency during DISE and treatment response with MAD (P < 0.01). The results of this study suggest that the use of a simulation bite in maximal comfortable protrusion (MCP) of the mandible, as used during DISE in patients with OSA, tends to be effective in predicting treatment response of MAD treatment.     

Association between proteomics and obstructive sleep apnea phenotypes in a community‐based cohort of women

Proteomic‐based technologies offer new opportunities to identify proteins that might reflect the cardiometabolic stress caused by different aspects of sleep‐disordered breathing. We aimed to investigate whether severe obstructive sleep apnea and severe obstructive sleep apnea during rapid eye movement sleep are associated with changed levels of inflammatory and cardiac disease‐related proteins in a population‐based cohort of women. In the community‐based “Sleep and Health in Women” (SHE) cohort study, 400 women underwent polysomnography, anthropometric measurements and blood sampling. Two proteomic assays (Olink Proseek^® Inflammation panel and Olink Proseek^® Cardiovascular II panel), each measuring 92 proteins, were analysed in a subsample of 253 women. p‐Values were adjusted for multiple testing, with false discovery rate set at 10%. In unadjusted models, 57 proteins were associated with apnea?hypopnea index, 56 proteins with oxygen desaturation index and 64 proteins with rapid eye movement?apnea?hypopnea index. After adjustment for age, body mass index and plate, there were no significant associations between apnea?hypopnea index or oxygen desaturation index and any of the proteins. Severe obstructive sleep apnea during rapid eye movement sleep (rapid eye movement?apnea?hypopnea index ≥ 30) was associated with decreased levels of two anti‐inflammatory proteins; Sirt2 (q‐value .016) and LAP‐TGF‐β₁ (q‐value .016). There was also a negative association between rapid eye movement?apnea?hypopnea index of ≥ 30 and Axin1 (q‐value .095), a protein thought to facilitate TGF‐β‐signalling. We conclude that severe obstructive sleep apnea during rapid eye movement sleep is associated with low levels of Sirt2, LAP‐TGF‐β₁ and Axin1, anti‐inflammatory proteins involved in metabolic regulation and in the atherosclerotic process. For obstructive sleep apnea based on a whole night, the associations with cardiac and inflammatory proteins are weaker, and explained to a large extent by age and body mass index.     

Low‐grade albuminuria in children with obstructive sleep apnea

Small urinary protein loss (low‐grade albuminuria or microalbuminuria) may reflect altered permeability of the glomerular filtration barrier. In the present study, it was hypothesized that children with obstructive sleep apnea have an increased risk of microalbuminuria compared with control subjects without sleep‐disordered breathing. Albumin‐to‐creatinine ratio was measured in morning spot urine specimens collected from consecutive children with or without snoring who were referred for polysomnography. Three groups were studied: (i) control subjects (no snoring, apnea–hypopnea index < 1 episode h^?1; n = 31); (ii) mild obstructive sleep apnea (snoring, apnea–hypopnea index = 1–5 episodes h^?1; n = 71); and (iii) moderate‐to‐severe obstructive sleep apnea (snoring, apnea–hypopnea index > 5 episodes?h^?1; n = 27). Indications for polysomnography in control subjects included nightmares, somnambulism and morning headaches. An albumin‐to‐creatinine ratio > median value in the control group (1.85 mg of albumin per g of creatinine) was defined as elevated. Logistic regression analysis revealed that children with moderate‐to‐severe obstructive sleep apnea, but not those with mild obstructive sleep apnea, had increased risk of elevated albumin‐to‐creatinine ratio relative to controls (reference) after adjustment for age, gender and presence of obesity: odds ratio 3.8 (95% confidence interval 1.1–12.6); P = 0.04 and 1.5 (0.6–3.7); P > 0.05, respectively. Oxygen desaturation of hemoglobin and respiratory arousal indices were significant predictors of albumin‐to‐creatinine ratio (r = 0.31, P = 0.01; and r = 0.43, P < 0.01, respectively). In conclusion, children with moderate‐to‐severe obstructive sleep apnea are at significantly higher risk of increased low‐grade excretion of albumin in the morning urine as compared with control subjects without obstructive sleep apnea. These findings may reflect altered permeability of the glomerular filtration barrier related to nocturnal hypoxemia and sympathetic activation which are induced by obstructive sleep apnea.     

Usefulness of cardiac parasympathetic index in CPAP‐treated patients with obstructive sleep apnea: A preliminary study

Cardiac autonomic indexes, including cardiac parasympathetic index and cardiac sympathetic index, have been reported to accurately identify patients with sleep disorders such as obstructive sleep apnea. Our study aimed to assess cardiac autonomic indexes in patients with obstructive sleep apnea before and during a single full‐night continuous positive airway pressure therapy using a combined approach. Our simultaneous heart rate variability‐polysomnographic study included 16 never‐treated obstructive sleep apnea patients. Two patients dropped out. Patients underwent combined recordings in two consecutive days, at baseline and during a single full‐night of acute continuous positive airway pressure treatment. We calculated cardiac parasympathetic index and cardiac sympathetic index as night/day ratio for high‐frequency and low‐frequency heart rate variability spectral components, respectively. Continuous positive airway pressure treatment significantly reduced cardiac autonomic indexes values in comparison with baseline values (cardiac parasympathetic index: p < .0001; cardiac sympathetic index: p = .001). After acute continuous positive airway pressure treatment, the percentage of decrease of cardiac parasympathetic index was greater than that of cardiac sympathetic index (51.02 ± 15.72 versus 34.64 ± 26.93). A positive statistical correlation was also found between decrease of cardiac parasympathetic index and decrease of apnea–hypopnea index after continuous positive airway pressure (p < .001). This study improves the knowledge on cardiac autonomic modulation during acute continuous positive airway pressure therapy in obstructive sleep apnea. Our results demonstrate that both autonomic indexes decreased significantly after a single‐night of acute continuous positive airway pressure therapy. Cardiac parasympathetic index more than cardiac sympathetic index was related to decrease of apnea–hypopnea index after continuous positive airway pressure therapy, thus representing a potential help in everyday clinical practice.     

Impact of sleep‐disordered breathing in patients with acute myocardial infarction: a retrospective analysis

Sleep‐disordered breathing (SDB) is associated with an increased risk of cardiovascular events. Previous studies showed that severe SDB has a negative impact on myocardial salvage and progression of left ventricular dysfunction after acute myocardial infarction (AMI). This study investigated the frequency of SDB and the effects of SDB on left ventricular function after AMI. This retrospective study enrolled all patients with AMI who had undergone cardiorespiratory polygraphy for SDB diagnosis. The apnea–hypopnea index was used as a standard metric of SDB severity. SDB was classified as mild (apnea–hypopnea index >5 to <15 per h), moderate (≥15 to <30 per h) or severe (apnea–hypopnea index ≥30 per h). According to the majority of events, SDB was classified as predominant obstructive sleep apnea, central sleep apnea or mixed sleep apnea (mixed SDB). A total of 223 patients with AMI (112 with ST elevation and 111 without ST elevation; 63.2 ± 11.2 years, 82% male, left ventricular ejection fraction 49 ± 12%) were enrolled. SDB was present in 85.6%, and was moderate‐to‐severe in 63.2%; 40.8% had obstructive sleep apnea, 41.7% had central sleep apnea and 3.1% had mixed SDB. Left ventricular ejection fraction was lower in patients with AMI with severe SDB (45 ± 14%) versus those without SDB (57 ± 7%; P < 0.005). In addition, lower left ventricular ejection fraction (≤45%) was associated with increased frequency (apnea–hypopnea index ≥5 per h in 96%) and severity (apnea–hypopnea index ≥30 per h in 48%) of SDB in general and a higher percentage of central sleep apnea (57%) in particular. SDB is highly frequent in patients with AMI. SDB severity appeared to be linked to impaired left ventricular function, especially in patients with central sleep apnea.     

Upper airway stimulation in obstructive sleep apnea improves glucose metabolism and reduces hedonic drive for food

Upper airway stimulation is a new and effective second‐line treatment for obstructive sleep apnea, but possible consequences on glucose metabolism and central regulation of food intake are unclear. Twenty patients were prospectively studied before and 12 months after obstructive sleep apnea treatment by upper airway stimulation. Respiratory parameters and daytime sleepiness were assessed to document effectiveness of treatment. Glucose metabolism was assessed by the oral glucose tolerance test, and hedonic versus homeostatic drive to eat was characterized. At 12 months, upper airway stimulation significantly improved measures of obstructive sleep apnea (all p < 0.01). Despite no change in body weight, fasting C‐peptide insulin resistance index (p = 0.01) as well as insulin and C‐peptide levels at 60 min during the oral glucose tolerance test (p < 0.02) were reduced. Hedonic drive to eat was strongly reduced (p < 0.05), while leptin and ghrelin remained unchanged (p > 0.15). Upper airway stimulation is effective in treatment of obstructive sleep apnea and improves glucose metabolism. Reduced hedonic drive to eat might contribute to these metabolic improvements. These promising findings are in need for long‐term controlled evaluation of metabolic sequelae of upper airway stimulation and to mechanistically evaluate the metabolic benefits of upper airway stimulation in patients with obstructive sleep apnea.     

Poor sleep quality impairs cognitive performance in older adults

The prevalence of insomnia increases with age. Short sleep duration is associated with deficits in cognitive performance. We hypothesized that short sleep duration and sleep quality influence cognitive performance in older adults. The study included 78 adults aged 60 years and over (72.2 ± 5.9 years). Total sleep time and sleep efficiency (total sleep time/time in bed × 100) were calculated using actigraphy. We evaluated cognitive performance with the continuous performance test‐identical pairs and the number‐back test. Sleep apnea was evaluated overnight with a portable home monitoring system. The accuracy of the 0‐back test significantly decreased in participants with total sleep time less than 5 h compared with those with total sleep time greater than 7 h, but there was no significant difference in continuous performance test‐identical pairs between the two groups. Participants with sleep efficiency <85% showed a significant decrease in 0‐ and 1‐back test accuracy compared with those with sleep efficiency ≥85%. There were no significant differences in the accuracy of number‐back tests and continuous performance test‐identical pairs between apnea–hypopnea index ≥15 h^?1 and apnea–hypopnea index <15 h^?1 groups, or among lowest SpO₂ ≥ 90%, lowest 80–90%, and lowest SpO₂ < 80% groups. Age, total sleep time and sleep efficiency were significantly correlated with accuracy on the 0‐back test. Age and sleep efficiency were significantly correlated with accuracy on the 1‐back test. Multiple regression analysis revealed that total sleep time was independently correlated with accuracy on the 0‐back test, while age was independently correlated with accuracy on the 1‐back test. Our findings suggest that sleep duration and sleep quality may play a role in cognitive performance in older adults.     

Incremental shuttle walk test in the assessment of patients with obstructive sleep apnea–hypopnea syndrome

Obstructive sleep apnea–hypopnea syndrome is associated independently with an increase in cardiovascular risk factors and is associated with self‐reported lack of exercise. We aimed to investigate the utility of the incremental shuttle walk test in routine clinical practice to monitor physical capacity of patients with obstructive sleep apnea–hypopnea syndrome and explore whether continuous positive airway pressure therapy alters exercise capacity. Participants with symptomatic moderate/severe obstructive sleep apnea–hypopnea syndrome attending for a trial of continuous positive airway pressure therapy completed questionnaires assessing sleepiness and physical activity and underwent an incremental shuttle walk test. Subjects compliant or partially compliant with continuous positive airway pressure therapy underwent reassessment at 2 weeks, 3 months and 6 months post‐initiation of therapy. Participants unable to tolerate continuous positive airway pressure therapy completed a single reassessment 6 months after their initial visit. Continuous positive airway pressure therapy resulted in an increased distance walked during the incremental shuttle walk test. Improvements in cardiovascular responses to exercise were identified. Compliant patients reported increased daily activity. The incremental shuttle walk test is a simple, reproducible and safe test that is responsive to continuous positive airway pressure treatment. Our findings support the use of the incremental shuttle walk test for monitoring the effects of continuous positive airway pressure treatment and may suggest its use in rehabilitation programmes designed to reduce obesity and cardiovascular risk factors in patients with obstructive sleep apnea–hypopnea syndrome.     

The prevalence and characteristics of obstructive sleep apnea in hospitalized patients with type 2 diabetes in China

Data on the prevalence of obstructive sleep apnea in subjects with type 2 diabetes mellitus in China is scarce. We conducted a multi‐centre, cross‐sectional study involving 12 hospitals from six regional cities to investigate the prevalence of obstructive sleep apnea in hospitalized patients with type 2 diabetes mellitus and to explore the association between obstructive sleep apnea and related risk factors, diabetic complications and comorbidities in China. Each hospital recruited at least 70 consecutive patients with type 2 diabetes mellitus who were admitted to the endocrinology ward. A total of 880 participants were enrolled and administered overnight sleep monitoring with a portable monitor (ApneaLink^?, ResMed, San Diego, CA, USA); other information was collected from medical charts and a standardized questionnaire. In this study, 60.0% (95% confidence interval: 56.8%, 63.2%) of hospitalized patients in China with type 2 diabetes mellitus had comorbid obstructive sleep apnea (apnea–hypopnea index ≥ 5). Only 1.5% (eight of 528) of the patients with both conditions had been diagnosed previously with obstructive sleep apnea. The prevalence of moderate–severe (apnea–hypopnea index ≥ 15) and severe obstructive sleep apnea (apnea–hypopnea index ≥ 30) was estimated to be 25.6% (22.7, 28.5%) and 10.3% (8.3, 12.4%), respectively. Age, sex, body mass index, snoring, reported breath‐holding in sleep or gasping or choking arousal, sleepiness, diabetes duration, hypertension, diabetic nephropathy and cardiovascular diseases history were correlated significantly with the severity of obstructive sleep apnea. In China, the prevalence of obstructive sleep apnea in hospitalized patients with type 2 diabetes mellitus is high. Routine screening for and treatment of obstructive sleep apnea is an important, but often neglected, part of the management of diabetes.     

Diaphragm and genioglossus corticomotor excitability in patients with obstructive sleep apnea and control subjects

Corticomotor excitability of peripheral muscles appears to be altered in patients with obstructive sleep apnea. However, there is no evidence of such alteration for upper airway/respiratory muscles that are involved in the pathophysiology of this disease. The aim of this study was to compare the effects of hypercapnic stimulation on diaphragm and genioglossus corticomotor excitability in awake healthy subjects versus patients with obstructive sleep apnea. Corticomotor excitability was assessed by transcranial magnetic stimulation in 12 untreated apneic men (48 ± 10 years; body mass index = 28.9 ± 4.7 kg m⁻²; apnea–hypopnoea index = 41 ± 23 events per hour) and nine control men (45 ± 10 years; body mass index = 27.3 ± 3.3 kg m⁻²; apnea–hypopnoea index = 7 ± 4 events per hour). Assessments included diaphragm and genioglossus expiratory motor thresholds, and transcranial magnetic stimulation‐induced motor‐evoked potential characteristics obtained while breathing room air or 5% CO₂ (random order) and then 7% CO₂ both balanced with pure O₂. Transcranial magnetic stimulation twitches were applied during early inspiration and end expiration. Diaphragm motor‐evoked potential amplitudes increased and expiratory diaphragm motor‐evoked potential latencies decreased during CO₂‐induced increase in ventilatory drive, with no difference in these responses between patients with obstructive sleep apnea and control subjects. Expiratory genioglossus motor‐evoked potential amplitudes were significantly lower in patients with obstructive sleep apnea than in control subjects. Baseline activity of the genioglossus increased with increasing FiCO₂, this effect being significantly higher in patients with obstructive sleep apnea than in control subjects. However, neither genioglossus motor‐evoked potential amplitudes nor latencies were significantly modified with increasing FiCO₂ both in patients with obstructive sleep apnea and in control subjects. Corticomotor excitability of genioglossus and diaphragm are not altered during CO₂‐induced increase in ventilatory drive in patients with obstructive sleep apnea.     

Added value of a mandible movement automated analysis in the screening of obstructive sleep apnea

In‐laboratory polysomnography is the ‘gold standard’ for diagnosing obstructive sleep apnea syndrome, but is time consuming and costly, with long waiting lists in many sleep laboratories. Therefore, the search for alternative methods to detect respiratory events is growing. In this prospective study, we compared attended polysomnography with two other methods, with or without mandible movement automated analysis provided by a distance‐meter and added to airflow and oxygen saturation analysis for the detection of respiratory events. The mandible movement automated analysis allows for the detection of salient mandible movement, which is a surrogate for arousal. All parameters were recorded simultaneously in 570 consecutive patients (M/F: 381/189; age: 50 ± 14 years; body mass index: 29 ± 7 kg m^?2) visiting a sleep laboratory. The most frequent main diagnoses were: obstructive sleep apnea (344; 60%); insomnia/anxiety/depression (75; 13%); and upper airway resistance syndrome (25; 4%). The correlation between polysomnography and the method with mandible movement automated analysis was excellent (r: 0.95; P < 0.001). Accuracy characteristics of the methods showed a statistical improvement in sensitivity and negative predictive value with the addition of mandible movement automated analysis. This was true for different diagnostic thresholds of obstructive sleep severity, with an excellent efficiency for moderate to severe index (apnea–hypopnea index ≥15 h^?1). A Bland & Altman plot corroborated the analysis. The addition of mandible movement automated analysis significantly improves the respiratory index calculation accuracy compared with an airflow and oxygen saturation analysis. This is an attractive method for the screening of obstructive sleep apnea syndrome, increasing the ability to detect hypopnea thanks to the salient mandible movement as a marker of arousals.