Moderate Obstructive Sleep Apnea Group Research Articles

Uric Acid as a Potential Mediator of Cardiovascular Morbidity in Obstructive Sleep Apnea Syndrome

Abstract Background and aims Obstructive sleep apnea (OSA) is now considered as an independent risk factor for cardiovascular (CV) disease. Although uric acid is increasingly being implicated in CV morbidity and mortality, no study attempted to determine independent role of uric acid in CV morbidity of OSA patients. We aimed to assess the role of serum uric acid as a potential mechanism of CV morbidity in a nonselected cohort of OSA patients. Methods This was a cohort study in which patients who had undergone a formal sleep study for diagnosis of OSA were recruited. Included patients were grouped according to apnea–hypopnea index (AHI) as mild, moderate and severe OSA. Patients with AHI Results 436 OSA patients included (72 controls, 97 with mild, 75 with moderate, and 192 with severe OSA). The severe group also had higher serum uric acid level compared with the control and other OSA groups. Linear regression showed that the Ln uric acid was positively associated with Ln AHI score. In unadjusted logistic regression, severe OSA was associated with higher odds of a cardiovascular event, OR = 2.81 (1.307–6.041), p = 0.0081 while the other categories of sleep apnea were not. However, severe OSA was no longer significant after adjusting for age, gender, diabetes mellitus status, hypertension status, BMI, and smoking, OR = 1.882 (0.826–4.287), p = 0.1322. Uric acid was significantly higher in those who had a cardiovascular event even in the mild, moderate and severe OSA groups. Conclusion Hyperuricemia is strongly associated with cardiovascular disease in OSA patients. This strong relationship persists even after controlling for well-known traditional risk factors for cardiovascular disease.

The effect of obstructive sleep apnea on olfactory functions

The aim of this study was to investigate the effect of obstructive sleep apnea (OSA) on the parameters of olfactory functions (odor threshold, odor discrimination, and odor identification tests) for orthonasal olfaction, retronasal olfactory testing, and olfactory bulb (OB) volumes. Prospective clinical study. This study was carried out in 78 volunteers between the ages of 20 and 60 years. The mean age of the patients was 46 ± 10.1 years. Patients were divided into three groups according to polysomnography results: 1) a control group, 2) a mild to moderate OSA group, and 3) a severe OSA group. Clinical features of the participants were evaluated with the Epworth Sleepiness Scale. Orthonasal and retronasal olfactory testing were performed with Sniffin' Sticks olfactory testing and retronasal olfactory testing, respectively. Olfactory bulb volumes were measured by planimetric manual contouring on magnetic resonance imaging (MRI). The current investigation produced four major findings: 1) The apnea-hypopnea index had a significant and strong negative correlation with odor threshold scores and odor discrimination scores; 2) The apnea-hypopnea index was significantly negatively correlated with odor identification score and both right and left OB volumes; 3) retronasal olfactory scores were not significantly affected by OSA; and 4) continuous O2 saturation had a significant positive correlation on orthonasal olfactory functions, particularly the odor threshold and discrimination scores. This study demonstrated that OSA had significant negative effects on all orthonasal olfactory tasks, especially on threshold and discrimination. MRI also revealed volumetric shrinkage of OB volumes.

Adjustment of apnea-hypopnea index with severity of obstruction events enhances detection of sleep apnea patients with the highest risk of severe health consequences

Presently, the severity of obstructive sleep apnea (OSA) is estimated based on the apnea-hypopnea index (AHI). Unfortunately, AHI does not provide information on the severity of individual obstruction events. Previously, the severity of individual obstruction events has been suggested to be related to the outcome of the disease. In this study, we incorporate this information into AHI and test whether this novel approach would aid in discriminating patients with the highest risk. We hypothesize that the introduced adjusted AHI parameter provides a valuable supplement to AHI in the diagnosis of the severity of OSA. This hypothesis was tested by means of retrospective follow-up (mean ± sd follow-up time 198.2 ± 24.7months) of 1,068 men originally referred to night polygraphy due to suspected OSA. After exclusion of the 264 patients using CPAP, the remaining 804 patients were divided into normal (AHI < 5) and OSA (AHI ≥ 5) categories based on conventional AHI and adjusted AHI. For a more detailed analysis, the patients were divided into normal, mild, moderate, and severe OSA categories based on conventional AHI and adjusted AHI. Subsequently, the mortality and cardiovascular morbidity in these groups were determined. Use of the severity of individual obstruction events for adjustment of AHI led to a significant rearrangement of patients between severity categories. Due to this rearrangement, the number of deceased patients diagnosed to have OSA was increased when adjusted AHI was used as the diagnostic index. Importantly, risk ratios of all-cause mortality and cardiovascular morbidity were higher in moderate and severe OSA groups formed based on the adjusted AHI parameter than in those formed based on conventional AHI. The adjusted AHI parameter was found to give valuable supplementary information to AHI and to potentially improve the recognition of OSA patients with the highest risk of mortality or cardiovascular morbidity.

Severe obstructive sleep apnea increases left atrial volume independent of left ventricular diastolic impairment

Purpose: Previous studies have demonstrated that severe obstructive sleep apnea (OSA) itself impairs directly left ventricular (LV) diastolic function. Meanwhile, left atrial (LA) volume index which is an independent predictor of future cardiovascular events is related to the OSA severity. Thus, the purpose of this study was to investigate whether OSA is associated with increase of LA volume index irrespective of LV diastolic function. Methods: We enrolled 450 middle-aged OSA{apnea hypopnea index (AHI) ≥5/h} patients without cardiac disease. All the patients underwent overnight fully attended polysomnograpy. They also underwent 2-dimensional echocardiography in order to estimate LA volumes and LV diastolic function which was assessed by the transmitral flow velocity (E/A ratio), deceleration time (DCT), systolic/diastolic pulmonary vein velocity (S/D), and mitral annular velocity (Ea) was derived from tissue Doppler imaging (TDI). Patients were divided into the mild to moderate OSA (5 ≤AHI < 30/h) group and the severe OSA (AHI ≥30/h) group, and compared LA volume index and LV diastolic function between the groups. Multivariate analysis performed whether OSA is the independent factor of LA volume index irrespective of LV diastolic function. Results: The LA volume index in the severe OSA group was significantly larger than those in the mild to moderate OSA group (23.6±5.9 vs. 21.2±5.0, P<0.0001). The E/A ratio and Ea in the severe OSA group was also significantly lower than those in the mild to moderate OSA group (P<0.0001), whereas the S/D ratio in the severe OSA group was significantly higher than that in the mild to moderate OSA group (P<0.001). AHI showed a statistically significant correlation with the LA volume index (r=0.2, P<0.0001), whereas statistically significant inverse correlations were observed between E/A ratio, Ea and AHI (r= -0.14, -0.26, P=0.003, <0.0001, respectively). Multivariate linear regression analysis revealed that severe OSA was independently related with LA volume index even after adjusting for age, blood pressure, body mass index (BMI), and LV diastolic function (β=0.113, P=0.02). Conclusions: These results suggest that severe OSA itself may increases directly LA volume irrespective of impaired LV diastolic function.

Obstructive sleep apnea and heart rate asymmetry microstructure during sleep

Heart rate decelerations and accelerations have unequal input to heart rate variability (HRV) and patterns created by consecutive cardiac cycles-this phenomenon is known as heart rate asymmetry (HRA). The analysis of monotonic runs of heart rate decelerations and accelerations provides a detailed insight into the HRA microstructure and thus of HRV. To evaluate the relation between the severity of obstructive sleep apnea (OSA) and the HRA microstructure during sleep. Seventy-eight patients with suspected OSA underwent overnight polysomnography. The 300-min ECGs from the polysomnography were selected and analyzed. The HRA microstructure was quantified by measuring (1) the contribution of monotonic runs of decelerations or accelerations of different lengths to the number of all sinus beats, and (2) the length of the longest deceleration and acceleration runs. There were 19 patients with no/mild OSA (Apnea/Hypopnea Index (AHI) 5.1 ± 2.5/h), 18 with moderate OSA (AHI 21.8 ± 4.0/h) and 41 with severe OSA (AHI 42.8 ± 17.4/h). Patients with severe OSA had significantly reduced deceleration and acceleration runs of length 1 compared to the moderate OSA group, and compared to patients with no/mild OSA they had an increased number of longer runs (from 5 to 10 for accelerations and from 5 to 8 for decelerations; p < 0.05 for all comparisons). The longest acceleration runs were significantly longer in severe OSA group (p < 0.05) than in subjects with no/mild OSA. HRA microstructure is related with OSA severity. An increased number of longer deceleration and acceleration runs is more common in severe OSA patients.

Levels of neuroglobin in serum and neurocognitive impairments in Chinese patients with obstructive sleep apnea

The impact of different severities of obstructive sleep apnea (OSA) on cognition has not well been documented. Neuroglobin, a recently discovered vertebrate protein, shows a neuroprotective function to modulate hypoxic-ischemic brain injury. This study investigated the cognitive function of patients with varying OSA severities and intended to explore the relationship between levels of neuroglobin in serum and cognitive deficits of OSA. Sixty Chinese adults aged 18-59 years old were enrolled and categorized into four groups based on apnea-hypopnea index (AHI): primary snoring (n = 7), mild (n = 13), moderate (n = 20), and severe (n = 20) OSA groups. Computer-based neurocognitive tests (including calculation, memory, and attention) and Epworth sleepiness scale were administered before polysomnographic monitoring, and blood sample was taken the next morning. Concentrations of serum neuroglobin were measured using ELISA. No significant difference was observed in cognitive function regardless of OSA severities, but patients with moderate and severe OSA presented significantly more sleepiness than patients with primary snoring and mild OSA. Memory significantly correlated with time spent with oxygen saturation below 90 % during nighttime (T < 90 %), as well as oxygen desaturation index, AHI, or NREM sleep. Calculation correlated significantly with sleepiness and respiratory arousal index. Levels of neuroglobin in serum of patients with varying OSA severities were significant elevated than that of patients with primary snoring. No relationship was found between the neurobehavioral ability index of neurocognitive tests and serum neuroglobin concentrations after controlling for gender, age, and BMI, whereas the unique association between levels of neuroglobin in serum and the scores of auditory digit span test was noted. Our findings suggest that different neurocognitive domains might specifically correlate to either sleepiness or hypoxemia. Changes of concentrations of neuroglobin in serum may possibly be used as an indicator to monitor the brain damage of OSA. Further investigations are needed to explore the relationship between regulation of neuroglobin in serum and severity of brain damage in OSA.

Use of SPECT to detect changes in diastolic and coronary reserve in patients with obstructive sleep apnea

To assess diastolic function and coronary artery reserve in patients with obstructive sleep apnea (OSA) using single-photon emission computer tomography (SPECT). Patients with OSA who had normal echocardiograph/electrocardiogram findings were divided into three groups based on OSA severity: mild (n = 15), moderate (n = 13), or severe (n = 18). A control group of participants without OSA (n = 17) was included. SPECT (with technetium-99 m-labeled red blood cells) was performed after the induction of cardiac stress by injection of dobutamine. The following ventricular parameters were determined: left ventricular ejection fraction, peak filling rate (PFR), peak ejection rate, 1/3 filling fraction (1/3FF), and regional ejection fractions (rEF). The median ages of OSA and control participants were 45.0 and 51.0 years, respectively. Median apnea-hypopnea index scores were 3.3, 9.1, 38.5, and 65.2 for the control, mild OSA, moderate OSA, and severe OSA groups, respectively. Post-stress, 1/3FF was significantly lower in the overall OSA group compared with the control group (P < 0.05). PFR was significantly lower in the overall OSA group compared with the control group (P < 0.05) and was significantly lower in the severe OSA group compared with the mild OSA group. Regional ejection fractions rEF3 (cardiac apex and a small part of the inferior wall) and rEF4 (anteroseptal wall) were significantly lower in the overall OSA group compared with the control group, suggesting decreased coronary artery reserve. Our findings suggest that SPECT can be used to detect abnormalities in diastolic function and coronary reserve in patients with OSA who have normal electrocardiogram or echocardiograph findings. SPECT may be useful for the early detection of cardiovascular disease in patients with OSA.

Elevated serum cystatin C in severe OSA younger men without complications

Serum cystatin C is a promising new biomarker of glomerular filtration rate and cardiovascular events, but few studies focused on serum cystatin C levels in obstructive sleep apnea (OSA) patients. The aim of our study was to evaluate the association between serum cystatin C and OSA in younger men (≤40 years old of age) without complications. We prospectively recruited consecutive participants without comorbidities who underwent polysomnography. Fasting blood samples were obtained from all subjects for biological profile measurements. Statistical analysis was used to evaluate the relationship between serum cystatin C and other parameters. The population consisted of 98 subjects (mean age = 32.5 years, mean body mass index = 27.93 kg/m(2)) that were divided according to polysomnographic finding into control group (n = 23), mild (n = 15), moderate (n = 24), and severe (n = 36) OSA group. Compared with the control group, patients with severe OSA were significantly heavier (body mass index, 29.69 ± 3.81 vs. 26.42 ± 3.10) and presented significantly higher levels of high sensitive C-reactive protein (hsCRP) (1.10 ± 0.28 vs. 0.88 ± 0.20 mg/l) and serum cystatin C (0.87 ± 0.12 vs. 0.74 ± 0.10 mg/l) (p < 0.05 for all comparisons). Cystatin C was correlated with Apnea Hypopnea Index (AHI), Oxygen Desaturation Index, hsCRP, creatinine, and estimated glomerular filtration rate (r = 0.319, 0.279, 0.321, 0.233, -0.241, p = 0.001, 0.005, 0.001, 0.021, 0.017, respectively). After adjustment for confounding factors, AHI was significantly and positively associated with serum cystatin C levels (β = 0.284, p = 0.007). Our finding indicated that serum cystatin C was associated with the severity of OSA in younger men. Further study is needed to find out whether OSA patients with increased serum cystatin C levels are prone to subclinical cardiovascular and renal diseases.

Severe obstructive sleep apnea increases mortality in patients with ischemic heart disease and myocardial injury

We hypothesized that obstructive sleep apnea(OSA) has a dose-dependent impact on mortality in those with ischemic heart disease or previous myocardial injury. We performed a retrospective cohort study of 281 consecutive OSA patients with a history of myocardial injury as determined by elevated troponin levels or with known existing ischemic heart disease. We compared survival between those with severe OSA [apnea–hypopneaindex (AHI) ≥30] and those with mild to moderate OSA(AHI >5 and <30). Of the 281 patients (mean age 65 years, mean BMI34, 98% male, 58% with diabetes), 151 patients had mild moderate OSA and 130 had severe OSA. During a mean follow-up of 4.1 years, there were significantly greater deaths in the severe OSA group compared to the mild moderate OSA group [53 deaths (41%) vs. 44 deaths(29%), respectively, p00.04]. The adjusted hazard ratio for mortality with severe OSA was 1.72 (95% confidence interval1.01–2.91, p00.04). The severity of obstructive sleep apnea is associated with increased risk of death, and risk stratification based on OSA severity is relevant even in the diseased cardiac patient.

Cardiovascular Mortality in Women With Obstructive Sleep Apnea With or Without Continuous Positive Airway Pressure Treatment

Obstructive sleep apnea (OSA) is a risk factor for cardiovascular death in men, but whether it is also a risk factor in women is unknown. To investigate whether OSA is a risk factor for cardiovascular death in women and assess whether continuous positive airway pressure (CPAP) treatment is associated with a change in risk. Prospective, observational cohort study. 2 sleep clinics in Spain. All women consecutively referred for suspected OSA between 1998 and 2007. Every woman had a diagnostic sleep study. Women with an apnea-hypopnea index (AHI) less than 10 were the control group. Obstructive sleep apnea was diagnosed when the AHI was 10 or higher (classified as mild to moderate [AHI of 10 to 29] or severe [AHI ≥30]). Patients with OSA were classified as CPAP-treated (adherence ≥4 hours per day) or untreated (adherence <4 hours per day or not prescribed). Participants were followed until December 2009. The end point was cardiovascular death. 1116 women were studied (median follow-up, 72 months [interquartile range, 52 to 88 months]). The control group had a lower cardiovascular mortality rate (0.28 per 100 person-years [95% CI, 0.10 to 0.91]) than the untreated groups with mild to moderate OSA (0.94 per 100 person-years [CI, 0.10 to 2.40]; P = 0.034) or severe OSA (3.71 per 100 person-years [CI, 0.09 to 7.50]; P < 0.001). Compared with the control group, the fully adjusted hazard ratios for cardiovascular mortality were 3.50 (CI, 1.23 to 9.98) for the untreated, severe OSA group; 0.55 (CI, 0.17 to 1.74) for the CPAP-treated, severe OSA group; 1.60 (CI, 0.52 to 4.90) for the untreated, mild to moderate OSA group; and 0.19 (CI, 0.02 to 1.67) for the CPAP-treated, mild to moderate OSA group. The study was observational and not randomized, and OSA was diagnosed by 2 different methods. Severe OSA is associated with cardiovascular death in women, and adequate CPAP treatment may reduce this risk. None.

Assessment of left atrial dysfunction in obstructive sleep apnea patients with the two dimensional speckle-tracking echocardiography

The aim of this study was to compare left atrial (LA) longutidinal myocardial function in obstructive sleep apnea (OSA) patients with healthy individuals using two-dimensional speckle-tracking echocardiography method (2D-STE). Twenty one healthy individuals and 58 OSA patients were included. According to the AHI (apnea hypopnea index) patients were examined in mild, moderate and severe OSA groups. Images of the LA were acquired from the apical two- and four-chamber views. LA strain(LA(S)) and strain rate(LA(SR)) parameters [systolic (S), early diastolic (E), late diastolic (A) during atrial contraction] were assessed. LA(S-S), LA(SR-S), LA(S-E) and LA(SR-E) values decreased with severity of OSA. Severe OSA patients have lower LA(S-S) and LA(SR-S) values (p < 0.03). While a difference in the LA(SR-E) value between groups was significant beginning with the moderate OSA group (p < 0.03), no LA(S-E) value differences were observed between moderate and mild OSA groups (p > 0.03). LA(S-A) and LA(SR-A) values were increasing with the disease severity up to moderate OSA. LA(S-A) and LA(SR-A) values of moderate OSA were greater than the mild OSA patients and healthy individuals (p < 0.03). These were lower in severe OSA than the moderate OSA (p < 0.03), however, they were greater than the healthy individuals (p < 0.03). The AHI was found to be negatively correlated with the LA(S-S), LA(SR-S) LA(S-E), LA(SR-E), whereas AHI was not correlated with the LA(S-A), LA(SR-A) values. LA remodeling and dysfunction that accompany OSA can be detected in the subclinical stage with a detailed evaluation of active and passive functions of the LA using the 2D-STE method.

Assessment of Obstructive Sleep Apnea and its Severity during Wakefulness

In this article, a novel technique for assessment of obstructive sleep apnea (OSA) during wakefulness is proposed; the technique is based on tracheal breath sound analysis of normal breathing in upright sitting and supine body positions. We recorded tracheal breath sounds of 17 non-apneic individuals and 35 people with various degrees of severity of OSA in supine and upright sitting positions during both nose and mouth breathing at medium flow rate. We calculated the power spectrum, Kurtosis, and Katz fractal dimensions of the recorded signals and used the one-way analysis of variance to select the features, which were statistically significant between the groups. Then, the maximum relevancy minimum redundancy method was used to reduce the number of characteristic features to two. Using the best two selected features, we classified the participant into severe OSA and non-OSA groups as well as non-OSA or mild vs. moderate and severe OSA groups; the results showed more than 91 and 83% accuracy; 85 and 81% specificity; 92 and 95% sensitivity, for the two types of classification, respectively. The results are encouraging for identifying people with OSA and also prediction of OSA severity. Once verified on a larger population, the proposed method offers a simple and non-invasive screening tool for prediction of OSA during wakefulness.

Severe obstructive sleep apnea impairs left ventricular diastolic function in non-obese men

To evaluate whether obstructive sleep apnea (OSA) contributes directly to left ventricular (LV) diastolic dysfunction. Seventy-four non-obese male OSA (apnea hypopnea index (AHI)⩾5/h) patients without cardiac disease, hypertension or diabetes were enrolled. Echocardiography, pulse wave velocity (PWV) measurements and laboratory testing were performed in all patients. LV diastolic function was assessed by the transmitral flow velocity (E/A ratio), and mitral annular velocity (Ea) was derived from tissue Doppler imaging (TDI). The E/A ratio and Ea in the severe OSA group (AHI⩾30/h) was significantly lower than those in the mild to moderate OSA group (5⩽AHI<30/h) (P<0.0001), whereas the S/D ratio, an indicator of pulmonary vein flow velocity, in the severe OSA group was significantly higher than that in the mild to moderate OSA group (P=0.04). AHI exhibited a statistically significant inverse correlation with the E/A ratio (r=-0.47, P=0.0001), but not with relative wall thickness (RWT), LV mass index (LVMI) or PWV. RWT, LVMI and PWV exhibited an inverse correlation with the E/A ratio. Multivariate linear regression analysis revealed that severe OSA was independently associated with the E/A ratio even after adjusting for age, insulin resistance, blood pressure, LV geometry, and PWV (β=-0.23, P=0.001). These results indicate that severe OSA itself may contribute directly to LV diastolic dysfunction irrespective of LV geometry, arterial stiffness, obesity and its associated cardiovascular risk factors.

Obstructive Sleep Apnea Is Independently Associated with the Metabolic Syndrome in Obese Asian Indians in Northern India

Obesity and the metabolic syndrome are rapidly increasing in developing countries. Whether the metabolic syndrome is independently associated with obstructive sleep apnea (OSA) is not clear. This study investigated the association between OSA and the metabolic syndrome in obese Asian Indians. We studied 240 obese subjects [body mass index (BMI) >25 kg/m2], 121 with OSA and 119 without OSA, matched for age, BMI, and percentage body fat (%BF). Full-montage digital polysomnography, fasting blood glucose (FBG), lipid levels, and blood pressure (BP) were done in all subjects. Subjects with OSA showed higher prevalence of the metabolic syndrome as compared to subjects without OSA [67.8% vs. 42.02%; χ2 = 16.08, P < 0.0001, odds ratio (OR) = 2.90, 95% confidence interval (CI)]. Prevalence of the metabolic syndrome was significantly higher in the severe OSA group as compared to the moderate OSA group (78.7% vs. 40.9%; χ2 = 11.57; P < 0.001; OR = 0.19, 95% CI). Fasting insulin levels were significantly higher in subjects with OSA as compared to subjects without OSA [median (range); 84.03(12.5-541.7) pmol/L vs. 64.4(10.4-520.8) pmol/L; P = 0.002)]. Regression analysis suggested that OSA was independently and positively associated with the metabolic syndrome, male gender, and fasting insulin levels. OSA is independently associated with the metabolic syndrome in Asian Indians in northern India.

Efficacy of continuous positive airway pressure on arrhythmias in obstructive sleep apnea patients

The purpose of this study was to determine the relationship between obstructive sleep apnea (OSA) and cardiovascular disorders in a large Japanese population, and to assess the efficacy of continuous positive airway pressure (CPAP) in the treatment of OSA-associated arrhythmias. The study population comprised 1394 Japanese subjects (1086 men and 308 women) who were divided into four groups on the basis of polysomnography (PSG) analysis as follows: the no sleep apnea (N-SA) group (n = 44, apnea-hypopnea index [AHI] < 5), the mild OSA (Mi-OSA) group (n = 197, 5 < AHI < 15), the moderate OSA (Mo) group (n = 368, 15 < AHI < 30), and severe OSA (SOSA) group (n = 785, AHI < 30). The following baseline characteristics were significantly associated with OSA: age (P < 0.001), gender (P < 0.001), body mass index (P < 0.001), hypertension (P < 0.001), diabetes (P = 0.009), and hyperlipidemia (P = 0.013). In the OSA group, PSG revealed the predominance of paroxysmal atrial fibrillation (PAF) (P = 0.051), premature atrial complex short run (P < 0.005), premature ventricular complex (PVC, P = 0.004), sinus bradycardia (P = 0.036), and sinus pause (arrest >2 s, P < 0.001) during the PSG recording. A total of 316 patients from the group underwent CPAP titration and were then re-evaluated. Continuous positive airway pressure therapy significantly reduced the occurrences of PAF (P < 0.001), PVC (P = 0.016), sinus bradycardia (P = 0.001), and sinus pause (P = 0.004). The results of this study demonstrate a significant relationship between OSA and several cardiac disorders, and also demonstrate the efficacy of CPAP in preventing OSA-associated arrhythmias in a large population of Japanese patients.

Clinical and Polysomnographic Characteristics in Rapid Eye Movement-Related Obstructive Sleep Apnea

Background and Objectives：To evaluate the clinical and polysomnographic features of rapid eye movement (REM)-related obstructive sleep apnea (OSA). Subjects and Method：185 consecutive OSA patients were classified as having REM and nonREM OSA. Subjective symptoms, anthropometric and polysomnographic characteristics between REM OSAS and non-REM OSAS patients were compared. Results：Thirty-eight of the 185 patients (20.5%) were classified as REM OSA, and 147 patients (79.5%) were classified as non-REM OSA. Ninety five percent of the REM OSA patients belonged to the mild or moderate OSA group. The dominant occurrence of apnea and hypopnea in REM sleep did notseem to affect subjective symptoms and daytime sleepiness. Anthropometric and polysomnographic features did not help to differentiate REM OSA from non-REM OSA. Conclusion：REM OSA may not be a separate and specific disease entity of OSA. (Korean J Otorhinolaryngol-Head Neck Surg 2009;52:36-40)

Correlation Between Severity of Obstructive Sleep Apnea and Prevalence of Silent Cerebrovascular Lesions

We investigated the prevalence of silent cerebrovascular lesions in patients with obstructive sleep apnea (OSA) and the correlation between OSA severity and prevalence of silent cerebrovascular lesions in Japanese patients. Study subjects were 192 polysomnography (PSG)-confirmed patients who visited the sleep disorders clinic in our university hospital. None had a history of cerebrovascular disease (CVD). We performed a cross-sectional study on OSA severity and the prevalence of silent cerebrovascular lesions detected by brain MRI analysis. The control (AHI < 5/h) group included 19 subjects with a mean AHI of 1.7 +/- 1.6/h, the mild OSAS (AHI 5 to < 15/h) group included 25 patients with a mean AHI of 9.5 +/- 3.7/h, the moderate OSAS (AHI 15 to < 30/h) group included 35 patients with a mean AHI of 22.0 +/- 7.0/h while the severe OSAS (AHI > or = 30/h) group included 113 patients with a mean AHI of 59.9 +/- 20.5/h. A larger percentage of patients with severe OSAS had a higher BMI and hyperglycemia than those with mild or moderate OSAS and control subjects (p < 0.05). Silent lacunar infarction was identified in 4 (21.1%) control subjects, 3 (12.0%) patients with mild OSA, 17 (48.6%) with moderate OSA and 61 (54.0%) with severe OSA. Among control subjects and the mild, moderate, and severe OSA groups, 4 (21.1%), 5 (20.0%), 19 (54.3%) and 61(54.0%), respectively, had periventricular hyperintensity (PVH); most PVH was mild to moderate. Results indicate that patients with moderate to severe (AHI > or = 15/h) OSA have a higher prevalence of silent cerebrovascular lesion than those with less severe OSA.