Cerebral blood flow and cognitive function in obstructive sleep apnea syndrome.

Neuropsychological deficits are among the main symptoms of obstructive sleep apnea syndrome (OSAS), which could be related to impaired cerebral blood flow (CBF). We conducted a study in 20 subjects tested in our Sleep Laboratory, to assess regional CBF and cognitive function in OSAS. Our measurements included technetium-99m hexamethylamino propylenamine oxime brain perfusion scintigraphy in wakeful state, i.e. in the morning after polysomnography and also cognitive function tests after polysomnography, in 20 patients, 16 male and 4 female, aging between 30 and 60 years. We found that apnea-hypopnea index was greater than or equal to 5 in 16 (85%) subjects, consistent with OSAS. Mean arterial oxygen saturation during sleep was correlated with CBF in all regions. Cognitive function test scores in verbal memory were positively correlated with percentage of sleep duration with less than 90% of oxygen saturation during sleep. Cerebral blood flow was not uniform in OSAS patients, and was significantly lower in the left frontal and left temporal regions as compared to that of these regions on the right hemisphere. In conclusion, our findings indicated association of CBF and verbal memory with hypoxemia during sleep and decreased perfusion after apneic episodes in the left frontal and temporal lobes in OSAS patients, which could also indicate impairment of upper airway motor control.

P-wave duration and dispersion in patients with obstructive sleep apnea.

AIM: P-wave dispersion (Pd) has been reported to be associated with inhomogeneous and discontinuous propagation of sinus impulses. The purpose of this study was to investigate Pd in patients with obstructive sleep apnea (OSA) and to determine its relationship with severity of the disease. METHODS: The study population included 67 patients referred to sleep laboratory. The Apnea-Hypopnea Index (AHI) was defined as the number of apneas and hypopneas per hour of sleep. Of the sixty-seven patients, 48 had AHI5 and were diagnosed as OSA. Nineteen of the patients had AHI<5 and were diagnosed as OSA (-) (Group 1), 32 of the patients had AHI between 5-30 (mild and moderate, group 2), 16 of the patients had AHI>30 (severe, group 3). The P-wave duration was calculated in all leads of the surface electrocardiogram. The difference between the maximum (Pmax) and minimum P (Pmin) wave duration was calculated and was defined as the P-wave dispersion (Pd). Echocardiographic examination was also performed. RESULTS: Pmax was longer in group 3 compared to group 2 and group 1 (p=0.002, p<0.001 respectively). Pmax was longer in group 2 compared to group 1 (s<0.001). Pd was greater in group 3 compared to group 2 and group 1 (p<0.001 for both comparison). Pd was greater in group 2 compared to group 1 (p<0.001). Pmin did not differ between the groups. In patients with OSA, Pd was positively correlated with AHI (r=0.56, p<0.001), BMI (r=0.43, p=0.03), and mitral early diastolic to late diastolic velocity (E/A) ratio (r=0.37, p=0.01). Multiple linear regression analysis showed that only AHI was independently associated with Pd (beta=0.39, p=0.02). CONCLUSION: Pd was found to be greater in patients with OSA than patients without OSA and to be associated with severity of the disease.

Early myocardial functional alterations in patients with obstructive sleep apnea syndrome.

BACKGROUND: There is limited information regarding myocardial alterations in patients with obstructive sleep apnea syndrome (OSAS) in the absence of pulmonary and cardiac comorbidity. In this study, we aimed to evaluate potential myocardial alterations of these patients and investigate the possible effects of OSAS-related pathological variations on left and right ventricular functions. METHODS: We studied 107 consecutive patients who were referred to our sleep laboratory for clinically suspected OSAS and 30 controls without any history or symptoms of sleep-related disorders. Severity of OSAS was quantified by polysomnography. Patients with apnea-hypopnea index (AHI) < 5 were included in the OSAS (-) group (Group 1, n = 22). Subjects with AHI > or = 5 were considered as OSAS and classified according to their AHI as mild-to-moderate (AHI > or = 5 and AHI < 30) (Group 2, n = 45) and severe (AHI > or = 30) OSAS groups (Group 3, n = 40). Conventional M-mode, 2D, and Doppler mitral inflow parameters, tissue Doppler velocities, myocardial peak systolic strain, and strain rate values of various segments were measured and compared between groups. RESULTS: Patients with OSAS displayed impairment of left ventricular diastolic function compared with controls. There were no significant differences between groups regarding parameters reflecting left ventricular systolic function. Myocardial strain analysis demonstrated significant decrement regarding apical right ventricular longitudinal peak systolic strain and strain rate values between groups in relation to the severity of OSAS. CONCLUSIONS: Patients with OSAS display a regional pattern of right ventricular dysfunction correlated with the severity of disease.

Reliability and validity studies of the Turkish version of the Epworth Sleepiness Scale.

The Epworth Sleepiness Scale (ESS) is a self-administered eight-item questionnaire that is widely used in English speaking countries for assessment of daytime sleepiness in adults. The aim of this study was to investigate the reliability and validity of the ESS in the Turkish language. The Turkish version of the ESS (ESStr) was applied to 194 healthy controls and 150 consecutive subjects attending the sleep centre with symptoms of sleep-disordered breathing. Test-retest reliability of the ESStr was tested in a separate group of 30 subjects. The ESStr scores of 60 subjects with mild to severe obstructive sleep apnoea (OSA) were compared with the ESStr scores of 60 healthy controls matched for age, gender, and body mass index (BMI). Concurrent validity with the Functional Outcomes of Sleep Questionnaire (FOSQtr) was also assessed in 12 subjects. The questionnaire had a high level of internal consistency as measured by Cronbach's alpha (> or =0.86). The test-retest intraclass correlation coefficient was r = 0.81 (95% confidence interval: 0.64-0.90) (p < 0.001) and Spearman's correlation coefficient was r = 0.80 (p = 0.01). The control group had lower ESStr scores than subjects with sleep-disordered breathing (3.6 +/- 3 vs 12.6 +/- 6, respectively; p < 0.001). Subjects with mild sleep-disordered breathing also had lower scores of the ESStr than those with moderate and severe sleep-disordered breathing (10 +/- 6.2 vs 14 +/- 5. and 10 +/- 6.2 vs 16 +/- 5.4, respectively; both p < 0.05), but there were no significant differences between moderate and severe subjects with sleep apnoea. There were significant correlations between the ESStr and total FOSQtr and its subscales (r = -0.22 to r = -0.92; all p = 0.05). Factor analysis of item scores showed that the ESStr had only one factor. The ESStr is a reliable and valid measure of daytime sleepiness. These features and the simplicity of the ESStr make it a valuable measure for clinical management and research.

Increased myocardial vulnerability and autonomic nervous system imbalance in obstructive sleep apnea syndrome.

BACKGROUND: Obstructive sleep apnea syndrome (OSAS) is characterized by the repeated episodes of upper airway obstruction during sleep, leading to significant hypoxia. Noninvasive evaluation of autonomic nervous system (ANS) and myocardial vulnerability may help determination of OSAS patients who are under high risk of malignant cardiac arrhythmias. The aim of this study was to show the effects of OSAS on predictors of arrhythmias by the evaluation of heart rate turbulence (HRT), heart rate variability (HRV) and QT dynamicity reflecting the ANS balance and myocardial vulnerability. METHODS: After polysomnographic study, 80 patients with OSAS and 55 age matched OSAS (-) subjects were included in the study. Twenty-four-hour Holter monitoring was performed in all subjects. HRT, HRV and QT dynamicity parameters were calculated. RESULTS: Turbulence slope was significantly decreased in OSAS patients whereas turbulence onset was increased (P<0.001). QT/RR slopes were significantly increased for QT end and QT apex (P<0.001). In HRV analysis, autonomic balance changed in favor of sympathetic system at night in OSAS patients. Furthermore, HRT and QT dynamicity parameters are found to be correlated with Apnea-Hypopnea Index (AHI). CONCLUSION: OSAS is associated with a significant worsening in HRV, HRT, and QT dynamicity parameters. Our results may indicate that HRV and QT dynamicity parameters can be useful noninvasive methods that may detect autonomic nervous system activity and ventricular vulnerability in OSAS.

Body fat composition: a predictive factor for obstructive sleep apnea.

OBJECTIVE: To investigate body fat composition, measured by bioelectrical impedance assay (BIA), for predicting the presence and severity of obstructive sleep apnea-hypopnea syndrome (OSAHS). Body fat composition was also compared with other well-known OSAHS predictors such as body mass index (BMI), neck circumference, and abdominal visceral fat. STUDY DESIGN: A prospective study was designed. Fifty-one patients (41 male, 10 female), who were referred to Hacettepe University Faculty of Medicine, Department of Otorhinolaryngology, Head and Neck Surgery with suspected OSAHS, between April 2003 and June 2004, were included in the study. METHODS: All patients underwent polysomnography (PSG) and were classified according to their apnea-hypopnea index (AHI) into four groups. The cross-sectional area of abdominal visceral fat was measured by computed tomography (CT) scanning in 33 of the patients. Neck circumference and BMI was measured for all patients. BIA was performed to determine body fat composition. The groups were compared, and correlation of the variables with AHI was investigated. RESULTS: Of the variables, BMI and percentage of body fat (determined by BIA) were found to be significantly correlated with AHI (r = 0.782, r = 0.647). CT of cross-sectional area of abdominal visceral fat provided 100% sensitivity and specificity (P < .001) in differentiating simple snorers from OSAHS patients. By combining percentage of body fat and body fat mass, higher levels of sensitivity (95%) and specificity (100%) were achieved for diagnosis of OSAHS. CONCLUSION: It was concluded that the BIA could be an inexpensive and practical alternative to prePSG screening tests and should be included in the evaluation of OSAHS patients.