Effects of apolipoprotein E genotype on serum lipids in obstructive sleep apnoea.

There is increasing evidence that intermittent hypoxia resulting from obstructive sleep apnoea (OSA) is independently associated with dyslipidaemia. Currently, no data exist on potential links between OSA-related dyslipidaemia and susceptibility genes for dyslipidaemia in such patients. Our aim was to study the effects of the apolipoprotein E (APOE) genotype and sleep apnoea severity on atherogenic dyslipidaemia in patients with OSA. 519 clinically stable subjects prospectively recruited at a tertiary referral teaching hospital underwent full polysomnography. APOE gene polymorphisms were assessed using real-time PCR. In all APOE genotype groups, serum triglycerides increased while high-density lipoprotein (HDL) cholesterol was reduced with increasing severity of OSA in each APOE genotype group, whereas the deleterious effects of OSA on serum apolipoprotein (Apo)B levels were observed in ε2 carriers and the ε3/ε3 genotype only. Nevertheless, the ε4 allele carriers had ApoB levels within the risk range, irrespective of nocturnal hypoxia. In addition, among patients with the high-risk ε4 genotype, those with the most severe nocturnal hypoxia had significantly higher triglyceride and lower HDL cholesterol levels compared with nonhypoxic ε4 subjects. APOE genotype and the oxygen desaturation index were both independent predictors of serum triglyceride levels (p=0.009 and p<0.001, respectively; R(2)=0.148) and ApoB levels (p=0.001 and p=0.003, respectively; R(2)=0.104). Our findings suggest that OSA has adverse effects on several lipid parameters over and above the effects carried by APOE genotype. Further st1udies are needed to analyse the effects of high-risk genotypes on metabolic and cardiovascular outcomes in patients with OSA.

Size and subclasses of low-density lipoproteins in patients with obstructive sleep apnea.

Patients with obstructive sleep apnea (OSA) have proatherogenic dyslipidemia. We analyzed predictors of low-density lipoproteins' (LDLs) size in patients with OSA. In a cross-sectional study including 58 participants with OSA (30 without the metabolic syndrome [MetS] and 28 with MetS), we evaluated the size of LDL by gradient gel electrophoresis. Compared with patients without the MetS, those with MetS showed lower LDL size (P = .007), due to a reduction in large LDL-I particles (P = .002) and an increase in small, dense LDL-IIIA (P = .048) and LDL-IIIB (P = .037). The size of LDL correlated inversely with age (r = -.268, P = .042) and serum triglycerides (r = -.364, P = .005), and positively with serum high-density lipoprotein cholesterol levels (r = .335, P = .010). In multiple regression analysis, the presence of the MetS was the only independent predictor of LDL size (P = 0.015). In patients with OSA, MetS is an independent predictor of LDL size and subclasses, whereas the severity of OSA does not contribute independently to alterations in LDL phenotype.

Risk factors and severity of obstructive sleep apnoea in central European Roma and non-Roma patients referred for a diagnostic polysomnography [corrected].

OBJECTIVE: Obesity and metabolic syndrome are common among Roma subjects in Slovakia. We hypothesised that Roma subjects are at high risk to suffer from severe obstructive sleep apnoea (OSA). METHODS: 137 non-Roma and 23 Roma subjects referred for a diagnostic polysomnography were consecutively recruited. Overnight polysomnography, anthropometric variables and standard biochemical analyses were analysed. RESULTS: Obstructive sleep apnoea was diagnosed in 91% Roma and 65% non-Roma subjects (p < 0.001). Roma subjects had higher apnoea-hypopnoea index (AHI) (61.2 ± 7.9 vs. 22.8 ± 2.3 events/h, p < 0.001), lower dip oxygen saturation (56.7 ± 4.9 vs. 79.3 ± 1.3%, p < 0.001), and higher waist circumference as compared to non-Roma subjects (121.3 ± 3.1 vs. 105.2 ± 2.4 cm, p < 0.001). In multiple regression analysis, Roma background (p < 0.001) and waist circumference (p < 0.001) were independent predictors of AHI (R (2) = 0.330). Roma background was associated with significantly higher risk of severe OSA (odds ratio 3.73; 95% confidence interval 1.20-11.65, p = 0.023), independently of age, gender and waist circumference. CONCLUSIONS: Among subjects referred for polysomnography, Roma background is associated with significantly higher risk of severe OSA. Knowledge of common OSA pattern in Roma patients may help in identifying high risk individuals and guide early therapy of this disease.

Predictors of compliance with continuous positive airway pressure treatment in patients with obstructive sleep apnea and metabolic syndrome.

OBJECTIVE: Continuous positive airway pressure (CPAP) applied via a tight-fitting mask is the most effective treatment for obstructive sleep apnea (OSA) and has potential to improve the cardiovascular prognosis in such patients. Adequate compliance with the use of CPAP is essential for achieving the cardiovascular and metabolic benefits of this treatment. This prospective study aimed to assess factors related to objective compliance with CPAP treatment in Slovakian patients with metabolic syndrome and newly diagnosed OSA. PATIENTS AND METHODS: Fifty-one patients (42 men) with metabolic syndrome and OSA (mean age, 54.5 +/- 1.5 years; mean apnea-hypopnea index 59.0 +/- 3.9 events/h of sleep; mean lowest sleep transcutaneous oxygen saturation [SpO(2)] 66.0 +/- 2.7%) underwent pressure titration during overnight polysomnography using the Autoset self-adjusting CPAP device. Metabolic syndrome was diagnosed according to the recent definition of the International Diabetes Federation. Objective compliance was assessed electronically at the 8-week follow-up visit. RESULTS: Obesity was present in all (100%) the patients and arterial hypertension in 48 (94%); fasting plasma glucose levels were increased in 27 (55%) patients and serum triglycerides in 36 (71%); serum HDL cholesterol was reduced in 30 (59%) patients. Two patients did not use CPAP at all and were excluded from further analyses. The remaining 49 patients were divided into two groups: CPAP compliant (>or=4 h/night, mean use 5.52 +/- 0.19 h/night, n = 30) and CPAP non-compliant (< 4 h/night; mean use 1.94 +/- 0.27 h/night, n = 19). Mask leak was significantly higher in the non-compliant patients (43.0 +/- 4.4 vs. 31.9 +/- 2.7 l/min, P = 0.027). No relationships were observed between CPAP compliance and age, apnea-hypopnea index, arousal index or variables of sleep architecture. In contrast, CPAP compliance was significantly related to mean sleep SpO(2) (r = 0.314, P = 0.028), the lowest sleep SpO(2) (r = 0.297, P = 0.038) and mask leak (r = -0.376, P = 0.008). A close relationship between BMI and mask leak was also observed (r = 0.579, P < 0.001). In multiple linear regression analyses with CPAP compliance as an independent variable, and age, sex, mask leak, BMI and mean sleep SpO(2) as dependent variables, mask leak was the only independent predictor of CPAP compliance (R(2) = 0.382, P = 0.009). CONCLUSION: The study demonstrates the relationship between reductions in mask leak and good compliance with CPAP treatment in central European patients with OSA and concurrent metabolic syndrome. Strategies to maintain low leakage of the CPAP mask are warranted, particularly in grossly overweight patients.