The relationship between volum status assessed by bioimpedance analysis and obstructive sleep-apnea syndrome in patients with stage 4 and 5 chronic kidney disease whom have not yet undergone dialysis treatment

Introduction: Obstructive sleep apnea syndrome (OSAS) is a common condition, characterised by repetitive sleep apnea due to collapse of the pharynx. According to the studies, the incidence of sleep apnea syndrome, most commonly obstructive sleep apnea, is consistently correlated with the stage of chronic kidney disease. Despite the main pathophysiology between two disorders is not yet explained, several studies in recent years have focused on a current entity, 'nocturnal rostral fluid shift theory', in the role of pathogenesis. In this theory, the shift of fluid accumulated in the legs during the day to the neck at night with supine position causes to upper respiratory airway collapse and, thus predisposing to obstructive sleep apnea. Thus, in this study, we aim to evaluate the prevalence of OSAS and association of hypervolemia with OSAS in patients with grade 4 and 5 chronic kidney disease not undergoing dialysis, as well as the possible role of other laboratory parameters.Material and methods: Patients with chronic kidney disease stage 4 and 5 according to MDRD equation, routinely followed in Nephrology Clinic in Dicle University Faculty of Medicine were included in this study. Multifrequency bioimpedance analysis (BIA) was used to assess fluid status. Overhydration (OH) / extracellular water (ECW) % was accepted as an indicator of fluid status and fluid overload was defined as OH/ ECW > 7%. Exclusion criterias were obesity (BMI > 30), heart failure (LVEF < 50%), hypothyroidism, acromegaly, hemodynamic unstability, pregnancy, pacemaker use, diuretic use, presence of amputated extremity, undergoing dialysis. Patients also were asked for increased daytime sleepiness, snoring and witnessed apnea episodes. 50 patients meeting these criterias were evaluated and then polisomnography were performed to all. SPSS 18.0 computer based program was used for statistical analysis of this study, which p values < 0.005 were considered statistically significant.Results: The gender distribution of the patients in our study was % 50 with 25 male and 25 female. The prevalence of OSAS in total was found % 52 (26 / 50), in which % 65.4 of them were male (p = 0.046). In OSAS patients, the prevalence of fluid overloaded (OH / ECW > %7) was found %73.1 (19/26), in contrast, the prevalence of non-fluid oveloaded (OH / ECW < %7) was %26.9 (7/26) (p < 0.001). In patients with OSAS, systolic and diastolic blood pressure were statistically found higher than in patients without OSAS (SBP: 141.54 + 10.24 vs 130.58 + 11.78, mmHg; p = 0.001, DBP: 87.85 + 7.06 vs 81.50 + 7.80, mmHg; p = 0.004). We also detected a positive correlation between AHI severity and elevation of systolic and diastolic blood pressure (p < 0.001). In volume overloaded patients, the severity of AHI (15.06 + 9.92 vs 2.91 + 3.11; p < 0.001) and time to entering REM (50.85 + 12.05 vs 25.63 + 10.14, min; p < 0.001) were statistically found higher than non-fluid overloaded patients, whereas sleep efficiency (91.71 + 4.91 vs 94.91 + 2.27; p = 0.004) was found statistically lower in fluid overloaded patients. According to multiple stepwise regression analysis, we found a powerful association between AHI severity and age (p < 0.001), female gender (p = 0.007) and OH / ECW ratio (p < 0.001), which were considered statistically significant.Conclusion: The prevalence of OSAS in chronic kidney disease and its association with age and gender in our study were found to be similar with the literature. In OSAS patients, the prevalence of volume overloaded was detected to be statistically significantly higher than in non-OSAS patients. In addition, our study revealed a relationship between volume overload and sleep parameters. Older age, female gender and OH/ECW ratio were found independently associated with AHI severity. In summary, we consider that the volume overload may be the principal cause for the increased prevalence of OSAS in advanced stage chronic kidney disease.