Rostral overnight fluid shift in end-stage renal disease: relationship with obstructive sleep apnea

Background. In both healthy male subjects and men with heart failure, the severity of obstructive sleep apnea (OSA) is related to the amount of fluid displaced from their legs into the neck overnight. Whether overnight rostral fluid shift contributes to the pathogenesis of OSA in patients with end-stage renal disease (ESRD) is unknown. We hypothesized that the change in neck circumference (NC) and severity of OSA are related to the extent of overnight change in leg fluid volume (LFV) in patients with ESRD. Methods. We studied 26 patients with ESRD (14 men) on conventional hemodialysis. All subjects underwent polysomnography. LFV was measured by bioelectric impedance at bedtime and repeated in the next morning on awakening. Results. Our cohort's overall apnea-hypopnea index was 22.8 +/- 26.8 episodes/h of sleep. Their overnight change in LFV was -243 +/- 278 mL. The change in LFV correlated with apnea-hypopnea time (AHT) (P = 0.001) and NC (P = 0.0016). Other independent factors associated with AHT included age (P = 0.005), baseline neck (P = 0.0002), sitting time (P = 0.008) and male gender. Stepwise multiple regression analysis revealed that age, change in LFV and male gender remained independent related to AHT. Conclusions. Nocturnal rostral fluid shift is associated with the severity of OSA in ESRD. Prospective evaluation of the effect of reducing fluid overload and severity of OSA in ESRD patients warrants further examination.