Relationship of arousals from sleep to sympathetic nervous system activityand BP in obstructive sleep apnea

Study objective: Obstructive sleep apnea (OSA) patients have a high frequen cy of arousals. We hypothesized that arousals significantly influence tonic sympathetic nervous system function. Design: We examined the association of 11 variables measuring sympathetic a ctivity, including plasma norepinephrine (IVE), urinary NE, and BP measurem ents, with movement and cortical arousals, Patients: Sixty-seven subjects with various degrees of hypertension and OSA were evaluated. All patients were free from antihypertensive medications. Results: The age (range, 35 to 60 years), weight (range, 100 to 150% of ide al body weight), and diet of the subjects were similar, The movement arousa l index was correlated with daytime baseline plasma NE (BNE), daytime urine NE, mean daytime diastolic BP, and systolic BP during rapid eye movement s leep (r = 0.39 to 0.53; p less than or equal to 0.002). Cortical arousals d id not correlate with any of the variables, A multiple regression procedure was performed to examine how well movement arousals predicted those variab les with significant correlations, The respiratory disturbance index (RDI) and nighttime pulse oxyhemoglobin saturation were included in the regressio n equation due to their close association with movement arousals. Movement arousals independently predicted BNE (t [48] = 2.06; p < 0.05). No other va riable independently predicted any of the measurements of sympathetic activ ity. Conclusions: These findings suggest that movement arousals may influence da ytime sympathetic tone independently of RDI and nighttime saturation.