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

Obstructive sleep apnea (OSA) patients have a high frequency of arousals. We hypothesized that arousals significantly influence tonic sympathetic nervous system function.

We examined the association of 11 variables measuring sympathetic activity, including plasma norepinephrine (NE), urinary NE, and BP measurements, with movement and cortical arousals.

Sixty-seven subjects with various degrees of hypertension and OSA were evaluated. All patients were free from antihypertensive medications.

The age (range, 35 to 60 years), weight (range, 100 to 150% of ideal body weight), and diet of the subjects were similar. The movement arousal index was correlated with daytime baseline plasma NE (BNE), daytime urine NE, mean daytime diastolic BP, and systolic BP during rapid eye movement sleep (r = 0.39 to 0.53; p < or = 0.002). Cortical arousals did not correlate with any of the variables. A multiple regression procedure was performed to examine how well movement arousals predicted those variables with significant correlations. The respiratory disturbance index (RDI) and nighttime pulse oxyhemoglobin saturation were included in the regression equation due to their close association with movement arousals. Movement arousals independently predicted BNE (t [48] = 2.06; p < 0.05). No other variable independently predicted any of the measurements of sympathetic activity.

These findings suggest that movement arousals may influence daytime sympathetic tone independently of RDI and nighttime saturation.