SYMPATHETIC NERVOUS-SYSTEM ALTERATIONS IN SLEEP-APNEA - THE RELATIVE IMPORTANCE OF RESPIRATORY DISTURBANCE, HYPOXIA, AND SLEEP QUALITY

Numerous alterations in the sympathetic nervous system have been repor ted in patients with obstructive sleep apnea. It is unclear whether su ch alterations can be attributed to the respiratory disturbance itself , the resulting hypoxia, or disruption of sleep. We examined urinary n orepinephrine levels in 45 individuals with varying amounts of respira tory disturbance and sleep disruption. All were of similar age (40 to 60 years) and body weight (100 to 160% ideal body weight), and all wer e free from antihypertensive medications that could influence norepine phrine levels. Twenty-four-hour urinary norepinephrine levels were cor related with respiratory disturbance index (r=0.39, p<0.01) and mean o xygen saturation (r=-0.36, p<0.05). These variables, together with the time in slow-wave sleep, accounted for a statistically significant bu t modest percentage of the variance in urinary norepinephrine (R(2)=0. 19, p<0.05). However, the variables were so tightly intercorrelated th at no single variable independently predicted norepinephrine levels in multiple regression analysis.