Environmental noise and sleep--a study of arousals, cardiac arrhythmia and urinary catecholamines

Nine adult subjects with documented cardiac arrhythmia were studied during 4 nights of sleep in a laboratory. A sleep polygraph and single-channel electrocardiogram were recorded continuously throughout each night. After the 1st night's familiarization, the subjects were presented with 1 night each of 50 calibrated aircraft or truck noise events. One other night was noise-free. Intervals containing noise and paired quiet intervals were examined for sleep stage at interval onset, number of sleep stage changes and ventricular premature contractions (VPCs). Overnight urinary catecholamines were also assayed. It was found that noise increased the likelihood of arousal responses to the same extent in all sleep stages (p < 0.05). Four subjects showed frequent VPCs during the experiment. These VPCs were significantly related to sleep stage (p < 0.05) but not to noise events. Excretion of urinary catecholamines did not differ between noise and quiet nights.