Infrequent periodic sleep disruption: effects on sleep, performance and mood.

In the first of two experiments, 12 normal young adults had their sleep periodically disturbed for two nights in the laboratory at three different rates: 10 min of sleep followed by 20 min of disturbance, 20 min of sleep followed by 40 min of disturbance and 40 min of sleep followed by 80 min of disturbance. Sleep and disturbance alternated throughout the night. While all disturbance conditions resulted in decreased daytime performance and increased sleepiness, the disturbance conditions did not differ from each other. In the second experiment, sleep was periodically disturbed for two nights at three new rates to act as control conditions for Experiment 1. The three conditions were: 2 min of sleep followed by 4 min of disturbance, 20 min of sleep followed by a single awakening, and 40 min of sleep followed by a single awakening. Sleep and disturbance again alternated throughout the night. As expected, sleep was less disturbed and daytime decrements were smaller in the conditions allowing 20 and 40 min of sleep followed by a single awakening. The data from both experiments were interpreted as support for sleep continuity theory; i.e., as the length of periods of consolidated sleep decrease, residual decrements increase.