Effects of sleep pressure on endogenous cardiac autonomic activity and body

Dawson. Effects of sleep pressure on endogenous cardiac autonomic activity and body temperature. J Appl Physiol 92: 2578–2584, 2002. First published February 22, 2002; 10.1152/japplphysiol.01106.2001.—This study investigated the effects of variations in sleep pressure on cardiac auto-nomic activity and body temperature. In a counterbalanced design, 12 healthy, young subjects (6 men and 6 women) remained recumbent during 30 h of wakefulness (high sleep pressure) and 6 h of wakefulness (low sleep pressure). Both periods of wakefulness were immediately followed by a sleep opportunity, and the first 2 h of sleep were analyzed. During extended hours of wakefulness, a reduction in heart rate was mediated by a decline in cardiac sympathetic activity (mea-sured via preejection period) and the maintenance of cardiac parasympathetic activity (measured via respiratory sinu