ENDOTOXIN ENHANCES EEG ALPHA-POWER AND BETA-POWER IN HUMAN SLEEP

Endotoxin, a lipopolysaccharide (0.4 or 0.8 ng/kg body weight), was in jected at 1900 hours in 17 healthy men in a single-blind, placebo-cont rolled experiment. The administration was followed by a 4-hour period of quiet wakefulness in bed (light intensity <200 lux). Unlimited slee p was allowed after 2300 hours (lights off) until the next morning. Th e electroencephalogram (EEG), electromyogram, electrooculogram, electr ocardiogram and rectal temperature were recorded throughout the experi mental session. Standard sleep stages were assessed, and the EEG was s ubmitted to a state-specific, serial spectral analysis. Endotoxin admi nistration induced a rise of body temperature and heart rate, which st arted approximately 2 hours after the injection and persisted through most of the sleep period. Sleep latency remained unchanged, whereas ra pid eye movement (REM) sleep latency increased from 60.3 to 89.0 minut es (paired t test; p = 0.06) compared to control values. Stage 2 sleep was elevated from 45.5 to 49.0% of time in bed (p < 0.05), and total nonrapid eye movement (NREM) sleep from 64.2 to 69.1% (p < 0.05). No s ignificant change could be observed in slow-wave sleep (SWS, stages 3 and 4). During the first 4 hours of the sleep period, NREM sleep EEG s pectral power was distinctly and markedly increased between 8 and 12 H z (alpha) and 15 and 20 Hz (beta) (p < 0.05), whereas at the same time EEG power between 1 and 8 Hz (delta, theta) was not significantly cha nged. We conclude that in humans the primary host response induced by endotoxin initially suppresses REM sleep and increases stage 2 NREM sl eep, but does not affect SWS. No clear modification of sleep EEG delta activity could be observed after endotoxin injection, despite marked endocrinological and physiological changes such as the elevation of bo dy temperature. Numerous factors related to the human primary host res ponse may be responsible for the EEG intensification of the alpha and beta range.