INFLUENCE OF ENDOTOXIN ON DAYTIME SLEEP IN HUMANS

Administration of endotoxin in the evening has been shown to transient ly suppress rapid eye movement (REM) and to promote non-REM sleep in h umans. In a single-blind placebo-controlled crossover design, we asses sed the effects of Salmonella abortus equi endotoxin administered intr avenously in the morning on the primary host response and on daytime s leep by use of a multiple napping protocol in healthy volunteers. The extent of the host response achieved by 0.8 ng of endotoxin per kg of body weight given at 0900 h was comparable to that previously reported to result from the administration of 0.4 ng/kg at 1900 h, However, sl eep was only slightly influenced. Endotoxin reduced the amount of REM sleep and increased REM latency. Non-REM sleep amount in the first nap , although not significantly changed, correlated negatively with the i ndividual peak levels of interleukin-6 (r = -0.73, P < 0.05). Subjecti ve tiredness, sleep onset latency, total sleep time, and the amounts o f slow-wave and nn-REM sleep were not affected by endotoxin throughout the entire experiment. Spectral analysis of the electroencephalogram obtained during non REM sleep yielded no condition differences. We con clude that endotoxin administration in the morning to healthy voluntee rs, while activating the host defense to the same extent as a lower do se that has been reported to promote non-REM sleep when given in the e vening, does not affect non-REM sleep, REM sleep suppression is, to da te, the most consistently reported effect of endotoxin on human sleep.