ENDOTOXIN-INDUCED CHANGES IN SLEEP AND SLEEPINESS DURING THE DAY

Sleepiness is a common symptom of infectious diseases. However, the pe culiarities and causes of impaired vigilance during host defense activ ation are largely unknown. It has been shown earlier that mild host de fense activation by endotoxin does not affect daytime sleepiness and n on-rapid eye movement (NREM) sleep in humans. In the present study we investigated the effects of a more intensive stimulation of the host d efense by Salmonella abortus equi endotoxin (0.8 ng/kg), administered 12 h following host response priming by granulocyte colony-stimulating factor (300 mu g sc), on daytime sleep and sleepiness in a placebo-co ntrolled design in ten healthy men. Six equidistant polysomnographical ly monitored naps were scheduled across the day and the time course of subjective sleepiness was assessed. Endotoxin induced prominent incre ases in rectal temperature, and in the plasma levels of tumor necrosis factor-alpha, interleukin-6, interleukin-1 receptor antagonist, and c ortisol. In the first nap, 1 h following endotoxin administration, tot al sleep time and NREM sleep stage 2 were reduced, whereas wakefulness and sleep onset latency were increased. Following this nap sleepiness transiently increased peaking prior to the second nap. However, this nap and the following ones were not influenced by endotoxin. These res ults suggest that prominent host defense activation reduces daytime NR EM sleep and increases sleepiness. One cause of daytime sleepiness dur ing infections may be prior sleep disruption and this kind of sleepine ss may not necessarily be associated with an increased sleep pressure. (C) 1998 Elsevier Science Ltd. All rights reserved.