Effects of sleep on endotoxin-induced host responses in healthy men

Objective: To examine whether increased sleep during viral or bacterial inf ections supports host defense mechanisms. Methods: To test this assumption in humans, healthy male subjects were assigned either to sleep from 2300 to 0700 hours (n = 10) or to stay awake through the night (n = 10). In the sl eeping subjects Salmonella abortus equi endotoxin (0.4 ng/kg) or placebo we re intravenously injected in balanced order during the first SWS episode. T he age-matched, sleep-deprived subjects were injected at the same time poin t. Results: As expected, endotoxin significantly increased rectal temperatu re, the plasma levels of cortisol, tumor necrosis factor-alpha (TNF-alpha), the soluble TNF receptors p55 and p75, Interleukin (IL)-6, the IL-1 recept or antagonist (RA), leukocyte, and granulocyte counts in both sleeping and sleep-deprived subjects, whereas lymphocyte and monocyte counts were transi ently reduced. Time courses of endotoxin-induced host responses did not dif fer between the sleep and sleep deprivation groups. Endotoxin did not affec t the amount of nocturnal wakefulness, nonrapid-eve-movement (NREM) sleep, or rapid-eye-movement (REM) sleep across the total night compared with plac ebo, but significantly increased electroencephalogram-arousals (EEG-arousal s) in stage 2 and decreased arousals in SWS. In addition, the amount of SWS , spectral EEG-delta and -theta power was increased at the beginning and at the end of the sleep period, respectively, when the degree of immune activ ation was relatively low. Conclusion: The present results support the notio n that short-term sleep deprivation is unlikely to harm the immune system a s far as unspecific acute responses are concerned. The effects of endotoxin on sleep in this case support prior observations that in humans, enhanced SWS and intensified NREM sleep occur when host defense activation is subtle .