The objective of this study was to evaluate the effects of nocturnal sleep, partial night sleep deprivation, and sleep stages on circulating concentrations of interleukin-6 (IL-6) in relation to the secretory profiles of GH, cortisol, and melatonin. In 31 healthy male volunteers, blood samples were obtained every 30 min during 2 nights: uninterrupted, baseline sleep and partial sleep deprivation-early night (awake until 0300 h). Sleep was measured by electroencephalogram polysomnography.

Sleep onset was associated with an increase in serum levels of IL-6 (P < 0.05) during baseline sleep. During PSD-E, the nocturnal increase in IL-6 was delayed until sleep at 0300 h. Sleep stage analyses indicated that the nocturnal increase in IL-6 occurred in association with stage 1–2 sleep and rapid eye movement sleep, but levels during slow wave sleep were not different from those while awake. The profile of GH across the 2 nights was similar to that of IL-6, whereas the circadian-driven hormones cortisol and melatonin showed no concordance with sleep.

Loss of sleep may serve to decrease nocturnal IL-6 levels, with effects on the integrity of immune system functioning. Alternatively, given the association between sleep stages and IL-6 levels, depressed or aged populations who show increased amounts of REM sleep and a relative loss of slow wave sleep may have elevated nocturnal concentrations of IL-6 with implications for inflammatory disease risk.