The present two experiments were designed to investigate the effects of a synthetic and of a natural corticosteroid on nocturnal sleep in humans. Both experiments were held double-blind and designed according to a within-subject cross-over comparison. In the first experiment, 1 mg of dexamethasone applied orally prior to sleep (11.00 p.m.) led to a reduction of the percent of time spent in REM and in stage 4 sleep. The amount of stage 2 sleep tended to be increased after dexamethasone. In the second experiment, an infusion of 100 mg hydrocortisone throughout the night also reduced REM, but increased stage 4 sleep. A statistical comparison of both experiments suggested that both steroids not only reduced REM sleep but also tended to enhance intermittent wakefulness. This analysis also confirmed opposite effects on measures of slow-wave sleep of both substances. The results represent a first demonstration of differential effects of synthetic and natural corticosteroids on sleep, which has to be substantiated in further studies directly comparing effects of these steroids.

The relationship between the plasma cortisol level and sleep stages was investigated in a single male subject across 17 nights. Blood samples were taken every 30 min from 11.00 p.m. until 02.30 a.m. and every 15 min during the rest of the night. Data analyses performed for the whole nights did not give evidence for strong relations between plasma cortisol and sleep stages. Analyses on data of the second part of the night, beginning with the onset of the first cortisol peak, revealed that plasma cortisol was primarily decreasing when rapid eye movement sleep (REM) was present. Sleep stage I and periods of wakefulness were associated with increasing cortisol levels. There was no evidence for a particular EEG event triggering the first rise of plasma cortisol during the night.