Caffeine is the world's most popular stimulant and is known to disrupt sleep. Administration of
caffeine can therefore be used in healthy volunteers to mimic the effects of
insomnia and thus to test the
hypnotic effects of medication. This study assessed the effects of
caffeine on sleep architecture and electroencephalography (EEG) spectrum alone and in combination with two different sleep-promoting medications. Home polysomnography was performed in 12 healthy male volunteers in a double-blind study whereby subjects received placebo,
caffeine (150 mg),
caffeine plus
zolpidem (10 mg) and
caffeine plus
trazodone (100 mg) at bedtime in a randomised crossover design. In addition to delaying sleep onset,
caffeine decreased total sleep time (TST), sleep efficiency (SE) and stage 2 sleep without significantly altering wake after sleep onset or the number of awakenings.
Zolpidem attenuated the
caffeine-induced decrease in SE and increased spindle density in the
caffeine plus
zolpidem combination compared with placebo.
Trazodone attenuated the decrease in SE and TST, and it also increased stage 3 sleep, decreased the number of awakenings and decreased the spindle density. No significant changes in rapid eye movement (REM) sleep were observed, neither was any significant alteration in slow wave activity nor other EEG spectral measures, although the direction of change was similar to that previously reported for
caffeine and appeared to 'normalise' after
trazodone. These data suggest that
caffeine mimics some, but not all of the sleep disruption seen in
insomnia and that its disruptive effects are differentially attenuated by the actions of sleep-promoting compounds with distinct mechanisms of action.