CAFFEINE-INDUCED SLEEP DISRUPTION - EFFECTS ON WAKING THE FOLLOWING DAY AND ITS REVERSAL WITH AN HYPNOTIC

The effects of 4 mg/kg and 8 mg/kg caffeine nocte as a model of insomn ia, and its potential for reversal with an hypnotic (temazepam 20 mg) were investigated in two double-blind placebo controlled crossover stu dies, each with six healthy volunteers. Following an adaption night an d day, two nights per treatment were assessed with multiple sleep late ncy tests (MSLTs), performance measures and subjective questionnaires undertaken the following day. In comparison to placebo significant (P< 0.05) increases in sleep onset latency of 30 and 40 min were seen for low and high doses respectively. Significant reductions in sleep durat ion were limited to the higher dose (total sleep time 80 min, sleep ef ficiency 17 per cent), as were reductions in slow wave sleep and non-R EM sleep which contrasted with increased waking. However, contrast ana lysis revealed significant dose-related effects for these measures, wh ilst the lower dose produced more stable effects across nights, sugges ting it as more suitable for a model of insomnia in healthy sleepers. Significant decrements in critical flicker fusion (CFF) performance an d reduced MSLT latencies reflected increased daytime sleepiness follow ing both doses; although significant subjective changes to sleep and s leep tendency next day were limited to the higher dose. Go-administrat ion of temazepam elixir successfully reversed increased sleep latency seen with the lower caffeine dose and improved subjective sleep, but s ignificant effects on other sleep measures were more limited despite i mproved mean Similarly, improvements in CFF performance and MSLT laten cies failed to achieve significance, suggesting a possible limitation of the hypnotic in overcoming the effects of sleep disturbance and con sequences for waking function next day.