Relationship between the effects of a hypnotic drug, zopiclone, on polysomnography and on daytime EEGs

Zopiclone to treat insomnia in older adults: A systematic review

Considering the global increase in use of Z-drugs to treat insomnia, the study objective was to conduct a systematic review on the efficacy and safety of zopiclone to treat sleep disorders in older adults compared to other sedative-hypnotics, to placebo or to non-pharmacological interventions. The literature search for original reports - clinical trials, cohort studies and cross-sectional, observational investigations - was done in eleven databases and web search engines followed PRISMA guidelines, and methodological quality was assessed using the Risk of Bias tool in the Cochrane Reviewers' Handbook. The search resulted in 12 randomized, placebo-controlled clinical trials along with 2 open studies and 2 observational reports. Overall, the studies suggest that zopiclone is effective to treat insomnia by reducing sleep latency, nocturnal awakenings and wake time after sleep onset while increasing total sleep time, with probable effects on sleep architecture. Zopiclone was found to be fairly tolerated, to induce a low rate of adverse events with non-severe impact on psychomotor or cognitive performance and to produce no major harm to the overall well-being and daily living abilities. However, the quality of most studies was classified as low or unclear. Though the studies available support benefits from zopiclone use, there is still a need for further evidence on long-term effects, tolerability and safety in the treatment of older adults by means of high-quality trials.

Ceiling and floor effects in sleep research

Ceiling and floor effects dictate that the efficacy of sleep-promoting stimuli should be proportional to the degree of pre-stimulus sleep impairment. This review addressed CF effects in polysomnographic research involving hypnotic drugs and exercise. Correlations of placebo/baseline levels of sleep with changes in sleep following hypnotic or exercise treatment were assessed across both literatures. CF effects were further addressed by comparing sleep-promoting effects of hypnotics vs exercise, after ANCOVA control for substantial baseline differences reported in studies of these stimuli. Significant correlations between placebo-baseline levels and sleep changes were observed following both hypnotic and exercise stimuli. Indeed, approximately 60% of the variance in improvement in sleep latency (SOL), wakefulness after sleep onset (WASO) and total sleep time (TST) following hypnotic treatment was associated with differences in baseline levels. ANCOVAs revealed significantly greater decreases in SOL and WASO following hypnotics compared with exercise. However, no significant difference between stimuli was found for TST, and exercise elicited a significantly greater increase in slow wave sleep. Similar results were found when a comparison between hypnotics and exercise was limited to good sleepers. The results show powerful CF influences on sleep responses to hypnotics and exercise and suggest a need for comparing these treatments in poor sleepers.