Conventional and power spectrum analysis of the effects of zolpidem on sleep EEG in patients with chronic primary insomnia

Study Objective: The purpose of this study was 1)to assess the effect of zo lpidem or a placebo on sleep in two groups of insomniac patients with a dia gnosis of moderate-to-severe chronic primary insomnia and 2) to determine t he effect of zolpidem on sleep structure using spectral analysis. Design: A randomized, double-blind, placebo-controlled trial. Setting: Sleep laboratory of the Department of Pharmacology and Therapeutic s at the Clinics Hospital. Participants: 12 female outpatients with chronic primary insomnia Interventions: Zolpidem was given at a daily dose of 10 mg for 15 nights. Results: The hypnotic drug reduced steep latency and waking time after slee p onset, and increased total sleep time and sleep efficiency. Values corres ponding to visually scored slow wave sleep (stage 3 and 4) showed no signif icant changes. Ail-night spectral analysis of the EEG revealed that power d ensity in NREM sleep was significantly increased in the low frequency band (0.25-1.0 Hz) in the zolpidem group during the first 2-h interval. Conclusions: In agreement: with previous findings obtained in patients with chronic primary insomnia, zolpidem significantly improved sleep induction and maintenance. Moreover, zolpidem increased power density in the 0.25-1.0 Hz band during short-term and intermediate-term treatment. Nevertheless, o ther frequency bands in the delta range showed a relative decrease which wa s not statistically significant.