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 zolpidem or a placebo on sleep in two groups of insomniac patients with a diagnosis of moderate-to-severe chronic primary insomnia and 2) to determine the 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 Therapeutics 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 sleep latency and waking time after sleep onset, and increased total sleep time and sleep efficiency. Values corresponding to visually scored slow wave sleep (stage 3 and 4) showed no significant changes. All-night spectral analysis of the EEG revealed that power density 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, other frequency bands in the delta range showed a relative decrease which was not statistically significant.