Macro and microstructure sleep changes in insomniacs with high dose abuse of BZ

Abstract

Introduction Chronic and high-dosage intake of benzodiazepine (BZ) is a common problem in patients with insomnia. No data have been reported on the effects on PSG variables induced by high doses of BZ in patients with chronic insomnia. The aim of this study was to evaluate sleep architecture, microstructure (CAP) and EEG power spectra of patients with chronic primary insomnia and chronically treated with high-dose BZ, that were referred to the Sleep Center for drug discontinuation. Materials and methods Consecutive enrolment of 20 subjects affected by primary insomnia (DSM-IV) and of 13 control subjects was carried out. All patients underwent a nocturnal polysomnographic recording. Sleep stages were scored following standard criteria on 30-s epochs while all CAP phases during NREM sleep were detected and classified into three subtypes (A1, A2, and A3) according to Terzano et al. (2001). Average relative power spectra were calculated using the sleep analysis software Hypnolab 1.2, by means of the Fast Fourier Transform, for frequencies between 0.5 and 25 Hz. Results A significant difference was found for Time in Bed, REM sleep latency and percentage of sleep stage 1 which were increased in BZ patients. Total CAP rate was dramatically decreased (8%) in patients (especially during sleep stage 2 and slow-wave sleep) because of the significant decrease in the number of CAP A1 and A2 subtypes. As concern power spectra, during NREM sleep, BZ patients show a clear decrease in the relative power of the delta band of NREM sleep, accompanied by a relative increase of the sigma and beta bans. A time-dependent general decrease of the delta power was observed for control subjects, but not for patients during sleep stage 2 and SWS. Conclusion Macrostructure of sleep seems to be quite preserved in BZ patients, while sleep instability is decreased to severe pathological values, lower than any other reduction that has been previously reported. This reduction could be responsible for the low sleep quality and the cognitive deficits usually reported. Also power spectral analysis confirm the reduction in slow wave activity and the loss of its dynamic regulation. BZ overuse and insomnia seem to interact both leading to a sleep whose continuity parameters are conserved, but whose organization and microstructure is completely altered.