Zolpidem and triazolam do not affect the nocturnal sleep-induced memory improvement

Rationale: It is widely accepted that sleep facilitates memory consolidation. Hypnotics (e.g., benzodiazepines), which reportedly increase sleep efficiency but also modify sleep architecture, could affect memory improvement that occurs during sleep. Objectives: The present study examined the effects of single doses of two short half-life hypnotics, zolpidem and triazolam, on sleep-induced improvement of memory. Methods: Twenty-two healthy volunteers participated in this randomized, double-blind, crossover study. All subjects received a single oral dose of zolpidem (10 mg), triazolam (0.25 mg) or placebo at 9 (P.M.) and slept for 7.5 +/- 0.2 h. The effect of sleep on memory was investigated by comparing the performance of this group of volunteers with a group of 21 subjects in wakefulness condition. Declarative memory was evaluated by using a free-recall test of ten standard word and seven nonword lists. Subjects memorized the word and nonword lists 1 h before dosing and they were asked to recall the memorized lists 10 h after dosing. Digit symbol substitution test (DSST) and forward and backward digit tests were also given 1 h before and 10 h after dosing. Results: Subjects who slept remembered more nonwords than those in wakefulness condition, but they did not recall significantly more standard words. Neither zolpidem nor triazolam affected the enhanced nonword recall observed after sleep. Finally, none of the hypnotics affected the improvement in the DSST performance of subjects who slept. Conclusions: The hypnotics tested did not interfere with the nocturnal sleep-induced improvement of memory.