Meta-analysis on the next-morning effects of hypnotic drugs on short- and long-term memory functioning in healthy adults and elderly

Introduction: Sleep medication taken at bedtime may negatively affect next-morning cognitive performance. The aim of these metaanalyses was to determine the effect of hypnotic drugs on next-day short- and long term memory functioning. Methods: A literature search (Pubmed, Embase, PsycInfo, Scopus, Web of Science, and Cochrane) yielded N = 33.969 potentially relevant articles. Studies were included if they assessed next-morning shortor long-term memory after bedtime administration of recommended dosages of hypnotic drugs, were double-blind, placebo-controlled, conducted in healthy volunteers, and sufficient data was reported, they were included in the meta-analyses. Separate analyses were performed for adults (18-65 years old) and elderly healthy volunteers (≥ 65 years old). Results: In adults, eight studies assessing next-morning short-term memory (after bedtime administration of nitrazepam, triazolam, temazepam, flurazepam, melatonin, zaleplon, lormetazepam, zolpidem), and five studies assessing long-term memory (after bedtime administration of triazolam, nitrazepam, zopiclone, flurazepam, zolpidem) were included in the meta-analyses. The analyses revealed that both next-morning short-term memory (ES = 0.427, p = 0.0001; 95%CI: 0.212 to 0.641) and long-term memory (ES = 0.536, p = 0.0001; 95%CI: 0.247 to 0.824) were significantly impaired. In elderly, three studies assessing next-morning short-term memory (after bedtime administration of flurazepam, zolpidem, temazepam), and three studies assessing long-term memory (after bedtime administration of flurazepam, zolpidem, temazepam) were included in the meta-analyses. The analyses revealed that in elderly next-morning short-term memory (ES = 0.412, p = 0.019; 95%CI: 0.068 to 0.757) was significantly impaired. No significant impairment was found for long-term memory (ES = -0.038, p = 0.825; 95%CI: -0.380 to 0.303). Conclusion: The meta-analysis results suggest that sleep medication, when administered in recommended dosages at bedtime, significantly impair next-morning short- and long term memory.