0075 Melatonin impairs morning cognition in healthy young adults without any benefit to sleep

Abstract

Abstract Introduction Exogenous melatonin has been shown to improve sleep in individuals with sleep disorders, such as insomnia and delayed sleep phase disorder. However, research on the effect of exogenous melatonin on sleep in healthy young adults is limited. Additionally, there is some evidence that melatonin can negatively affect cognitive processes, such as long-term memory, working memory, and attention. Therefore, we assessed the effect of melatonin supplementation on nocturnal sleep and morning cognition in healthy undergraduates. Methods In the evening, participants (N = 120) completed three cognitive tasks: the Psychomotor Vigilance Task (PVT; a measure of attention), UNRAVEL (a measure of procedural placekeeping), and the Paired Associates Learning (PAL) test (a measure of long-term memory). We then asked participants to take a pill under double-blind conditions that contained either melatonin or placebo. Afterwards, participants received an 8-hour sleep opportunity monitored with polysomnography (PSG). One hour after waking, participants completed PAL, UNRAVEL, and PVT again. Results We compared morning cognitive performance across the melatonin and placebo conditions, with evening performance as a covariate. Interestingly, melatonin participants had more placekeeping errors than placebo. However, melatonin did not affect PVT or PAL performance. We found no significant differences between the melatonin and sleep groups on any of our sleep measures. Conclusion The results suggest that negative performance effects of exogenous melatonin may outweigh any benefits for healthy young adults, particularly when cognitive performance is measured shortly after the sleep opportunity. Our results also suggest that sleep factors captured by PSG may not accurately predict next-day cognitive performance, and that researchers should consider additional factors, such as melatonin concentration, when assessing the relationship between sleep and performance. Support (if any) This work was funded by the Office of Naval Research (N00014-20-1-2739).