Effects of sleep extension on cognitive performance in military-aged adults: A systematic review

Abstract: INTRODUCTION: U.S. military service members (SM) rarely achieve enough sleep. Insufficient sleep in this population has been associated with deterioration of adequate cognitive performance necessary for combat effectiveness. Sleep extension is a strategy proposed by the military to counteract the effects of insufficient sleep. No systematic review exists that explores sleep extension's effects on cognitive performance in military-aged adults. The purpose of this study was to systematically review the literature and present evidence for the impact of sleep extension on cognitive performance in military-aged adults. MATERIALS AND METHODS: The reviewers searched EBSCOhost, PsychINFO, and PubMED databases for articles published between 2002 and 2022.The database search resulted in a total of 1,950 articles. Duplication removal and application of exclusion criteria to study titles eliminated 1,741 articles. Of the remaining 209 articles, screening for eligibility using inclusion and exclusion criteria removed 198 articles, resulting in 9 articles for the systematic review. The authors independently assessed the quality of each study's methodological rigor using a 24-item critical appraisal tool. RESULTS: Of the 9 studies included for review, most employed randomized cross-over or randomized control research designs (7/9), and were of moderate quality (8/9). The studies investigated the effects of sleep extension on various domains of cognitive performance and its effect on sleep deprivation or restriction. Reviewed articles revealed that sleep extension had positive effects on sustained attention and reaction time but no beneficial effects on executive functions. Beneficial effects of sleep extension were evident but short-lived in canceling sleep debt or protecting cognitive performance from sleep debt. It is possible that the relatively short-lived benefits of sleep extension found in these studies could have been attributable to pre-existing sleep debt and that perhaps the amount of sleep extension provided was insufficient to overcome or pay-off such debt. CONCLUSIONS: This review does not support the use of sleep extension as a sole intervention to mitigate cognitive performance deficits following occurrence of sleep debt for military-aged adults. Future research focused on examining the cognitive effects of sleep extension should include sleep-satiated SMs and account for the unique operational context in which SMs sleep, during the study design.