Sustained military operations and cognitive performance

Introduction: Cognitive performance is crucial during military operations. It is suggested that impaired cognitive performance accounts for most of the accidents during training courses and actual battle. There is a need to define when soldiers' operational readiness becomes impaired. The objective of this systematic review was to investigate the effects of sustained military operations (SUSOPS) on vigilance, reaction time, working memory, and reasoning in order to select good indicators for performance impairment. Methods: A systematic literature search was performed using publicly accessible databases (IngentaConnect, PubMed, Science Direct, and Defense Technical Information Center online) that were screened until July 2015. Keywords were military, sustained operations, (cognitive) performance, soldier, and training. Results: Only 7 out of 589 studies met the inclusion criteria. Selected studies were difficult to compare due to different methodologies, cognitive tasks, and military courses. Vigilance, reaction time, and working memory were affected after only a few hours, showing severe impairment. They are linearly related to military stress up to 80 h of SUSOPS. These three indicators needed little recovery time to return to baseline levels. After more than 80 h of SUSOPS, no significant impairments of those indicators were observed. Reasoning becomes impaired after high stress levels of relatively short duration and can remain affected after more than 80 h of SUSOPS. Discussion: Vigilance, reaction time, and working memory are affected after only a few hours while little recovery time is needed. For reasoning to return to baseline values, longer recovery is needed than the time available during SUSOPS