Fatigue management: a systematic review of objective measurement techniques for cognitive fatigue

BACKGROUND: Cognitive fatigue is a complex psychobiological state whereby task performance cannot be maintained. Return-to-work protocols typically rely on self-report measures, therefore the current systematic review aimed to identify "real-time" measures of objective cognitive fatigue to inform return-to-work protocols. METHODS: Studies were included if participants were at least 18 years old, assessed "real-time" objective cognitive fatigue that could be used outside of the lab (neuroimaging measures were, therefore, excluded), used an induction task that was separate to the measurement, were adequately powered, compared objective cognitive fatigue at baseline and post-induction, and included a cognitive fatigue induction task that was at least 30 minutes long.Nine electronic databases were searched until 31 December 2022 (MEDLINE; PsychArticle; PubMED, ProQuest; ProQuest for gray literature; Google Scholar; The Cochrane Library; The Health Technology Assessment Database; and Web of Science), with alerts set up on Google Scholar to notify of new relevant research since this date (reviewed until December 2023). The checklist for quasi-experimental studies (Joanna Briggs Institute, 2014) was used to assess the risk of bias. Whilst a meta-analysis was planned, the data were unsuitable so only a narrative synthesis was conducted. RESULTS: Fifty-seven studies were included, which were conducted within a variety of settings including naturalistic work scenarios, driving, aviation, and artificial computer-based tasks.Whilst the review found a range of potential measurements, there were inconsistencies in findings across studies highlighting the need for more research into the reliable measurement of objective cognitive fatigue in natural settings. DISCUSSION: The findings suggest that eye- and body-related measures may be sensitive measures of objective cognitive fatigue. However, comparisons across measurement types should be cautiously interpreted because eye-related and cognitive measures were far more common. The review highlighted the need for more consistent and transparent reporting across the field to advance our understanding of cognitive fatigue.