Validation of a Smartphone-Based Approach to In Situ Cognitive Fatigue Assessment

Background: Acquired Brain Injury can result in multiple detrimental cognitive effects such as reduced memory capability, concentration and planning. These effects can lead to cognitive fatigue, which can exacerbate the symptoms of Acquired Brain Injury and hinder management and recovery. Assessing cognitive fatigue is difficult due to the largely subjective nature of the condition and existing assessment approaches. Traditional methods of assessment use self-assessment questionnaires delivered in a medical setting. However, recent work has attempted to employ more objective cognitive tests as a way of evaluating cognitive fatigue. However, these tests are still predominantly delivered within a medical environment, limiting their utility and efficacy. Objective: The aim of the research was to investigate how cognitive fatigue can be accurately assessed in-situ, during the quotidian activities of life. It was hypothesised that this could be achieved through the use of mobile assistive technology to assess: working memory, sustained attention, information processing speed, reaction time, and cognitive throughput. Methods: The study used a bespoke smartphone application to track daily cognitive performance in order to assess potential levels of cognitive fatigue. 21 participants with no prior reported brain injuries took place in a two-week study, resulting in 81 individual testing instances being collected. The smartphone application delivered three cognitive tests on a daily basis: (1) Spatial Span to measure visuospatial working memory; (2) Psychomotor Vigilance Task to measure sustained attention, information processing speed and reaction time; (3) a Mental Arithmetic test to measure cognitive throughput. A smartphone optimised version of the Mental Fatigue Scale self-assessment questionnaire was used as a baseline to assess the validity of the three cognitive tests, as the questionnaire has already been validated in multiple peer reviewed studies. Results: Highest correlated results were from the Psychomotor Vigilance Task, and showed a positive correlation with those from the pre-validated Mental Fatigue Scale, measuring 0.342, p <.008. Scores from the cognitive tests were entered into a regression model and showed that only reaction time in the Psychomotor Vigilance Task was a significant predictor of fatigue (p = .016, F = 2.682, 95% CI 9.0 to 84.2). Higher scores on the Mental Fatigue Scale were related to increases in reaction time during our mobile variant of the Psychomotor Vigilance Task.