Uncovering the relationships between fatigue, sleep, and cognition after an acquired brain injury: A systematic...

Objective: Fatigue, sleep disturbance, and cognitive impairment are among the most common and enduring consequences of acquired brain injury (ABI). Despite this, the understanding of how these post-injury factors interact remains limited. This systematic review synthesized existing literature to investigate the interrelationships underlying mental fatigue after ABI, and identified cognitive domains most consistently associated with fatigue and sleep difficulties. Method: Following PRISMA guidelines, a comprehensive search of MEDLINE, PsycINFO, ScienceDirect, Scopus, EMBASE, Web of Science, CINAHL, and grey literature identified peer-reviewed English-language studies on adults aged 16 to 70 years with an ABI diagnosis. Eligible studies used validated measures and reported quantitative relationships between fatigue, sleep, and cognition. Studies focusing on neurodegenerative or neurodevelopmental disorders were excluded. Risk of bias was assessed using the NHLBI Quality Assessment Tool. Results: The review synthesized data from 17 studies involving 2,523 participants. Medium-to-large associations were found between fatigue, sleep and cognition post-ABI. Attention, processing speed, executive functioning, and memory were most consistently associated with trait fatigue and sleep disturbances. A small number of studies suggested a potential role for sleep disturbances in the fatigue-cognition relationship post-ABI, though findings were limited and inconclusive. While most studies demonstrated low to fair risk of bias, heterogeneity in study design and measures limited direct comparability. Conclusions: This review highlights attention, processing speed, executive function, and memory as key cognitive domains in post-ABI fatigue and sleep difficulties. More focused research on specific cognitive domains and the role of sleep is needed to clarify post-ABI fatigue mechanisms.