Objectives: Fatigue is one of the most common symptoms associated with chronic noncommunicable diseases, and it may also increase cognitive impairment. However, associations between fatigue and cognitive impairment in chronic illnesses remain unclear. Therefore, the purpose of this systematic review was to examine research that investigated associations between level of fatigue and cognitive status.
Methods: PubMed/Medline, PsycINFO, CINAHL, and Cochrane Database were searched for articles published between 2012 and 2018 using search terms fatigue, cognition, and various iterations of these terms. Study quality was assessed by the Joanna Briggs Institute Critical Appraisal Checklist tool.
Results: Of 1799 citations, 10 studies in samples of individuals with cancer, multiple sclerosis, neurosarcoidosis, and chronic fatigue syndrome met the inclusion criteria. Fatigue was found to be significantly correlated with cognitive impairment in one cancer-related study (r = -.480, p < .001), one multiple sclerosis study (β= -0.52, p < .0001), and two chronic fatigue syndrome studies (r = 0.397, p < .001; r = 0.388, p < .001).
Discussion: There is insufficient evidence examining the relationship between fatigue and cognitive impairment in patients with chronic illnesses. As a result, more studies are needed that examine potential relationships between these two symptoms in order to develop effective treatments for individuals living with a chronic noncommunicable disease.
Keywords: Fatigue; chronic illness; chronic noncommunicable disease; cognition; systematic review.