Brain Small-Worldness Properties and Perceived Fatigue in Mild Cognitive Impairment

Background: Perceived fatigue is among the most common complaints in older adults and is substantially influenced by diminished resources or impaired structure of widespread cortical and subcortical regions. Alzheimer's disease and its preclinical stage-mild cognitive impairment (MCI)-are considered a brain network disease. It is unknown, however, whether those with MCI will therefore perceive worse fatigue, and whether an impaired global brain network will worsen their experience of fatigue. Methods: In this pilot case-control study of age-, sex-, and education-matched MCI and their cognitively healthy counterparts (HCs), perceived fatigue was measured using Multidimensional Fatigue Inventory, and diffusion tensor imaging tractography data were analyzed using graph theory methods to explore small-worldness properties: segregation and integration. Results: Perceived fatigue was more severe in MCI than HCs. Despite a trend for greater network alterations in MCI, there were no significant group differences in integration or segregation. Greater perceived fatigue was related to higher segregation across groups; more perceived fatigue was related to higher segregation and lower integration in MCI but not HCs. Conclusion: Findings of this study support the notion that altered whole-brain small-worldness properties in brain aging or neurodegeneration may underpin perceived fatigue.