Neuroimaging markers of chronic fatigue in older people: a narrative review.

BACKGROUND: Chronic fatigue is a common symptom in older adults. Although some studies have attempted to identify the neuronal correlates of fatigue associated with chronic diseases, the scientific evidence is scarce regarding fatigue in older people not suffering from a specific disease. AIMS: To gather available evidence of neuroimaging studies investigating the associations between fatigue and brain health in older adults out of the context of a specific disease, and to identify potential brain structures associated with this symptom. METHODS: Studies considering exclusively patients with a specific disease and/or studies focusing on physiological mechanisms of acute fatigue induced by the realization of cognitive and physical tasks were excluded. RESULTS: Very few studies on the associations of fatigue with neuroimaging markers are currently available. Fatigue was associated with reduced hippocampus volumes and with hippocampal amyloid deposition. Regarding the association between fatigue and the circuit of basal ganglia, putamen and thalamus were associated with physical fatigability, whereas amygdala and thalamus with mental fatigability. Very limited evidence about white matter integrity found that healthy individuals with high levels of fatigue had a greater total volume of leukoaraiosis. CONCLUSION: This review suggests that hippocampus damage and potentially loss of function in basal ganglia networks could play a role on chronic fatigue during aging. Further studies are needed to assess the associations of fatigue with white matter alterations.