Examining the effect of perceived fatigability on cognitive function abilities in older adults with MCI

Background Chronic fatigue with cognitive and daily functioning decline is a major public health concern in older adults The association between fatigue and neurodegenerative conditions (e g , multiple sclerosis) has been studied for many years But, it is not known the relationship between Alzheimer's pathology and perceived fatigability, a phenotype characterized by the relationship between an individual's perceived fatigue and the activity level with which the fatigue is associated We examined the role of fatigability on the link between cognitive function and cognitive function abilities and the effect of sleep on this indirect link in older adults with mild cognitive impairment (MCI) Methods Adults age > 55 years who met the ADNI criteria for MCI were included Depression assessed by the DSM-V criteria and a GDS>5 was exclusionary We conducted the study with the PROMIS Cognitive Function-Abilities (CogAb), Sleep Disturbances (SD), Sleep-related Impairment (SRI), and the Neuro-QOL Cognitive Function (CogF) and Fatigue, including Fatigue symptom score (item1-3&7) and Fatigability score (item4-6&8) Linear regression models were fit to Fatigue and Fatigability included sleep outcomes and their interaction as predictors Mediation models were fit to assess whether fatigability mediated the effect of CogF on CogAb Results Before the COVID pandemic, 36 subjects were recruited, with the mean age= 68 8 ±9 3, 58 3% female, 78% white, and 15 2% Hispanic The results revealed that CogF predicted CogAb (b= 0 78, t(34)=4 83, p0 05) after controlling for age SRI had no direct effect on CogAb Conclusions Perceived fatigability partially mediated the link between CogF and CogAb and sleep outcomes had no significant impact on this indirect link The results suggested that fatigability could be a biological construct of Alzheimer's pathology, independent from sleep and depression