Cognitive-Affective Predictors of Exertion-Related Fatigue in Primary Biliary Cholangitis: An Experimental Substudy of the SOMA.LIV Project.

PURPOSE: Primary biliary cholangitis (PBC) is a chronic autoimmune liver disease frequently accompanied by severe fatigue. This exploratory and feasibility SOMA.LIV substudy examined associations between subjective fatigue, psychological factors, heart rate variability (HRV), and physical performance during a brief stair-climbing task in PBC. Fatigue in this study refers to self-reported fatigue, with a focus on subjective post-exertional and post-recovery fatigue in relation to baseline disease-related fatigue. PATIENTS AND METHODS: The analysis included 42 participants with PBC (93% female; mean age 56 years) who performed a stair-climbing task with continuous heart rate and HRV monitoring. Self-reports assessed fatigue (pre-, post-, post-recovery), anticipated fatigue, and fear of movement. HRV indices were measured at rest and recovery. Correlational and regression analyses identified predictors of fatigue and task performance. RESULTS: Psychological factors and HRV were unrelated to performance. Anticipated fatigue strongly predicted post-task fatigue (β = 0.69, p <0.001), while post-task fatigue predicted fatigue after recovery (β = 0.61, p <0.001). HRV indices showed no association with fatigue. CONCLUSION: Findings suggest that fatigue responses to brief physical exertion in individuals with PBC are driven partly by cognitive-affective expectations, particularly anticipated fatigue, while fear of movement showed only a trend-level association. These results should be interpreted in light of the study's limitations, including sample size and methodological constraints. Future studies should use larger samples and more demanding exertion paradigms to further elucidate mechanisms underlying exertion-related fatigue in PBC.