Nonimprovement in Chronic Fatigue Syndrome: Relation to Activity Patterns, Uplifts and Hassles, and Autonomic Dysfunction.

OBJECTIVE:To test a model of nonimprovement in chronic fatigue syndrome (CFS) using self-report activity patterns (e.g., "push-crash"), uplifts and hassles, and a biological measure of cardiac autonomic function. Activity pattern impacts on symptoms and objective measures of autonomic and physical activity were also examined. METHODS:This prospective study in CFS collected all data remotely, including 6 months of weekly web diaries that recorded symptom ratings, activity patterns, and hassles and uplifts. In addition, 6 months of weekly heart monitoring and 3 months of daily waking actigraphy data were collected. Improvement or nonimprovement status was assessed using semistructured interviews at the 6-month follow-up. RESULTS:A total of 148 individuals (87.2% female) were enrolled, and 12.2% were lost to follow-up. Participants reporting nonimprovement ( n = 92), as compared with improvement ( n = 38), showed greater autonomic dysfunction (lower heart rate variability, group difference = 5.93 [SE = 2.73] milliseconds; p = .032) and lower mean intensity of behavioral uplifts (group difference = 0.14 [SE = 0.16]; p = .043), but no significant differences in any activity pattern, including push-crash, limiting activity, and healthy pacing. CONCLUSIONS:This study provided evidence for linking patient-reported nonimprovement to a biological variable indexing autonomic dysfunction and a behavioral measure indicating a deficit in psychological uplifts. These findings suggest a possible marker of illness trajectory that could potentially advance the biomedical underpinnings of CFS.Trial Registration:ClinicalTrials.gov ID: NCT02948556.