Fatigue severity remains stable over time and independently associated with orthostatic symptoms in chronic fatigue syndrome: a longitudinal study.

Observed Findings

• Fatigue severity remained stable in most patients from 2005 to 2009, despite individual variation (39% improved, 45% worsened by ≥10 points on FIS).
• Orthostatic symptoms (dizziness, lightheadedness) remained stable over 4 years and were independently associated with current fatigue.
• Patients reported characteristic daily fatigue patterns: highest in morning (6.4/10) and evening (7.0/10), lower at midday (6.2/10).
• Depression and anxiety scores improved during follow-up, but change in anxiety independently predicted current fatigue.
• Fatigue ratings were consistent week-to-week and day-to-day, suggesting stable rather than highly variable fatigue perception.

Inferred Conclusions

• Fatigue in ME/CFS is a relatively stable symptom over years, not a rapidly fluctuating complaint.
• Orthostatic dysfunction appears to be an independent driver of fatigue severity and may be a key therapeutic target.
• Mood disorders (depression and anxiety) are intertwined with fatigue, and changes in anxiety contribute to fatigue burden independent of baseline depressive symptoms.
• Targeted management of autonomic symptoms and mood disturbance may be more effective for fatigue management than general symptom approaches.

Remaining Questions