cluster analysis, factor analysis, fibromyalgia, outcome assessment, symptoms



  1. Rutledge, Dana N.
  2. Mouttapa, Michele
  3. Wood, Patrick B.


Background: Recent evidence points to the likelihood of heterogeneity in the presentation and, perhaps, etiology offibromyalgia (FM). A clearer understanding of the symptomatology and consideration of potential FM subtypes could add insights regarding this condition.


Objective: The aim of this study was to determine whether clusters could be identified among 20 symptoms that participants in a prior online study identified and to elucidate the underlying structure of resultant clusters.


Methods: Factor analysis was used on data from a study sponsored by the National Fibromyalgia Association in which 2,569 persons with FM responded to an online survey during a 3-day period in 2005.


Results: In this well-educated, primarily Caucasian sample, morning stiffness, fatigue, and not feeling rested in the morning were the symptoms with the highest severity scores. A series of exploratory factor analyses and subsequent confirmatory factor analysis with Cronbach's [alpha] testing led to a five-factor model with the following domains containing 17 symptoms: Somatic, Distress, Fibromyalgia Core, Dyscognition, and Sleep Problems.


Discussion: The findings support the heterogeneity of the FM experience and the presence of symptom clusters within the greater spectrum of symptoms comprising the FM syndrome. These observations suggest the possibility of tailoring interventions based upon individual patient symptomatology. Further work is needed to develop symptom inventories that can be used in clinical trials as outcome metrics and by healthcare providers to describe clinical burden and effect of treatments.