Subgroups of Fibromyalgia Patients: Evidence for Heterogeneity and an Examination of Differential Effects Following a Community-Based Intervention

Abstract

Objectives: The present study had three purposes: 1. to use cluster analysis to determine whether the same three clusters of pain patients [adaptive copers, dysfunctional, and interpersonally distressed] identified in the literature would emerge, using different measures that assess similar constructs in a sample of fibromyalgia [FMS] patients; 2. to validate the classification, using variables associated with FMS, but not used in the cluster analysis; and 3. to determine whether the clusters would respond differently to a year-long community-based intervention focused on social support and education.

Methods: Participants were 600 members of a large health maintenance organization, primarily Caucasian [85 percent] and female [95 percent], with an average age of 53.9 [SD = 11.4]. Participants were part of a larger study examining the effects of social support and education on FMS symptoms and health care use.

Results: Cluster analysis revealed three clusters that were congruent with past research; follow-up analyses validated the uniqueness of each cluster. There was no evidence that the intervention differentially affected the clusters. There were a number of cluster by time interaction effects, suggesting that both the dysfunctional and interpersonally distressed groups improved in symptoms [e.g., pain, depression] over time, regardless of intervention group.

Conclusions: People with FMS may fall into distinct subgroups; however, the utility of dividing participants into these groups in planning interventions remains unclear. Results emphasize the need to take into account the fluctuating nature of the syndrome, as well as the statistical phenomenon of regression toward the mean, when examining treatment outcomes.

KEYWORDS:

• Fibromyalgia
• pain
• clusters
• intervention