Understanding the association of fatigue with other symptoms of fibromyalgia: Development of a cluster model.
OBJECTIVE: The study's purpose was to develop symptoms cluster model that can describe factors of FMS associated with fatigue severity as reported by the sample. The study will also explore FMS clinical symptom sub-clusters based on varying symptom intensities.
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METHODS: FMS individuals (n = 120; 82% between 31-60 years of age, 90% women, 59% Caucasian) diagnosed with the 1990 or 2010 American College of Rheumatology diagnostic criteria were enrolled. Participants completed multiple validated self-report questionnaires to measure fatigue, pain, depression, anxiety, pain catastrophizing, daytime sleepiness, cognitive function, and FMS-related polysymptomatic distress. Cluster analysis using SPSS 19.0 and Structural Equation Modeling using AMOS 17.0 were used.
RESULTS: Final Structural Equation Modeling symptoms cluster model showed good fit and revealed that FMS fatigue was associated with widespread pain, symptoms severity, pain intensity, pain interference, cognitive dysfunction, catastrophizing, anxiety, and depression (χ2 = 121.72, df = 98, p > 0.05, χ2 /df = 1.242, CFI = 0.982, RMSEA = 0.045). Two distinct clinical symptom sub-clusters emerged; sub-cluster 1 (78% of total subjects) defined by widespread pain, unrefreshed waking, and somatic symptoms and sub-cluster 2 (22% of total subjects) defined by fatigue and cognitive dysfunction with pain being a less severe and less widespread complaint.
CONCLUSION: Overall, sub-cluster 1 had more intense symptoms than sub-cluster 2. FMS symptoms may be categorized into two clinical sub-clusters. These findings have implications for an illness whose diagnosis and management are symptom-dependent. A longitudinal study capturing the variability in symptom experience of FMS subjects is warranted.
This article is protected by copyright. All rights reserved. © 2015, American College of Rheumatology.
Source: Arthritis Care & Research, May 25, 2015. By Nada Lukkahatai, Brian Walitt, Alexandra Espina, Alves Gelio and Leorey N. Saligan. School of Nursing, University of Nevada, Las Vegas, Las Vegas, NV. National Institute of Nursing Research, National Institutes of Health, Bethesda, MD.