The Principal Components of Autonomic Dysfunction in Fibromyalgia Assessed by the Refined and Abbreviated Composite Autonomic Symptom Score

Abstract

Background: We have recently confirmed that non-pain autonomic dysfunction symptoms occur in fibromyalgia and can be assessed with the 31-item Composite Autonomic Symptom Score (COMPASS 31) instrument. Fibromyalgia patients have been found to have higher scores than matched controls across all six domains of this instrument. Objectives: To analyse the principal components of the autonomic COMPASS 31 domain scores in fibromyalgia patients to understand better the fundamental dimensions of dysautonomia in this disorder. Methods: A principal component analysis of fibromyalgia autonomic domain scores was carried out using a varimax orthogonal rotation with decomposition being based on the correlation matrix and setting a threshold of greater than one for the eigenvalues. Results: Three mutually orthogonal principal components, accounting for over 80% of the total variance, were identified. The first was a function of the secretomotor, orthostatic intolerance and pupillomotor domains; the second was a function of the vasomotor and urinary bladder domains; and the third was a function of the gastrointestinal and orthostatic intolerance domains. There was a positive correlation between symptom domain scores of the Revised Fibromyalgia Impact Questionnaire and the first principal component scores (rs = 0.536, p = 0.006). Conclusion: This analysis has reduced the dimensionality of autonomic dysfunction in fibromyalgia patients from six to three. The internal structure of the fibromyalgia dysautonomia data reflected by these results may help in the elucidation of the aetiology of this complex and difficult-to-treat disorder.