Andrea Burri, Peter Hilpert, Peter McNair, Frances M Williams

Chronic widespread musculoskeletal pain (CWP) is a condition manifesting varied co-symptomatology and considerable heterogeneity in symptom profiles. This poses an obstacle for disease definition and effective treatment. Latent class analysis (LCA) provides an opportunity to find subtypes of cases in multivariate data. In this study, LCA was used to investigate whether and how individuals with CWP could be classified according to 12 additional somatic symptoms (migraine headaches, insomnia, stiffness, etc.). In a second step, the role of psychological and coping factors for the severity of these co-symptoms was investigated. Data were available for a total of N = 3,057 individuals (mean age = 56.6 years), with 15.4% suffering from CWP. In the latter group, LCA resulted in a three-class solution (ngroup1 = 123; ngroup2 = 306; ngroup3 = 43) with groups differing in a graded fashion (i.e., severity) rather than qualitatively for somatic co-symptom endorsements. A consistent picture emerged, with individuals in the first group reporting the lowest scores and individuals in group 3 reporting the highest. Additionally, more co-symptomatology was associated with higher rates of anxiety sensitivity and depression, as well as more extraversion and emotional instability. No group differences for any of the coping strategies could be identified. The findings suggest that CWP has several detectable subtypes with distinct psychological correlates. The identification of CWP subgroups is important for understanding disease mechanisms and refining prognosis as well as stratifying patients in clinical trials and targeting specific treatment at the subgroups most likely to respond.