Background Many patients with IIMs exibit chronic muscle weakness and functional disability despite treatment. In polymyositis/ dermatomyositis (PM/DM), male sex, higher prednisone dosage and older age have been associated with muscle weakness and functional disability.[1,2] Sporadic inclusion body myositis (sIBM) itself is associated with major end-stage disability. The ACR functional status (ACRFS) criteria have been used as a core measure of the consequences of impairment in IIM. However, its association with known or suspected risk factors of disability warrants further investigation.
Objectives To determine predictors of current/ worst ever ACRFS with known or suspected risk factors of disability and muscle weakness in patients with IIM.
Methods Data were obtained from chart reviews of IIM and overlap myositis (OM) cases seen in the Rheumatology and Neurology Clinics at the University of Kentucky from May/06 until July/12. Current and worst ever ACRFS, demographic and clinical characteristics were abstracted from medical records. One-way ANOVA and Fisher’s exact/ Chi-square tests were used to compare groups on continuous/ categorical variables, respectively. Ordinal logistic regression was applied to estimate the effects of IIM type, age, sex and disease duration from diagnosis on current and worst ever ACRFS.
Results 90 patients with IIM and OM were included: 38 PM, 29 DM, 12 IBM and 11 OM. When patient ages were divided into tertiles, sIBM patients were significantly older (p= 0.03). Females predominated in the PM, DM and OM groups. In sIBM, females were slightly outnumbered. Mean duration of disease from diagnosis was highest in sIBM (73 mo) compared to PM (39 mo), DM (18 mo) and OM (35 mo) (p=0.01). sIBM was more likely to be associated with presence of some degree of disability at the last time of assessment (91%), compared to all other groups combined (73%) (p=0.001). In the multivariable analysis, poorer current ACRFS and worst ever ACRFS were independently associated with higher age, and higher age and longer disease duration, respectively, controlling for all other variables.
Conclusions The demographic and clinical characteristics of our cohort are consistent with previous reports. As expected, sIBM was associated with increased odds of disability. In the multivariate analysis, higher age and disease duration were identified as independent risk factors for disability.
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Acknowledgements This study was supported by the Arthritis Foundation, the Center for Clinical and Translational Science (CCTS) at the University of Kentucky, the University of Kentucky College of Medicine Clinical Scholars Program and Research Data Capture (REDCap).
Disclosure of Interest None Declared