Multimorbidity in systemic lupus erythematosus in a population-based cohort: the Lupus Midwest Network

Objectives The objectives of this study were to assess the prevalence and incidence of multimorbidity and its association with the SLICC/ACR damage index (SDI) among patients with SLE.Methods Using prevalent and incident population-based cohorts of patients with SLE and their matched comparators, we assessed 57 chronic conditions. Chronic conditions were categorized as SDI-related or SDI-unrelated. Multimorbidity was defined as the presence of two or more chronic conditions. The prevalence of multimorbidity for both cohorts was compared using logistic regression. Cox models were used to examine the development of multimorbidity after SLE incidence.Results The prevalent cohort included 449 patients with established SLE on 1 January 2015. They were three times more likely to have multimorbidity compared with non-SLE comparators [odds ratio (OR) 2.98, 95% CI 2.18-4.11]. The incident cohort included 270 patients with new-onset SLE. At SLE incidence, patients with SLE were more likely to have multimorbidity than comparators (OR 2.27, 95% CI 1.59-3.27). After incidence, the risk of developing multimorbidity was 2-fold higher among patients with SLE than among comparators [hazard ratio (HR) 2.11, 95% CI 1.59-2.80]. The development of multimorbidity was higher in patients with SLE based on SDI-related conditions (HR 2.91, 95% CI 2.17-3.88) than on SDI-unrelated conditions (HR 1.73, 95% CI, 1.32-2.26).Conclusion Patients with SLE had a higher burden of multimorbidity, even before the onset of the disease. The risk disparity continued after SLE classification and was also seen in a prevalent SLE cohort. Multimorbidity was driven both by SDI-related and unrelated conditions.