Multimorbidity in systemic lupus erythematosus in a population-based cohort: the lupus Midwest network.

OBJECTIVES: To assess the prevalence and incidence of multimorbidity and the association with the SLICC/ACR damage index (SDI) among patients with systemic lupus erythematosus (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 2+ chronic conditions. Multimorbidity at prevalence and incidence/index was compared between cohorts using logistic regression. Cox models were used to examine development of multimorbidity after SLE incidence. RESULTS: The prevalent cohort included 449 patients with established SLE on January 1, 2015. They were three times more likely to have multimorbidity compared with non-SLE comparators (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 comparators (hazard ratio (HR) 2.11, 95% CI 1.59-2.80). Development of multimorbidity was higher in patients with SLE based on SDI-related (HR 2.91, 95% CI 2.17-3.88) and SDI-unrelated conditions (HR 1.73, 95% CI, 1.32-2.26). CONCLUSION: Patients with SLE have a higher burden of multimorbidity, even before the onset of the disease. The risk disparity continues after SLE classification and is also seen in a prevalent SLE cohort. Multimorbidity is driven both by SDI-related and unrelated conditions.