IntroductionAdmissions are frequent in SLE patients and the main causes are activity of the disease and infections.ObjectiveTo analyze frequency and causes of hospitalizations in SLE patients as well as its main associated factors.MethodsCross sectional study in SLE patients included in RELESSAR registry. Sociodemographic data, autoantibodies, manifestations of the disease and treatments received at the moment of the admission were collected. The sample was divided in two groups according to present or not hospitalization. Number, causes and associated factors to hospitalization were described.ResultsA total of 1515 adult SLE patients were analyzed and 53.7% (n: 815) of patients had at least one hospitalization during the evolution of the disease: 203 patients were admitted due to serious infection, 612 patients due to activity of the disease and 162 patients for both reasons. In multivariate analysis, variables independently associated with hospitalization were education level (OR 0.95, 95% CI 0.91-0.99, p = .021), diagnosis delay (OR 0.93, 95% CI 0.88-0.99, p = .029), pleuritis (OR 2.12, 95% CI 1.46-3.10, p < .001), hypocomplementemia (OR 1.96, 95% CI 1.22-3.18, p = .006), use of IvIg (OR 5.87, 95% CI 1.92-26.4, p = .006), use of cyclophosphamide (OR 1.59, 95% CI 1.09-2.34, p = .017) and corticosteroids (<10 mg of prednisone [OR 3.01, 95% CI 1.71-5.47, p < .001], 10-30 mg [12.8, 95% CI 7.53-22.8, p < .001], 30-60 mg/day [OR 22.6, 95% CI 12.1-43.9, p < .001]) and damage (OR 1.29, 95% CI 1.12-1.49, p < .001).ConclusionMore than half of SLE patients had at least one hospitalization and infections and activity of the disease were the most frequent causes. Education level, diagnosis delay, pleuritis, hypocomplementemia, use of IvIg, cyclophosphamide and corticosteroids and damage were associated with admissions.