Temporal trends and clinical characteristics of infections in patients with systemic lupus erythematosus from 2014 to 2024

Background　Infection by various pathogens is a leading cause of mortality in patients with systemic lupus erythematosus (SLE). However, the long-term epidemiological trends, seasonal patterns, and clinical characteristics of infections in SLE patients remain unclear and warrant further investigation. Objective　To analyze the epidemiological characteristics of infections in SLE cohort, evaluate their spatiotemporal distribution patterns, and compare the clinical features between patients with and without infections. Methods　This retrospective study collected data from patients with SLE who attended Chinese PLA General Hospital from January 2014 to August 2024. Infection was identified based on the hospital electronic medical record system and was defined by the presence of any of the following: a documented ICD-9 or ICD-10 diagnostic code for an infectious disease, a positive microbiological culture, or initiation of a new systemic anti-infective treatment. Patients were classified into infection group and non-infection group according to whether infection occurred. Chi-square tests, locally estimated scatterplot smoothing (LOESS) curves, and other statistical methods were used to assess annual trends and seasonal patterns in infection rates and to compare differences across periods. Demographic characteristics, laboratory findings, and treatment regimens were compared between the two groups to summarize the clinical features of infected patients. Results　A total of 5 839 patients were included, including 5 081 women (87.0%) and 758 men (13.0%), with a median age of 37 (3727,49 vs 3525,50) years. Among them, 1 851 patients (31.7%) developed infection. Compared with non-infected patients, those with infection had higher disease activity, more frequent major organ involvement, more severe inflammatory responses, and stronger background of immunosuppressive therapy (all P＜0.05). The infection rate showed significant and sustained downward trend from 2014 to 2024 (P＜0.001). Infection also showed a significant seasonal pattern, with the highest rate in winter (35.6%, P=0.004) and the lowest in summer (29.3%, P=0.034). Compared with the period before December 2019, the overall infection rate decreased markedly from January 2020 to December 2022 and from January 2023 onward (44.5% vs 24.3% and 22.0%, respectively; P＜0.001). Conclusion　From 2014 to 2024, the infection burden in patients with SLE showed significant downward trend, with clear winter predominance. Patients with infection exhibit more severe disease activity and greater immune dysregulation. These findings provide important evidence for developing season-specific surveillance strategies and identifying high-risk clinical profiles in patients with SLE, with the ultimate goal of reducing infectionrelate adverse events and mortality and improving patient outcomes.