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. 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. Clinical features were compared between the patients with and without infections.

Results A total of 5 839 patients were included, including 758 men (13.0%) and 5 081 women (87.0%), with a median age of 37 (IQR: 27 - 50) years. Among them, 1 851 patients (31.7%) developed infection. Compared with non-infection patients, those with infection had higher disease activity score, more frequent major organs involvement, more severe inflammatory responses, and more 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). Relative to the period prior to December 2019, the total incidence rate declined significantly in the periods spanning January 2020 to December 2022 and from January 2023 onwards (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.