Incidence, Prevalence, and Mortality of Lupus Nephritis: 20-Year Territory-Wide Analysis of Electronic Health Records in Hong Kong

Background: Lupus nephritis (LN) is a serious complication of systemic lupus erythematosus (SLE). This study provides an up-to-date analysis of the prevalence, incidence, and mortality in the current era of LN management. Methods: We established a large retrospective cohort of LN patients using the Clinical Data Analysis and Reporting System (CDARS, an electronic health records system from Hong Kong) between 1995 and 2024. LN cases were defined by the first occurrence of either an ICD-coded LN diagnosis, SLE with proteinuria (24-hour urine protein >0.5 g/day or UPC ratio >50 mg/mmol), or SLE with two consecutive eGFR measurements within 3 months showing ≥15% decline from a baseline eGFR of more than 60 mL/min/1.73m2. The incidence, prevalence and all-cause mortality were evaluated between 2005 and 2024, and age-standardization was based on the WHO standard population. Trends were assessed by the estimated annual percentage change (EAPC). Results: Between 2005 and 2024, 4,784 incident LN cases were identified, representing 56 percent of all SLE cases. By 2024, the prevalence of LN reached 5,959 cases (79.2 per 100,000), marking a significant increase from 29.9 per 100,000 in 2005 [EAPC: 5.0 (95% CI: 4.7–5.4)]. The crude prevalence rates for female and male were 129.9 and 18.2, respectively, by 2024. While the crude incidence rate remained stable over the study period [3.2 vs. 3.3 per 100,000; EAPC: -0.3 (-1.1 to 0.6)], the crude mortality rate rose from 0.6 to 1.8 [EAPC: 5.6 (4.6 to 6.7)]. A significant surge in both crude and age-standardized death rates occurred in 2022. Conclusion: The rising prevalence of LN reflects the advancements in disease management and improved patient survival over time. The surge in mortality rates in 2022 may be related to COVID-19, highlighting the susceptibility of LN patients.The trends in rates and numbers of prevalence, incidence, and death in LN.