Temporal Trends in the Incidence of Systemic Lupus Erythematosus in the United States: Holding Steady?

Objectives Systemic lupus erythematosus (SLE) is associated with significant morbidity and healthcare burden. Estimates of SLE incidence help inform research and public health initiatives, including rheumatology workforce planning. SLE incidence estimates may be affected by health care access or care-seeking behavior (impacted by COVID-19 pandemic years, 2020-2022) and/or by environmental factors (eg, viral triggers, climate change). We estimated annual SLE incidence rates over time, using real-world US data. Methods Using the Merative™ MarketScan® Commercial (±Medicare Supplemental) databases, we identified adults (18+) with >2 years of continuous enrollment and no SLE diagnoses during those 2 years between Jan. 2016-Dec. 2022. Among these, a 20% random sample was selected for analysis. Time zero was first qualifying date for cohort entry. Incident SLE was defined by International Classification of Diseases diagnostic codes, based on ≥2 physician visits ≥8 weeks apart within 2 years and/or ≥1 hospitalization. Individuals were followed from time zero until earliest SLE diagnosis, health plan disenrollment, or end of follow-up. Annual SLE incidence rates were calculated with 95% confidence intervals (CI). We report incidence overall and stratified by sex. Female-specific rates were further stratified according to whether person-time was contributed during reproductive age (age < 52). We assessed age (continuous) and sex in a multivariate hazard regression predicting SLE onset, controlling for calendar year. Results We analyzed 4.6 million individuals followed an average of 2.8 years (standard deviation, SD 2.2); 52.6% were female, mean age at time zero was 43.1 years (SD 14.8). During this period, 1,593 new SLE cases (89.2% female) were identified across 12.9 million person-years (12.3 events per 100,000 person-years). No clear difference in incidence comparing 2020-2022 (12.6 events /100,000 person-years) vs 2016-2019 (12.2 events/100,000 person-years). In any given calendar year, incidence was much greater among females, with a higher incidence during reproductive years (23.3 events/100,000 person-years; 95% CI 21.9-24.9) vs later (16.8 events/100,000 person-years; 95% CI 15.3-18.5) (Table 1). In multivariate models, hazard ratios (HR) for female sex was 7.47 (95% CI 6.38-8.75) and for age (continuous),1.00 (95% CI 1.00, 1.01). Table 1: Annual SLE incidence by 10,000 person-years with 95% CI, US MarketScan, 2016-2022* Conclusion These clinically relevant real-world data suggest SLE incidence in the US is holding steady, during the period 2016-2022. Limitations of our analyses include selection bias (all individuals had private insurance), short average follow-up time, and possible outcome misclassification (eg, prevalent SLE cases mischaracterized as incident). Ongoing analyses will consider other factors, such as urban-vs-rural residence, race/ethnicity, and environmental exposures over longer periods.