Systemic lupus erythematosus incidence and prevalence in a large population-based study in northeastern Italy

We aimed at estimating the incidence and prevalence of SLE in northeastern Italy over the period 2012-20.

A retrospective population-based study was conducted in Veneto Region (4.9 million people) using the population registry, an administrative health database where all residents are recorded. Between 2012 and 2020, SLE prevalence was defined by a healthcare co-payment exemption for SLE (national registry code 028) or any hospital diagnosis of SLE (International Classification of Disease , Ninth Revision, Clinical Modification 710.0), whichever came first. Incident SLE was defined from 2013 to 2020 to exclude prevalent cases. Standardized incidence and prevalence rates were reported by age and sex.

During the study period, we identified 4283 SLE patients (85% female), with 1092 incident cases. Across the study period, SLE standardized point prevalence increased from 63.5 (95% CI 61.2, 65.8) to 70.6 (95% CI 68.3, 73.0) per 100 000 residents, corresponding to an annual increment of 1.14% (P < 0.0001). The highest prevalence was observed in females aged 60-69 years. SLE incidence corresponded to 2.8 per 100 000 person-years (95% CI 2.6, 2.9), with an annual decline of 7.3% (P < 0.0001). Incidence was 5-fold higher in females (female-to-male incidence rate ratio: 5.00, 95% CI 4.25, 5.87; P < 0.0001), with a peak among women aged 30-39 years. At diagnosis, women were significantly younger (45 years, IQR 33-58) than men (52 years, IQR 38-64).

Over the last decade, SLE prevalence has increased, while incidence has stably declined. In view of the introduction of new high-cost drugs, a clear definition of the epidemiology of SLE is crucial for all healthcare stakeholders.