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Global epidemiology of systemic lupus erythematosus: a comprehensive systematic analysis and modelling study

Comment on:

  • “Global epidemiology of systemic lupus erythematosus: a comprehensive systematic analysis and modelling study.” Tian J, et al. Ann Rheum Dis 2023;82:351–356. doi:10.1136/ard-2022-223035.
  • “Systemic lupus erythematosus incidence and prevalence in a large population-based study in northeastern Italy.” Zen M, et al. Rheumatology 2022 (published online: Dec 10). doi: 10.1093/rheumatology/keac685.

Commented by: Luís S. Inês, Professor of Rheumatology. Rheumatology Department, Centro Hospitalar Universitário de Coimbra & School of Health Sciences, University of Beira Interior, Portugal.

A better knowledge of the epidemiology of SLE around the world is much needed, to raise awareness and improve allocation of healthcare resources. A major contribution is provided by the newly published study from Tian et al. The authors performed a systematic review and meta-analysis, including 112 studies on SLE epidemiology published over 30 years, from 1992 to 2022. Tian et al applied a Bayesian hierarchical linear mixed model, to estimate incidence and prevalence data for each individual country globally with or without SLE epidemiological data, including the 79.8% of countries worldwide that lacked epidemiological data. Importantly, there were few epidemiological data from developing countries. The study also provides global, regional, and country-specific estimates of the annual population with newly diagnosed SLE and the overall population with SLE.

The global SLE incidence and newly diagnosed population were estimated to be 5.14 (1.4 to 15.13) per 100 000 person-years and 0.40 million annually, respectively. The worldwide SLE prevalence and affected population were estimated to be 43.7 (15.87 to 108.92) per 100 000 persons and 3.41 million people, respectively.

As expected, the epidemiological estimates of SLE varied substantially worldwide, with the highest values identified in high-income countries and the northern hemisphere. However, the incidence and prevalence estimates presented wide 95% confidence intervals, that largely overlaps among countries and regions of the world. Furthermore, differences in epidemiological estimates may be biased due to differences in quality of healthcare systems and medical records, access to physicians able to elicit the diagnosis of SLE and public awareness of SLE. Notably, in more than half of the epidemiological studies, the criteria used to diagnose the SLE cases were not reported. For the remaining studies, most applied the ACR classification criteria to identify the SLE cases. Interestingly, the global incidence and prevalence estimates from the studies applying the ACR criteria for case-definition were higher, despite the low sensitivity of these criteria as compared to the EULAR/ACR 2019 classification criteria. Thus, the results of this study need to be interpreted with caution. it can be hypothesized that the true incidence and prevalence of SLE may be closer to the upper boundary of the 95% confidence intervals reported in this study.

In addition to the study from Tian et al, a newly published study from Zen et al, estimated the incidence and prevalence of SLE in northeastern Italy over the period 2012–2020. Interestingly, the authors found significant trends over the study period, with standardized point prevalence presenting an annual increment of 1.14%, while the incidence had an annual decline of 7.3%. The increase in SLE prevalence may be justified by improvements in diagnostic accuracy and disease management, with a possible improvement in survival.

In addition to an improved knowledge on the incidence and prevalence of SLE and its time trends, there is an important unmet need to increase the epidemiological understanding of the burden of the disease. Notably, it remains unknown across Europe, as well as in other world regions, the number and proportion of SLE patients that fails to reach the management targets, due to frequent flares of disease activity or to persistently active disease as well as those taking unacceptably high-dose, long-term glucocorticoids. This epidemiological knowledge will be crucial to all healthcare stakeholders for devising strategies to improving management of SLE patients.