Background/Purpose: The main objective was to study the incidence of Systemic Lupus Erythematosus (SLE) within a defined area in Southern Sweden over a period of more than 25 years. By prospectively identifying all new cases within this region using validated retrieval methods. A secondary objective was to investigate whether the phenotypic expression of SLE has changed during the study period.

Methods: The health care district of Lund-Orup had a mean population during 1981-2006 of 176.460 persons (>15 yrs of age). SLE cases were identified from multiple sources including diagnosis registries and from central laboratory databases using a previously validated  “capture-recapture” methodology (Jonsson et al). The patients were observed prospectively within a structured follow-up program. Diagnosis of SLE was based on the presence of two clinical manifestations typical for SLE together with immunological abnormalities. Other causes for these manifestations were excluded and the diagnosis was continuously re-evaluated during the follow-up.

Results: One-hundred seventy-five new cases were diagnosed with SLE from 1981-2006. There were 148 women and 27 male patients that received the diagnosis of SLE, with a mean age of diagnosis at 44.3 years. In the first half of the study, from 1981-1993, the incidence of SLE was 5.0/100.000 inhabitants compared to the second half of the study, 1994-2006, where it had decreased to an annual incidence of 2.8/100.000 inhabitants (p≤0.001). During the first half of the study period the highest incidence was among females between the ages 45-54 were it was 15.1/100.000 inhabitants whereas in the second half of the study the incidence was reduced to 3.8/100.000 in this age group (p≤0.001).  Between the years 1994-2006 the highest age and sex specific incidence was amongst women between 25-34 years of age (6.6/100.000 inhabitants), unchanged from the prior period. During the whole period the age and sex specific was highest among women between the ages 45-54 (8.9/100.000 inhabitants). The point prevalence of SLE on 31^stof December 1993 was 55/100.000 inhabitants compared to the 31th of December 2006 where it was 66/100.000 inhabitants. 163 of the 175 patients fulfilled 4 or more ACR classification criteria SLE giving the criteria a sensitivity of 93 % for diagnosing SLE in our cohort. The disease phenotype did not vary over time.

Conclusion: The incidence rate of SLE in Southern Sweden remains stable in younger females over a 26 year period from 1981-2006. However, the incidence was reduced significantly in the older patients groups in the later period of the study.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/incidence-studies-of-systemic-lupus-erythematosus-in-southern-sweden-have-the-tides-turned/