Incidence of systemic lupus erythematosus race and gender differences

Abstract

Objective. To examine racial differences in the incidence of systemic lupus erythematosus (SLE). Methods. A population‐based registry of SLE patients in Allegheny County, Pennsylvania, was used to identify incident cases of SLE diagnosed between January 1, 1985 and December 31, 1990, from 3 sources, by medical record review (University of Pittsburgh Lupus Databank, rheumatologists, and hospitals). Capture‐recapture methods using log‐linear models were used to estimate the level of case‐finding and to calculate 95% confidence intervals (CI). Incidence rates were calculated per 100,000 population. Results. A total of 191 definite and 78 probable incident cases of SLE were identified, and the overall annual incidence rates were 2.4 (95% CI 2.1–2.8) and 1.0 (95% CI 0.8–1.3), respectively. The crude incidence rates of definite SLE were 0.4 for white males, 3.5 for white females, 0.7 for African‐American males, and 9.2 for African‐American females. The annual incidence rates of definite SLE remained fairly constant over the study interval. African‐American females with definite SLE had a younger mean age at diagnosis compared with white females (P < 0.05). Since the overall ascertainment rate was high (85%; 95% CI 78–92%), the ascertainment‐corrected incidence rate for definite SLE, 2.8 (95% CI 2.6–3.2), was similar to the crude rate. Conclusion. Our rates clearly confirm previous reports of an excess incidence of SLE among females compared with males and among African‐Americans compared with whites. We have used capture–recapture methods to improve the accuracy of SLE incidence rates, and we advocate their use to facilitate comparisons across studies.