Objective: To study ethnic differences in mortality from systemic lupus erythematosus (lupus) in two large, population-based datasets.
Methods: We analysed the national death data (1979-98) from the National Center for Health Statistics (Hyattsville, Maryland, USA) and hospitalisation data (1993-2002) from the Nationwide Inpatient Sample (NIS), the largest hospitalisation database in the US.
Results: The overall, unadjusted, lupus mortality in the National Center for Health Statistics data was 4.6 per million, whereas the proportion of in-hospital mortality from the NIS was 2.9%. African-Americans had disproportionately higher mortality risk than Caucasians (all-cause mortality relative risk adjusted for age = 1.24 (women), 1.36 (men); lupus mortality relative risk = 3.91 (women), 2.40 (men)). Excess risk was found among in-hospital deaths (odds ratio adjusted for age = 1.4 (women), 1.3 (men)). Lupus death rates increased overall from 1979 to 98 (p<0.001). The proportional increase was greatest among African-Americans. Among Caucasian men, death rates declined significantly (p<0.001), but rates did not change substantially for African-American men. The African-American:Caucasian mortality ratio rose with time among men, but there was little change among women. In analyses of the NIS data adjusted for age, the in-hospital mortality risk decreased with time among Caucasian women (p<0.001).
Conclusions: African-Americans with lupus have 2-3-fold higher lupus mortality risk than Caucasians. The magnitude of the risk disparity is disproportionately higher than the disparity in all-cause mortality. A lupus-specific biological factor, as opposed to socioeconomic and access-to-care factors, may be responsible for this phenomenon.