Ethnicity and mortality from systemic lupus erythematosus in the US

To study ethnic differences in mortality from systemic lupus erythematosus (lupus) in two large, population-based datasets.

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.

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).

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.