Racial aspects of comorbidity in systemic lupus erythematosus.

OBJECTIVE: To investigate racial differences in the expression of systemic lupus erythematosus (SLE) by comparing comorbidity at death among individuals with SLE.
METHODS: Proportional mortality rates were estimated for common contributing causes of death among white and black females in the United States, 1989-1991, whose death certificates listed SLE as an underlying or contributing cause. Logistic regression analysis was used to assess the effects of SLE and race on variation in proportional mortality using rates from non-SLE deaths as a comparison baseline.
RESULTS: Common contributing causes of death listed with SLE included conditions that are known sequelae of the disease. Proportional mortality rates for these conditions varied with race and age. However, among black deaths that listed SLE, the rates of renal disease surpassed those of all other conditions regardless of age. When rates of renal disease among black SLE deaths or among white SLE deaths in any age group were compared to those among white non-SLE deaths, proportional mortality ratios were significantly greater than 1. This also held when rates of renal disease among black non-SLE deaths were compared to rates among white non-SLE deaths. However, across all ages, the proportional mortality ratios for renal disease in black SLE deaths significantly exceeded corresponding ratios for white SLE deaths and for black non-SLE deaths.
CONCLUSION: Black females who die with SLE appear to experience a combination of the excess renal disease reported for persons with SLE and for all blacks. This combination may be a source of the elevated SLE mortality rates observed among US blacks.