Objective: To determine if differences in morbidity of systemic lupus erythematosus (SLE) as measured by (1) important renal disease, (2) number of hospitalizations, and (3) neurologic disease can be explained by race, socioeconomic status (SES), or measures of compliance.
Design: The interrelationship of black race, SES, and the physician's assessment of compliance as risk factors for morbidity was examined in a cohort of 198 patients with SLE (179 female, 115 black). SES was measured with Nam-Powers scores for education (years), income, and job status, and source of insurance; compliance was assessed by physician global assessment and percent of protocol visits kept. Morbidity outcomes were important renal disease (creatinine level 1.5 mg/dL or greater, renal failure, nephrotic syndrome), neurologic involvement, and number of hospitalizations.
Setting: The Johns Hopkins Rheumatology Faculty Practice, in which both private and clinic patients are seen.
Results: Black patients had significantly lower SES on all measures (p less than 0.0001) and were also less compliant by physician global assessment (odds ratio [OR] = 0.39, p = 0.002). Univariate analyses showed that blacks had a higher frequency of important renal disease (OR = 2.07, 95% confidence interval [CI] 1.05 to 4.11) and hypertension (OR = 1.80, 95% CI 1.01 to 3.23). Important renal disease was associated with the physician global assessment of compliance (p = 0.009) and hypertension (p less than 0.001). Multiple regression models for important renal disease, including race, physician global assessment of compliance, hypertension, SES, age, and gender, identified significant associations with only physician global assessment of compliance (OR = 0.40, 95% CI 0.17 to 0.91) and hypertension (OR = 5.37, 95% CI 2.40 to 11.98); black race was not significant (OR = 1.60, 95% CI 0.68 to 3.76). The second morbidity measure, number of hospitalizations, was associated with renal disease, neurologic disease, mouth ulcers, duration of disease, and public insurance but not with black race, in the best log-linear model. Neither race, SES variables, nor physician assessment of compliance was significantly associated with neurologic disease, the third morbidity measure.
Conclusions: These data fail to support an independent association of black race with morbidity in SLE; rather, they suggest that noncompliance (as measured by physician global assessment) and type of medical insurance are important factors in morbidity. Classical epidemiologic measures of SES (education, income, occupation) do not appear to be significant confounders of the relationship of race to morbidity in SLE.