Association between African American race/ethnicity and low bone mineral density in women with systemic lupus erythematosus

Objective. To determine the association between race/ethnicity and bone mineral density (BMD) in women with systemic lupus erythematosus (SLE). Methods. Women with SLE (n = 298), including 77 African Americans and 221 whites, completed this cross-sectional study conducted from 1996 to 2002. Hip and lumbar spine BMD were measured by dual-energy x-ray absorptiometry. Study participants completed a self-administered questionnaire and a physician completed the Systemic Lupus International Collaborating Clinics/American College of Rheumatology Damage Index (SDI). BMD results were expressed as Z scores. Analyses were performed to identify factors, including race/ethnicity, associated with low BMD defined as a Z score -1.0 or less at the hip or lumbar spine. Results. African Americans compared with whites were younger at study visit (mean ± SD 39.7 ± 8.4 years versus 42.9 ± 11.6 years) and had higher SDI (mean ± SD 1.8 ± 2.0 versus 1.0 ± 1.6), but similar proportions of women were postmenopausal (31.2% versus 38.0%). African Americans had significantly lower mean BMD Z scores at the hip (-0.49 versus -0.07; group difference -0.41; 95% confidence interval [95% CI] -0.70, -0.13) and at the lumbar spine (-1.03 versus 0.10; group difference -1.13; 95% CI -1.48, -0.78) compared with whites. African American race/ethnicity was strongly associated with low BMD at the lumbar spine (adjusted odds ratio 4.42; 95% CI 2.19, 8.91) but not at the hip, adjusting for factors associated with low BMD. Conclusion. African American women compared with white women with SLE had lower BMD at the hip and lumbar spine. African American race/ethnicity was associated with low BMD at the lumbar spine controlling for relevant clinical covariates.