Poor bone health is common in systemic lupus erythematosus (SLE) patients. This study was undertaken to evaluate fracture risks among low-income SLE and lupus nephritis patients compared to those without SLE.
We performed a cohort study among SLE patients for whom there were Medicaid claims in 2007-2010, and age- and sex-matched non-SLE comparators. SLE was defined by the presence of ≥3 International Classification of Diseases, Ninth Revision codes for SLE. Patients with lupus nephritis additionally had ≥2 codes for renal disease. The primary outcome measure was fracture of the pelvis, wrist, hip, or humerus. Demographics, prescriptions, and comorbidities were assessed during the 180-day baseline period. We calculated fracture incidence rates and 95% confidence intervals (95% CIs) in SLE, lupus nephritis, and non-SLE comparator cohorts, and estimated adjusted hazard ratios (HRs) for fractures. Sensitivity analyses evaluated the impact of glucocorticoids and comorbidities. We compared subsets of SLE patients with and those without lupus nephritis.
Among 47,709 SLE patients (19.8% with lupus nephritis) matched to 190,836 non-SLE comparators, the mean age was 41.4 years and 92.6% were female. The fracture incidence rate was highest among SLE patients with lupus nephritis (4.60 per 1,000 person-years). SLE patients had 2-fold higher fracture risks than matched comparators (HR 2.09 [95% CI 1.85-2.37]; P < 0.01). Lupus nephritis patients had the greatest fracture risks versus matched comparators (HR 3.06 [95% CI 2.24-4.17]; P < 0.01), and had a 1.6 times higher fracture risk than SLE patients without nephritis (HR 1.58 [95% CI 1.20-2.07]; P < 0.01). Adjustment for glucocorticoid use and comorbidities slightly attenuated risks.
Fracture risks were increased in SLE patients, particularly those with lupus nephritis, compared to matched non-SLE Medicaid recipients. Increased risks persisted after adjustment for baseline glucocorticoid treatment and comorbidities.