Initiation of tumor necrosis factor α antagonists and risk of fractures in patients with selected rheumatic and autoimmune diseases

Abstract

Objective: We tested the hypothesis that initiation of tumor necrosis factor α (TNFα) antagonists reduced the risk of fractures compared to nonbiologic comparators in patients with autoimmune diseases.

Methods: Using 4 large administrative databases, we assembled retrospective cohorts of patients with autoimmune diseases who initiated either a TNFα antagonist or a nonbiologic medication. We identified 3 mutually exclusive disease groups: rheumatoid arthritis (RA), inflammatory bowel disease (IBD), and a combined group: psoriasis (PsO), psoriatic arthritis (PsA), or ankylosing spondylitis (AS). We used baseline covariate data to calculate propensity scores (PS) for each disease group and used Cox regression to calculate hazard ratios (HRs) and 95% confidence intervals (95% CIs). We compared the risk of combined hip, radius/ulna, humerus, or pelvic fractures between PS-matched cohorts of new users of TNFα antagonists and nonbiologic comparators.

Results: We identified 9,020, 2,014, and 2,663 new PS-matched episodes of TNFα antagonist and nonbiologic comparator use in RA, IBD, and PsO-PsA-AS cohorts, respectively. The risk of combined fractures was similar between new users of TNFα antagonists and nonbiologic comparators for each disease (HR 1.17, 95% CI 0.91-1.51; HR 1.49, 95% CI 0.72-3.11; and HR 0.92, 95% CI 0.47-1.82 for RA, IBD, and PsO-PsA-AS, respectively). In RA, the risk of combined fractures was associated with an average daily dosage of prednisone equivalents >10 mg/day at baseline compared with no glucocorticoid (HR 1.54, 95% CI 1.03-2.30).

Conclusion: The risk of fractures did not differ between initiators of a biologic agent and a nonbiologic comparator for any disease studied. Among RA patients, use of >10 mg/day of prednisone equivalents at baseline increased the fracture risk.

Figure 1. Assembly of the retrospective cohort of patients with autoimmune disease. Episode is the observation time from the initiation to the end of follow-up

Abbreviations: MAX/MED, National Medicare and Medicaid database; TennCare, Tennessee’s Medicaid database; PAAD/PACE, New Jersey’s Pharmaceutical Assistance to the Age and Disabled and Pennsylvania Pharmaceutical Assistance Contract for the Elderly database; KPNC, Kaiser Permanente Northern California database; RA, rheumatoid arthritis; IBD, inflammatory bowel disease; PsO, psoriasis; PsA, psoriatic arthritis; AS, ankylosing spondylitis; TNFα, tumor necrosis factor alpha; HCQ, hydroxychloroquine; SSZ, sulfasalazine; LEF, leflunomide; INF, infliximab; ADA, adalimumab; AZA, azathioprine; 6MP, 6 mercaptopurine; PS, propensity score.

Figure 2. Time to event for fractures in patients with rheumatoid arthritis in propensity score matched cohorts, SABER 1998–2007

Combined fracture includes hip, pelvis, ulna/radius, humerus; and vertebral fractures are limited to clinical vertebral fractures. Abbreviations: TNFα, tumor necrosis factor alpha; HCQ, hydroxychloroquine; SSZ, sulfasalazine; LEF, leflunomide.