Impact of bisphosphonate compliance on the risk of osteoporotic fracture in France

Abstract

Summary: Limited information is available on the impact of bisphosphonate compliance levels on fracture risk in osteoporosis patients in France. The results of this nested case-control, retrospective study suggest that fracture risk did not significantly change with bisphosphonate compliance levels, except for highly compliant patients. Purpose/introduction: This was the first study conducted in France to evaluate the impact of compliance levels for bisphosphonates, the most frequently prescribed first-line anti-osteoporotic treatment, on fracture risk. Methods: This retrospective nested case-control study included patients ≥ 50 years old, who were recorded in a random sample of French claims data, did not die between 2006 and 2013, and received ≥ 1 reimbursement for anti-osteoporotic treatment between 2007 and 2013. Cases (patients hospitalised for osteoporosis-related fractures) were matched to 1–3 controls (patients hospitalised for other reasons). Patients hospitalised for fractures within 12 months preceding the first delivery of anti-osteoporotic treatment or during the first 24 months of follow-up were excluded. Bisphosphonate compliance during the 24 months preceding hospitalisation was calculated by the Continuous measure of Medication Acquisition version 7 (CMA7). We evaluated the impact of bisphosphonate compliance (CMA7 ≥ 80%) and very good compliance levels (CMA7 > 90%) on fracture risk. Results: In the main analysis, the mean CMA7 values during the 24 months preceding hospitalisation were 48.4% for the 434 cases and 51.3% for the 1123 age-matched controls. An adjusted conditional logistic regression showed no significant impact (odds ratio: 0.851 [95% confidence interval: 0.668, 1.084]) of bisphosphonate compliance on fracture occurrence. In the sensitivity analysis, including one randomly selected control per case and only controls with CMA7 values > 90%, occurrence of fractures was lower (odds ratio: 0.741 [95% confidence interval: 0.608, 0.903]) among the 119 controls. Conclusion: In conclusion, this study suggested that very high levels of compliance with bisphosphonates are necessary to induce significant decreases in fracture risk.