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

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.