This study aims to estimate bisphosphonate effectiveness by comparing fracture incidence over time on therapy in glucocorticoid-induced osteoporosis (GIO). From this observational study, alendronate and risedronate decreased clinical vertebral and nonvertebral fractures over time. The effectiveness of each bisphosphonate is consistent with their efficacies demonstrated on surrogate markers in randomized controlled trials (RCTs).
Introduction: This study aims to estimate bisphosphonate effectiveness by comparing fracture incidence over time on therapy with fracture incidence during a short period after starting a therapy.
Methods: The study population was a subgroup of a larger cohort study comprising two cohorts of women aged ≥65 years, prescribed with alendronate or risedronate. Within the two study cohorts, 11,007 women were identified as having received glucocorticoids. Within each cohort, the baseline incidence of clinical fractures at nonvertebral and vertebral sites was defined by the initial 3-month period after starting therapy. Relative to these baseline data, we then compared the fracture incidence during the subsequent 12 months on therapy.
Results: The baseline incidence of clinical nonvertebral and vertebral fractures was similar in the alendronate cohort (5.22 and 5.79/100 person-years, respectively) and in the risedronate cohort (5.51 and 5.68/100 person-years, respectively). Relative to the baseline incidence, fracture incidence was significantly lower in the subsequent 12 months in both cohorts of alendronate (33 % lower at nonvertebral sites and 59 % at vertebral sites) and risedronate (28 % lower at nonvertebral sites and 54 % at vertebral sites).
Conclusion: From this observational study not designed to compare drugs, both alendronate and risedronate decreased clinical vertebral and nonvertebral fractures over time. The reductions observed in fracture incidence, within each cohort, suggest that the effectiveness of each bisphosphonate in clinical practice is consistent with their efficacies demonstrated on surrogate markers in randomized controlled trials.